1//===- ScalarEvolutionExpander.cpp - Scalar Evolution Analysis --*- C++ -*-===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file contains the implementation of the scalar evolution expander,
11// which is used to generate the code corresponding to a given scalar evolution
12// expression.
13//
14//===----------------------------------------------------------------------===//
15
16#include "llvm/Analysis/ScalarEvolutionExpander.h"
17#include "llvm/ADT/STLExtras.h"
18#include "llvm/ADT/SmallSet.h"
19#include "llvm/Analysis/InstructionSimplify.h"
20#include "llvm/Analysis/LoopInfo.h"
21#include "llvm/Analysis/TargetTransformInfo.h"
22#include "llvm/IR/DataLayout.h"
23#include "llvm/IR/Dominators.h"
24#include "llvm/IR/IntrinsicInst.h"
25#include "llvm/IR/LLVMContext.h"
26#include "llvm/Support/Debug.h"
27
28using namespace llvm;
29
30/// ReuseOrCreateCast - Arrange for there to be a cast of V to Ty at IP,
31/// reusing an existing cast if a suitable one exists, moving an existing
32/// cast if a suitable one exists but isn't in the right place, or
33/// creating a new one.
34Value *SCEVExpander::ReuseOrCreateCast(Value *V, Type *Ty,
35 Instruction::CastOps Op,
36 BasicBlock::iterator IP) {
37 // This function must be called with the builder having a valid insertion
38 // point. It doesn't need to be the actual IP where the uses of the returned
39 // cast will be added, but it must dominate such IP.
40 // We use this precondition to produce a cast that will dominate all its
41 // uses. In particular, this is crucial for the case where the builder's
42 // insertion point *is* the point where we were asked to put the cast.
43 // Since we don't know the builder's insertion point is actually
44 // where the uses will be added (only that it dominates it), we are
45 // not allowed to move it.
46 BasicBlock::iterator BIP = Builder.GetInsertPoint();
47
48 Instruction *Ret = nullptr;
49
50 // Check to see if there is already a cast!
51 for (User *U : V->users())
52 if (U->getType() == Ty)
53 if (CastInst *CI = dyn_cast<CastInst>(U))
54 if (CI->getOpcode() == Op) {
55 // If the cast isn't where we want it, create a new cast at IP.
56 // Likewise, do not reuse a cast at BIP because it must dominate
57 // instructions that might be inserted before BIP.
58 if (BasicBlock::iterator(CI) != IP || BIP == IP) {
59 // Create a new cast, and leave the old cast in place in case
60 // it is being used as an insert point. Clear its operand
61 // so that it doesn't hold anything live.
62 Ret = CastInst::Create(Op, V, Ty, "", IP);
63 Ret->takeName(CI);
64 CI->replaceAllUsesWith(Ret);
65 CI->setOperand(0, UndefValue::get(V->getType()));
66 break;
67 }
68 Ret = CI;
69 break;
70 }
71
72 // Create a new cast.
73 if (!Ret)
74 Ret = CastInst::Create(Op, V, Ty, V->getName(), IP);
75
76 // We assert at the end of the function since IP might point to an
77 // instruction with different dominance properties than a cast
78 // (an invoke for example) and not dominate BIP (but the cast does).
79 assert(SE.DT->dominates(Ret, BIP));
80
81 rememberInstruction(Ret);
82 return Ret;
83}
84
85/// InsertNoopCastOfTo - Insert a cast of V to the specified type,
86/// which must be possible with a noop cast, doing what we can to share
87/// the casts.
88Value *SCEVExpander::InsertNoopCastOfTo(Value *V, Type *Ty) {
89 Instruction::CastOps Op = CastInst::getCastOpcode(V, false, Ty, false);
90 assert((Op == Instruction::BitCast ||
91 Op == Instruction::PtrToInt ||
92 Op == Instruction::IntToPtr) &&
93 "InsertNoopCastOfTo cannot perform non-noop casts!");
94 assert(SE.getTypeSizeInBits(V->getType()) == SE.getTypeSizeInBits(Ty) &&
95 "InsertNoopCastOfTo cannot change sizes!");
96
97 // Short-circuit unnecessary bitcasts.
98 if (Op == Instruction::BitCast) {
99 if (V->getType() == Ty)
100 return V;
101 if (CastInst *CI = dyn_cast<CastInst>(V)) {
102 if (CI->getOperand(0)->getType() == Ty)
103 return CI->getOperand(0);
104 }
105 }
106 // Short-circuit unnecessary inttoptr<->ptrtoint casts.
107 if ((Op == Instruction::PtrToInt || Op == Instruction::IntToPtr) &&
108 SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(V->getType())) {
109 if (CastInst *CI = dyn_cast<CastInst>(V))
110 if ((CI->getOpcode() == Instruction::PtrToInt ||
111 CI->getOpcode() == Instruction::IntToPtr) &&
112 SE.getTypeSizeInBits(CI->getType()) ==
113 SE.getTypeSizeInBits(CI->getOperand(0)->getType()))
114 return CI->getOperand(0);
115 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
116 if ((CE->getOpcode() == Instruction::PtrToInt ||
117 CE->getOpcode() == Instruction::IntToPtr) &&
118 SE.getTypeSizeInBits(CE->getType()) ==
119 SE.getTypeSizeInBits(CE->getOperand(0)->getType()))
120 return CE->getOperand(0);
121 }
122
123 // Fold a cast of a constant.
124 if (Constant *C = dyn_cast<Constant>(V))
125 return ConstantExpr::getCast(Op, C, Ty);
126
127 // Cast the argument at the beginning of the entry block, after
128 // any bitcasts of other arguments.
129 if (Argument *A = dyn_cast<Argument>(V)) {
130 BasicBlock::iterator IP = A->getParent()->getEntryBlock().begin();
131 while ((isa<BitCastInst>(IP) &&
132 isa<Argument>(cast<BitCastInst>(IP)->getOperand(0)) &&
133 cast<BitCastInst>(IP)->getOperand(0) != A) ||
134 isa<DbgInfoIntrinsic>(IP) ||
135 isa<LandingPadInst>(IP))
136 ++IP;
137 return ReuseOrCreateCast(A, Ty, Op, IP);
138 }
139
140 // Cast the instruction immediately after the instruction.
141 Instruction *I = cast<Instruction>(V);
142 BasicBlock::iterator IP = I; ++IP;
143 if (InvokeInst *II = dyn_cast<InvokeInst>(I))
144 IP = II->getNormalDest()->begin();
145 while (isa<PHINode>(IP) || isa<LandingPadInst>(IP))
146 ++IP;
147 return ReuseOrCreateCast(I, Ty, Op, IP);
148}
149
150/// InsertBinop - Insert the specified binary operator, doing a small amount
151/// of work to avoid inserting an obviously redundant operation.
152Value *SCEVExpander::InsertBinop(Instruction::BinaryOps Opcode,
153 Value *LHS, Value *RHS) {
154 // Fold a binop with constant operands.
155 if (Constant *CLHS = dyn_cast<Constant>(LHS))
156 if (Constant *CRHS = dyn_cast<Constant>(RHS))
157 return ConstantExpr::get(Opcode, CLHS, CRHS);
158
159 // Do a quick scan to see if we have this binop nearby. If so, reuse it.
160 unsigned ScanLimit = 6;
161 BasicBlock::iterator BlockBegin = Builder.GetInsertBlock()->begin();
162 // Scanning starts from the last instruction before the insertion point.
163 BasicBlock::iterator IP = Builder.GetInsertPoint();
164 if (IP != BlockBegin) {
165 --IP;
166 for (; ScanLimit; --IP, --ScanLimit) {
167 // Don't count dbg.value against the ScanLimit, to avoid perturbing the
168 // generated code.
169 if (isa<DbgInfoIntrinsic>(IP))
170 ScanLimit++;
171 if (IP->getOpcode() == (unsigned)Opcode && IP->getOperand(0) == LHS &&
172 IP->getOperand(1) == RHS)
173 return IP;
174 if (IP == BlockBegin) break;
175 }
176 }
177
178 // Save the original insertion point so we can restore it when we're done.
179 DebugLoc Loc = Builder.GetInsertPoint()->getDebugLoc();
180 BuilderType::InsertPointGuard Guard(Builder);
181
182 // Move the insertion point out of as many loops as we can.
183 while (const Loop *L = SE.LI->getLoopFor(Builder.GetInsertBlock())) {
184 if (!L->isLoopInvariant(LHS) || !L->isLoopInvariant(RHS)) break;
185 BasicBlock *Preheader = L->getLoopPreheader();
186 if (!Preheader) break;
187
188 // Ok, move up a level.
189 Builder.SetInsertPoint(Preheader, Preheader->getTerminator());
190 }
191
192 // If we haven't found this binop, insert it.
193 Instruction *BO = cast<Instruction>(Builder.CreateBinOp(Opcode, LHS, RHS));
194 BO->setDebugLoc(Loc);
195 rememberInstruction(BO);
196
197 return BO;
198}
199
200/// FactorOutConstant - Test if S is divisible by Factor, using signed
201/// division. If so, update S with Factor divided out and return true.
202/// S need not be evenly divisible if a reasonable remainder can be
203/// computed.
204/// TODO: When ScalarEvolution gets a SCEVSDivExpr, this can be made
205/// unnecessary; in its place, just signed-divide Ops[i] by the scale and
206/// check to see if the divide was folded.
207static bool FactorOutConstant(const SCEV *&S,
208 const SCEV *&Remainder,
209 const SCEV *Factor,
210 ScalarEvolution &SE,
211 const DataLayout *DL) {
212 // Everything is divisible by one.
213 if (Factor->isOne())
214 return true;
215
216 // x/x == 1.
217 if (S == Factor) {
218 S = SE.getConstant(S->getType(), 1);
219 return true;
220 }
221
222 // For a Constant, check for a multiple of the given factor.
223 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
224 // 0/x == 0.
225 if (C->isZero())
226 return true;
227 // Check for divisibility.
228 if (const SCEVConstant *FC = dyn_cast<SCEVConstant>(Factor)) {
229 ConstantInt *CI =
230 ConstantInt::get(SE.getContext(),
231 C->getValue()->getValue().sdiv(
232 FC->getValue()->getValue()));
233 // If the quotient is zero and the remainder is non-zero, reject
234 // the value at this scale. It will be considered for subsequent
235 // smaller scales.
236 if (!CI->isZero()) {
237 const SCEV *Div = SE.getConstant(CI);
238 S = Div;
239 Remainder =
240 SE.getAddExpr(Remainder,
241 SE.getConstant(C->getValue()->getValue().srem(
242 FC->getValue()->getValue())));
243 return true;
244 }
245 }
246 }
247
248 // In a Mul, check if there is a constant operand which is a multiple
249 // of the given factor.
250 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
251 if (DL) {
252 // With DataLayout, the size is known. Check if there is a constant
253 // operand which is a multiple of the given factor. If so, we can
254 // factor it.
255 const SCEVConstant *FC = cast<SCEVConstant>(Factor);
256 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(M->getOperand(0)))
257 if (!C->getValue()->getValue().srem(FC->getValue()->getValue())) {
258 SmallVector<const SCEV *, 4> NewMulOps(M->op_begin(), M->op_end());
259 NewMulOps[0] =
260 SE.getConstant(C->getValue()->getValue().sdiv(
261 FC->getValue()->getValue()));
262 S = SE.getMulExpr(NewMulOps);
263 return true;
264 }
265 } else {
266 // Without DataLayout, check if Factor can be factored out of any of the
267 // Mul's operands. If so, we can just remove it.
268 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
269 const SCEV *SOp = M->getOperand(i);
270 const SCEV *Remainder = SE.getConstant(SOp->getType(), 0);
271 if (FactorOutConstant(SOp, Remainder, Factor, SE, DL) &&
272 Remainder->isZero()) {
273 SmallVector<const SCEV *, 4> NewMulOps(M->op_begin(), M->op_end());
274 NewMulOps[i] = SOp;
275 S = SE.getMulExpr(NewMulOps);
276 return true;
277 }
278 }
279 }
280 }
281
282 // In an AddRec, check if both start and step are divisible.
283 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
284 const SCEV *Step = A->getStepRecurrence(SE);
285 const SCEV *StepRem = SE.getConstant(Step->getType(), 0);
286 if (!FactorOutConstant(Step, StepRem, Factor, SE, DL))
287 return false;
288 if (!StepRem->isZero())
289 return false;
290 const SCEV *Start = A->getStart();
291 if (!FactorOutConstant(Start, Remainder, Factor, SE, DL))
292 return false;
293 S = SE.getAddRecExpr(Start, Step, A->getLoop(),
294 A->getNoWrapFlags(SCEV::FlagNW));
295 return true;
296 }
297
298 return false;
299}
300
301/// SimplifyAddOperands - Sort and simplify a list of add operands. NumAddRecs
302/// is the number of SCEVAddRecExprs present, which are kept at the end of
303/// the list.
304///
305static void SimplifyAddOperands(SmallVectorImpl<const SCEV *> &Ops,
306 Type *Ty,
307 ScalarEvolution &SE) {
308 unsigned NumAddRecs = 0;
309 for (unsigned i = Ops.size(); i > 0 && isa<SCEVAddRecExpr>(Ops[i-1]); --i)
310 ++NumAddRecs;
311 // Group Ops into non-addrecs and addrecs.
312 SmallVector<const SCEV *, 8> NoAddRecs(Ops.begin(), Ops.end() - NumAddRecs);
313 SmallVector<const SCEV *, 8> AddRecs(Ops.end() - NumAddRecs, Ops.end());
314 // Let ScalarEvolution sort and simplify the non-addrecs list.
315 const SCEV *Sum = NoAddRecs.empty() ?
316 SE.getConstant(Ty, 0) :
317 SE.getAddExpr(NoAddRecs);
318 // If it returned an add, use the operands. Otherwise it simplified
319 // the sum into a single value, so just use that.
320 Ops.clear();
321 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Sum))
322 Ops.append(Add->op_begin(), Add->op_end());
323 else if (!Sum->isZero())
324 Ops.push_back(Sum);
325 // Then append the addrecs.
326 Ops.append(AddRecs.begin(), AddRecs.end());
327}
328
329/// SplitAddRecs - Flatten a list of add operands, moving addrec start values
330/// out to the top level. For example, convert {a + b,+,c} to a, b, {0,+,d}.
331/// This helps expose more opportunities for folding parts of the expressions
332/// into GEP indices.
333///
334static void SplitAddRecs(SmallVectorImpl<const SCEV *> &Ops,
335 Type *Ty,
336 ScalarEvolution &SE) {
337 // Find the addrecs.
338 SmallVector<const SCEV *, 8> AddRecs;
339 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
340 while (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Ops[i])) {
341 const SCEV *Start = A->getStart();
342 if (Start->isZero()) break;
343 const SCEV *Zero = SE.getConstant(Ty, 0);
344 AddRecs.push_back(SE.getAddRecExpr(Zero,
345 A->getStepRecurrence(SE),
346 A->getLoop(),
347 A->getNoWrapFlags(SCEV::FlagNW)));
348 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Start)) {
349 Ops[i] = Zero;
350 Ops.append(Add->op_begin(), Add->op_end());
351 e += Add->getNumOperands();
352 } else {
353 Ops[i] = Start;
354 }
355 }
356 if (!AddRecs.empty()) {
357 // Add the addrecs onto the end of the list.
358 Ops.append(AddRecs.begin(), AddRecs.end());
359 // Resort the operand list, moving any constants to the front.
360 SimplifyAddOperands(Ops, Ty, SE);
361 }
362}
363
364/// expandAddToGEP - Expand an addition expression with a pointer type into
365/// a GEP instead of using ptrtoint+arithmetic+inttoptr. This helps
366/// BasicAliasAnalysis and other passes analyze the result. See the rules
367/// for getelementptr vs. inttoptr in
368/// http://llvm.org/docs/LangRef.html#pointeraliasing
369/// for details.
370///
371/// Design note: The correctness of using getelementptr here depends on
372/// ScalarEvolution not recognizing inttoptr and ptrtoint operators, as
373/// they may introduce pointer arithmetic which may not be safely converted
374/// into getelementptr.
375///
376/// Design note: It might seem desirable for this function to be more
377/// loop-aware. If some of the indices are loop-invariant while others
378/// aren't, it might seem desirable to emit multiple GEPs, keeping the
379/// loop-invariant portions of the overall computation outside the loop.
380/// However, there are a few reasons this is not done here. Hoisting simple
381/// arithmetic is a low-level optimization that often isn't very
382/// important until late in the optimization process. In fact, passes
383/// like InstructionCombining will combine GEPs, even if it means
384/// pushing loop-invariant computation down into loops, so even if the
385/// GEPs were split here, the work would quickly be undone. The
386/// LoopStrengthReduction pass, which is usually run quite late (and
387/// after the last InstructionCombining pass), takes care of hoisting
388/// loop-invariant portions of expressions, after considering what
389/// can be folded using target addressing modes.
390///
391Value *SCEVExpander::expandAddToGEP(const SCEV *const *op_begin,
392 const SCEV *const *op_end,
393 PointerType *PTy,
394 Type *Ty,
395 Value *V) {
396 Type *ElTy = PTy->getElementType();
397 SmallVector<Value *, 4> GepIndices;
398 SmallVector<const SCEV *, 8> Ops(op_begin, op_end);
399 bool AnyNonZeroIndices = false;
400
401 // Split AddRecs up into parts as either of the parts may be usable
402 // without the other.
403 SplitAddRecs(Ops, Ty, SE);
404
405 Type *IntPtrTy = SE.DL
406 ? SE.DL->getIntPtrType(PTy)
407 : Type::getInt64Ty(PTy->getContext());
408
409 // Descend down the pointer's type and attempt to convert the other
410 // operands into GEP indices, at each level. The first index in a GEP
411 // indexes into the array implied by the pointer operand; the rest of
412 // the indices index into the element or field type selected by the
413 // preceding index.
414 for (;;) {
415 // If the scale size is not 0, attempt to factor out a scale for
416 // array indexing.
417 SmallVector<const SCEV *, 8> ScaledOps;
418 if (ElTy->isSized()) {
419 const SCEV *ElSize = SE.getSizeOfExpr(IntPtrTy, ElTy);
420 if (!ElSize->isZero()) {
421 SmallVector<const SCEV *, 8> NewOps;
422 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
423 const SCEV *Op = Ops[i];
424 const SCEV *Remainder = SE.getConstant(Ty, 0);
425 if (FactorOutConstant(Op, Remainder, ElSize, SE, SE.DL)) {
426 // Op now has ElSize factored out.
427 ScaledOps.push_back(Op);
428 if (!Remainder->isZero())
429 NewOps.push_back(Remainder);
430 AnyNonZeroIndices = true;
431 } else {
432 // The operand was not divisible, so add it to the list of operands
433 // we'll scan next iteration.
434 NewOps.push_back(Ops[i]);
435 }
436 }
437 // If we made any changes, update Ops.
438 if (!ScaledOps.empty()) {
439 Ops = NewOps;
440 SimplifyAddOperands(Ops, Ty, SE);
441 }
442 }
443 }
444
445 // Record the scaled array index for this level of the type. If
446 // we didn't find any operands that could be factored, tentatively
447 // assume that element zero was selected (since the zero offset
448 // would obviously be folded away).
449 Value *Scaled = ScaledOps.empty() ?
450 Constant::getNullValue(Ty) :
451 expandCodeFor(SE.getAddExpr(ScaledOps), Ty);
452 GepIndices.push_back(Scaled);
453
454 // Collect struct field index operands.
455 while (StructType *STy = dyn_cast<StructType>(ElTy)) {
456 bool FoundFieldNo = false;
457 // An empty struct has no fields.
458 if (STy->getNumElements() == 0) break;
459 if (SE.DL) {
460 // With DataLayout, field offsets are known. See if a constant offset
461 // falls within any of the struct fields.
462 if (Ops.empty()) break;
463 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[0]))
464 if (SE.getTypeSizeInBits(C->getType()) <= 64) {
465 const StructLayout &SL = *SE.DL->getStructLayout(STy);
466 uint64_t FullOffset = C->getValue()->getZExtValue();
467 if (FullOffset < SL.getSizeInBytes()) {
468 unsigned ElIdx = SL.getElementContainingOffset(FullOffset);
469 GepIndices.push_back(
470 ConstantInt::get(Type::getInt32Ty(Ty->getContext()), ElIdx));
471 ElTy = STy->getTypeAtIndex(ElIdx);
472 Ops[0] =
473 SE.getConstant(Ty, FullOffset - SL.getElementOffset(ElIdx));
474 AnyNonZeroIndices = true;
475 FoundFieldNo = true;
476 }
477 }
478 } else {
479 // Without DataLayout, just check for an offsetof expression of the
480 // appropriate struct type.
481 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
482 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Ops[i])) {
483 Type *CTy;
484 Constant *FieldNo;
485 if (U->isOffsetOf(CTy, FieldNo) && CTy == STy) {
486 GepIndices.push_back(FieldNo);
487 ElTy =
488 STy->getTypeAtIndex(cast<ConstantInt>(FieldNo)->getZExtValue());
489 Ops[i] = SE.getConstant(Ty, 0);
490 AnyNonZeroIndices = true;
491 FoundFieldNo = true;
492 break;
493 }
494 }
495 }
496 // If no struct field offsets were found, tentatively assume that
497 // field zero was selected (since the zero offset would obviously
498 // be folded away).
499 if (!FoundFieldNo) {
500 ElTy = STy->getTypeAtIndex(0u);
501 GepIndices.push_back(
502 Constant::getNullValue(Type::getInt32Ty(Ty->getContext())));
503 }
504 }
505
506 if (ArrayType *ATy = dyn_cast<ArrayType>(ElTy))
507 ElTy = ATy->getElementType();
508 else
509 break;
510 }
511
512 // If none of the operands were convertible to proper GEP indices, cast
513 // the base to i8* and do an ugly getelementptr with that. It's still
514 // better than ptrtoint+arithmetic+inttoptr at least.
515 if (!AnyNonZeroIndices) {
516 // Cast the base to i8*.
517 V = InsertNoopCastOfTo(V,
518 Type::getInt8PtrTy(Ty->getContext(), PTy->getAddressSpace()));
519
520 assert(!isa<Instruction>(V) ||
521 SE.DT->dominates(cast<Instruction>(V), Builder.GetInsertPoint()));
522
523 // Expand the operands for a plain byte offset.
524 Value *Idx = expandCodeFor(SE.getAddExpr(Ops), Ty);
525
526 // Fold a GEP with constant operands.
527 if (Constant *CLHS = dyn_cast<Constant>(V))
528 if (Constant *CRHS = dyn_cast<Constant>(Idx))
529 return ConstantExpr::getGetElementPtr(CLHS, CRHS);
530
531 // Do a quick scan to see if we have this GEP nearby. If so, reuse it.
532 unsigned ScanLimit = 6;
533 BasicBlock::iterator BlockBegin = Builder.GetInsertBlock()->begin();
534 // Scanning starts from the last instruction before the insertion point.
535 BasicBlock::iterator IP = Builder.GetInsertPoint();
536 if (IP != BlockBegin) {
537 --IP;
538 for (; ScanLimit; --IP, --ScanLimit) {
539 // Don't count dbg.value against the ScanLimit, to avoid perturbing the
540 // generated code.
541 if (isa<DbgInfoIntrinsic>(IP))
542 ScanLimit++;
543 if (IP->getOpcode() == Instruction::GetElementPtr &&
544 IP->getOperand(0) == V && IP->getOperand(1) == Idx)
545 return IP;
546 if (IP == BlockBegin) break;
547 }
548 }
549
550 // Save the original insertion point so we can restore it when we're done.
551 BuilderType::InsertPointGuard Guard(Builder);
552
553 // Move the insertion point out of as many loops as we can.
554 while (const Loop *L = SE.LI->getLoopFor(Builder.GetInsertBlock())) {
555 if (!L->isLoopInvariant(V) || !L->isLoopInvariant(Idx)) break;
556 BasicBlock *Preheader = L->getLoopPreheader();
557 if (!Preheader) break;
558
559 // Ok, move up a level.
560 Builder.SetInsertPoint(Preheader, Preheader->getTerminator());
561 }
562
563 // Emit a GEP.
564 Value *GEP = Builder.CreateGEP(V, Idx, "uglygep");
565 rememberInstruction(GEP);
566
567 return GEP;
568 }
569
570 // Save the original insertion point so we can restore it when we're done.
571 BuilderType::InsertPoint SaveInsertPt = Builder.saveIP();
572
573 // Move the insertion point out of as many loops as we can.
574 while (const Loop *L = SE.LI->getLoopFor(Builder.GetInsertBlock())) {
575 if (!L->isLoopInvariant(V)) break;
576
577 bool AnyIndexNotLoopInvariant = false;
578 for (SmallVectorImpl<Value *>::const_iterator I = GepIndices.begin(),
579 E = GepIndices.end(); I != E; ++I)
580 if (!L->isLoopInvariant(*I)) {
581 AnyIndexNotLoopInvariant = true;
582 break;
583 }
584 if (AnyIndexNotLoopInvariant)
585 break;
586
587 BasicBlock *Preheader = L->getLoopPreheader();
588 if (!Preheader) break;
589
590 // Ok, move up a level.
591 Builder.SetInsertPoint(Preheader, Preheader->getTerminator());
592 }
593
594 // Insert a pretty getelementptr. Note that this GEP is not marked inbounds,
595 // because ScalarEvolution may have changed the address arithmetic to
596 // compute a value which is beyond the end of the allocated object.
597 Value *Casted = V;
598 if (V->getType() != PTy)
599 Casted = InsertNoopCastOfTo(Casted, PTy);
600 Value *GEP = Builder.CreateGEP(Casted,
601 GepIndices,
602 "scevgep");
603 Ops.push_back(SE.getUnknown(GEP));
604 rememberInstruction(GEP);
605
606 // Restore the original insert point.
607 Builder.restoreIP(SaveInsertPt);
608
609 return expand(SE.getAddExpr(Ops));
610}
611
612/// PickMostRelevantLoop - Given two loops pick the one that's most relevant for
613/// SCEV expansion. If they are nested, this is the most nested. If they are
614/// neighboring, pick the later.
615static const Loop *PickMostRelevantLoop(const Loop *A, const Loop *B,
616 DominatorTree &DT) {
617 if (!A) return B;
618 if (!B) return A;
619 if (A->contains(B)) return B;
620 if (B->contains(A)) return A;
621 if (DT.dominates(A->getHeader(), B->getHeader())) return B;
622 if (DT.dominates(B->getHeader(), A->getHeader())) return A;
623 return A; // Arbitrarily break the tie.
624}
625
626/// getRelevantLoop - Get the most relevant loop associated with the given
627/// expression, according to PickMostRelevantLoop.
628const Loop *SCEVExpander::getRelevantLoop(const SCEV *S) {
629 // Test whether we've already computed the most relevant loop for this SCEV.
630 std::pair<DenseMap<const SCEV *, const Loop *>::iterator, bool> Pair =
631 RelevantLoops.insert(std::make_pair(S, nullptr));
632 if (!Pair.second)
633 return Pair.first->second;
634
635 if (isa<SCEVConstant>(S))
636 // A constant has no relevant loops.
637 return nullptr;
638 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
639 if (const Instruction *I = dyn_cast<Instruction>(U->getValue()))
640 return Pair.first->second = SE.LI->getLoopFor(I->getParent());
641 // A non-instruction has no relevant loops.
642 return nullptr;
643 }
644 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S)) {
645 const Loop *L = nullptr;
646 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
647 L = AR->getLoop();
648 for (SCEVNAryExpr::op_iterator I = N->op_begin(), E = N->op_end();
649 I != E; ++I)
650 L = PickMostRelevantLoop(L, getRelevantLoop(*I), *SE.DT);
651 return RelevantLoops[N] = L;
652 }
653 if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S)) {
654 const Loop *Result = getRelevantLoop(C->getOperand());
655 return RelevantLoops[C] = Result;
656 }
657 if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
658 const Loop *Result =
659 PickMostRelevantLoop(getRelevantLoop(D->getLHS()),
660 getRelevantLoop(D->getRHS()),
661 *SE.DT);
662 return RelevantLoops[D] = Result;
663 }
664 llvm_unreachable("Unexpected SCEV type!");
665}
666
667namespace {
668
669/// LoopCompare - Compare loops by PickMostRelevantLoop.
670class LoopCompare {
671 DominatorTree &DT;
672public:
673 explicit LoopCompare(DominatorTree &dt) : DT(dt) {}
674
675 bool operator()(std::pair<const Loop *, const SCEV *> LHS,
676 std::pair<const Loop *, const SCEV *> RHS) const {
677 // Keep pointer operands sorted at the end.
678 if (LHS.second->getType()->isPointerTy() !=
679 RHS.second->getType()->isPointerTy())
680 return LHS.second->getType()->isPointerTy();
681
682 // Compare loops with PickMostRelevantLoop.
683 if (LHS.first != RHS.first)
684 return PickMostRelevantLoop(LHS.first, RHS.first, DT) != LHS.first;
685
686 // If one operand is a non-constant negative and the other is not,
687 // put the non-constant negative on the right so that a sub can
688 // be used instead of a negate and add.
689 if (LHS.second->isNonConstantNegative()) {
690 if (!RHS.second->isNonConstantNegative())
691 return false;
692 } else if (RHS.second->isNonConstantNegative())
693 return true;
694
695 // Otherwise they are equivalent according to this comparison.
696 return false;
697 }
698};
699
700}
701
702Value *SCEVExpander::visitAddExpr(const SCEVAddExpr *S) {
703 Type *Ty = SE.getEffectiveSCEVType(S->getType());
704
705 // Collect all the add operands in a loop, along with their associated loops.
706 // Iterate in reverse so that constants are emitted last, all else equal, and
707 // so that pointer operands are inserted first, which the code below relies on
708 // to form more involved GEPs.
709 SmallVector<std::pair<const Loop *, const SCEV *>, 8> OpsAndLoops;
710 for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(S->op_end()),
711 E(S->op_begin()); I != E; ++I)
712 OpsAndLoops.push_back(std::make_pair(getRelevantLoop(*I), *I));
713
714 // Sort by loop. Use a stable sort so that constants follow non-constants and
715 // pointer operands precede non-pointer operands.
716 std::stable_sort(OpsAndLoops.begin(), OpsAndLoops.end(), LoopCompare(*SE.DT));
717
718 // Emit instructions to add all the operands. Hoist as much as possible
719 // out of loops, and form meaningful getelementptrs where possible.
720 Value *Sum = nullptr;
721 for (SmallVectorImpl<std::pair<const Loop *, const SCEV *> >::iterator
722 I = OpsAndLoops.begin(), E = OpsAndLoops.end(); I != E; ) {
723 const Loop *CurLoop = I->first;
724 const SCEV *Op = I->second;
725 if (!Sum) {
726 // This is the first operand. Just expand it.
727 Sum = expand(Op);
728 ++I;
729 } else if (PointerType *PTy = dyn_cast<PointerType>(Sum->getType())) {
730 // The running sum expression is a pointer. Try to form a getelementptr
731 // at this level with that as the base.
732 SmallVector<const SCEV *, 4> NewOps;
733 for (; I != E && I->first == CurLoop; ++I) {
734 // If the operand is SCEVUnknown and not instructions, peek through
735 // it, to enable more of it to be folded into the GEP.
736 const SCEV *X = I->second;
737 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(X))
738 if (!isa<Instruction>(U->getValue()))
739 X = SE.getSCEV(U->getValue());
740 NewOps.push_back(X);
741 }
742 Sum = expandAddToGEP(NewOps.begin(), NewOps.end(), PTy, Ty, Sum);
743 } else if (PointerType *PTy = dyn_cast<PointerType>(Op->getType())) {
744 // The running sum is an integer, and there's a pointer at this level.
745 // Try to form a getelementptr. If the running sum is instructions,
746 // use a SCEVUnknown to avoid re-analyzing them.
747 SmallVector<const SCEV *, 4> NewOps;
748 NewOps.push_back(isa<Instruction>(Sum) ? SE.getUnknown(Sum) :
749 SE.getSCEV(Sum));
750 for (++I; I != E && I->first == CurLoop; ++I)
751 NewOps.push_back(I->second);
752 Sum = expandAddToGEP(NewOps.begin(), NewOps.end(), PTy, Ty, expand(Op));
753 } else if (Op->isNonConstantNegative()) {
754 // Instead of doing a negate and add, just do a subtract.
755 Value *W = expandCodeFor(SE.getNegativeSCEV(Op), Ty);
756 Sum = InsertNoopCastOfTo(Sum, Ty);
757 Sum = InsertBinop(Instruction::Sub, Sum, W);
758 ++I;
759 } else {
760 // A simple add.
761 Value *W = expandCodeFor(Op, Ty);
762 Sum = InsertNoopCastOfTo(Sum, Ty);
763 // Canonicalize a constant to the RHS.
764 if (isa<Constant>(Sum)) std::swap(Sum, W);
765 Sum = InsertBinop(Instruction::Add, Sum, W);
766 ++I;
767 }
768 }
769
770 return Sum;
771}
772
773Value *SCEVExpander::visitMulExpr(const SCEVMulExpr *S) {
774 Type *Ty = SE.getEffectiveSCEVType(S->getType());
775
776 // Collect all the mul operands in a loop, along with their associated loops.
777 // Iterate in reverse so that constants are emitted last, all else equal.
778 SmallVector<std::pair<const Loop *, const SCEV *>, 8> OpsAndLoops;
779 for (std::reverse_iterator<SCEVMulExpr::op_iterator> I(S->op_end()),
780 E(S->op_begin()); I != E; ++I)
781 OpsAndLoops.push_back(std::make_pair(getRelevantLoop(*I), *I));
782
783 // Sort by loop. Use a stable sort so that constants follow non-constants.
784 std::stable_sort(OpsAndLoops.begin(), OpsAndLoops.end(), LoopCompare(*SE.DT));
785
786 // Emit instructions to mul all the operands. Hoist as much as possible
787 // out of loops.
788 Value *Prod = nullptr;
789 for (SmallVectorImpl<std::pair<const Loop *, const SCEV *> >::iterator
790 I = OpsAndLoops.begin(), E = OpsAndLoops.end(); I != E; ) {
791 const SCEV *Op = I->second;
792 if (!Prod) {
793 // This is the first operand. Just expand it.
794 Prod = expand(Op);
795 ++I;
796 } else if (Op->isAllOnesValue()) {
797 // Instead of doing a multiply by negative one, just do a negate.
798 Prod = InsertNoopCastOfTo(Prod, Ty);
799 Prod = InsertBinop(Instruction::Sub, Constant::getNullValue(Ty), Prod);
800 ++I;
801 } else {
802 // A simple mul.
803 Value *W = expandCodeFor(Op, Ty);
804 Prod = InsertNoopCastOfTo(Prod, Ty);
805 // Canonicalize a constant to the RHS.
806 if (isa<Constant>(Prod)) std::swap(Prod, W);
807 Prod = InsertBinop(Instruction::Mul, Prod, W);
808 ++I;
809 }
810 }
811
812 return Prod;
813}
814
815Value *SCEVExpander::visitUDivExpr(const SCEVUDivExpr *S) {
816 Type *Ty = SE.getEffectiveSCEVType(S->getType());
817
818 Value *LHS = expandCodeFor(S->getLHS(), Ty);
819 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getRHS())) {
820 const APInt &RHS = SC->getValue()->getValue();
821 if (RHS.isPowerOf2())
822 return InsertBinop(Instruction::LShr, LHS,
823 ConstantInt::get(Ty, RHS.logBase2()));
824 }
825
826 Value *RHS = expandCodeFor(S->getRHS(), Ty);
827 return InsertBinop(Instruction::UDiv, LHS, RHS);
828}
829
830/// Move parts of Base into Rest to leave Base with the minimal
831/// expression that provides a pointer operand suitable for a
832/// GEP expansion.
833static void ExposePointerBase(const SCEV *&Base, const SCEV *&Rest,
834 ScalarEvolution &SE) {
835 while (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Base)) {
836 Base = A->getStart();
837 Rest = SE.getAddExpr(Rest,
838 SE.getAddRecExpr(SE.getConstant(A->getType(), 0),
839 A->getStepRecurrence(SE),
840 A->getLoop(),
841 A->getNoWrapFlags(SCEV::FlagNW)));
842 }
843 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(Base)) {
844 Base = A->getOperand(A->getNumOperands()-1);
845 SmallVector<const SCEV *, 8> NewAddOps(A->op_begin(), A->op_end());
846 NewAddOps.back() = Rest;
847 Rest = SE.getAddExpr(NewAddOps);
848 ExposePointerBase(Base, Rest, SE);
849 }
850}
851
852/// Determine if this is a well-behaved chain of instructions leading back to
853/// the PHI. If so, it may be reused by expanded expressions.
854bool SCEVExpander::isNormalAddRecExprPHI(PHINode *PN, Instruction *IncV,
855 const Loop *L) {
856 if (IncV->getNumOperands() == 0 || isa<PHINode>(IncV) ||
857 (isa<CastInst>(IncV) && !isa<BitCastInst>(IncV)))
858 return false;
859 // If any of the operands don't dominate the insert position, bail.
860 // Addrec operands are always loop-invariant, so this can only happen
861 // if there are instructions which haven't been hoisted.
862 if (L == IVIncInsertLoop) {
863 for (User::op_iterator OI = IncV->op_begin()+1,
864 OE = IncV->op_end(); OI != OE; ++OI)
865 if (Instruction *OInst = dyn_cast<Instruction>(OI))
866 if (!SE.DT->dominates(OInst, IVIncInsertPos))
867 return false;
868 }
869 // Advance to the next instruction.
870 IncV = dyn_cast<Instruction>(IncV->getOperand(0));
871 if (!IncV)
872 return false;
873
874 if (IncV->mayHaveSideEffects())
875 return false;
876
877 if (IncV != PN)
878 return true;
879
880 return isNormalAddRecExprPHI(PN, IncV, L);
881}
882
883/// getIVIncOperand returns an induction variable increment's induction
884/// variable operand.
885///
886/// If allowScale is set, any type of GEP is allowed as long as the nonIV
887/// operands dominate InsertPos.
888///
889/// If allowScale is not set, ensure that a GEP increment conforms to one of the
890/// simple patterns generated by getAddRecExprPHILiterally and
891/// expandAddtoGEP. If the pattern isn't recognized, return NULL.
892Instruction *SCEVExpander::getIVIncOperand(Instruction *IncV,
893 Instruction *InsertPos,
894 bool allowScale) {
895 if (IncV == InsertPos)
896 return nullptr;
897
898 switch (IncV->getOpcode()) {
899 default:
900 return nullptr;
901 // Check for a simple Add/Sub or GEP of a loop invariant step.
902 case Instruction::Add:
903 case Instruction::Sub: {
904 Instruction *OInst = dyn_cast<Instruction>(IncV->getOperand(1));
905 if (!OInst || SE.DT->dominates(OInst, InsertPos))
906 return dyn_cast<Instruction>(IncV->getOperand(0));
907 return nullptr;
908 }
909 case Instruction::BitCast:
910 return dyn_cast<Instruction>(IncV->getOperand(0));
911 case Instruction::GetElementPtr:
912 for (Instruction::op_iterator I = IncV->op_begin()+1, E = IncV->op_end();
913 I != E; ++I) {
914 if (isa<Constant>(*I))
915 continue;
916 if (Instruction *OInst = dyn_cast<Instruction>(*I)) {
917 if (!SE.DT->dominates(OInst, InsertPos))
918 return nullptr;
919 }
920 if (allowScale) {
921 // allow any kind of GEP as long as it can be hoisted.
922 continue;
923 }
924 // This must be a pointer addition of constants (pretty), which is already
925 // handled, or some number of address-size elements (ugly). Ugly geps
926 // have 2 operands. i1* is used by the expander to represent an
927 // address-size element.
928 if (IncV->getNumOperands() != 2)
929 return nullptr;
930 unsigned AS = cast<PointerType>(IncV->getType())->getAddressSpace();
931 if (IncV->getType() != Type::getInt1PtrTy(SE.getContext(), AS)
932 && IncV->getType() != Type::getInt8PtrTy(SE.getContext(), AS))
933 return nullptr;
934 break;
935 }
936 return dyn_cast<Instruction>(IncV->getOperand(0));
937 }
938}
939
940/// hoistStep - Attempt to hoist a simple IV increment above InsertPos to make
941/// it available to other uses in this loop. Recursively hoist any operands,
942/// until we reach a value that dominates InsertPos.
943bool SCEVExpander::hoistIVInc(Instruction *IncV, Instruction *InsertPos) {
944 if (SE.DT->dominates(IncV, InsertPos))
945 return true;
946
947 // InsertPos must itself dominate IncV so that IncV's new position satisfies
948 // its existing users.
949 if (isa<PHINode>(InsertPos)
950 || !SE.DT->dominates(InsertPos->getParent(), IncV->getParent()))
951 return false;
952
953 // Check that the chain of IV operands leading back to Phi can be hoisted.
954 SmallVector<Instruction*, 4> IVIncs;
955 for(;;) {
956 Instruction *Oper = getIVIncOperand(IncV, InsertPos, /*allowScale*/true);
957 if (!Oper)
958 return false;
959 // IncV is safe to hoist.
960 IVIncs.push_back(IncV);
961 IncV = Oper;
962 if (SE.DT->dominates(IncV, InsertPos))
963 break;
964 }
965 for (SmallVectorImpl<Instruction*>::reverse_iterator I = IVIncs.rbegin(),
966 E = IVIncs.rend(); I != E; ++I) {
967 (*I)->moveBefore(InsertPos);
968 }
969 return true;
970}
971
972/// Determine if this cyclic phi is in a form that would have been generated by
973/// LSR. We don't care if the phi was actually expanded in this pass, as long
974/// as it is in a low-cost form, for example, no implied multiplication. This
975/// should match any patterns generated by getAddRecExprPHILiterally and
976/// expandAddtoGEP.
977bool SCEVExpander::isExpandedAddRecExprPHI(PHINode *PN, Instruction *IncV,
978 const Loop *L) {
979 for(Instruction *IVOper = IncV;
980 (IVOper = getIVIncOperand(IVOper, L->getLoopPreheader()->getTerminator(),
981 /*allowScale=*/false));) {
982 if (IVOper == PN)
983 return true;
984 }
985 return false;
986}
987
988/// expandIVInc - Expand an IV increment at Builder's current InsertPos.
989/// Typically this is the LatchBlock terminator or IVIncInsertPos, but we may
990/// need to materialize IV increments elsewhere to handle difficult situations.
991Value *SCEVExpander::expandIVInc(PHINode *PN, Value *StepV, const Loop *L,
992 Type *ExpandTy, Type *IntTy,
993 bool useSubtract) {
994 Value *IncV;
995 // If the PHI is a pointer, use a GEP, otherwise use an add or sub.
996 if (ExpandTy->isPointerTy()) {
997 PointerType *GEPPtrTy = cast<PointerType>(ExpandTy);
998 // If the step isn't constant, don't use an implicitly scaled GEP, because
999 // that would require a multiply inside the loop.
1000 if (!isa<ConstantInt>(StepV))
1001 GEPPtrTy = PointerType::get(Type::getInt1Ty(SE.getContext()),
1002 GEPPtrTy->getAddressSpace());
1003 const SCEV *const StepArray[1] = { SE.getSCEV(StepV) };
1004 IncV = expandAddToGEP(StepArray, StepArray+1, GEPPtrTy, IntTy, PN);
1005 if (IncV->getType() != PN->getType()) {
1006 IncV = Builder.CreateBitCast(IncV, PN->getType());
1007 rememberInstruction(IncV);
1008 }
1009 } else {
1010 IncV = useSubtract ?
1011 Builder.CreateSub(PN, StepV, Twine(IVName) + ".iv.next") :
1012 Builder.CreateAdd(PN, StepV, Twine(IVName) + ".iv.next");
1013 rememberInstruction(IncV);
1014 }
1015 return IncV;
1016}
1017
1018/// \brief Hoist the addrec instruction chain rooted in the loop phi above the
1019/// position. This routine assumes that this is possible (has been checked).
1020static void hoistBeforePos(DominatorTree *DT, Instruction *InstToHoist,
1021 Instruction *Pos, PHINode *LoopPhi) {
1022 do {
1023 if (DT->dominates(InstToHoist, Pos))
1024 break;
1025 // Make sure the increment is where we want it. But don't move it
1026 // down past a potential existing post-inc user.
1027 InstToHoist->moveBefore(Pos);
1028 Pos = InstToHoist;
1029 InstToHoist = cast<Instruction>(InstToHoist->getOperand(0));
1030 } while (InstToHoist != LoopPhi);
1031}
1032
1033/// \brief Check whether we can cheaply express the requested SCEV in terms of
1034/// the available PHI SCEV by truncation and/or invertion of the step.
1035static bool canBeCheaplyTransformed(ScalarEvolution &SE,
1036 const SCEVAddRecExpr *Phi,
1037 const SCEVAddRecExpr *Requested,
1038 bool &InvertStep) {
1039 Type *PhiTy = SE.getEffectiveSCEVType(Phi->getType());
1040 Type *RequestedTy = SE.getEffectiveSCEVType(Requested->getType());
1041
1042 if (RequestedTy->getIntegerBitWidth() > PhiTy->getIntegerBitWidth())
1043 return false;
1044
1045 // Try truncate it if necessary.
1046 Phi = dyn_cast<SCEVAddRecExpr>(SE.getTruncateOrNoop(Phi, RequestedTy));
1047 if (!Phi)
1048 return false;
1049
1050 // Check whether truncation will help.
1051 if (Phi == Requested) {
1052 InvertStep = false;
1053 return true;
1054 }
1055
1056 // Check whether inverting will help: {R,+,-1} == R - {0,+,1}.
1057 if (SE.getAddExpr(Requested->getStart(),
1058 SE.getNegativeSCEV(Requested)) == Phi) {
1059 InvertStep = true;
1060 return true;
1061 }
1062
1063 return false;
1064}
1065
1066/// getAddRecExprPHILiterally - Helper for expandAddRecExprLiterally. Expand
1067/// the base addrec, which is the addrec without any non-loop-dominating
1068/// values, and return the PHI.
1069PHINode *
1070SCEVExpander::getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,
1071 const Loop *L,
1072 Type *ExpandTy,
1073 Type *IntTy,
1074 Type *&TruncTy,
1075 bool &InvertStep) {
1076 assert((!IVIncInsertLoop||IVIncInsertPos) && "Uninitialized insert position");
1077
1078 // Reuse a previously-inserted PHI, if present.
1079 BasicBlock *LatchBlock = L->getLoopLatch();
1080 if (LatchBlock) {
1081 PHINode *AddRecPhiMatch = nullptr;
1082 Instruction *IncV = nullptr;
1083 TruncTy = nullptr;
1084 InvertStep = false;
1085
1086 // Only try partially matching scevs that need truncation and/or
1087 // step-inversion if we know this loop is outside the current loop.
1088 bool TryNonMatchingSCEV = IVIncInsertLoop &&
1089 SE.DT->properlyDominates(LatchBlock, IVIncInsertLoop->getHeader());
1090
1091 for (BasicBlock::iterator I = L->getHeader()->begin();
1092 PHINode *PN = dyn_cast<PHINode>(I); ++I) {
1093 if (!SE.isSCEVable(PN->getType()))
1094 continue;
1095
1096 const SCEVAddRecExpr *PhiSCEV = dyn_cast<SCEVAddRecExpr>(SE.getSCEV(PN));
1097 if (!PhiSCEV)
1098 continue;
1099
1100 bool IsMatchingSCEV = PhiSCEV == Normalized;
1101 // We only handle truncation and inversion of phi recurrences for the
1102 // expanded expression if the expanded expression's loop dominates the
1103 // loop we insert to. Check now, so we can bail out early.
1104 if (!IsMatchingSCEV && !TryNonMatchingSCEV)
1105 continue;
1106
1107 Instruction *TempIncV =
1108 cast<Instruction>(PN->getIncomingValueForBlock(LatchBlock));
1109
1110 // Check whether we can reuse this PHI node.
1111 if (LSRMode) {
1112 if (!isExpandedAddRecExprPHI(PN, TempIncV, L))
1113 continue;
1114 if (L == IVIncInsertLoop && !hoistIVInc(TempIncV, IVIncInsertPos))
1115 continue;
1116 } else {
1117 if (!isNormalAddRecExprPHI(PN, TempIncV, L))
1118 continue;
1119 }
1120
1121 // Stop if we have found an exact match SCEV.
1122 if (IsMatchingSCEV) {
1123 IncV = TempIncV;
1124 TruncTy = nullptr;
1125 InvertStep = false;
1126 AddRecPhiMatch = PN;
1127 break;
1128 }
1129
1130 // Try whether the phi can be translated into the requested form
1131 // (truncated and/or offset by a constant).
1132 if ((!TruncTy || InvertStep) &&
1133 canBeCheaplyTransformed(SE, PhiSCEV, Normalized, InvertStep)) {
1134 // Record the phi node. But don't stop we might find an exact match
1135 // later.
1136 AddRecPhiMatch = PN;
1137 IncV = TempIncV;
1138 TruncTy = SE.getEffectiveSCEVType(Normalized->getType());
1139 }
1140 }
1141
1142 if (AddRecPhiMatch) {
1143 // Potentially, move the increment. We have made sure in
1144 // isExpandedAddRecExprPHI or hoistIVInc that this is possible.
1145 if (L == IVIncInsertLoop)
1146 hoistBeforePos(SE.DT, IncV, IVIncInsertPos, AddRecPhiMatch);
1147
1148 // Ok, the add recurrence looks usable.
1149 // Remember this PHI, even in post-inc mode.
1150 InsertedValues.insert(AddRecPhiMatch);
1151 // Remember the increment.
1152 rememberInstruction(IncV);
1153 return AddRecPhiMatch;
1154 }
1155 }
1156
1157 // Save the original insertion point so we can restore it when we're done.
1158 BuilderType::InsertPointGuard Guard(Builder);
1159
1160 // Another AddRec may need to be recursively expanded below. For example, if
1161 // this AddRec is quadratic, the StepV may itself be an AddRec in this
1162 // loop. Remove this loop from the PostIncLoops set before expanding such
1163 // AddRecs. Otherwise, we cannot find a valid position for the step
1164 // (i.e. StepV can never dominate its loop header). Ideally, we could do
1165 // SavedIncLoops.swap(PostIncLoops), but we generally have a single element,
1166 // so it's not worth implementing SmallPtrSet::swap.
1167 PostIncLoopSet SavedPostIncLoops = PostIncLoops;
1168 PostIncLoops.clear();
1169
1170 // Expand code for the start value.
1171 Value *StartV = expandCodeFor(Normalized->getStart(), ExpandTy,
1172 L->getHeader()->begin());
1173
1174 // StartV must be hoisted into L's preheader to dominate the new phi.
1175 assert(!isa<Instruction>(StartV) ||
1176 SE.DT->properlyDominates(cast<Instruction>(StartV)->getParent(),
1177 L->getHeader()));
1178
1179 // Expand code for the step value. Do this before creating the PHI so that PHI
1180 // reuse code doesn't see an incomplete PHI.
1181 const SCEV *Step = Normalized->getStepRecurrence(SE);
1182 // If the stride is negative, insert a sub instead of an add for the increment
1183 // (unless it's a constant, because subtracts of constants are canonicalized
1184 // to adds).
1185 bool useSubtract = !ExpandTy->isPointerTy() && Step->isNonConstantNegative();
1186 if (useSubtract)
1187 Step = SE.getNegativeSCEV(Step);
1188 // Expand the step somewhere that dominates the loop header.
1189 Value *StepV = expandCodeFor(Step, IntTy, L->getHeader()->begin());
1190
1191 // Create the PHI.
1192 BasicBlock *Header = L->getHeader();
1193 Builder.SetInsertPoint(Header, Header->begin());
1194 pred_iterator HPB = pred_begin(Header), HPE = pred_end(Header);
1195 PHINode *PN = Builder.CreatePHI(ExpandTy, std::distance(HPB, HPE),
1196 Twine(IVName) + ".iv");
1197 rememberInstruction(PN);
1198
1199 // Create the step instructions and populate the PHI.
1200 for (pred_iterator HPI = HPB; HPI != HPE; ++HPI) {
1201 BasicBlock *Pred = *HPI;
1202
1203 // Add a start value.
1204 if (!L->contains(Pred)) {
1205 PN->addIncoming(StartV, Pred);
1206 continue;
1207 }
1208
1209 // Create a step value and add it to the PHI.
1210 // If IVIncInsertLoop is non-null and equal to the addrec's loop, insert the
1211 // instructions at IVIncInsertPos.
1212 Instruction *InsertPos = L == IVIncInsertLoop ?
1213 IVIncInsertPos : Pred->getTerminator();
1214 Builder.SetInsertPoint(InsertPos);
1215 Value *IncV = expandIVInc(PN, StepV, L, ExpandTy, IntTy, useSubtract);
1216 if (isa<OverflowingBinaryOperator>(IncV)) {
1217 if (Normalized->getNoWrapFlags(SCEV::FlagNUW))
1218 cast<BinaryOperator>(IncV)->setHasNoUnsignedWrap();
1219 if (Normalized->getNoWrapFlags(SCEV::FlagNSW))
1220 cast<BinaryOperator>(IncV)->setHasNoSignedWrap();
1221 }
1222 PN->addIncoming(IncV, Pred);
1223 }
1224
1225 // After expanding subexpressions, restore the PostIncLoops set so the caller
1226 // can ensure that IVIncrement dominates the current uses.
1227 PostIncLoops = SavedPostIncLoops;
1228
1229 // Remember this PHI, even in post-inc mode.
1230 InsertedValues.insert(PN);
1231
1232 return PN;
1233}
1234
1235Value *SCEVExpander::expandAddRecExprLiterally(const SCEVAddRecExpr *S) {
1236 Type *STy = S->getType();
1237 Type *IntTy = SE.getEffectiveSCEVType(STy);
1238 const Loop *L = S->getLoop();
1239
1240 // Determine a normalized form of this expression, which is the expression
1241 // before any post-inc adjustment is made.
1242 const SCEVAddRecExpr *Normalized = S;
1243 if (PostIncLoops.count(L)) {
1244 PostIncLoopSet Loops;
1245 Loops.insert(L);
1246 Normalized =
1247 cast<SCEVAddRecExpr>(TransformForPostIncUse(Normalize, S, nullptr,
1248 nullptr, Loops, SE, *SE.DT));
1249 }
1250
1251 // Strip off any non-loop-dominating component from the addrec start.
1252 const SCEV *Start = Normalized->getStart();
1253 const SCEV *PostLoopOffset = nullptr;
1254 if (!SE.properlyDominates(Start, L->getHeader())) {
1255 PostLoopOffset = Start;
1256 Start = SE.getConstant(Normalized->getType(), 0);
1257 Normalized = cast<SCEVAddRecExpr>(
1258 SE.getAddRecExpr(Start, Normalized->getStepRecurrence(SE),
1259 Normalized->getLoop(),
1260 Normalized->getNoWrapFlags(SCEV::FlagNW)));
1261 }
1262
1263 // Strip off any non-loop-dominating component from the addrec step.
1264 const SCEV *Step = Normalized->getStepRecurrence(SE);
1265 const SCEV *PostLoopScale = nullptr;
1266 if (!SE.dominates(Step, L->getHeader())) {
1267 PostLoopScale = Step;
1268 Step = SE.getConstant(Normalized->getType(), 1);
1269 Normalized =
1270 cast<SCEVAddRecExpr>(SE.getAddRecExpr(
1271 Start, Step, Normalized->getLoop(),
1272 Normalized->getNoWrapFlags(SCEV::FlagNW)));
1273 }
1274
1275 // Expand the core addrec. If we need post-loop scaling, force it to
1276 // expand to an integer type to avoid the need for additional casting.
1277 Type *ExpandTy = PostLoopScale ? IntTy : STy;
1278 // In some cases, we decide to reuse an existing phi node but need to truncate
1279 // it and/or invert the step.
1280 Type *TruncTy = nullptr;
1281 bool InvertStep = false;
1282 PHINode *PN = getAddRecExprPHILiterally(Normalized, L, ExpandTy, IntTy,
1283 TruncTy, InvertStep);
1284
1285 // Accommodate post-inc mode, if necessary.
1286 Value *Result;
1287 if (!PostIncLoops.count(L))
1288 Result = PN;
1289 else {
1290 // In PostInc mode, use the post-incremented value.
1291 BasicBlock *LatchBlock = L->getLoopLatch();
1292 assert(LatchBlock && "PostInc mode requires a unique loop latch!");
1293 Result = PN->getIncomingValueForBlock(LatchBlock);
1294
1295 // For an expansion to use the postinc form, the client must call
1296 // expandCodeFor with an InsertPoint that is either outside the PostIncLoop
1297 // or dominated by IVIncInsertPos.
1298 if (isa<Instruction>(Result)
1299 && !SE.DT->dominates(cast<Instruction>(Result),
1300 Builder.GetInsertPoint())) {
1301 // The induction variable's postinc expansion does not dominate this use.
1302 // IVUsers tries to prevent this case, so it is rare. However, it can
1303 // happen when an IVUser outside the loop is not dominated by the latch
1304 // block. Adjusting IVIncInsertPos before expansion begins cannot handle
1305 // all cases. Consider a phi outide whose operand is replaced during
1306 // expansion with the value of the postinc user. Without fundamentally
1307 // changing the way postinc users are tracked, the only remedy is
1308 // inserting an extra IV increment. StepV might fold into PostLoopOffset,
1309 // but hopefully expandCodeFor handles that.
1310 bool useSubtract =
1311 !ExpandTy->isPointerTy() && Step->isNonConstantNegative();
1312 if (useSubtract)
1313 Step = SE.getNegativeSCEV(Step);
1314 Value *StepV;
1315 {
1316 // Expand the step somewhere that dominates the loop header.
1317 BuilderType::InsertPointGuard Guard(Builder);
1318 StepV = expandCodeFor(Step, IntTy, L->getHeader()->begin());
1319 }
1320 Result = expandIVInc(PN, StepV, L, ExpandTy, IntTy, useSubtract);
1321 }
1322 }
1323
1324 // We have decided to reuse an induction variable of a dominating loop. Apply
1325 // truncation and/or invertion of the step.
1326 if (TruncTy) {
1327 Type *ResTy = Result->getType();
1328 // Normalize the result type.
1329 if (ResTy != SE.getEffectiveSCEVType(ResTy))
1330 Result = InsertNoopCastOfTo(Result, SE.getEffectiveSCEVType(ResTy));
1331 // Truncate the result.
1332 if (TruncTy != Result->getType()) {
1333 Result = Builder.CreateTrunc(Result, TruncTy);
1334 rememberInstruction(Result);
1335 }
1336 // Invert the result.
1337 if (InvertStep) {
1338 Result = Builder.CreateSub(expandCodeFor(Normalized->getStart(), TruncTy),
1339 Result);
1340 rememberInstruction(Result);
1341 }
1342 }
1343
1344 // Re-apply any non-loop-dominating scale.
1345 if (PostLoopScale) {
1346 assert(S->isAffine() && "Can't linearly scale non-affine recurrences.");
1347 Result = InsertNoopCastOfTo(Result, IntTy);
1348 Result = Builder.CreateMul(Result,
1349 expandCodeFor(PostLoopScale, IntTy));
1350 rememberInstruction(Result);
1351 }
1352
1353 // Re-apply any non-loop-dominating offset.
1354 if (PostLoopOffset) {
1355 if (PointerType *PTy = dyn_cast<PointerType>(ExpandTy)) {
1356 const SCEV *const OffsetArray[1] = { PostLoopOffset };
1357 Result = expandAddToGEP(OffsetArray, OffsetArray+1, PTy, IntTy, Result);
1358 } else {
1359 Result = InsertNoopCastOfTo(Result, IntTy);
1360 Result = Builder.CreateAdd(Result,
1361 expandCodeFor(PostLoopOffset, IntTy));
1362 rememberInstruction(Result);
1363 }
1364 }
1365
1366 return Result;
1367}
1368
1369Value *SCEVExpander::visitAddRecExpr(const SCEVAddRecExpr *S) {
1370 if (!CanonicalMode) return expandAddRecExprLiterally(S);
1371
1372 Type *Ty = SE.getEffectiveSCEVType(S->getType());
1373 const Loop *L = S->getLoop();
1374
1375 // First check for an existing canonical IV in a suitable type.
1376 PHINode *CanonicalIV = nullptr;
1377 if (PHINode *PN = L->getCanonicalInductionVariable())
1378 if (SE.getTypeSizeInBits(PN->getType()) >= SE.getTypeSizeInBits(Ty))
1379 CanonicalIV = PN;
1380
1381 // Rewrite an AddRec in terms of the canonical induction variable, if
1382 // its type is more narrow.
1383 if (CanonicalIV &&
1384 SE.getTypeSizeInBits(CanonicalIV->getType()) >
1385 SE.getTypeSizeInBits(Ty)) {
1386 SmallVector<const SCEV *, 4> NewOps(S->getNumOperands());
1387 for (unsigned i = 0, e = S->getNumOperands(); i != e; ++i)
1388 NewOps[i] = SE.getAnyExtendExpr(S->op_begin()[i], CanonicalIV->getType());
1389 Value *V = expand(SE.getAddRecExpr(NewOps, S->getLoop(),
1390 S->getNoWrapFlags(SCEV::FlagNW)));
1391 BasicBlock::iterator NewInsertPt =
1392 std::next(BasicBlock::iterator(cast<Instruction>(V)));
1393 BuilderType::InsertPointGuard Guard(Builder);
1394 while (isa<PHINode>(NewInsertPt) || isa<DbgInfoIntrinsic>(NewInsertPt) ||
1395 isa<LandingPadInst>(NewInsertPt))
1396 ++NewInsertPt;
1397 V = expandCodeFor(SE.getTruncateExpr(SE.getUnknown(V), Ty), nullptr,
1398 NewInsertPt);
1399 return V;
1400 }
1401
1402 // {X,+,F} --> X + {0,+,F}
1403 if (!S->getStart()->isZero()) {
1404 SmallVector<const SCEV *, 4> NewOps(S->op_begin(), S->op_end());
1405 NewOps[0] = SE.getConstant(Ty, 0);
1406 const SCEV *Rest = SE.getAddRecExpr(NewOps, L,
1407 S->getNoWrapFlags(SCEV::FlagNW));
1408
1409 // Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the
1410 // comments on expandAddToGEP for details.
1411 const SCEV *Base = S->getStart();
1412 const SCEV *RestArray[1] = { Rest };
1413 // Dig into the expression to find the pointer base for a GEP.
1414 ExposePointerBase(Base, RestArray[0], SE);
1415 // If we found a pointer, expand the AddRec with a GEP.
1416 if (PointerType *PTy = dyn_cast<PointerType>(Base->getType())) {
1417 // Make sure the Base isn't something exotic, such as a multiplied
1418 // or divided pointer value. In those cases, the result type isn't
1419 // actually a pointer type.
1420 if (!isa<SCEVMulExpr>(Base) && !isa<SCEVUDivExpr>(Base)) {
1421 Value *StartV = expand(Base);
1422 assert(StartV->getType() == PTy && "Pointer type mismatch for GEP!");
1423 return expandAddToGEP(RestArray, RestArray+1, PTy, Ty, StartV);
1424 }
1425 }
1426
1427 // Just do a normal add. Pre-expand the operands to suppress folding.
1428 return expand(SE.getAddExpr(SE.getUnknown(expand(S->getStart())),
1429 SE.getUnknown(expand(Rest))));
1430 }
1431
1432 // If we don't yet have a canonical IV, create one.
1433 if (!CanonicalIV) {
1434 // Create and insert the PHI node for the induction variable in the
1435 // specified loop.
1436 BasicBlock *Header = L->getHeader();
1437 pred_iterator HPB = pred_begin(Header), HPE = pred_end(Header);
1438 CanonicalIV = PHINode::Create(Ty, std::distance(HPB, HPE), "indvar",
1439 Header->begin());
1440 rememberInstruction(CanonicalIV);
1441
1442 SmallSet<BasicBlock *, 4> PredSeen;
1443 Constant *One = ConstantInt::get(Ty, 1);
1444 for (pred_iterator HPI = HPB; HPI != HPE; ++HPI) {
1445 BasicBlock *HP = *HPI;
1446 if (!PredSeen.insert(HP).second) {
1447 // There must be an incoming value for each predecessor, even the
1448 // duplicates!
1449 CanonicalIV->addIncoming(CanonicalIV->getIncomingValueForBlock(HP), HP);
1450 continue;
1451 }
1452
1453 if (L->contains(HP)) {
1454 // Insert a unit add instruction right before the terminator
1455 // corresponding to the back-edge.
1456 Instruction *Add = BinaryOperator::CreateAdd(CanonicalIV, One,
1457 "indvar.next",
1458 HP->getTerminator());
1459 Add->setDebugLoc(HP->getTerminator()->getDebugLoc());
1460 rememberInstruction(Add);
1461 CanonicalIV->addIncoming(Add, HP);
1462 } else {
1463 CanonicalIV->addIncoming(Constant::getNullValue(Ty), HP);
1464 }
1465 }
1466 }
1467
1468 // {0,+,1} --> Insert a canonical induction variable into the loop!
1469 if (S->isAffine() && S->getOperand(1)->isOne()) {
1470 assert(Ty == SE.getEffectiveSCEVType(CanonicalIV->getType()) &&
1471 "IVs with types different from the canonical IV should "
1472 "already have been handled!");
1473 return CanonicalIV;
1474 }
1475
1476 // {0,+,F} --> {0,+,1} * F
1477
1478 // If this is a simple linear addrec, emit it now as a special case.
1479 if (S->isAffine()) // {0,+,F} --> i*F
1480 return
1481 expand(SE.getTruncateOrNoop(
1482 SE.getMulExpr(SE.getUnknown(CanonicalIV),
1483 SE.getNoopOrAnyExtend(S->getOperand(1),
1484 CanonicalIV->getType())),
1485 Ty));
1486
1487 // If this is a chain of recurrences, turn it into a closed form, using the
1488 // folders, then expandCodeFor the closed form. This allows the folders to
1489 // simplify the expression without having to build a bunch of special code
1490 // into this folder.
1491 const SCEV *IH = SE.getUnknown(CanonicalIV); // Get I as a "symbolic" SCEV.
1492
1493 // Promote S up to the canonical IV type, if the cast is foldable.
1494 const SCEV *NewS = S;
1495 const SCEV *Ext = SE.getNoopOrAnyExtend(S, CanonicalIV->getType());
1496 if (isa<SCEVAddRecExpr>(Ext))
1497 NewS = Ext;
1498
1499 const SCEV *V = cast<SCEVAddRecExpr>(NewS)->evaluateAtIteration(IH, SE);
1500 //cerr << "Evaluated: " << *this << "\n to: " << *V << "\n";
1501
1502 // Truncate the result down to the original type, if needed.
1503 const SCEV *T = SE.getTruncateOrNoop(V, Ty);
1504 return expand(T);
1505}
1506
1507Value *SCEVExpander::visitTruncateExpr(const SCEVTruncateExpr *S) {
1508 Type *Ty = SE.getEffectiveSCEVType(S->getType());
1509 Value *V = expandCodeFor(S->getOperand(),
1510 SE.getEffectiveSCEVType(S->getOperand()->getType()));
1511 Value *I = Builder.CreateTrunc(V, Ty);
1512 rememberInstruction(I);
1513 return I;
1514}
1515
1516Value *SCEVExpander::visitZeroExtendExpr(const SCEVZeroExtendExpr *S) {
1517 Type *Ty = SE.getEffectiveSCEVType(S->getType());
1518 Value *V = expandCodeFor(S->getOperand(),
1519 SE.getEffectiveSCEVType(S->getOperand()->getType()));
1520 Value *I = Builder.CreateZExt(V, Ty);
1521 rememberInstruction(I);
1522 return I;
1523}
1524
1525Value *SCEVExpander::visitSignExtendExpr(const SCEVSignExtendExpr *S) {
1526 Type *Ty = SE.getEffectiveSCEVType(S->getType());
1527 Value *V = expandCodeFor(S->getOperand(),
1528 SE.getEffectiveSCEVType(S->getOperand()->getType()));
1529 Value *I = Builder.CreateSExt(V, Ty);
1530 rememberInstruction(I);
1531 return I;
1532}
1533
1534Value *SCEVExpander::visitSMaxExpr(const SCEVSMaxExpr *S) {
1535 Value *LHS = expand(S->getOperand(S->getNumOperands()-1));
1536 Type *Ty = LHS->getType();
1537 for (int i = S->getNumOperands()-2; i >= 0; --i) {
1538 // In the case of mixed integer and pointer types, do the
1539 // rest of the comparisons as integer.
1540 if (S->getOperand(i)->getType() != Ty) {
1541 Ty = SE.getEffectiveSCEVType(Ty);
1542 LHS = InsertNoopCastOfTo(LHS, Ty);
1543 }
1544 Value *RHS = expandCodeFor(S->getOperand(i), Ty);
1545 Value *ICmp = Builder.CreateICmpSGT(LHS, RHS);
1546 rememberInstruction(ICmp);
1547 Value *Sel = Builder.CreateSelect(ICmp, LHS, RHS, "smax");
1548 rememberInstruction(Sel);
1549 LHS = Sel;
1550 }
1551 // In the case of mixed integer and pointer types, cast the
1552 // final result back to the pointer type.
1553 if (LHS->getType() != S->getType())
1554 LHS = InsertNoopCastOfTo(LHS, S->getType());
1555 return LHS;
1556}
1557
1558Value *SCEVExpander::visitUMaxExpr(const SCEVUMaxExpr *S) {
1559 Value *LHS = expand(S->getOperand(S->getNumOperands()-1));
1560 Type *Ty = LHS->getType();
1561 for (int i = S->getNumOperands()-2; i >= 0; --i) {
1562 // In the case of mixed integer and pointer types, do the
1563 // rest of the comparisons as integer.
1564 if (S->getOperand(i)->getType() != Ty) {
1565 Ty = SE.getEffectiveSCEVType(Ty);
1566 LHS = InsertNoopCastOfTo(LHS, Ty);
1567 }
1568 Value *RHS = expandCodeFor(S->getOperand(i), Ty);
1569 Value *ICmp = Builder.CreateICmpUGT(LHS, RHS);
1570 rememberInstruction(ICmp);
1571 Value *Sel = Builder.CreateSelect(ICmp, LHS, RHS, "umax");
1572 rememberInstruction(Sel);
1573 LHS = Sel;
1574 }
1575 // In the case of mixed integer and pointer types, cast the
1576 // final result back to the pointer type.
1577 if (LHS->getType() != S->getType())
1578 LHS = InsertNoopCastOfTo(LHS, S->getType());
1579 return LHS;
1580}
1581
1582Value *SCEVExpander::expandCodeFor(const SCEV *SH, Type *Ty,
1583 Instruction *IP) {
1584 Builder.SetInsertPoint(IP->getParent(), IP);
1585 return expandCodeFor(SH, Ty);
1586}
1587
1588Value *SCEVExpander::expandCodeFor(const SCEV *SH, Type *Ty) {
1589 // Expand the code for this SCEV.
1590 Value *V = expand(SH);
1591 if (Ty) {
1592 assert(SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(SH->getType()) &&
1593 "non-trivial casts should be done with the SCEVs directly!");
1594 V = InsertNoopCastOfTo(V, Ty);
1595 }
1596 return V;
1597}
1598
1599Value *SCEVExpander::expand(const SCEV *S) {
1600 // Compute an insertion point for this SCEV object. Hoist the instructions
1601 // as far out in the loop nest as possible.
1602 Instruction *InsertPt = Builder.GetInsertPoint();
1603 for (Loop *L = SE.LI->getLoopFor(Builder.GetInsertBlock()); ;
1604 L = L->getParentLoop())
1605 if (SE.isLoopInvariant(S, L)) {
1606 if (!L) break;
1607 if (BasicBlock *Preheader = L->getLoopPreheader())
1608 InsertPt = Preheader->getTerminator();
1609 else {
1610 // LSR sets the insertion point for AddRec start/step values to the
1611 // block start to simplify value reuse, even though it's an invalid
1612 // position. SCEVExpander must correct for this in all cases.
1613 InsertPt = L->getHeader()->getFirstInsertionPt();
1614 }
1615 } else {
1616 // If the SCEV is computable at this level, insert it into the header
1617 // after the PHIs (and after any other instructions that we've inserted
1618 // there) so that it is guaranteed to dominate any user inside the loop.
1619 if (L && SE.hasComputableLoopEvolution(S, L) && !PostIncLoops.count(L))
1620 InsertPt = L->getHeader()->getFirstInsertionPt();
1621 while (InsertPt != Builder.GetInsertPoint()
1622 && (isInsertedInstruction(InsertPt)
1623 || isa<DbgInfoIntrinsic>(InsertPt))) {
1624 InsertPt = std::next(BasicBlock::iterator(InsertPt));
1625 }
1626 break;
1627 }
1628
1629 // Check to see if we already expanded this here.
1630 std::map<std::pair<const SCEV *, Instruction *>, TrackingVH<Value> >::iterator
1631 I = InsertedExpressions.find(std::make_pair(S, InsertPt));
1632 if (I != InsertedExpressions.end())
1633 return I->second;
1634
1635 BuilderType::InsertPointGuard Guard(Builder);
1636 Builder.SetInsertPoint(InsertPt->getParent(), InsertPt);
1637
1638 // Expand the expression into instructions.
1639 Value *V = visit(S);
1640
1641 // Remember the expanded value for this SCEV at this location.
1642 //
1643 // This is independent of PostIncLoops. The mapped value simply materializes
1644 // the expression at this insertion point. If the mapped value happened to be
1645 // a postinc expansion, it could be reused by a non-postinc user, but only if
1646 // its insertion point was already at the head of the loop.
1647 InsertedExpressions[std::make_pair(S, InsertPt)] = V;
1648 return V;
1649}
1650
1651void SCEVExpander::rememberInstruction(Value *I) {
1652 if (!PostIncLoops.empty())
1653 InsertedPostIncValues.insert(I);
1654 else
1655 InsertedValues.insert(I);
1656}
1657
1658/// getOrInsertCanonicalInductionVariable - This method returns the
1659/// canonical induction variable of the specified type for the specified
1660/// loop (inserting one if there is none). A canonical induction variable
1661/// starts at zero and steps by one on each iteration.
1662PHINode *
1663SCEVExpander::getOrInsertCanonicalInductionVariable(const Loop *L,
1664 Type *Ty) {
1665 assert(Ty->isIntegerTy() && "Can only insert integer induction variables!");
1666
1667 // Build a SCEV for {0,+,1}<L>.
1668 // Conservatively use FlagAnyWrap for now.
1669 const SCEV *H = SE.getAddRecExpr(SE.getConstant(Ty, 0),
1670 SE.getConstant(Ty, 1), L, SCEV::FlagAnyWrap);
1671
1672 // Emit code for it.
1673 BuilderType::InsertPointGuard Guard(Builder);
1674 PHINode *V = cast<PHINode>(expandCodeFor(H, nullptr,
1675 L->getHeader()->begin()));
1676
1677 return V;
1678}
1679
1680/// replaceCongruentIVs - Check for congruent phis in this loop header and
1681/// replace them with their most canonical representative. Return the number of
1682/// phis eliminated.
1683///
1684/// This does not depend on any SCEVExpander state but should be used in
1685/// the same context that SCEVExpander is used.
1686unsigned SCEVExpander::replaceCongruentIVs(Loop *L, const DominatorTree *DT,
1687 SmallVectorImpl<WeakVH> &DeadInsts,
1688 const TargetTransformInfo *TTI) {
1689 // Find integer phis in order of increasing width.
1690 SmallVector<PHINode*, 8> Phis;
1691 for (BasicBlock::iterator I = L->getHeader()->begin();
1692 PHINode *Phi = dyn_cast<PHINode>(I); ++I) {
1693 Phis.push_back(Phi);
1694 }
1695 if (TTI)
1696 std::sort(Phis.begin(), Phis.end(), [](Value *LHS, Value *RHS) {
1697 // Put pointers at the back and make sure pointer < pointer = false.
1698 if (!LHS->getType()->isIntegerTy() || !RHS->getType()->isIntegerTy())
1699 return RHS->getType()->isIntegerTy() && !LHS->getType()->isIntegerTy();
1700 return RHS->getType()->getPrimitiveSizeInBits() <
1701 LHS->getType()->getPrimitiveSizeInBits();
1702 });
1703
1704 unsigned NumElim = 0;
1705 DenseMap<const SCEV *, PHINode *> ExprToIVMap;
1706 // Process phis from wide to narrow. Mapping wide phis to the their truncation
1707 // so narrow phis can reuse them.
1708 for (SmallVectorImpl<PHINode*>::const_iterator PIter = Phis.begin(),
1709 PEnd = Phis.end(); PIter != PEnd; ++PIter) {
1710 PHINode *Phi = *PIter;
1711
1712 // Fold constant phis. They may be congruent to other constant phis and
1713 // would confuse the logic below that expects proper IVs.
1714 if (Value *V = SimplifyInstruction(Phi, SE.DL, SE.TLI, SE.DT, SE.AC)) {
1715 Phi->replaceAllUsesWith(V);
1716 DeadInsts.push_back(Phi);
1717 ++NumElim;
1718 DEBUG_WITH_TYPE(DebugType, dbgs()
1719 << "INDVARS: Eliminated constant iv: " << *Phi << '\n');
1720 continue;
1721 }
1722
1723 if (!SE.isSCEVable(Phi->getType()))
1724 continue;
1725
1726 PHINode *&OrigPhiRef = ExprToIVMap[SE.getSCEV(Phi)];
1727 if (!OrigPhiRef) {
1728 OrigPhiRef = Phi;
1729 if (Phi->getType()->isIntegerTy() && TTI
1730 && TTI->isTruncateFree(Phi->getType(), Phis.back()->getType())) {
1731 // This phi can be freely truncated to the narrowest phi type. Map the
1732 // truncated expression to it so it will be reused for narrow types.
1733 const SCEV *TruncExpr =
1734 SE.getTruncateExpr(SE.getSCEV(Phi), Phis.back()->getType());
1735 ExprToIVMap[TruncExpr] = Phi;
1736 }
1737 continue;
1738 }
1739
1740 // Replacing a pointer phi with an integer phi or vice-versa doesn't make
1741 // sense.
1742 if (OrigPhiRef->getType()->isPointerTy() != Phi->getType()->isPointerTy())
1743 continue;
1744
1745 if (BasicBlock *LatchBlock = L->getLoopLatch()) {
1746 Instruction *OrigInc =
1747 cast<Instruction>(OrigPhiRef->getIncomingValueForBlock(LatchBlock));
1748 Instruction *IsomorphicInc =
1749 cast<Instruction>(Phi->getIncomingValueForBlock(LatchBlock));
1750
1751 // If this phi has the same width but is more canonical, replace the
1752 // original with it. As part of the "more canonical" determination,
1753 // respect a prior decision to use an IV chain.
1754 if (OrigPhiRef->getType() == Phi->getType()
1755 && !(ChainedPhis.count(Phi)
1756 || isExpandedAddRecExprPHI(OrigPhiRef, OrigInc, L))
1757 && (ChainedPhis.count(Phi)
1758 || isExpandedAddRecExprPHI(Phi, IsomorphicInc, L))) {
1759 std::swap(OrigPhiRef, Phi);
1760 std::swap(OrigInc, IsomorphicInc);
1761 }
1762 // Replacing the congruent phi is sufficient because acyclic redundancy
1763 // elimination, CSE/GVN, should handle the rest. However, once SCEV proves
1764 // that a phi is congruent, it's often the head of an IV user cycle that
1765 // is isomorphic with the original phi. It's worth eagerly cleaning up the
1766 // common case of a single IV increment so that DeleteDeadPHIs can remove
1767 // cycles that had postinc uses.
1768 const SCEV *TruncExpr = SE.getTruncateOrNoop(SE.getSCEV(OrigInc),
1769 IsomorphicInc->getType());
1770 if (OrigInc != IsomorphicInc
1771 && TruncExpr == SE.getSCEV(IsomorphicInc)
1772 && ((isa<PHINode>(OrigInc) && isa<PHINode>(IsomorphicInc))
1773 || hoistIVInc(OrigInc, IsomorphicInc))) {
1774 DEBUG_WITH_TYPE(DebugType, dbgs()
1775 << "INDVARS: Eliminated congruent iv.inc: "
1776 << *IsomorphicInc << '\n');
1777 Value *NewInc = OrigInc;
1778 if (OrigInc->getType() != IsomorphicInc->getType()) {
| 1//===- ScalarEvolutionExpander.cpp - Scalar Evolution Analysis --*- C++ -*-===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file contains the implementation of the scalar evolution expander,
11// which is used to generate the code corresponding to a given scalar evolution
12// expression.
13//
14//===----------------------------------------------------------------------===//
15
16#include "llvm/Analysis/ScalarEvolutionExpander.h"
17#include "llvm/ADT/STLExtras.h"
18#include "llvm/ADT/SmallSet.h"
19#include "llvm/Analysis/InstructionSimplify.h"
20#include "llvm/Analysis/LoopInfo.h"
21#include "llvm/Analysis/TargetTransformInfo.h"
22#include "llvm/IR/DataLayout.h"
23#include "llvm/IR/Dominators.h"
24#include "llvm/IR/IntrinsicInst.h"
25#include "llvm/IR/LLVMContext.h"
26#include "llvm/Support/Debug.h"
27
28using namespace llvm;
29
30/// ReuseOrCreateCast - Arrange for there to be a cast of V to Ty at IP,
31/// reusing an existing cast if a suitable one exists, moving an existing
32/// cast if a suitable one exists but isn't in the right place, or
33/// creating a new one.
34Value *SCEVExpander::ReuseOrCreateCast(Value *V, Type *Ty,
35 Instruction::CastOps Op,
36 BasicBlock::iterator IP) {
37 // This function must be called with the builder having a valid insertion
38 // point. It doesn't need to be the actual IP where the uses of the returned
39 // cast will be added, but it must dominate such IP.
40 // We use this precondition to produce a cast that will dominate all its
41 // uses. In particular, this is crucial for the case where the builder's
42 // insertion point *is* the point where we were asked to put the cast.
43 // Since we don't know the builder's insertion point is actually
44 // where the uses will be added (only that it dominates it), we are
45 // not allowed to move it.
46 BasicBlock::iterator BIP = Builder.GetInsertPoint();
47
48 Instruction *Ret = nullptr;
49
50 // Check to see if there is already a cast!
51 for (User *U : V->users())
52 if (U->getType() == Ty)
53 if (CastInst *CI = dyn_cast<CastInst>(U))
54 if (CI->getOpcode() == Op) {
55 // If the cast isn't where we want it, create a new cast at IP.
56 // Likewise, do not reuse a cast at BIP because it must dominate
57 // instructions that might be inserted before BIP.
58 if (BasicBlock::iterator(CI) != IP || BIP == IP) {
59 // Create a new cast, and leave the old cast in place in case
60 // it is being used as an insert point. Clear its operand
61 // so that it doesn't hold anything live.
62 Ret = CastInst::Create(Op, V, Ty, "", IP);
63 Ret->takeName(CI);
64 CI->replaceAllUsesWith(Ret);
65 CI->setOperand(0, UndefValue::get(V->getType()));
66 break;
67 }
68 Ret = CI;
69 break;
70 }
71
72 // Create a new cast.
73 if (!Ret)
74 Ret = CastInst::Create(Op, V, Ty, V->getName(), IP);
75
76 // We assert at the end of the function since IP might point to an
77 // instruction with different dominance properties than a cast
78 // (an invoke for example) and not dominate BIP (but the cast does).
79 assert(SE.DT->dominates(Ret, BIP));
80
81 rememberInstruction(Ret);
82 return Ret;
83}
84
85/// InsertNoopCastOfTo - Insert a cast of V to the specified type,
86/// which must be possible with a noop cast, doing what we can to share
87/// the casts.
88Value *SCEVExpander::InsertNoopCastOfTo(Value *V, Type *Ty) {
89 Instruction::CastOps Op = CastInst::getCastOpcode(V, false, Ty, false);
90 assert((Op == Instruction::BitCast ||
91 Op == Instruction::PtrToInt ||
92 Op == Instruction::IntToPtr) &&
93 "InsertNoopCastOfTo cannot perform non-noop casts!");
94 assert(SE.getTypeSizeInBits(V->getType()) == SE.getTypeSizeInBits(Ty) &&
95 "InsertNoopCastOfTo cannot change sizes!");
96
97 // Short-circuit unnecessary bitcasts.
98 if (Op == Instruction::BitCast) {
99 if (V->getType() == Ty)
100 return V;
101 if (CastInst *CI = dyn_cast<CastInst>(V)) {
102 if (CI->getOperand(0)->getType() == Ty)
103 return CI->getOperand(0);
104 }
105 }
106 // Short-circuit unnecessary inttoptr<->ptrtoint casts.
107 if ((Op == Instruction::PtrToInt || Op == Instruction::IntToPtr) &&
108 SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(V->getType())) {
109 if (CastInst *CI = dyn_cast<CastInst>(V))
110 if ((CI->getOpcode() == Instruction::PtrToInt ||
111 CI->getOpcode() == Instruction::IntToPtr) &&
112 SE.getTypeSizeInBits(CI->getType()) ==
113 SE.getTypeSizeInBits(CI->getOperand(0)->getType()))
114 return CI->getOperand(0);
115 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
116 if ((CE->getOpcode() == Instruction::PtrToInt ||
117 CE->getOpcode() == Instruction::IntToPtr) &&
118 SE.getTypeSizeInBits(CE->getType()) ==
119 SE.getTypeSizeInBits(CE->getOperand(0)->getType()))
120 return CE->getOperand(0);
121 }
122
123 // Fold a cast of a constant.
124 if (Constant *C = dyn_cast<Constant>(V))
125 return ConstantExpr::getCast(Op, C, Ty);
126
127 // Cast the argument at the beginning of the entry block, after
128 // any bitcasts of other arguments.
129 if (Argument *A = dyn_cast<Argument>(V)) {
130 BasicBlock::iterator IP = A->getParent()->getEntryBlock().begin();
131 while ((isa<BitCastInst>(IP) &&
132 isa<Argument>(cast<BitCastInst>(IP)->getOperand(0)) &&
133 cast<BitCastInst>(IP)->getOperand(0) != A) ||
134 isa<DbgInfoIntrinsic>(IP) ||
135 isa<LandingPadInst>(IP))
136 ++IP;
137 return ReuseOrCreateCast(A, Ty, Op, IP);
138 }
139
140 // Cast the instruction immediately after the instruction.
141 Instruction *I = cast<Instruction>(V);
142 BasicBlock::iterator IP = I; ++IP;
143 if (InvokeInst *II = dyn_cast<InvokeInst>(I))
144 IP = II->getNormalDest()->begin();
145 while (isa<PHINode>(IP) || isa<LandingPadInst>(IP))
146 ++IP;
147 return ReuseOrCreateCast(I, Ty, Op, IP);
148}
149
150/// InsertBinop - Insert the specified binary operator, doing a small amount
151/// of work to avoid inserting an obviously redundant operation.
152Value *SCEVExpander::InsertBinop(Instruction::BinaryOps Opcode,
153 Value *LHS, Value *RHS) {
154 // Fold a binop with constant operands.
155 if (Constant *CLHS = dyn_cast<Constant>(LHS))
156 if (Constant *CRHS = dyn_cast<Constant>(RHS))
157 return ConstantExpr::get(Opcode, CLHS, CRHS);
158
159 // Do a quick scan to see if we have this binop nearby. If so, reuse it.
160 unsigned ScanLimit = 6;
161 BasicBlock::iterator BlockBegin = Builder.GetInsertBlock()->begin();
162 // Scanning starts from the last instruction before the insertion point.
163 BasicBlock::iterator IP = Builder.GetInsertPoint();
164 if (IP != BlockBegin) {
165 --IP;
166 for (; ScanLimit; --IP, --ScanLimit) {
167 // Don't count dbg.value against the ScanLimit, to avoid perturbing the
168 // generated code.
169 if (isa<DbgInfoIntrinsic>(IP))
170 ScanLimit++;
171 if (IP->getOpcode() == (unsigned)Opcode && IP->getOperand(0) == LHS &&
172 IP->getOperand(1) == RHS)
173 return IP;
174 if (IP == BlockBegin) break;
175 }
176 }
177
178 // Save the original insertion point so we can restore it when we're done.
179 DebugLoc Loc = Builder.GetInsertPoint()->getDebugLoc();
180 BuilderType::InsertPointGuard Guard(Builder);
181
182 // Move the insertion point out of as many loops as we can.
183 while (const Loop *L = SE.LI->getLoopFor(Builder.GetInsertBlock())) {
184 if (!L->isLoopInvariant(LHS) || !L->isLoopInvariant(RHS)) break;
185 BasicBlock *Preheader = L->getLoopPreheader();
186 if (!Preheader) break;
187
188 // Ok, move up a level.
189 Builder.SetInsertPoint(Preheader, Preheader->getTerminator());
190 }
191
192 // If we haven't found this binop, insert it.
193 Instruction *BO = cast<Instruction>(Builder.CreateBinOp(Opcode, LHS, RHS));
194 BO->setDebugLoc(Loc);
195 rememberInstruction(BO);
196
197 return BO;
198}
199
200/// FactorOutConstant - Test if S is divisible by Factor, using signed
201/// division. If so, update S with Factor divided out and return true.
202/// S need not be evenly divisible if a reasonable remainder can be
203/// computed.
204/// TODO: When ScalarEvolution gets a SCEVSDivExpr, this can be made
205/// unnecessary; in its place, just signed-divide Ops[i] by the scale and
206/// check to see if the divide was folded.
207static bool FactorOutConstant(const SCEV *&S,
208 const SCEV *&Remainder,
209 const SCEV *Factor,
210 ScalarEvolution &SE,
211 const DataLayout *DL) {
212 // Everything is divisible by one.
213 if (Factor->isOne())
214 return true;
215
216 // x/x == 1.
217 if (S == Factor) {
218 S = SE.getConstant(S->getType(), 1);
219 return true;
220 }
221
222 // For a Constant, check for a multiple of the given factor.
223 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
224 // 0/x == 0.
225 if (C->isZero())
226 return true;
227 // Check for divisibility.
228 if (const SCEVConstant *FC = dyn_cast<SCEVConstant>(Factor)) {
229 ConstantInt *CI =
230 ConstantInt::get(SE.getContext(),
231 C->getValue()->getValue().sdiv(
232 FC->getValue()->getValue()));
233 // If the quotient is zero and the remainder is non-zero, reject
234 // the value at this scale. It will be considered for subsequent
235 // smaller scales.
236 if (!CI->isZero()) {
237 const SCEV *Div = SE.getConstant(CI);
238 S = Div;
239 Remainder =
240 SE.getAddExpr(Remainder,
241 SE.getConstant(C->getValue()->getValue().srem(
242 FC->getValue()->getValue())));
243 return true;
244 }
245 }
246 }
247
248 // In a Mul, check if there is a constant operand which is a multiple
249 // of the given factor.
250 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
251 if (DL) {
252 // With DataLayout, the size is known. Check if there is a constant
253 // operand which is a multiple of the given factor. If so, we can
254 // factor it.
255 const SCEVConstant *FC = cast<SCEVConstant>(Factor);
256 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(M->getOperand(0)))
257 if (!C->getValue()->getValue().srem(FC->getValue()->getValue())) {
258 SmallVector<const SCEV *, 4> NewMulOps(M->op_begin(), M->op_end());
259 NewMulOps[0] =
260 SE.getConstant(C->getValue()->getValue().sdiv(
261 FC->getValue()->getValue()));
262 S = SE.getMulExpr(NewMulOps);
263 return true;
264 }
265 } else {
266 // Without DataLayout, check if Factor can be factored out of any of the
267 // Mul's operands. If so, we can just remove it.
268 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
269 const SCEV *SOp = M->getOperand(i);
270 const SCEV *Remainder = SE.getConstant(SOp->getType(), 0);
271 if (FactorOutConstant(SOp, Remainder, Factor, SE, DL) &&
272 Remainder->isZero()) {
273 SmallVector<const SCEV *, 4> NewMulOps(M->op_begin(), M->op_end());
274 NewMulOps[i] = SOp;
275 S = SE.getMulExpr(NewMulOps);
276 return true;
277 }
278 }
279 }
280 }
281
282 // In an AddRec, check if both start and step are divisible.
283 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
284 const SCEV *Step = A->getStepRecurrence(SE);
285 const SCEV *StepRem = SE.getConstant(Step->getType(), 0);
286 if (!FactorOutConstant(Step, StepRem, Factor, SE, DL))
287 return false;
288 if (!StepRem->isZero())
289 return false;
290 const SCEV *Start = A->getStart();
291 if (!FactorOutConstant(Start, Remainder, Factor, SE, DL))
292 return false;
293 S = SE.getAddRecExpr(Start, Step, A->getLoop(),
294 A->getNoWrapFlags(SCEV::FlagNW));
295 return true;
296 }
297
298 return false;
299}
300
301/// SimplifyAddOperands - Sort and simplify a list of add operands. NumAddRecs
302/// is the number of SCEVAddRecExprs present, which are kept at the end of
303/// the list.
304///
305static void SimplifyAddOperands(SmallVectorImpl<const SCEV *> &Ops,
306 Type *Ty,
307 ScalarEvolution &SE) {
308 unsigned NumAddRecs = 0;
309 for (unsigned i = Ops.size(); i > 0 && isa<SCEVAddRecExpr>(Ops[i-1]); --i)
310 ++NumAddRecs;
311 // Group Ops into non-addrecs and addrecs.
312 SmallVector<const SCEV *, 8> NoAddRecs(Ops.begin(), Ops.end() - NumAddRecs);
313 SmallVector<const SCEV *, 8> AddRecs(Ops.end() - NumAddRecs, Ops.end());
314 // Let ScalarEvolution sort and simplify the non-addrecs list.
315 const SCEV *Sum = NoAddRecs.empty() ?
316 SE.getConstant(Ty, 0) :
317 SE.getAddExpr(NoAddRecs);
318 // If it returned an add, use the operands. Otherwise it simplified
319 // the sum into a single value, so just use that.
320 Ops.clear();
321 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Sum))
322 Ops.append(Add->op_begin(), Add->op_end());
323 else if (!Sum->isZero())
324 Ops.push_back(Sum);
325 // Then append the addrecs.
326 Ops.append(AddRecs.begin(), AddRecs.end());
327}
328
329/// SplitAddRecs - Flatten a list of add operands, moving addrec start values
330/// out to the top level. For example, convert {a + b,+,c} to a, b, {0,+,d}.
331/// This helps expose more opportunities for folding parts of the expressions
332/// into GEP indices.
333///
334static void SplitAddRecs(SmallVectorImpl<const SCEV *> &Ops,
335 Type *Ty,
336 ScalarEvolution &SE) {
337 // Find the addrecs.
338 SmallVector<const SCEV *, 8> AddRecs;
339 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
340 while (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Ops[i])) {
341 const SCEV *Start = A->getStart();
342 if (Start->isZero()) break;
343 const SCEV *Zero = SE.getConstant(Ty, 0);
344 AddRecs.push_back(SE.getAddRecExpr(Zero,
345 A->getStepRecurrence(SE),
346 A->getLoop(),
347 A->getNoWrapFlags(SCEV::FlagNW)));
348 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Start)) {
349 Ops[i] = Zero;
350 Ops.append(Add->op_begin(), Add->op_end());
351 e += Add->getNumOperands();
352 } else {
353 Ops[i] = Start;
354 }
355 }
356 if (!AddRecs.empty()) {
357 // Add the addrecs onto the end of the list.
358 Ops.append(AddRecs.begin(), AddRecs.end());
359 // Resort the operand list, moving any constants to the front.
360 SimplifyAddOperands(Ops, Ty, SE);
361 }
362}
363
364/// expandAddToGEP - Expand an addition expression with a pointer type into
365/// a GEP instead of using ptrtoint+arithmetic+inttoptr. This helps
366/// BasicAliasAnalysis and other passes analyze the result. See the rules
367/// for getelementptr vs. inttoptr in
368/// http://llvm.org/docs/LangRef.html#pointeraliasing
369/// for details.
370///
371/// Design note: The correctness of using getelementptr here depends on
372/// ScalarEvolution not recognizing inttoptr and ptrtoint operators, as
373/// they may introduce pointer arithmetic which may not be safely converted
374/// into getelementptr.
375///
376/// Design note: It might seem desirable for this function to be more
377/// loop-aware. If some of the indices are loop-invariant while others
378/// aren't, it might seem desirable to emit multiple GEPs, keeping the
379/// loop-invariant portions of the overall computation outside the loop.
380/// However, there are a few reasons this is not done here. Hoisting simple
381/// arithmetic is a low-level optimization that often isn't very
382/// important until late in the optimization process. In fact, passes
383/// like InstructionCombining will combine GEPs, even if it means
384/// pushing loop-invariant computation down into loops, so even if the
385/// GEPs were split here, the work would quickly be undone. The
386/// LoopStrengthReduction pass, which is usually run quite late (and
387/// after the last InstructionCombining pass), takes care of hoisting
388/// loop-invariant portions of expressions, after considering what
389/// can be folded using target addressing modes.
390///
391Value *SCEVExpander::expandAddToGEP(const SCEV *const *op_begin,
392 const SCEV *const *op_end,
393 PointerType *PTy,
394 Type *Ty,
395 Value *V) {
396 Type *ElTy = PTy->getElementType();
397 SmallVector<Value *, 4> GepIndices;
398 SmallVector<const SCEV *, 8> Ops(op_begin, op_end);
399 bool AnyNonZeroIndices = false;
400
401 // Split AddRecs up into parts as either of the parts may be usable
402 // without the other.
403 SplitAddRecs(Ops, Ty, SE);
404
405 Type *IntPtrTy = SE.DL
406 ? SE.DL->getIntPtrType(PTy)
407 : Type::getInt64Ty(PTy->getContext());
408
409 // Descend down the pointer's type and attempt to convert the other
410 // operands into GEP indices, at each level. The first index in a GEP
411 // indexes into the array implied by the pointer operand; the rest of
412 // the indices index into the element or field type selected by the
413 // preceding index.
414 for (;;) {
415 // If the scale size is not 0, attempt to factor out a scale for
416 // array indexing.
417 SmallVector<const SCEV *, 8> ScaledOps;
418 if (ElTy->isSized()) {
419 const SCEV *ElSize = SE.getSizeOfExpr(IntPtrTy, ElTy);
420 if (!ElSize->isZero()) {
421 SmallVector<const SCEV *, 8> NewOps;
422 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
423 const SCEV *Op = Ops[i];
424 const SCEV *Remainder = SE.getConstant(Ty, 0);
425 if (FactorOutConstant(Op, Remainder, ElSize, SE, SE.DL)) {
426 // Op now has ElSize factored out.
427 ScaledOps.push_back(Op);
428 if (!Remainder->isZero())
429 NewOps.push_back(Remainder);
430 AnyNonZeroIndices = true;
431 } else {
432 // The operand was not divisible, so add it to the list of operands
433 // we'll scan next iteration.
434 NewOps.push_back(Ops[i]);
435 }
436 }
437 // If we made any changes, update Ops.
438 if (!ScaledOps.empty()) {
439 Ops = NewOps;
440 SimplifyAddOperands(Ops, Ty, SE);
441 }
442 }
443 }
444
445 // Record the scaled array index for this level of the type. If
446 // we didn't find any operands that could be factored, tentatively
447 // assume that element zero was selected (since the zero offset
448 // would obviously be folded away).
449 Value *Scaled = ScaledOps.empty() ?
450 Constant::getNullValue(Ty) :
451 expandCodeFor(SE.getAddExpr(ScaledOps), Ty);
452 GepIndices.push_back(Scaled);
453
454 // Collect struct field index operands.
455 while (StructType *STy = dyn_cast<StructType>(ElTy)) {
456 bool FoundFieldNo = false;
457 // An empty struct has no fields.
458 if (STy->getNumElements() == 0) break;
459 if (SE.DL) {
460 // With DataLayout, field offsets are known. See if a constant offset
461 // falls within any of the struct fields.
462 if (Ops.empty()) break;
463 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[0]))
464 if (SE.getTypeSizeInBits(C->getType()) <= 64) {
465 const StructLayout &SL = *SE.DL->getStructLayout(STy);
466 uint64_t FullOffset = C->getValue()->getZExtValue();
467 if (FullOffset < SL.getSizeInBytes()) {
468 unsigned ElIdx = SL.getElementContainingOffset(FullOffset);
469 GepIndices.push_back(
470 ConstantInt::get(Type::getInt32Ty(Ty->getContext()), ElIdx));
471 ElTy = STy->getTypeAtIndex(ElIdx);
472 Ops[0] =
473 SE.getConstant(Ty, FullOffset - SL.getElementOffset(ElIdx));
474 AnyNonZeroIndices = true;
475 FoundFieldNo = true;
476 }
477 }
478 } else {
479 // Without DataLayout, just check for an offsetof expression of the
480 // appropriate struct type.
481 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
482 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Ops[i])) {
483 Type *CTy;
484 Constant *FieldNo;
485 if (U->isOffsetOf(CTy, FieldNo) && CTy == STy) {
486 GepIndices.push_back(FieldNo);
487 ElTy =
488 STy->getTypeAtIndex(cast<ConstantInt>(FieldNo)->getZExtValue());
489 Ops[i] = SE.getConstant(Ty, 0);
490 AnyNonZeroIndices = true;
491 FoundFieldNo = true;
492 break;
493 }
494 }
495 }
496 // If no struct field offsets were found, tentatively assume that
497 // field zero was selected (since the zero offset would obviously
498 // be folded away).
499 if (!FoundFieldNo) {
500 ElTy = STy->getTypeAtIndex(0u);
501 GepIndices.push_back(
502 Constant::getNullValue(Type::getInt32Ty(Ty->getContext())));
503 }
504 }
505
506 if (ArrayType *ATy = dyn_cast<ArrayType>(ElTy))
507 ElTy = ATy->getElementType();
508 else
509 break;
510 }
511
512 // If none of the operands were convertible to proper GEP indices, cast
513 // the base to i8* and do an ugly getelementptr with that. It's still
514 // better than ptrtoint+arithmetic+inttoptr at least.
515 if (!AnyNonZeroIndices) {
516 // Cast the base to i8*.
517 V = InsertNoopCastOfTo(V,
518 Type::getInt8PtrTy(Ty->getContext(), PTy->getAddressSpace()));
519
520 assert(!isa<Instruction>(V) ||
521 SE.DT->dominates(cast<Instruction>(V), Builder.GetInsertPoint()));
522
523 // Expand the operands for a plain byte offset.
524 Value *Idx = expandCodeFor(SE.getAddExpr(Ops), Ty);
525
526 // Fold a GEP with constant operands.
527 if (Constant *CLHS = dyn_cast<Constant>(V))
528 if (Constant *CRHS = dyn_cast<Constant>(Idx))
529 return ConstantExpr::getGetElementPtr(CLHS, CRHS);
530
531 // Do a quick scan to see if we have this GEP nearby. If so, reuse it.
532 unsigned ScanLimit = 6;
533 BasicBlock::iterator BlockBegin = Builder.GetInsertBlock()->begin();
534 // Scanning starts from the last instruction before the insertion point.
535 BasicBlock::iterator IP = Builder.GetInsertPoint();
536 if (IP != BlockBegin) {
537 --IP;
538 for (; ScanLimit; --IP, --ScanLimit) {
539 // Don't count dbg.value against the ScanLimit, to avoid perturbing the
540 // generated code.
541 if (isa<DbgInfoIntrinsic>(IP))
542 ScanLimit++;
543 if (IP->getOpcode() == Instruction::GetElementPtr &&
544 IP->getOperand(0) == V && IP->getOperand(1) == Idx)
545 return IP;
546 if (IP == BlockBegin) break;
547 }
548 }
549
550 // Save the original insertion point so we can restore it when we're done.
551 BuilderType::InsertPointGuard Guard(Builder);
552
553 // Move the insertion point out of as many loops as we can.
554 while (const Loop *L = SE.LI->getLoopFor(Builder.GetInsertBlock())) {
555 if (!L->isLoopInvariant(V) || !L->isLoopInvariant(Idx)) break;
556 BasicBlock *Preheader = L->getLoopPreheader();
557 if (!Preheader) break;
558
559 // Ok, move up a level.
560 Builder.SetInsertPoint(Preheader, Preheader->getTerminator());
561 }
562
563 // Emit a GEP.
564 Value *GEP = Builder.CreateGEP(V, Idx, "uglygep");
565 rememberInstruction(GEP);
566
567 return GEP;
568 }
569
570 // Save the original insertion point so we can restore it when we're done.
571 BuilderType::InsertPoint SaveInsertPt = Builder.saveIP();
572
573 // Move the insertion point out of as many loops as we can.
574 while (const Loop *L = SE.LI->getLoopFor(Builder.GetInsertBlock())) {
575 if (!L->isLoopInvariant(V)) break;
576
577 bool AnyIndexNotLoopInvariant = false;
578 for (SmallVectorImpl<Value *>::const_iterator I = GepIndices.begin(),
579 E = GepIndices.end(); I != E; ++I)
580 if (!L->isLoopInvariant(*I)) {
581 AnyIndexNotLoopInvariant = true;
582 break;
583 }
584 if (AnyIndexNotLoopInvariant)
585 break;
586
587 BasicBlock *Preheader = L->getLoopPreheader();
588 if (!Preheader) break;
589
590 // Ok, move up a level.
591 Builder.SetInsertPoint(Preheader, Preheader->getTerminator());
592 }
593
594 // Insert a pretty getelementptr. Note that this GEP is not marked inbounds,
595 // because ScalarEvolution may have changed the address arithmetic to
596 // compute a value which is beyond the end of the allocated object.
597 Value *Casted = V;
598 if (V->getType() != PTy)
599 Casted = InsertNoopCastOfTo(Casted, PTy);
600 Value *GEP = Builder.CreateGEP(Casted,
601 GepIndices,
602 "scevgep");
603 Ops.push_back(SE.getUnknown(GEP));
604 rememberInstruction(GEP);
605
606 // Restore the original insert point.
607 Builder.restoreIP(SaveInsertPt);
608
609 return expand(SE.getAddExpr(Ops));
610}
611
612/// PickMostRelevantLoop - Given two loops pick the one that's most relevant for
613/// SCEV expansion. If they are nested, this is the most nested. If they are
614/// neighboring, pick the later.
615static const Loop *PickMostRelevantLoop(const Loop *A, const Loop *B,
616 DominatorTree &DT) {
617 if (!A) return B;
618 if (!B) return A;
619 if (A->contains(B)) return B;
620 if (B->contains(A)) return A;
621 if (DT.dominates(A->getHeader(), B->getHeader())) return B;
622 if (DT.dominates(B->getHeader(), A->getHeader())) return A;
623 return A; // Arbitrarily break the tie.
624}
625
626/// getRelevantLoop - Get the most relevant loop associated with the given
627/// expression, according to PickMostRelevantLoop.
628const Loop *SCEVExpander::getRelevantLoop(const SCEV *S) {
629 // Test whether we've already computed the most relevant loop for this SCEV.
630 std::pair<DenseMap<const SCEV *, const Loop *>::iterator, bool> Pair =
631 RelevantLoops.insert(std::make_pair(S, nullptr));
632 if (!Pair.second)
633 return Pair.first->second;
634
635 if (isa<SCEVConstant>(S))
636 // A constant has no relevant loops.
637 return nullptr;
638 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
639 if (const Instruction *I = dyn_cast<Instruction>(U->getValue()))
640 return Pair.first->second = SE.LI->getLoopFor(I->getParent());
641 // A non-instruction has no relevant loops.
642 return nullptr;
643 }
644 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S)) {
645 const Loop *L = nullptr;
646 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
647 L = AR->getLoop();
648 for (SCEVNAryExpr::op_iterator I = N->op_begin(), E = N->op_end();
649 I != E; ++I)
650 L = PickMostRelevantLoop(L, getRelevantLoop(*I), *SE.DT);
651 return RelevantLoops[N] = L;
652 }
653 if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S)) {
654 const Loop *Result = getRelevantLoop(C->getOperand());
655 return RelevantLoops[C] = Result;
656 }
657 if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
658 const Loop *Result =
659 PickMostRelevantLoop(getRelevantLoop(D->getLHS()),
660 getRelevantLoop(D->getRHS()),
661 *SE.DT);
662 return RelevantLoops[D] = Result;
663 }
664 llvm_unreachable("Unexpected SCEV type!");
665}
666
667namespace {
668
669/// LoopCompare - Compare loops by PickMostRelevantLoop.
670class LoopCompare {
671 DominatorTree &DT;
672public:
673 explicit LoopCompare(DominatorTree &dt) : DT(dt) {}
674
675 bool operator()(std::pair<const Loop *, const SCEV *> LHS,
676 std::pair<const Loop *, const SCEV *> RHS) const {
677 // Keep pointer operands sorted at the end.
678 if (LHS.second->getType()->isPointerTy() !=
679 RHS.second->getType()->isPointerTy())
680 return LHS.second->getType()->isPointerTy();
681
682 // Compare loops with PickMostRelevantLoop.
683 if (LHS.first != RHS.first)
684 return PickMostRelevantLoop(LHS.first, RHS.first, DT) != LHS.first;
685
686 // If one operand is a non-constant negative and the other is not,
687 // put the non-constant negative on the right so that a sub can
688 // be used instead of a negate and add.
689 if (LHS.second->isNonConstantNegative()) {
690 if (!RHS.second->isNonConstantNegative())
691 return false;
692 } else if (RHS.second->isNonConstantNegative())
693 return true;
694
695 // Otherwise they are equivalent according to this comparison.
696 return false;
697 }
698};
699
700}
701
702Value *SCEVExpander::visitAddExpr(const SCEVAddExpr *S) {
703 Type *Ty = SE.getEffectiveSCEVType(S->getType());
704
705 // Collect all the add operands in a loop, along with their associated loops.
706 // Iterate in reverse so that constants are emitted last, all else equal, and
707 // so that pointer operands are inserted first, which the code below relies on
708 // to form more involved GEPs.
709 SmallVector<std::pair<const Loop *, const SCEV *>, 8> OpsAndLoops;
710 for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(S->op_end()),
711 E(S->op_begin()); I != E; ++I)
712 OpsAndLoops.push_back(std::make_pair(getRelevantLoop(*I), *I));
713
714 // Sort by loop. Use a stable sort so that constants follow non-constants and
715 // pointer operands precede non-pointer operands.
716 std::stable_sort(OpsAndLoops.begin(), OpsAndLoops.end(), LoopCompare(*SE.DT));
717
718 // Emit instructions to add all the operands. Hoist as much as possible
719 // out of loops, and form meaningful getelementptrs where possible.
720 Value *Sum = nullptr;
721 for (SmallVectorImpl<std::pair<const Loop *, const SCEV *> >::iterator
722 I = OpsAndLoops.begin(), E = OpsAndLoops.end(); I != E; ) {
723 const Loop *CurLoop = I->first;
724 const SCEV *Op = I->second;
725 if (!Sum) {
726 // This is the first operand. Just expand it.
727 Sum = expand(Op);
728 ++I;
729 } else if (PointerType *PTy = dyn_cast<PointerType>(Sum->getType())) {
730 // The running sum expression is a pointer. Try to form a getelementptr
731 // at this level with that as the base.
732 SmallVector<const SCEV *, 4> NewOps;
733 for (; I != E && I->first == CurLoop; ++I) {
734 // If the operand is SCEVUnknown and not instructions, peek through
735 // it, to enable more of it to be folded into the GEP.
736 const SCEV *X = I->second;
737 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(X))
738 if (!isa<Instruction>(U->getValue()))
739 X = SE.getSCEV(U->getValue());
740 NewOps.push_back(X);
741 }
742 Sum = expandAddToGEP(NewOps.begin(), NewOps.end(), PTy, Ty, Sum);
743 } else if (PointerType *PTy = dyn_cast<PointerType>(Op->getType())) {
744 // The running sum is an integer, and there's a pointer at this level.
745 // Try to form a getelementptr. If the running sum is instructions,
746 // use a SCEVUnknown to avoid re-analyzing them.
747 SmallVector<const SCEV *, 4> NewOps;
748 NewOps.push_back(isa<Instruction>(Sum) ? SE.getUnknown(Sum) :
749 SE.getSCEV(Sum));
750 for (++I; I != E && I->first == CurLoop; ++I)
751 NewOps.push_back(I->second);
752 Sum = expandAddToGEP(NewOps.begin(), NewOps.end(), PTy, Ty, expand(Op));
753 } else if (Op->isNonConstantNegative()) {
754 // Instead of doing a negate and add, just do a subtract.
755 Value *W = expandCodeFor(SE.getNegativeSCEV(Op), Ty);
756 Sum = InsertNoopCastOfTo(Sum, Ty);
757 Sum = InsertBinop(Instruction::Sub, Sum, W);
758 ++I;
759 } else {
760 // A simple add.
761 Value *W = expandCodeFor(Op, Ty);
762 Sum = InsertNoopCastOfTo(Sum, Ty);
763 // Canonicalize a constant to the RHS.
764 if (isa<Constant>(Sum)) std::swap(Sum, W);
765 Sum = InsertBinop(Instruction::Add, Sum, W);
766 ++I;
767 }
768 }
769
770 return Sum;
771}
772
773Value *SCEVExpander::visitMulExpr(const SCEVMulExpr *S) {
774 Type *Ty = SE.getEffectiveSCEVType(S->getType());
775
776 // Collect all the mul operands in a loop, along with their associated loops.
777 // Iterate in reverse so that constants are emitted last, all else equal.
778 SmallVector<std::pair<const Loop *, const SCEV *>, 8> OpsAndLoops;
779 for (std::reverse_iterator<SCEVMulExpr::op_iterator> I(S->op_end()),
780 E(S->op_begin()); I != E; ++I)
781 OpsAndLoops.push_back(std::make_pair(getRelevantLoop(*I), *I));
782
783 // Sort by loop. Use a stable sort so that constants follow non-constants.
784 std::stable_sort(OpsAndLoops.begin(), OpsAndLoops.end(), LoopCompare(*SE.DT));
785
786 // Emit instructions to mul all the operands. Hoist as much as possible
787 // out of loops.
788 Value *Prod = nullptr;
789 for (SmallVectorImpl<std::pair<const Loop *, const SCEV *> >::iterator
790 I = OpsAndLoops.begin(), E = OpsAndLoops.end(); I != E; ) {
791 const SCEV *Op = I->second;
792 if (!Prod) {
793 // This is the first operand. Just expand it.
794 Prod = expand(Op);
795 ++I;
796 } else if (Op->isAllOnesValue()) {
797 // Instead of doing a multiply by negative one, just do a negate.
798 Prod = InsertNoopCastOfTo(Prod, Ty);
799 Prod = InsertBinop(Instruction::Sub, Constant::getNullValue(Ty), Prod);
800 ++I;
801 } else {
802 // A simple mul.
803 Value *W = expandCodeFor(Op, Ty);
804 Prod = InsertNoopCastOfTo(Prod, Ty);
805 // Canonicalize a constant to the RHS.
806 if (isa<Constant>(Prod)) std::swap(Prod, W);
807 Prod = InsertBinop(Instruction::Mul, Prod, W);
808 ++I;
809 }
810 }
811
812 return Prod;
813}
814
815Value *SCEVExpander::visitUDivExpr(const SCEVUDivExpr *S) {
816 Type *Ty = SE.getEffectiveSCEVType(S->getType());
817
818 Value *LHS = expandCodeFor(S->getLHS(), Ty);
819 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(S->getRHS())) {
820 const APInt &RHS = SC->getValue()->getValue();
821 if (RHS.isPowerOf2())
822 return InsertBinop(Instruction::LShr, LHS,
823 ConstantInt::get(Ty, RHS.logBase2()));
824 }
825
826 Value *RHS = expandCodeFor(S->getRHS(), Ty);
827 return InsertBinop(Instruction::UDiv, LHS, RHS);
828}
829
830/// Move parts of Base into Rest to leave Base with the minimal
831/// expression that provides a pointer operand suitable for a
832/// GEP expansion.
833static void ExposePointerBase(const SCEV *&Base, const SCEV *&Rest,
834 ScalarEvolution &SE) {
835 while (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(Base)) {
836 Base = A->getStart();
837 Rest = SE.getAddExpr(Rest,
838 SE.getAddRecExpr(SE.getConstant(A->getType(), 0),
839 A->getStepRecurrence(SE),
840 A->getLoop(),
841 A->getNoWrapFlags(SCEV::FlagNW)));
842 }
843 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(Base)) {
844 Base = A->getOperand(A->getNumOperands()-1);
845 SmallVector<const SCEV *, 8> NewAddOps(A->op_begin(), A->op_end());
846 NewAddOps.back() = Rest;
847 Rest = SE.getAddExpr(NewAddOps);
848 ExposePointerBase(Base, Rest, SE);
849 }
850}
851
852/// Determine if this is a well-behaved chain of instructions leading back to
853/// the PHI. If so, it may be reused by expanded expressions.
854bool SCEVExpander::isNormalAddRecExprPHI(PHINode *PN, Instruction *IncV,
855 const Loop *L) {
856 if (IncV->getNumOperands() == 0 || isa<PHINode>(IncV) ||
857 (isa<CastInst>(IncV) && !isa<BitCastInst>(IncV)))
858 return false;
859 // If any of the operands don't dominate the insert position, bail.
860 // Addrec operands are always loop-invariant, so this can only happen
861 // if there are instructions which haven't been hoisted.
862 if (L == IVIncInsertLoop) {
863 for (User::op_iterator OI = IncV->op_begin()+1,
864 OE = IncV->op_end(); OI != OE; ++OI)
865 if (Instruction *OInst = dyn_cast<Instruction>(OI))
866 if (!SE.DT->dominates(OInst, IVIncInsertPos))
867 return false;
868 }
869 // Advance to the next instruction.
870 IncV = dyn_cast<Instruction>(IncV->getOperand(0));
871 if (!IncV)
872 return false;
873
874 if (IncV->mayHaveSideEffects())
875 return false;
876
877 if (IncV != PN)
878 return true;
879
880 return isNormalAddRecExprPHI(PN, IncV, L);
881}
882
883/// getIVIncOperand returns an induction variable increment's induction
884/// variable operand.
885///
886/// If allowScale is set, any type of GEP is allowed as long as the nonIV
887/// operands dominate InsertPos.
888///
889/// If allowScale is not set, ensure that a GEP increment conforms to one of the
890/// simple patterns generated by getAddRecExprPHILiterally and
891/// expandAddtoGEP. If the pattern isn't recognized, return NULL.
892Instruction *SCEVExpander::getIVIncOperand(Instruction *IncV,
893 Instruction *InsertPos,
894 bool allowScale) {
895 if (IncV == InsertPos)
896 return nullptr;
897
898 switch (IncV->getOpcode()) {
899 default:
900 return nullptr;
901 // Check for a simple Add/Sub or GEP of a loop invariant step.
902 case Instruction::Add:
903 case Instruction::Sub: {
904 Instruction *OInst = dyn_cast<Instruction>(IncV->getOperand(1));
905 if (!OInst || SE.DT->dominates(OInst, InsertPos))
906 return dyn_cast<Instruction>(IncV->getOperand(0));
907 return nullptr;
908 }
909 case Instruction::BitCast:
910 return dyn_cast<Instruction>(IncV->getOperand(0));
911 case Instruction::GetElementPtr:
912 for (Instruction::op_iterator I = IncV->op_begin()+1, E = IncV->op_end();
913 I != E; ++I) {
914 if (isa<Constant>(*I))
915 continue;
916 if (Instruction *OInst = dyn_cast<Instruction>(*I)) {
917 if (!SE.DT->dominates(OInst, InsertPos))
918 return nullptr;
919 }
920 if (allowScale) {
921 // allow any kind of GEP as long as it can be hoisted.
922 continue;
923 }
924 // This must be a pointer addition of constants (pretty), which is already
925 // handled, or some number of address-size elements (ugly). Ugly geps
926 // have 2 operands. i1* is used by the expander to represent an
927 // address-size element.
928 if (IncV->getNumOperands() != 2)
929 return nullptr;
930 unsigned AS = cast<PointerType>(IncV->getType())->getAddressSpace();
931 if (IncV->getType() != Type::getInt1PtrTy(SE.getContext(), AS)
932 && IncV->getType() != Type::getInt8PtrTy(SE.getContext(), AS))
933 return nullptr;
934 break;
935 }
936 return dyn_cast<Instruction>(IncV->getOperand(0));
937 }
938}
939
940/// hoistStep - Attempt to hoist a simple IV increment above InsertPos to make
941/// it available to other uses in this loop. Recursively hoist any operands,
942/// until we reach a value that dominates InsertPos.
943bool SCEVExpander::hoistIVInc(Instruction *IncV, Instruction *InsertPos) {
944 if (SE.DT->dominates(IncV, InsertPos))
945 return true;
946
947 // InsertPos must itself dominate IncV so that IncV's new position satisfies
948 // its existing users.
949 if (isa<PHINode>(InsertPos)
950 || !SE.DT->dominates(InsertPos->getParent(), IncV->getParent()))
951 return false;
952
953 // Check that the chain of IV operands leading back to Phi can be hoisted.
954 SmallVector<Instruction*, 4> IVIncs;
955 for(;;) {
956 Instruction *Oper = getIVIncOperand(IncV, InsertPos, /*allowScale*/true);
957 if (!Oper)
958 return false;
959 // IncV is safe to hoist.
960 IVIncs.push_back(IncV);
961 IncV = Oper;
962 if (SE.DT->dominates(IncV, InsertPos))
963 break;
964 }
965 for (SmallVectorImpl<Instruction*>::reverse_iterator I = IVIncs.rbegin(),
966 E = IVIncs.rend(); I != E; ++I) {
967 (*I)->moveBefore(InsertPos);
968 }
969 return true;
970}
971
972/// Determine if this cyclic phi is in a form that would have been generated by
973/// LSR. We don't care if the phi was actually expanded in this pass, as long
974/// as it is in a low-cost form, for example, no implied multiplication. This
975/// should match any patterns generated by getAddRecExprPHILiterally and
976/// expandAddtoGEP.
977bool SCEVExpander::isExpandedAddRecExprPHI(PHINode *PN, Instruction *IncV,
978 const Loop *L) {
979 for(Instruction *IVOper = IncV;
980 (IVOper = getIVIncOperand(IVOper, L->getLoopPreheader()->getTerminator(),
981 /*allowScale=*/false));) {
982 if (IVOper == PN)
983 return true;
984 }
985 return false;
986}
987
988/// expandIVInc - Expand an IV increment at Builder's current InsertPos.
989/// Typically this is the LatchBlock terminator or IVIncInsertPos, but we may
990/// need to materialize IV increments elsewhere to handle difficult situations.
991Value *SCEVExpander::expandIVInc(PHINode *PN, Value *StepV, const Loop *L,
992 Type *ExpandTy, Type *IntTy,
993 bool useSubtract) {
994 Value *IncV;
995 // If the PHI is a pointer, use a GEP, otherwise use an add or sub.
996 if (ExpandTy->isPointerTy()) {
997 PointerType *GEPPtrTy = cast<PointerType>(ExpandTy);
998 // If the step isn't constant, don't use an implicitly scaled GEP, because
999 // that would require a multiply inside the loop.
1000 if (!isa<ConstantInt>(StepV))
1001 GEPPtrTy = PointerType::get(Type::getInt1Ty(SE.getContext()),
1002 GEPPtrTy->getAddressSpace());
1003 const SCEV *const StepArray[1] = { SE.getSCEV(StepV) };
1004 IncV = expandAddToGEP(StepArray, StepArray+1, GEPPtrTy, IntTy, PN);
1005 if (IncV->getType() != PN->getType()) {
1006 IncV = Builder.CreateBitCast(IncV, PN->getType());
1007 rememberInstruction(IncV);
1008 }
1009 } else {
1010 IncV = useSubtract ?
1011 Builder.CreateSub(PN, StepV, Twine(IVName) + ".iv.next") :
1012 Builder.CreateAdd(PN, StepV, Twine(IVName) + ".iv.next");
1013 rememberInstruction(IncV);
1014 }
1015 return IncV;
1016}
1017
1018/// \brief Hoist the addrec instruction chain rooted in the loop phi above the
1019/// position. This routine assumes that this is possible (has been checked).
1020static void hoistBeforePos(DominatorTree *DT, Instruction *InstToHoist,
1021 Instruction *Pos, PHINode *LoopPhi) {
1022 do {
1023 if (DT->dominates(InstToHoist, Pos))
1024 break;
1025 // Make sure the increment is where we want it. But don't move it
1026 // down past a potential existing post-inc user.
1027 InstToHoist->moveBefore(Pos);
1028 Pos = InstToHoist;
1029 InstToHoist = cast<Instruction>(InstToHoist->getOperand(0));
1030 } while (InstToHoist != LoopPhi);
1031}
1032
1033/// \brief Check whether we can cheaply express the requested SCEV in terms of
1034/// the available PHI SCEV by truncation and/or invertion of the step.
1035static bool canBeCheaplyTransformed(ScalarEvolution &SE,
1036 const SCEVAddRecExpr *Phi,
1037 const SCEVAddRecExpr *Requested,
1038 bool &InvertStep) {
1039 Type *PhiTy = SE.getEffectiveSCEVType(Phi->getType());
1040 Type *RequestedTy = SE.getEffectiveSCEVType(Requested->getType());
1041
1042 if (RequestedTy->getIntegerBitWidth() > PhiTy->getIntegerBitWidth())
1043 return false;
1044
1045 // Try truncate it if necessary.
1046 Phi = dyn_cast<SCEVAddRecExpr>(SE.getTruncateOrNoop(Phi, RequestedTy));
1047 if (!Phi)
1048 return false;
1049
1050 // Check whether truncation will help.
1051 if (Phi == Requested) {
1052 InvertStep = false;
1053 return true;
1054 }
1055
1056 // Check whether inverting will help: {R,+,-1} == R - {0,+,1}.
1057 if (SE.getAddExpr(Requested->getStart(),
1058 SE.getNegativeSCEV(Requested)) == Phi) {
1059 InvertStep = true;
1060 return true;
1061 }
1062
1063 return false;
1064}
1065
1066/// getAddRecExprPHILiterally - Helper for expandAddRecExprLiterally. Expand
1067/// the base addrec, which is the addrec without any non-loop-dominating
1068/// values, and return the PHI.
1069PHINode *
1070SCEVExpander::getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,
1071 const Loop *L,
1072 Type *ExpandTy,
1073 Type *IntTy,
1074 Type *&TruncTy,
1075 bool &InvertStep) {
1076 assert((!IVIncInsertLoop||IVIncInsertPos) && "Uninitialized insert position");
1077
1078 // Reuse a previously-inserted PHI, if present.
1079 BasicBlock *LatchBlock = L->getLoopLatch();
1080 if (LatchBlock) {
1081 PHINode *AddRecPhiMatch = nullptr;
1082 Instruction *IncV = nullptr;
1083 TruncTy = nullptr;
1084 InvertStep = false;
1085
1086 // Only try partially matching scevs that need truncation and/or
1087 // step-inversion if we know this loop is outside the current loop.
1088 bool TryNonMatchingSCEV = IVIncInsertLoop &&
1089 SE.DT->properlyDominates(LatchBlock, IVIncInsertLoop->getHeader());
1090
1091 for (BasicBlock::iterator I = L->getHeader()->begin();
1092 PHINode *PN = dyn_cast<PHINode>(I); ++I) {
1093 if (!SE.isSCEVable(PN->getType()))
1094 continue;
1095
1096 const SCEVAddRecExpr *PhiSCEV = dyn_cast<SCEVAddRecExpr>(SE.getSCEV(PN));
1097 if (!PhiSCEV)
1098 continue;
1099
1100 bool IsMatchingSCEV = PhiSCEV == Normalized;
1101 // We only handle truncation and inversion of phi recurrences for the
1102 // expanded expression if the expanded expression's loop dominates the
1103 // loop we insert to. Check now, so we can bail out early.
1104 if (!IsMatchingSCEV && !TryNonMatchingSCEV)
1105 continue;
1106
1107 Instruction *TempIncV =
1108 cast<Instruction>(PN->getIncomingValueForBlock(LatchBlock));
1109
1110 // Check whether we can reuse this PHI node.
1111 if (LSRMode) {
1112 if (!isExpandedAddRecExprPHI(PN, TempIncV, L))
1113 continue;
1114 if (L == IVIncInsertLoop && !hoistIVInc(TempIncV, IVIncInsertPos))
1115 continue;
1116 } else {
1117 if (!isNormalAddRecExprPHI(PN, TempIncV, L))
1118 continue;
1119 }
1120
1121 // Stop if we have found an exact match SCEV.
1122 if (IsMatchingSCEV) {
1123 IncV = TempIncV;
1124 TruncTy = nullptr;
1125 InvertStep = false;
1126 AddRecPhiMatch = PN;
1127 break;
1128 }
1129
1130 // Try whether the phi can be translated into the requested form
1131 // (truncated and/or offset by a constant).
1132 if ((!TruncTy || InvertStep) &&
1133 canBeCheaplyTransformed(SE, PhiSCEV, Normalized, InvertStep)) {
1134 // Record the phi node. But don't stop we might find an exact match
1135 // later.
1136 AddRecPhiMatch = PN;
1137 IncV = TempIncV;
1138 TruncTy = SE.getEffectiveSCEVType(Normalized->getType());
1139 }
1140 }
1141
1142 if (AddRecPhiMatch) {
1143 // Potentially, move the increment. We have made sure in
1144 // isExpandedAddRecExprPHI or hoistIVInc that this is possible.
1145 if (L == IVIncInsertLoop)
1146 hoistBeforePos(SE.DT, IncV, IVIncInsertPos, AddRecPhiMatch);
1147
1148 // Ok, the add recurrence looks usable.
1149 // Remember this PHI, even in post-inc mode.
1150 InsertedValues.insert(AddRecPhiMatch);
1151 // Remember the increment.
1152 rememberInstruction(IncV);
1153 return AddRecPhiMatch;
1154 }
1155 }
1156
1157 // Save the original insertion point so we can restore it when we're done.
1158 BuilderType::InsertPointGuard Guard(Builder);
1159
1160 // Another AddRec may need to be recursively expanded below. For example, if
1161 // this AddRec is quadratic, the StepV may itself be an AddRec in this
1162 // loop. Remove this loop from the PostIncLoops set before expanding such
1163 // AddRecs. Otherwise, we cannot find a valid position for the step
1164 // (i.e. StepV can never dominate its loop header). Ideally, we could do
1165 // SavedIncLoops.swap(PostIncLoops), but we generally have a single element,
1166 // so it's not worth implementing SmallPtrSet::swap.
1167 PostIncLoopSet SavedPostIncLoops = PostIncLoops;
1168 PostIncLoops.clear();
1169
1170 // Expand code for the start value.
1171 Value *StartV = expandCodeFor(Normalized->getStart(), ExpandTy,
1172 L->getHeader()->begin());
1173
1174 // StartV must be hoisted into L's preheader to dominate the new phi.
1175 assert(!isa<Instruction>(StartV) ||
1176 SE.DT->properlyDominates(cast<Instruction>(StartV)->getParent(),
1177 L->getHeader()));
1178
1179 // Expand code for the step value. Do this before creating the PHI so that PHI
1180 // reuse code doesn't see an incomplete PHI.
1181 const SCEV *Step = Normalized->getStepRecurrence(SE);
1182 // If the stride is negative, insert a sub instead of an add for the increment
1183 // (unless it's a constant, because subtracts of constants are canonicalized
1184 // to adds).
1185 bool useSubtract = !ExpandTy->isPointerTy() && Step->isNonConstantNegative();
1186 if (useSubtract)
1187 Step = SE.getNegativeSCEV(Step);
1188 // Expand the step somewhere that dominates the loop header.
1189 Value *StepV = expandCodeFor(Step, IntTy, L->getHeader()->begin());
1190
1191 // Create the PHI.
1192 BasicBlock *Header = L->getHeader();
1193 Builder.SetInsertPoint(Header, Header->begin());
1194 pred_iterator HPB = pred_begin(Header), HPE = pred_end(Header);
1195 PHINode *PN = Builder.CreatePHI(ExpandTy, std::distance(HPB, HPE),
1196 Twine(IVName) + ".iv");
1197 rememberInstruction(PN);
1198
1199 // Create the step instructions and populate the PHI.
1200 for (pred_iterator HPI = HPB; HPI != HPE; ++HPI) {
1201 BasicBlock *Pred = *HPI;
1202
1203 // Add a start value.
1204 if (!L->contains(Pred)) {
1205 PN->addIncoming(StartV, Pred);
1206 continue;
1207 }
1208
1209 // Create a step value and add it to the PHI.
1210 // If IVIncInsertLoop is non-null and equal to the addrec's loop, insert the
1211 // instructions at IVIncInsertPos.
1212 Instruction *InsertPos = L == IVIncInsertLoop ?
1213 IVIncInsertPos : Pred->getTerminator();
1214 Builder.SetInsertPoint(InsertPos);
1215 Value *IncV = expandIVInc(PN, StepV, L, ExpandTy, IntTy, useSubtract);
1216 if (isa<OverflowingBinaryOperator>(IncV)) {
1217 if (Normalized->getNoWrapFlags(SCEV::FlagNUW))
1218 cast<BinaryOperator>(IncV)->setHasNoUnsignedWrap();
1219 if (Normalized->getNoWrapFlags(SCEV::FlagNSW))
1220 cast<BinaryOperator>(IncV)->setHasNoSignedWrap();
1221 }
1222 PN->addIncoming(IncV, Pred);
1223 }
1224
1225 // After expanding subexpressions, restore the PostIncLoops set so the caller
1226 // can ensure that IVIncrement dominates the current uses.
1227 PostIncLoops = SavedPostIncLoops;
1228
1229 // Remember this PHI, even in post-inc mode.
1230 InsertedValues.insert(PN);
1231
1232 return PN;
1233}
1234
1235Value *SCEVExpander::expandAddRecExprLiterally(const SCEVAddRecExpr *S) {
1236 Type *STy = S->getType();
1237 Type *IntTy = SE.getEffectiveSCEVType(STy);
1238 const Loop *L = S->getLoop();
1239
1240 // Determine a normalized form of this expression, which is the expression
1241 // before any post-inc adjustment is made.
1242 const SCEVAddRecExpr *Normalized = S;
1243 if (PostIncLoops.count(L)) {
1244 PostIncLoopSet Loops;
1245 Loops.insert(L);
1246 Normalized =
1247 cast<SCEVAddRecExpr>(TransformForPostIncUse(Normalize, S, nullptr,
1248 nullptr, Loops, SE, *SE.DT));
1249 }
1250
1251 // Strip off any non-loop-dominating component from the addrec start.
1252 const SCEV *Start = Normalized->getStart();
1253 const SCEV *PostLoopOffset = nullptr;
1254 if (!SE.properlyDominates(Start, L->getHeader())) {
1255 PostLoopOffset = Start;
1256 Start = SE.getConstant(Normalized->getType(), 0);
1257 Normalized = cast<SCEVAddRecExpr>(
1258 SE.getAddRecExpr(Start, Normalized->getStepRecurrence(SE),
1259 Normalized->getLoop(),
1260 Normalized->getNoWrapFlags(SCEV::FlagNW)));
1261 }
1262
1263 // Strip off any non-loop-dominating component from the addrec step.
1264 const SCEV *Step = Normalized->getStepRecurrence(SE);
1265 const SCEV *PostLoopScale = nullptr;
1266 if (!SE.dominates(Step, L->getHeader())) {
1267 PostLoopScale = Step;
1268 Step = SE.getConstant(Normalized->getType(), 1);
1269 Normalized =
1270 cast<SCEVAddRecExpr>(SE.getAddRecExpr(
1271 Start, Step, Normalized->getLoop(),
1272 Normalized->getNoWrapFlags(SCEV::FlagNW)));
1273 }
1274
1275 // Expand the core addrec. If we need post-loop scaling, force it to
1276 // expand to an integer type to avoid the need for additional casting.
1277 Type *ExpandTy = PostLoopScale ? IntTy : STy;
1278 // In some cases, we decide to reuse an existing phi node but need to truncate
1279 // it and/or invert the step.
1280 Type *TruncTy = nullptr;
1281 bool InvertStep = false;
1282 PHINode *PN = getAddRecExprPHILiterally(Normalized, L, ExpandTy, IntTy,
1283 TruncTy, InvertStep);
1284
1285 // Accommodate post-inc mode, if necessary.
1286 Value *Result;
1287 if (!PostIncLoops.count(L))
1288 Result = PN;
1289 else {
1290 // In PostInc mode, use the post-incremented value.
1291 BasicBlock *LatchBlock = L->getLoopLatch();
1292 assert(LatchBlock && "PostInc mode requires a unique loop latch!");
1293 Result = PN->getIncomingValueForBlock(LatchBlock);
1294
1295 // For an expansion to use the postinc form, the client must call
1296 // expandCodeFor with an InsertPoint that is either outside the PostIncLoop
1297 // or dominated by IVIncInsertPos.
1298 if (isa<Instruction>(Result)
1299 && !SE.DT->dominates(cast<Instruction>(Result),
1300 Builder.GetInsertPoint())) {
1301 // The induction variable's postinc expansion does not dominate this use.
1302 // IVUsers tries to prevent this case, so it is rare. However, it can
1303 // happen when an IVUser outside the loop is not dominated by the latch
1304 // block. Adjusting IVIncInsertPos before expansion begins cannot handle
1305 // all cases. Consider a phi outide whose operand is replaced during
1306 // expansion with the value of the postinc user. Without fundamentally
1307 // changing the way postinc users are tracked, the only remedy is
1308 // inserting an extra IV increment. StepV might fold into PostLoopOffset,
1309 // but hopefully expandCodeFor handles that.
1310 bool useSubtract =
1311 !ExpandTy->isPointerTy() && Step->isNonConstantNegative();
1312 if (useSubtract)
1313 Step = SE.getNegativeSCEV(Step);
1314 Value *StepV;
1315 {
1316 // Expand the step somewhere that dominates the loop header.
1317 BuilderType::InsertPointGuard Guard(Builder);
1318 StepV = expandCodeFor(Step, IntTy, L->getHeader()->begin());
1319 }
1320 Result = expandIVInc(PN, StepV, L, ExpandTy, IntTy, useSubtract);
1321 }
1322 }
1323
1324 // We have decided to reuse an induction variable of a dominating loop. Apply
1325 // truncation and/or invertion of the step.
1326 if (TruncTy) {
1327 Type *ResTy = Result->getType();
1328 // Normalize the result type.
1329 if (ResTy != SE.getEffectiveSCEVType(ResTy))
1330 Result = InsertNoopCastOfTo(Result, SE.getEffectiveSCEVType(ResTy));
1331 // Truncate the result.
1332 if (TruncTy != Result->getType()) {
1333 Result = Builder.CreateTrunc(Result, TruncTy);
1334 rememberInstruction(Result);
1335 }
1336 // Invert the result.
1337 if (InvertStep) {
1338 Result = Builder.CreateSub(expandCodeFor(Normalized->getStart(), TruncTy),
1339 Result);
1340 rememberInstruction(Result);
1341 }
1342 }
1343
1344 // Re-apply any non-loop-dominating scale.
1345 if (PostLoopScale) {
1346 assert(S->isAffine() && "Can't linearly scale non-affine recurrences.");
1347 Result = InsertNoopCastOfTo(Result, IntTy);
1348 Result = Builder.CreateMul(Result,
1349 expandCodeFor(PostLoopScale, IntTy));
1350 rememberInstruction(Result);
1351 }
1352
1353 // Re-apply any non-loop-dominating offset.
1354 if (PostLoopOffset) {
1355 if (PointerType *PTy = dyn_cast<PointerType>(ExpandTy)) {
1356 const SCEV *const OffsetArray[1] = { PostLoopOffset };
1357 Result = expandAddToGEP(OffsetArray, OffsetArray+1, PTy, IntTy, Result);
1358 } else {
1359 Result = InsertNoopCastOfTo(Result, IntTy);
1360 Result = Builder.CreateAdd(Result,
1361 expandCodeFor(PostLoopOffset, IntTy));
1362 rememberInstruction(Result);
1363 }
1364 }
1365
1366 return Result;
1367}
1368
1369Value *SCEVExpander::visitAddRecExpr(const SCEVAddRecExpr *S) {
1370 if (!CanonicalMode) return expandAddRecExprLiterally(S);
1371
1372 Type *Ty = SE.getEffectiveSCEVType(S->getType());
1373 const Loop *L = S->getLoop();
1374
1375 // First check for an existing canonical IV in a suitable type.
1376 PHINode *CanonicalIV = nullptr;
1377 if (PHINode *PN = L->getCanonicalInductionVariable())
1378 if (SE.getTypeSizeInBits(PN->getType()) >= SE.getTypeSizeInBits(Ty))
1379 CanonicalIV = PN;
1380
1381 // Rewrite an AddRec in terms of the canonical induction variable, if
1382 // its type is more narrow.
1383 if (CanonicalIV &&
1384 SE.getTypeSizeInBits(CanonicalIV->getType()) >
1385 SE.getTypeSizeInBits(Ty)) {
1386 SmallVector<const SCEV *, 4> NewOps(S->getNumOperands());
1387 for (unsigned i = 0, e = S->getNumOperands(); i != e; ++i)
1388 NewOps[i] = SE.getAnyExtendExpr(S->op_begin()[i], CanonicalIV->getType());
1389 Value *V = expand(SE.getAddRecExpr(NewOps, S->getLoop(),
1390 S->getNoWrapFlags(SCEV::FlagNW)));
1391 BasicBlock::iterator NewInsertPt =
1392 std::next(BasicBlock::iterator(cast<Instruction>(V)));
1393 BuilderType::InsertPointGuard Guard(Builder);
1394 while (isa<PHINode>(NewInsertPt) || isa<DbgInfoIntrinsic>(NewInsertPt) ||
1395 isa<LandingPadInst>(NewInsertPt))
1396 ++NewInsertPt;
1397 V = expandCodeFor(SE.getTruncateExpr(SE.getUnknown(V), Ty), nullptr,
1398 NewInsertPt);
1399 return V;
1400 }
1401
1402 // {X,+,F} --> X + {0,+,F}
1403 if (!S->getStart()->isZero()) {
1404 SmallVector<const SCEV *, 4> NewOps(S->op_begin(), S->op_end());
1405 NewOps[0] = SE.getConstant(Ty, 0);
1406 const SCEV *Rest = SE.getAddRecExpr(NewOps, L,
1407 S->getNoWrapFlags(SCEV::FlagNW));
1408
1409 // Turn things like ptrtoint+arithmetic+inttoptr into GEP. See the
1410 // comments on expandAddToGEP for details.
1411 const SCEV *Base = S->getStart();
1412 const SCEV *RestArray[1] = { Rest };
1413 // Dig into the expression to find the pointer base for a GEP.
1414 ExposePointerBase(Base, RestArray[0], SE);
1415 // If we found a pointer, expand the AddRec with a GEP.
1416 if (PointerType *PTy = dyn_cast<PointerType>(Base->getType())) {
1417 // Make sure the Base isn't something exotic, such as a multiplied
1418 // or divided pointer value. In those cases, the result type isn't
1419 // actually a pointer type.
1420 if (!isa<SCEVMulExpr>(Base) && !isa<SCEVUDivExpr>(Base)) {
1421 Value *StartV = expand(Base);
1422 assert(StartV->getType() == PTy && "Pointer type mismatch for GEP!");
1423 return expandAddToGEP(RestArray, RestArray+1, PTy, Ty, StartV);
1424 }
1425 }
1426
1427 // Just do a normal add. Pre-expand the operands to suppress folding.
1428 return expand(SE.getAddExpr(SE.getUnknown(expand(S->getStart())),
1429 SE.getUnknown(expand(Rest))));
1430 }
1431
1432 // If we don't yet have a canonical IV, create one.
1433 if (!CanonicalIV) {
1434 // Create and insert the PHI node for the induction variable in the
1435 // specified loop.
1436 BasicBlock *Header = L->getHeader();
1437 pred_iterator HPB = pred_begin(Header), HPE = pred_end(Header);
1438 CanonicalIV = PHINode::Create(Ty, std::distance(HPB, HPE), "indvar",
1439 Header->begin());
1440 rememberInstruction(CanonicalIV);
1441
1442 SmallSet<BasicBlock *, 4> PredSeen;
1443 Constant *One = ConstantInt::get(Ty, 1);
1444 for (pred_iterator HPI = HPB; HPI != HPE; ++HPI) {
1445 BasicBlock *HP = *HPI;
1446 if (!PredSeen.insert(HP).second) {
1447 // There must be an incoming value for each predecessor, even the
1448 // duplicates!
1449 CanonicalIV->addIncoming(CanonicalIV->getIncomingValueForBlock(HP), HP);
1450 continue;
1451 }
1452
1453 if (L->contains(HP)) {
1454 // Insert a unit add instruction right before the terminator
1455 // corresponding to the back-edge.
1456 Instruction *Add = BinaryOperator::CreateAdd(CanonicalIV, One,
1457 "indvar.next",
1458 HP->getTerminator());
1459 Add->setDebugLoc(HP->getTerminator()->getDebugLoc());
1460 rememberInstruction(Add);
1461 CanonicalIV->addIncoming(Add, HP);
1462 } else {
1463 CanonicalIV->addIncoming(Constant::getNullValue(Ty), HP);
1464 }
1465 }
1466 }
1467
1468 // {0,+,1} --> Insert a canonical induction variable into the loop!
1469 if (S->isAffine() && S->getOperand(1)->isOne()) {
1470 assert(Ty == SE.getEffectiveSCEVType(CanonicalIV->getType()) &&
1471 "IVs with types different from the canonical IV should "
1472 "already have been handled!");
1473 return CanonicalIV;
1474 }
1475
1476 // {0,+,F} --> {0,+,1} * F
1477
1478 // If this is a simple linear addrec, emit it now as a special case.
1479 if (S->isAffine()) // {0,+,F} --> i*F
1480 return
1481 expand(SE.getTruncateOrNoop(
1482 SE.getMulExpr(SE.getUnknown(CanonicalIV),
1483 SE.getNoopOrAnyExtend(S->getOperand(1),
1484 CanonicalIV->getType())),
1485 Ty));
1486
1487 // If this is a chain of recurrences, turn it into a closed form, using the
1488 // folders, then expandCodeFor the closed form. This allows the folders to
1489 // simplify the expression without having to build a bunch of special code
1490 // into this folder.
1491 const SCEV *IH = SE.getUnknown(CanonicalIV); // Get I as a "symbolic" SCEV.
1492
1493 // Promote S up to the canonical IV type, if the cast is foldable.
1494 const SCEV *NewS = S;
1495 const SCEV *Ext = SE.getNoopOrAnyExtend(S, CanonicalIV->getType());
1496 if (isa<SCEVAddRecExpr>(Ext))
1497 NewS = Ext;
1498
1499 const SCEV *V = cast<SCEVAddRecExpr>(NewS)->evaluateAtIteration(IH, SE);
1500 //cerr << "Evaluated: " << *this << "\n to: " << *V << "\n";
1501
1502 // Truncate the result down to the original type, if needed.
1503 const SCEV *T = SE.getTruncateOrNoop(V, Ty);
1504 return expand(T);
1505}
1506
1507Value *SCEVExpander::visitTruncateExpr(const SCEVTruncateExpr *S) {
1508 Type *Ty = SE.getEffectiveSCEVType(S->getType());
1509 Value *V = expandCodeFor(S->getOperand(),
1510 SE.getEffectiveSCEVType(S->getOperand()->getType()));
1511 Value *I = Builder.CreateTrunc(V, Ty);
1512 rememberInstruction(I);
1513 return I;
1514}
1515
1516Value *SCEVExpander::visitZeroExtendExpr(const SCEVZeroExtendExpr *S) {
1517 Type *Ty = SE.getEffectiveSCEVType(S->getType());
1518 Value *V = expandCodeFor(S->getOperand(),
1519 SE.getEffectiveSCEVType(S->getOperand()->getType()));
1520 Value *I = Builder.CreateZExt(V, Ty);
1521 rememberInstruction(I);
1522 return I;
1523}
1524
1525Value *SCEVExpander::visitSignExtendExpr(const SCEVSignExtendExpr *S) {
1526 Type *Ty = SE.getEffectiveSCEVType(S->getType());
1527 Value *V = expandCodeFor(S->getOperand(),
1528 SE.getEffectiveSCEVType(S->getOperand()->getType()));
1529 Value *I = Builder.CreateSExt(V, Ty);
1530 rememberInstruction(I);
1531 return I;
1532}
1533
1534Value *SCEVExpander::visitSMaxExpr(const SCEVSMaxExpr *S) {
1535 Value *LHS = expand(S->getOperand(S->getNumOperands()-1));
1536 Type *Ty = LHS->getType();
1537 for (int i = S->getNumOperands()-2; i >= 0; --i) {
1538 // In the case of mixed integer and pointer types, do the
1539 // rest of the comparisons as integer.
1540 if (S->getOperand(i)->getType() != Ty) {
1541 Ty = SE.getEffectiveSCEVType(Ty);
1542 LHS = InsertNoopCastOfTo(LHS, Ty);
1543 }
1544 Value *RHS = expandCodeFor(S->getOperand(i), Ty);
1545 Value *ICmp = Builder.CreateICmpSGT(LHS, RHS);
1546 rememberInstruction(ICmp);
1547 Value *Sel = Builder.CreateSelect(ICmp, LHS, RHS, "smax");
1548 rememberInstruction(Sel);
1549 LHS = Sel;
1550 }
1551 // In the case of mixed integer and pointer types, cast the
1552 // final result back to the pointer type.
1553 if (LHS->getType() != S->getType())
1554 LHS = InsertNoopCastOfTo(LHS, S->getType());
1555 return LHS;
1556}
1557
1558Value *SCEVExpander::visitUMaxExpr(const SCEVUMaxExpr *S) {
1559 Value *LHS = expand(S->getOperand(S->getNumOperands()-1));
1560 Type *Ty = LHS->getType();
1561 for (int i = S->getNumOperands()-2; i >= 0; --i) {
1562 // In the case of mixed integer and pointer types, do the
1563 // rest of the comparisons as integer.
1564 if (S->getOperand(i)->getType() != Ty) {
1565 Ty = SE.getEffectiveSCEVType(Ty);
1566 LHS = InsertNoopCastOfTo(LHS, Ty);
1567 }
1568 Value *RHS = expandCodeFor(S->getOperand(i), Ty);
1569 Value *ICmp = Builder.CreateICmpUGT(LHS, RHS);
1570 rememberInstruction(ICmp);
1571 Value *Sel = Builder.CreateSelect(ICmp, LHS, RHS, "umax");
1572 rememberInstruction(Sel);
1573 LHS = Sel;
1574 }
1575 // In the case of mixed integer and pointer types, cast the
1576 // final result back to the pointer type.
1577 if (LHS->getType() != S->getType())
1578 LHS = InsertNoopCastOfTo(LHS, S->getType());
1579 return LHS;
1580}
1581
1582Value *SCEVExpander::expandCodeFor(const SCEV *SH, Type *Ty,
1583 Instruction *IP) {
1584 Builder.SetInsertPoint(IP->getParent(), IP);
1585 return expandCodeFor(SH, Ty);
1586}
1587
1588Value *SCEVExpander::expandCodeFor(const SCEV *SH, Type *Ty) {
1589 // Expand the code for this SCEV.
1590 Value *V = expand(SH);
1591 if (Ty) {
1592 assert(SE.getTypeSizeInBits(Ty) == SE.getTypeSizeInBits(SH->getType()) &&
1593 "non-trivial casts should be done with the SCEVs directly!");
1594 V = InsertNoopCastOfTo(V, Ty);
1595 }
1596 return V;
1597}
1598
1599Value *SCEVExpander::expand(const SCEV *S) {
1600 // Compute an insertion point for this SCEV object. Hoist the instructions
1601 // as far out in the loop nest as possible.
1602 Instruction *InsertPt = Builder.GetInsertPoint();
1603 for (Loop *L = SE.LI->getLoopFor(Builder.GetInsertBlock()); ;
1604 L = L->getParentLoop())
1605 if (SE.isLoopInvariant(S, L)) {
1606 if (!L) break;
1607 if (BasicBlock *Preheader = L->getLoopPreheader())
1608 InsertPt = Preheader->getTerminator();
1609 else {
1610 // LSR sets the insertion point for AddRec start/step values to the
1611 // block start to simplify value reuse, even though it's an invalid
1612 // position. SCEVExpander must correct for this in all cases.
1613 InsertPt = L->getHeader()->getFirstInsertionPt();
1614 }
1615 } else {
1616 // If the SCEV is computable at this level, insert it into the header
1617 // after the PHIs (and after any other instructions that we've inserted
1618 // there) so that it is guaranteed to dominate any user inside the loop.
1619 if (L && SE.hasComputableLoopEvolution(S, L) && !PostIncLoops.count(L))
1620 InsertPt = L->getHeader()->getFirstInsertionPt();
1621 while (InsertPt != Builder.GetInsertPoint()
1622 && (isInsertedInstruction(InsertPt)
1623 || isa<DbgInfoIntrinsic>(InsertPt))) {
1624 InsertPt = std::next(BasicBlock::iterator(InsertPt));
1625 }
1626 break;
1627 }
1628
1629 // Check to see if we already expanded this here.
1630 std::map<std::pair<const SCEV *, Instruction *>, TrackingVH<Value> >::iterator
1631 I = InsertedExpressions.find(std::make_pair(S, InsertPt));
1632 if (I != InsertedExpressions.end())
1633 return I->second;
1634
1635 BuilderType::InsertPointGuard Guard(Builder);
1636 Builder.SetInsertPoint(InsertPt->getParent(), InsertPt);
1637
1638 // Expand the expression into instructions.
1639 Value *V = visit(S);
1640
1641 // Remember the expanded value for this SCEV at this location.
1642 //
1643 // This is independent of PostIncLoops. The mapped value simply materializes
1644 // the expression at this insertion point. If the mapped value happened to be
1645 // a postinc expansion, it could be reused by a non-postinc user, but only if
1646 // its insertion point was already at the head of the loop.
1647 InsertedExpressions[std::make_pair(S, InsertPt)] = V;
1648 return V;
1649}
1650
1651void SCEVExpander::rememberInstruction(Value *I) {
1652 if (!PostIncLoops.empty())
1653 InsertedPostIncValues.insert(I);
1654 else
1655 InsertedValues.insert(I);
1656}
1657
1658/// getOrInsertCanonicalInductionVariable - This method returns the
1659/// canonical induction variable of the specified type for the specified
1660/// loop (inserting one if there is none). A canonical induction variable
1661/// starts at zero and steps by one on each iteration.
1662PHINode *
1663SCEVExpander::getOrInsertCanonicalInductionVariable(const Loop *L,
1664 Type *Ty) {
1665 assert(Ty->isIntegerTy() && "Can only insert integer induction variables!");
1666
1667 // Build a SCEV for {0,+,1}<L>.
1668 // Conservatively use FlagAnyWrap for now.
1669 const SCEV *H = SE.getAddRecExpr(SE.getConstant(Ty, 0),
1670 SE.getConstant(Ty, 1), L, SCEV::FlagAnyWrap);
1671
1672 // Emit code for it.
1673 BuilderType::InsertPointGuard Guard(Builder);
1674 PHINode *V = cast<PHINode>(expandCodeFor(H, nullptr,
1675 L->getHeader()->begin()));
1676
1677 return V;
1678}
1679
1680/// replaceCongruentIVs - Check for congruent phis in this loop header and
1681/// replace them with their most canonical representative. Return the number of
1682/// phis eliminated.
1683///
1684/// This does not depend on any SCEVExpander state but should be used in
1685/// the same context that SCEVExpander is used.
1686unsigned SCEVExpander::replaceCongruentIVs(Loop *L, const DominatorTree *DT,
1687 SmallVectorImpl<WeakVH> &DeadInsts,
1688 const TargetTransformInfo *TTI) {
1689 // Find integer phis in order of increasing width.
1690 SmallVector<PHINode*, 8> Phis;
1691 for (BasicBlock::iterator I = L->getHeader()->begin();
1692 PHINode *Phi = dyn_cast<PHINode>(I); ++I) {
1693 Phis.push_back(Phi);
1694 }
1695 if (TTI)
1696 std::sort(Phis.begin(), Phis.end(), [](Value *LHS, Value *RHS) {
1697 // Put pointers at the back and make sure pointer < pointer = false.
1698 if (!LHS->getType()->isIntegerTy() || !RHS->getType()->isIntegerTy())
1699 return RHS->getType()->isIntegerTy() && !LHS->getType()->isIntegerTy();
1700 return RHS->getType()->getPrimitiveSizeInBits() <
1701 LHS->getType()->getPrimitiveSizeInBits();
1702 });
1703
1704 unsigned NumElim = 0;
1705 DenseMap<const SCEV *, PHINode *> ExprToIVMap;
1706 // Process phis from wide to narrow. Mapping wide phis to the their truncation
1707 // so narrow phis can reuse them.
1708 for (SmallVectorImpl<PHINode*>::const_iterator PIter = Phis.begin(),
1709 PEnd = Phis.end(); PIter != PEnd; ++PIter) {
1710 PHINode *Phi = *PIter;
1711
1712 // Fold constant phis. They may be congruent to other constant phis and
1713 // would confuse the logic below that expects proper IVs.
1714 if (Value *V = SimplifyInstruction(Phi, SE.DL, SE.TLI, SE.DT, SE.AC)) {
1715 Phi->replaceAllUsesWith(V);
1716 DeadInsts.push_back(Phi);
1717 ++NumElim;
1718 DEBUG_WITH_TYPE(DebugType, dbgs()
1719 << "INDVARS: Eliminated constant iv: " << *Phi << '\n');
1720 continue;
1721 }
1722
1723 if (!SE.isSCEVable(Phi->getType()))
1724 continue;
1725
1726 PHINode *&OrigPhiRef = ExprToIVMap[SE.getSCEV(Phi)];
1727 if (!OrigPhiRef) {
1728 OrigPhiRef = Phi;
1729 if (Phi->getType()->isIntegerTy() && TTI
1730 && TTI->isTruncateFree(Phi->getType(), Phis.back()->getType())) {
1731 // This phi can be freely truncated to the narrowest phi type. Map the
1732 // truncated expression to it so it will be reused for narrow types.
1733 const SCEV *TruncExpr =
1734 SE.getTruncateExpr(SE.getSCEV(Phi), Phis.back()->getType());
1735 ExprToIVMap[TruncExpr] = Phi;
1736 }
1737 continue;
1738 }
1739
1740 // Replacing a pointer phi with an integer phi or vice-versa doesn't make
1741 // sense.
1742 if (OrigPhiRef->getType()->isPointerTy() != Phi->getType()->isPointerTy())
1743 continue;
1744
1745 if (BasicBlock *LatchBlock = L->getLoopLatch()) {
1746 Instruction *OrigInc =
1747 cast<Instruction>(OrigPhiRef->getIncomingValueForBlock(LatchBlock));
1748 Instruction *IsomorphicInc =
1749 cast<Instruction>(Phi->getIncomingValueForBlock(LatchBlock));
1750
1751 // If this phi has the same width but is more canonical, replace the
1752 // original with it. As part of the "more canonical" determination,
1753 // respect a prior decision to use an IV chain.
1754 if (OrigPhiRef->getType() == Phi->getType()
1755 && !(ChainedPhis.count(Phi)
1756 || isExpandedAddRecExprPHI(OrigPhiRef, OrigInc, L))
1757 && (ChainedPhis.count(Phi)
1758 || isExpandedAddRecExprPHI(Phi, IsomorphicInc, L))) {
1759 std::swap(OrigPhiRef, Phi);
1760 std::swap(OrigInc, IsomorphicInc);
1761 }
1762 // Replacing the congruent phi is sufficient because acyclic redundancy
1763 // elimination, CSE/GVN, should handle the rest. However, once SCEV proves
1764 // that a phi is congruent, it's often the head of an IV user cycle that
1765 // is isomorphic with the original phi. It's worth eagerly cleaning up the
1766 // common case of a single IV increment so that DeleteDeadPHIs can remove
1767 // cycles that had postinc uses.
1768 const SCEV *TruncExpr = SE.getTruncateOrNoop(SE.getSCEV(OrigInc),
1769 IsomorphicInc->getType());
1770 if (OrigInc != IsomorphicInc
1771 && TruncExpr == SE.getSCEV(IsomorphicInc)
1772 && ((isa<PHINode>(OrigInc) && isa<PHINode>(IsomorphicInc))
1773 || hoistIVInc(OrigInc, IsomorphicInc))) {
1774 DEBUG_WITH_TYPE(DebugType, dbgs()
1775 << "INDVARS: Eliminated congruent iv.inc: "
1776 << *IsomorphicInc << '\n');
1777 Value *NewInc = OrigInc;
1778 if (OrigInc->getType() != IsomorphicInc->getType()) {
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