1//===-- DwarfEHPrepare - Prepare exception handling for code generation ---===//
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 pass mulches exception handling code into a form adapted to code
11// generation. Required if using dwarf exception handling.
12//
13//===----------------------------------------------------------------------===//
14
15#define DEBUG_TYPE "dwarfehprepare"
16#include "llvm/Function.h"
17#include "llvm/Instructions.h"
18#include "llvm/IntrinsicInst.h"
19#include "llvm/Module.h"
20#include "llvm/Pass.h"
21#include "llvm/ADT/Statistic.h"
22#include "llvm/Analysis/Dominators.h"
23#include "llvm/CodeGen/Passes.h"
24#include "llvm/MC/MCAsmInfo.h"
25#include "llvm/Target/TargetLowering.h"
26#include "llvm/Transforms/Utils/BasicBlockUtils.h"
27#include "llvm/Transforms/Utils/PromoteMemToReg.h"
28using namespace llvm;
29
30STATISTIC(NumLandingPadsSplit, "Number of landing pads split");
31STATISTIC(NumUnwindsLowered, "Number of unwind instructions lowered");
32STATISTIC(NumExceptionValuesMoved, "Number of eh.exception calls moved");
33STATISTIC(NumStackTempsIntroduced, "Number of stack temporaries introduced");
34
35namespace {
36 class DwarfEHPrepare : public FunctionPass {
37 const TargetLowering *TLI;
38 bool CompileFast;
39
40 // The eh.exception intrinsic.
41 Function *ExceptionValueIntrinsic;
42
43 // The eh.selector intrinsic.
44 Function *SelectorIntrinsic;
45
46 // _Unwind_Resume_or_Rethrow call.
47 Constant *URoR;
48
49 // The EH language-specific catch-all type.
50 GlobalVariable *EHCatchAllValue;
51
52 // _Unwind_Resume or the target equivalent.
53 Constant *RewindFunction;
54
55 // Dominator info is used when turning stack temporaries into registers.
56 DominatorTree *DT;
57 DominanceFrontier *DF;
58
59 // The function we are running on.
60 Function *F;
61
62 // The landing pads for this function.
63 typedef SmallPtrSet<BasicBlock*, 8> BBSet;
64 BBSet LandingPads;
65
66 // Stack temporary used to hold eh.exception values.
67 AllocaInst *ExceptionValueVar;
68
69 bool NormalizeLandingPads();
70 bool LowerUnwinds();
71 bool MoveExceptionValueCalls();
72 bool FinishStackTemporaries();
73 bool PromoteStackTemporaries();
74
75 Instruction *CreateExceptionValueCall(BasicBlock *BB);
76 Instruction *CreateValueLoad(BasicBlock *BB);
77
78 /// CreateReadOfExceptionValue - Return the result of the eh.exception
79 /// intrinsic by calling the intrinsic if in a landing pad, or loading it
80 /// from the exception value variable otherwise.
81 Instruction *CreateReadOfExceptionValue(BasicBlock *BB) {
82 return LandingPads.count(BB) ?
83 CreateExceptionValueCall(BB) : CreateValueLoad(BB);
84 }
85
86 /// CleanupSelectors - Any remaining eh.selector intrinsic calls which still
87 /// use the ".llvm.eh.catch.all.value" call need to convert to using it's
88 /// initializer instead.
89 bool CleanupSelectors();
90
91 /// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups.
92 void FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels);
93
94 /// FindAllURoRInvokes - Find all URoR invokes in the function.
95 void FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes);
96
97 /// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow"
98 /// calls. The "unwind" part of these invokes jump to a landing pad within
99 /// the current function. This is a candidate to merge the selector
100 /// associated with the URoR invoke with the one from the URoR's landing
101 /// pad.
102 bool HandleURoRInvokes();
103
104 /// FindSelectorAndURoR - Find the eh.selector call and URoR call associated
105 /// with the eh.exception call. This recursively looks past instructions
106 /// which don't change the EH pointer value, like casts or PHI nodes.
107 bool FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke,
108 SmallPtrSet<IntrinsicInst*, 8> &SelCalls);
109
110 /// DoMem2RegPromotion - Take an alloca call and promote it from memory to a
111 /// register.
112 bool DoMem2RegPromotion(Value *V) {
113 AllocaInst *AI = dyn_cast<AllocaInst>(V);
114 if (!AI || !isAllocaPromotable(AI)) return false;
115
116 // Turn the alloca into a register.
117 std::vector<AllocaInst*> Allocas(1, AI);
118 PromoteMemToReg(Allocas, *DT, *DF);
119 return true;
120 }
121
122 /// PromoteStoreInst - Perform Mem2Reg on a StoreInst.
123 bool PromoteStoreInst(StoreInst *SI) {
124 if (!SI || !DT || !DF) return false;
125 if (DoMem2RegPromotion(SI->getOperand(1)))
126 return true;
127 return false;
128 }
129
130 /// PromoteEHPtrStore - Promote the storing of an EH pointer into a
131 /// register. This should get rid of the store and subsequent loads.
132 bool PromoteEHPtrStore(IntrinsicInst *II) {
133 if (!DT || !DF) return false;
134
135 bool Changed = false;
136 StoreInst *SI;
137
138 while (1) {
139 SI = 0;
140 for (Value::use_iterator
141 I = II->use_begin(), E = II->use_end(); I != E; ++I) {
142 SI = dyn_cast<StoreInst>(I);
143 if (SI) break;
144 }
145
146 if (!PromoteStoreInst(SI))
147 break;
148
149 Changed = true;
150 }
151
152 return false;
153 }
154
155 public:
156 static char ID; // Pass identification, replacement for typeid.
157 DwarfEHPrepare(const TargetLowering *tli, bool fast) :
158 FunctionPass(&ID), TLI(tli), CompileFast(fast),
159 ExceptionValueIntrinsic(0), SelectorIntrinsic(0),
160 URoR(0), EHCatchAllValue(0), RewindFunction(0) {}
161
162 virtual bool runOnFunction(Function &Fn);
163
164 // getAnalysisUsage - We need dominance frontiers for memory promotion.
165 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
166 if (!CompileFast)
167 AU.addRequired<DominatorTree>();
168 AU.addPreserved<DominatorTree>();
169 if (!CompileFast)
170 AU.addRequired<DominanceFrontier>();
171 AU.addPreserved<DominanceFrontier>();
172 }
173
174 const char *getPassName() const {
175 return "Exception handling preparation";
176 }
177
178 };
179} // end anonymous namespace
180
181char DwarfEHPrepare::ID = 0;
182
183FunctionPass *llvm::createDwarfEHPass(const TargetLowering *tli, bool fast) {
184 return new DwarfEHPrepare(tli, fast);
185}
186
187/// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups.
188void DwarfEHPrepare::
189FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels) {
190 for (Value::use_iterator
191 I = SelectorIntrinsic->use_begin(),
192 E = SelectorIntrinsic->use_end(); I != E; ++I) {
193 IntrinsicInst *SI = cast<IntrinsicInst>(I);
194 if (!SI || SI->getParent()->getParent() != F) continue;
195
196 unsigned NumOps = SI->getNumOperands();
197 if (NumOps > 4) continue;
198 bool IsCleanUp = (NumOps == 3);
199
200 if (!IsCleanUp)
201 if (ConstantInt *CI = dyn_cast<ConstantInt>(SI->getOperand(3)))
202 IsCleanUp = (CI->getZExtValue() == 0);
203
204 if (IsCleanUp)
205 Sels.insert(SI);
206 }
207}
208
209/// FindAllURoRInvokes - Find all URoR invokes in the function.
210void DwarfEHPrepare::
211FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes) {
212 for (Value::use_iterator
213 I = URoR->use_begin(),
214 E = URoR->use_end(); I != E; ++I) {
215 if (InvokeInst *II = dyn_cast<InvokeInst>(I))
216 URoRInvokes.insert(II);
217 }
218}
219
220/// CleanupSelectors - Any remaining eh.selector intrinsic calls which still use
221/// the ".llvm.eh.catch.all.value" call need to convert to using it's
222/// initializer instead.
223bool DwarfEHPrepare::CleanupSelectors() {
224 if (!EHCatchAllValue) return false;
225
226 if (!SelectorIntrinsic) {
227 SelectorIntrinsic =
228 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector);
229 if (!SelectorIntrinsic) return false;
230 }
231
232 bool Changed = false;
233 for (Value::use_iterator
234 I = SelectorIntrinsic->use_begin(),
235 E = SelectorIntrinsic->use_end(); I != E; ++I) {
236 IntrinsicInst *Sel = dyn_cast<IntrinsicInst>(I);
237 if (!Sel || Sel->getParent()->getParent() != F) continue;
238
239 // Index of the ".llvm.eh.catch.all.value" variable.
240 unsigned OpIdx = Sel->getNumOperands() - 1;
241 GlobalVariable *GV = dyn_cast<GlobalVariable>(Sel->getOperand(OpIdx));
242 if (GV != EHCatchAllValue) continue;
243 Sel->setOperand(OpIdx, EHCatchAllValue->getInitializer());
244 Changed = true;
245 }
246
247 return Changed;
248}
249
250/// FindSelectorAndURoR - Find the eh.selector call associated with the
251/// eh.exception call. And indicate if there is a URoR "invoke" associated with
252/// the eh.exception call. This recursively looks past instructions which don't
253/// change the EH pointer value, like casts or PHI nodes.
254bool
255DwarfEHPrepare::FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke,
256 SmallPtrSet<IntrinsicInst*, 8> &SelCalls) {
257 SmallPtrSet<PHINode*, 32> SeenPHIs;
258 bool Changed = false;
259
260 restart:
261 for (Value::use_iterator
262 I = Inst->use_begin(), E = Inst->use_end(); I != E; ++I) {
263 Instruction *II = dyn_cast<Instruction>(I);
264 if (!II || II->getParent()->getParent() != F) continue;
265
266 if (IntrinsicInst *Sel = dyn_cast<IntrinsicInst>(II)) {
267 if (Sel->getIntrinsicID() == Intrinsic::eh_selector)
268 SelCalls.insert(Sel);
269 } else if (InvokeInst *Invoke = dyn_cast<InvokeInst>(II)) {
270 if (Invoke->getCalledFunction() == URoR)
271 URoRInvoke = true;
272 } else if (CastInst *CI = dyn_cast<CastInst>(II)) {
273 Changed |= FindSelectorAndURoR(CI, URoRInvoke, SelCalls);
274 } else if (StoreInst *SI = dyn_cast<StoreInst>(II)) {
275 if (!PromoteStoreInst(SI)) continue;
276 Changed = true;
277 SeenPHIs.clear();
278 goto restart; // Uses may have changed, restart loop.
279 } else if (PHINode *PN = dyn_cast<PHINode>(II)) {
280 if (SeenPHIs.insert(PN))
281 // Don't process a PHI node more than once.
282 Changed |= FindSelectorAndURoR(PN, URoRInvoke, SelCalls);
283 }
284 }
285
286 return Changed;
287}
288
289/// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" calls. The
290/// "unwind" part of these invokes jump to a landing pad within the current
291/// function. This is a candidate to merge the selector associated with the URoR
292/// invoke with the one from the URoR's landing pad.
293bool DwarfEHPrepare::HandleURoRInvokes() {
294 if (!DT) return CleanupSelectors(); // We require DominatorTree information.
295
296 if (!EHCatchAllValue) {
297 EHCatchAllValue =
298 F->getParent()->getNamedGlobal(".llvm.eh.catch.all.value");
299 if (!EHCatchAllValue) return false;
300 }
301
302 if (!SelectorIntrinsic) {
303 SelectorIntrinsic =
304 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector);
305 if (!SelectorIntrinsic) return false;
306 }
307
308 if (!URoR) {
309 URoR = F->getParent()->getFunction("_Unwind_Resume_or_Rethrow");
310 if (!URoR) return CleanupSelectors();
311 }
312
313 SmallPtrSet<IntrinsicInst*, 32> Sels;
314 SmallPtrSet<InvokeInst*, 32> URoRInvokes;
315 FindAllCleanupSelectors(Sels);
316 FindAllURoRInvokes(URoRInvokes);
317
318 SmallPtrSet<IntrinsicInst*, 32> SelsToConvert;
319
320 for (SmallPtrSet<IntrinsicInst*, 32>::iterator
321 SI = Sels.begin(), SE = Sels.end(); SI != SE; ++SI) {
322 const BasicBlock *SelBB = (*SI)->getParent();
323 for (SmallPtrSet<InvokeInst*, 32>::iterator
324 UI = URoRInvokes.begin(), UE = URoRInvokes.end(); UI != UE; ++UI) {
325 const BasicBlock *URoRBB = (*UI)->getParent();
326 if (SelBB == URoRBB || DT->dominates(SelBB, URoRBB)) {
327 SelsToConvert.insert(*SI);
328 break;
329 }
330 }
331 }
332
333 bool Changed = false;
334
335 if (Sels.size() != SelsToConvert.size()) {
336 // If we haven't been able to convert all of the clean-up selectors, then
337 // loop through the slow way to see if they still need to be converted.
338 if (!ExceptionValueIntrinsic) {
339 ExceptionValueIntrinsic =
340 Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_exception);
341 if (!ExceptionValueIntrinsic) return CleanupSelectors();
342 }
343
344 for (Value::use_iterator
345 I = ExceptionValueIntrinsic->use_begin(),
346 E = ExceptionValueIntrinsic->use_end(); I != E; ++I) {
347 IntrinsicInst *EHPtr = dyn_cast<IntrinsicInst>(I);
348 if (!EHPtr || EHPtr->getParent()->getParent() != F) continue;
349
350 Changed |= PromoteEHPtrStore(EHPtr);
351
352 bool URoRInvoke = false;
353 SmallPtrSet<IntrinsicInst*, 8> SelCalls;
354 Changed |= FindSelectorAndURoR(EHPtr, URoRInvoke, SelCalls);
355
356 if (URoRInvoke) {
357 // This EH pointer is being used by an invoke of an URoR instruction and
358 // an eh.selector intrinsic call. If the eh.selector is a 'clean-up', we
359 // need to convert it to a 'catch-all'.
360 for (SmallPtrSet<IntrinsicInst*, 8>::iterator
361 SI = SelCalls.begin(), SE = SelCalls.end(); SI != SE; ++SI) {
362 IntrinsicInst *II = *SI;
363 unsigned NumOps = II->getNumOperands();
364
365 if (NumOps <= 4) {
366 bool IsCleanUp = (NumOps == 3);
367
368 if (!IsCleanUp)
369 if (ConstantInt *CI = dyn_cast<ConstantInt>(II->getOperand(3)))
370 IsCleanUp = (CI->getZExtValue() == 0);
371
372 if (IsCleanUp)
373 SelsToConvert.insert(II);
374 }
375 }
376 }
377 }
378 }
379
380 if (!SelsToConvert.empty()) {
381 // Convert all clean-up eh.selectors, which are associated with "invokes" of
382 // URoR calls, into catch-all eh.selectors.
383 Changed = true;
384
385 for (SmallPtrSet<IntrinsicInst*, 8>::iterator
386 SI = SelsToConvert.begin(), SE = SelsToConvert.end();
387 SI != SE; ++SI) {
388 IntrinsicInst *II = *SI;
389 SmallVector<Value*, 8> Args;
390
391 // Use the exception object pointer and the personality function
392 // from the original selector.
393 Args.push_back(II->getOperand(1)); // Exception object pointer.
394 Args.push_back(II->getOperand(2)); // Personality function.
395 Args.push_back(EHCatchAllValue->getInitializer()); // Catch-all indicator.
396
397 CallInst *NewSelector =
398 CallInst::Create(SelectorIntrinsic, Args.begin(), Args.end(),
399 "eh.sel.catch.all", II);
400
401 NewSelector->setTailCall(II->isTailCall());
402 NewSelector->setAttributes(II->getAttributes());
403 NewSelector->setCallingConv(II->getCallingConv());
404
405 II->replaceAllUsesWith(NewSelector);
406 II->eraseFromParent();
407 }
408 }
409
410 Changed |= CleanupSelectors();
411 return Changed;
412}
413
414/// NormalizeLandingPads - Normalize and discover landing pads, noting them
415/// in the LandingPads set. A landing pad is normal if the only CFG edges
416/// that end at it are unwind edges from invoke instructions. If we inlined
417/// through an invoke we could have a normal branch from the previous
418/// unwind block through to the landing pad for the original invoke.
419/// Abnormal landing pads are fixed up by redirecting all unwind edges to
420/// a new basic block which falls through to the original.
421bool DwarfEHPrepare::NormalizeLandingPads() {
422 bool Changed = false;
423
424 const MCAsmInfo *MAI = TLI->getTargetMachine().getMCAsmInfo();
425 bool usingSjLjEH = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
426
427 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
428 TerminatorInst *TI = I->getTerminator();
429 if (!isa<InvokeInst>(TI))
430 continue;
431 BasicBlock *LPad = TI->getSuccessor(1);
432 // Skip landing pads that have already been normalized.
433 if (LandingPads.count(LPad))
434 continue;
435
436 // Check that only invoke unwind edges end at the landing pad.
437 bool OnlyUnwoundTo = true;
438 bool SwitchOK = usingSjLjEH;
439 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad);
440 PI != PE; ++PI) {
441 TerminatorInst *PT = (*PI)->getTerminator();
442 // The SjLj dispatch block uses a switch instruction. This is effectively
443 // an unwind edge, so we can disregard it here. There will only ever
444 // be one dispatch, however, so if there are multiple switches, one
445 // of them truly is a normal edge, not an unwind edge.
446 if (SwitchOK && isa<SwitchInst>(PT)) {
447 SwitchOK = false;
448 continue;
449 }
450 if (!isa<InvokeInst>(PT) || LPad == PT->getSuccessor(0)) {
451 OnlyUnwoundTo = false;
452 break;
453 }
454 }
455
456 if (OnlyUnwoundTo) {
457 // Only unwind edges lead to the landing pad. Remember the landing pad.
458 LandingPads.insert(LPad);
459 continue;
460 }
461
462 // At least one normal edge ends at the landing pad. Redirect the unwind
463 // edges to a new basic block which falls through into this one.
464
465 // Create the new basic block.
466 BasicBlock *NewBB = BasicBlock::Create(F->getContext(),
467 LPad->getName() + "_unwind_edge");
468
469 // Insert it into the function right before the original landing pad.
470 LPad->getParent()->getBasicBlockList().insert(LPad, NewBB);
471
472 // Redirect unwind edges from the original landing pad to NewBB.
473 for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ) {
474 TerminatorInst *PT = (*PI++)->getTerminator();
475 if (isa<InvokeInst>(PT) && PT->getSuccessor(1) == LPad)
476 // Unwind to the new block.
477 PT->setSuccessor(1, NewBB);
478 }
479
480 // If there are any PHI nodes in LPad, we need to update them so that they
481 // merge incoming values from NewBB instead.
482 for (BasicBlock::iterator II = LPad->begin(); isa<PHINode>(II); ++II) {
483 PHINode *PN = cast<PHINode>(II);
484 pred_iterator PB = pred_begin(NewBB), PE = pred_end(NewBB);
485
486 // Check to see if all of the values coming in via unwind edges are the
487 // same. If so, we don't need to create a new PHI node.
488 Value *InVal = PN->getIncomingValueForBlock(*PB);
489 for (pred_iterator PI = PB; PI != PE; ++PI) {
490 if (PI != PB && InVal != PN->getIncomingValueForBlock(*PI)) {
491 InVal = 0;
492 break;
493 }
494 }
495
496 if (InVal == 0) {
497 // Different unwind edges have different values. Create a new PHI node
498 // in NewBB.
499 PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName()+".unwind",
500 NewBB);
501 // Add an entry for each unwind edge, using the value from the old PHI.
502 for (pred_iterator PI = PB; PI != PE; ++PI)
503 NewPN->addIncoming(PN->getIncomingValueForBlock(*PI), *PI);
504
505 // Now use this new PHI as the common incoming value for NewBB in PN.
506 InVal = NewPN;
507 }
508
509 // Revector exactly one entry in the PHI node to come from NewBB
510 // and delete all other entries that come from unwind edges. If
511 // there are both normal and unwind edges from the same predecessor,
512 // this leaves an entry for the normal edge.
513 for (pred_iterator PI = PB; PI != PE; ++PI)
514 PN->removeIncomingValue(*PI);
515 PN->addIncoming(InVal, NewBB);
516 }
517
518 // Add a fallthrough from NewBB to the original landing pad.
519 BranchInst::Create(LPad, NewBB);
520
521 // Now update DominatorTree and DominanceFrontier analysis information.
522 if (DT)
523 DT->splitBlock(NewBB);
524 if (DF)
525 DF->splitBlock(NewBB);
526
527 // Remember the newly constructed landing pad. The original landing pad
528 // LPad is no longer a landing pad now that all unwind edges have been
529 // revectored to NewBB.
530 LandingPads.insert(NewBB);
531 ++NumLandingPadsSplit;
532 Changed = true;
533 }
534
535 return Changed;
536}
537
538/// LowerUnwinds - Turn unwind instructions into calls to _Unwind_Resume,
539/// rethrowing any previously caught exception. This will crash horribly
540/// at runtime if there is no such exception: using unwind to throw a new
541/// exception is currently not supported.
542bool DwarfEHPrepare::LowerUnwinds() {
543 SmallVector<TerminatorInst*, 16> UnwindInsts;
544
545 for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
546 TerminatorInst *TI = I->getTerminator();
547 if (isa<UnwindInst>(TI))
548 UnwindInsts.push_back(TI);
549 }
550
551 if (UnwindInsts.empty()) return false;
552
553 // Find the rewind function if we didn't already.
554 if (!RewindFunction) {
555 LLVMContext &Ctx = UnwindInsts[0]->getContext();
556 std::vector<const Type*>
557 Params(1, Type::getInt8PtrTy(Ctx));
558 FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx),
559 Params, false);
560 const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME);
561 RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy);
562 }
563
564 bool Changed = false;
565
566 for (SmallVectorImpl<TerminatorInst*>::iterator
567 I = UnwindInsts.begin(), E = UnwindInsts.end(); I != E; ++I) {
568 TerminatorInst *TI = *I;
569
570 // Replace the unwind instruction with a call to _Unwind_Resume (or the
571 // appropriate target equivalent) followed by an UnreachableInst.
572
573 // Create the call...
574 CallInst *CI = CallInst::Create(RewindFunction,
575 CreateReadOfExceptionValue(TI->getParent()),
576 "", TI);
577 CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
578 // ...followed by an UnreachableInst.
579 new UnreachableInst(TI->getContext(), TI);
580
581 // Nuke the unwind instruction.
582 TI->eraseFromParent();
583 ++NumUnwindsLowered;
584 Changed = true;
585 }
586
587 return Changed;
588}
589
590/// MoveExceptionValueCalls - Ensure that eh.exception is only ever called from
591/// landing pads by replacing calls outside of landing pads with loads from a
592/// stack temporary. Move eh.exception calls inside landing pads to the start
593/// of the landing pad (optional, but may make things simpler for later passes).
594bool DwarfEHPrepare::MoveExceptionValueCalls() {
595 // If the eh.exception intrinsic is not declared in the module then there is
596 // nothing to do. Speed up compilation by checking for this common case.
597 if (!ExceptionValueIntrinsic &&
598 !F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_exception)))
599 return false;
600
601 bool Changed = false;
602
603 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
604 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;)
605 if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(II++))
606 if (CI->getIntrinsicID() == Intrinsic::eh_exception) {
607 if (!CI->use_empty()) {
608 Value *ExceptionValue = CreateReadOfExceptionValue(BB);
609 if (CI == ExceptionValue) {
610 // The call was at the start of a landing pad - leave it alone.
611 assert(LandingPads.count(BB) &&
612 "Created eh.exception call outside landing pad!");
613 continue;
614 }
615 CI->replaceAllUsesWith(ExceptionValue);
616 }
617 CI->eraseFromParent();
618 ++NumExceptionValuesMoved;
619 Changed = true;
620 }
621 }
622
623 return Changed;
624}
625
626/// FinishStackTemporaries - If we introduced a stack variable to hold the
627/// exception value then initialize it in each landing pad.
628bool DwarfEHPrepare::FinishStackTemporaries() {
629 if (!ExceptionValueVar)
630 // Nothing to do.
631 return false;
632
633 bool Changed = false;
634
635 // Make sure that there is a store of the exception value at the start of
636 // each landing pad.
637 for (BBSet::iterator LI = LandingPads.begin(), LE = LandingPads.end();
638 LI != LE; ++LI) {
639 Instruction *ExceptionValue = CreateReadOfExceptionValue(*LI);
640 Instruction *Store = new StoreInst(ExceptionValue, ExceptionValueVar);
641 Store->insertAfter(ExceptionValue);
642 Changed = true;
643 }
644
645 return Changed;
646}
647
648/// PromoteStackTemporaries - Turn any stack temporaries we introduced into
649/// registers if possible.
650bool DwarfEHPrepare::PromoteStackTemporaries() {
651 if (ExceptionValueVar && DT && DF && isAllocaPromotable(ExceptionValueVar)) {
652 // Turn the exception temporary into registers and phi nodes if possible.
653 std::vector<AllocaInst*> Allocas(1, ExceptionValueVar);
654 PromoteMemToReg(Allocas, *DT, *DF);
655 return true;
656 }
657 return false;
658}
659
660/// CreateExceptionValueCall - Insert a call to the eh.exception intrinsic at
661/// the start of the basic block (unless there already is one, in which case
662/// the existing call is returned).
663Instruction *DwarfEHPrepare::CreateExceptionValueCall(BasicBlock *BB) {
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