ConstantFold.cpp revision 256281
1295011Sandrew//===- ConstantFold.cpp - LLVM constant folder ----------------------------===// 2295011Sandrew// 3295011Sandrew// The LLVM Compiler Infrastructure 4295011Sandrew// 5295011Sandrew// This file is distributed under the University of Illinois Open Source 6295011Sandrew// License. See LICENSE.TXT for details. 7295011Sandrew// 8295011Sandrew//===----------------------------------------------------------------------===// 9295011Sandrew// 10295011Sandrew// This file implements folding of constants for LLVM. This implements the 11295011Sandrew// (internal) ConstantFold.h interface, which is used by the 12295011Sandrew// ConstantExpr::get* methods to automatically fold constants when possible. 13295011Sandrew// 14295011Sandrew// The current constant folding implementation is implemented in two pieces: the 15295011Sandrew// pieces that don't need DataLayout, and the pieces that do. This is to avoid 16295011Sandrew// a dependence in IR on Target. 17295011Sandrew// 18295011Sandrew//===----------------------------------------------------------------------===// 19295011Sandrew 20295011Sandrew#include "ConstantFold.h" 21295011Sandrew#include "llvm/ADT/SmallVector.h" 22295011Sandrew#include "llvm/IR/Constants.h" 23295011Sandrew#include "llvm/IR/DerivedTypes.h" 24295011Sandrew#include "llvm/IR/Function.h" 25295011Sandrew#include "llvm/IR/GlobalAlias.h" 26295011Sandrew#include "llvm/IR/GlobalVariable.h" 27295011Sandrew#include "llvm/IR/Instructions.h" 28295011Sandrew#include "llvm/IR/Operator.h" 29295011Sandrew#include "llvm/Support/Compiler.h" 30295011Sandrew#include "llvm/Support/ErrorHandling.h" 31295011Sandrew#include "llvm/Support/GetElementPtrTypeIterator.h" 32295011Sandrew#include "llvm/Support/ManagedStatic.h" 33295011Sandrew#include "llvm/Support/MathExtras.h" 34295011Sandrew#include <limits> 35295011Sandrewusing namespace llvm; 36295011Sandrew 37295011Sandrew//===----------------------------------------------------------------------===// 38295011Sandrew// ConstantFold*Instruction Implementations 39295011Sandrew//===----------------------------------------------------------------------===// 40295011Sandrew 41295011Sandrew/// BitCastConstantVector - Convert the specified vector Constant node to the 42295011Sandrew/// specified vector type. At this point, we know that the elements of the 43295011Sandrew/// input vector constant are all simple integer or FP values. 44295011Sandrewstatic Constant *BitCastConstantVector(Constant *CV, VectorType *DstTy) { 45295011Sandrew 46295011Sandrew if (CV->isAllOnesValue()) return Constant::getAllOnesValue(DstTy); 47295011Sandrew if (CV->isNullValue()) return Constant::getNullValue(DstTy); 48295011Sandrew 49295011Sandrew // If this cast changes element count then we can't handle it here: 50295011Sandrew // doing so requires endianness information. This should be handled by 51295011Sandrew // Analysis/ConstantFolding.cpp 52295011Sandrew unsigned NumElts = DstTy->getNumElements(); 53295011Sandrew if (NumElts != CV->getType()->getVectorNumElements()) 54295011Sandrew return 0; 55295011Sandrew 56295011Sandrew Type *DstEltTy = DstTy->getElementType(); 57295011Sandrew 58295011Sandrew SmallVector<Constant*, 16> Result; 59295011Sandrew Type *Ty = IntegerType::get(CV->getContext(), 32); 60295011Sandrew for (unsigned i = 0; i != NumElts; ++i) { 61295011Sandrew Constant *C = 62295011Sandrew ConstantExpr::getExtractElement(CV, ConstantInt::get(Ty, i)); 63295011Sandrew C = ConstantExpr::getBitCast(C, DstEltTy); 64295011Sandrew Result.push_back(C); 65295011Sandrew } 66295011Sandrew 67295011Sandrew return ConstantVector::get(Result); 68295011Sandrew} 69295011Sandrew 70295011Sandrew/// This function determines which opcode to use to fold two constant cast 71295011Sandrew/// expressions together. It uses CastInst::isEliminableCastPair to determine 72295011Sandrew/// the opcode. Consequently its just a wrapper around that function. 73295011Sandrew/// @brief Determine if it is valid to fold a cast of a cast 74295011Sandrewstatic unsigned 75295011SandrewfoldConstantCastPair( 76295011Sandrew unsigned opc, ///< opcode of the second cast constant expression 77295011Sandrew ConstantExpr *Op, ///< the first cast constant expression 78295011Sandrew Type *DstTy ///< desintation type of the first cast 79295011Sandrew) { 80295011Sandrew assert(Op && Op->isCast() && "Can't fold cast of cast without a cast!"); 81295011Sandrew assert(DstTy && DstTy->isFirstClassType() && "Invalid cast destination type"); 82295011Sandrew assert(CastInst::isCast(opc) && "Invalid cast opcode"); 83295011Sandrew 84295011Sandrew // The the types and opcodes for the two Cast constant expressions 85295011Sandrew Type *SrcTy = Op->getOperand(0)->getType(); 86295011Sandrew Type *MidTy = Op->getType(); 87295011Sandrew Instruction::CastOps firstOp = Instruction::CastOps(Op->getOpcode()); 88295011Sandrew Instruction::CastOps secondOp = Instruction::CastOps(opc); 89295011Sandrew 90295011Sandrew // Assume that pointers are never more than 64 bits wide. 91295011Sandrew IntegerType *FakeIntPtrTy = Type::getInt64Ty(DstTy->getContext()); 92295011Sandrew 93295011Sandrew // Let CastInst::isEliminableCastPair do the heavy lifting. 94295011Sandrew return CastInst::isEliminableCastPair(firstOp, secondOp, SrcTy, MidTy, DstTy, 95295011Sandrew FakeIntPtrTy, FakeIntPtrTy, 96295011Sandrew FakeIntPtrTy); 97295011Sandrew} 98295011Sandrew 99295011Sandrewstatic Constant *FoldBitCast(Constant *V, Type *DestTy) { 100295011Sandrew Type *SrcTy = V->getType(); 101295011Sandrew if (SrcTy == DestTy) 102295011Sandrew return V; // no-op cast 103295011Sandrew 104295011Sandrew // Check to see if we are casting a pointer to an aggregate to a pointer to 105295011Sandrew // the first element. If so, return the appropriate GEP instruction. 106295011Sandrew if (PointerType *PTy = dyn_cast<PointerType>(V->getType())) 107295011Sandrew if (PointerType *DPTy = dyn_cast<PointerType>(DestTy)) 108295011Sandrew if (PTy->getAddressSpace() == DPTy->getAddressSpace() 109295011Sandrew && DPTy->getElementType()->isSized()) { 110295011Sandrew SmallVector<Value*, 8> IdxList; 111295011Sandrew Value *Zero = 112295011Sandrew Constant::getNullValue(Type::getInt32Ty(DPTy->getContext())); 113295011Sandrew IdxList.push_back(Zero); 114295011Sandrew Type *ElTy = PTy->getElementType(); 115295011Sandrew while (ElTy != DPTy->getElementType()) { 116295011Sandrew if (StructType *STy = dyn_cast<StructType>(ElTy)) { 117295011Sandrew if (STy->getNumElements() == 0) break; 118295011Sandrew ElTy = STy->getElementType(0); 119295011Sandrew IdxList.push_back(Zero); 120295011Sandrew } else if (SequentialType *STy = 121295011Sandrew dyn_cast<SequentialType>(ElTy)) { 122295011Sandrew if (ElTy->isPointerTy()) break; // Can't index into pointers! 123295011Sandrew ElTy = STy->getElementType(); 124295011Sandrew IdxList.push_back(Zero); 125295011Sandrew } else { 126295011Sandrew break; 127295011Sandrew } 128295011Sandrew } 129295011Sandrew 130295011Sandrew if (ElTy == DPTy->getElementType()) 131295011Sandrew // This GEP is inbounds because all indices are zero. 132295011Sandrew return ConstantExpr::getInBoundsGetElementPtr(V, IdxList); 133295011Sandrew } 134295011Sandrew 135295011Sandrew // Handle casts from one vector constant to another. We know that the src 136295011Sandrew // and dest type have the same size (otherwise its an illegal cast). 137295011Sandrew if (VectorType *DestPTy = dyn_cast<VectorType>(DestTy)) { 138295011Sandrew if (VectorType *SrcTy = dyn_cast<VectorType>(V->getType())) { 139295011Sandrew assert(DestPTy->getBitWidth() == SrcTy->getBitWidth() && 140295011Sandrew "Not cast between same sized vectors!"); 141295011Sandrew SrcTy = NULL; 142295011Sandrew // First, check for null. Undef is already handled. 143295011Sandrew if (isa<ConstantAggregateZero>(V)) 144295011Sandrew return Constant::getNullValue(DestTy); 145295011Sandrew 146295011Sandrew // Handle ConstantVector and ConstantAggregateVector. 147295011Sandrew return BitCastConstantVector(V, DestPTy); 148295011Sandrew } 149295011Sandrew 150295011Sandrew // Canonicalize scalar-to-vector bitcasts into vector-to-vector bitcasts 151295011Sandrew // This allows for other simplifications (although some of them 152295011Sandrew // can only be handled by Analysis/ConstantFolding.cpp). 153295011Sandrew if (isa<ConstantInt>(V) || isa<ConstantFP>(V)) 154295011Sandrew return ConstantExpr::getBitCast(ConstantVector::get(V), DestPTy); 155295011Sandrew } 156295011Sandrew 157295011Sandrew // Finally, implement bitcast folding now. The code below doesn't handle 158295011Sandrew // bitcast right. 159295011Sandrew if (isa<ConstantPointerNull>(V)) // ptr->ptr cast. 160295011Sandrew return ConstantPointerNull::get(cast<PointerType>(DestTy)); 161295011Sandrew 162295011Sandrew // Handle integral constant input. 163295011Sandrew if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 164295011Sandrew if (DestTy->isIntegerTy()) 165295011Sandrew // Integral -> Integral. This is a no-op because the bit widths must 166295011Sandrew // be the same. Consequently, we just fold to V. 167295011Sandrew return V; 168295011Sandrew 169295011Sandrew if (DestTy->isFloatingPointTy()) 170295011Sandrew return ConstantFP::get(DestTy->getContext(), 171295011Sandrew APFloat(DestTy->getFltSemantics(), 172295011Sandrew CI->getValue())); 173295011Sandrew 174295011Sandrew // Otherwise, can't fold this (vector?) 175295011Sandrew return 0; 176295011Sandrew } 177295011Sandrew 178295011Sandrew // Handle ConstantFP input: FP -> Integral. 179295011Sandrew if (ConstantFP *FP = dyn_cast<ConstantFP>(V)) 180295011Sandrew return ConstantInt::get(FP->getContext(), 181295011Sandrew FP->getValueAPF().bitcastToAPInt()); 182295011Sandrew 183295011Sandrew return 0; 184295011Sandrew} 185295011Sandrew 186295011Sandrew 187295011Sandrew/// ExtractConstantBytes - V is an integer constant which only has a subset of 188295011Sandrew/// its bytes used. The bytes used are indicated by ByteStart (which is the 189295011Sandrew/// first byte used, counting from the least significant byte) and ByteSize, 190295011Sandrew/// which is the number of bytes used. 191295011Sandrew/// 192295011Sandrew/// This function analyzes the specified constant to see if the specified byte 193295011Sandrew/// range can be returned as a simplified constant. If so, the constant is 194295011Sandrew/// returned, otherwise null is returned. 195295011Sandrew/// 196295011Sandrewstatic Constant *ExtractConstantBytes(Constant *C, unsigned ByteStart, 197295011Sandrew unsigned ByteSize) { 198295011Sandrew assert(C->getType()->isIntegerTy() && 199295011Sandrew (cast<IntegerType>(C->getType())->getBitWidth() & 7) == 0 && 200295011Sandrew "Non-byte sized integer input"); 201295011Sandrew unsigned CSize = cast<IntegerType>(C->getType())->getBitWidth()/8; 202295011Sandrew assert(ByteSize && "Must be accessing some piece"); 203295011Sandrew assert(ByteStart+ByteSize <= CSize && "Extracting invalid piece from input"); 204295011Sandrew assert(ByteSize != CSize && "Should not extract everything"); 205295011Sandrew 206295011Sandrew // Constant Integers are simple. 207295011Sandrew if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) { 208295011Sandrew APInt V = CI->getValue(); 209295011Sandrew if (ByteStart) 210295011Sandrew V = V.lshr(ByteStart*8); 211295011Sandrew V = V.trunc(ByteSize*8); 212295011Sandrew return ConstantInt::get(CI->getContext(), V); 213295011Sandrew } 214295011Sandrew 215295011Sandrew // In the input is a constant expr, we might be able to recursively simplify. 216295011Sandrew // If not, we definitely can't do anything. 217295011Sandrew ConstantExpr *CE = dyn_cast<ConstantExpr>(C); 218295011Sandrew if (CE == 0) return 0; 219295011Sandrew 220295011Sandrew switch (CE->getOpcode()) { 221295011Sandrew default: return 0; 222295011Sandrew case Instruction::Or: { 223295011Sandrew Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize); 224295011Sandrew if (RHS == 0) 225295011Sandrew return 0; 226295011Sandrew 227295011Sandrew // X | -1 -> -1. 228295011Sandrew if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) 229295011Sandrew if (RHSC->isAllOnesValue()) 230295011Sandrew return RHSC; 231295011Sandrew 232295011Sandrew Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize); 233295011Sandrew if (LHS == 0) 234295011Sandrew return 0; 235295011Sandrew return ConstantExpr::getOr(LHS, RHS); 236295011Sandrew } 237295011Sandrew case Instruction::And: { 238295011Sandrew Constant *RHS = ExtractConstantBytes(CE->getOperand(1), ByteStart,ByteSize); 239295011Sandrew if (RHS == 0) 240295011Sandrew return 0; 241295011Sandrew 242295011Sandrew // X & 0 -> 0. 243295011Sandrew if (RHS->isNullValue()) 244295011Sandrew return RHS; 245295011Sandrew 246295011Sandrew Constant *LHS = ExtractConstantBytes(CE->getOperand(0), ByteStart,ByteSize); 247295011Sandrew if (LHS == 0) 248295011Sandrew return 0; 249295011Sandrew return ConstantExpr::getAnd(LHS, RHS); 250295011Sandrew } 251295011Sandrew case Instruction::LShr: { 252295011Sandrew ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1)); 253295011Sandrew if (Amt == 0) 254295011Sandrew return 0; 255295011Sandrew unsigned ShAmt = Amt->getZExtValue(); 256295011Sandrew // Cannot analyze non-byte shifts. 257295011Sandrew if ((ShAmt & 7) != 0) 258295011Sandrew return 0; 259295011Sandrew ShAmt >>= 3; 260295011Sandrew 261295011Sandrew // If the extract is known to be all zeros, return zero. 262295011Sandrew if (ByteStart >= CSize-ShAmt) 263295011Sandrew return Constant::getNullValue(IntegerType::get(CE->getContext(), 264295011Sandrew ByteSize*8)); 265295011Sandrew // If the extract is known to be fully in the input, extract it. 266295011Sandrew if (ByteStart+ByteSize+ShAmt <= CSize) 267295011Sandrew return ExtractConstantBytes(CE->getOperand(0), ByteStart+ShAmt, ByteSize); 268295011Sandrew 269295011Sandrew // TODO: Handle the 'partially zero' case. 270295011Sandrew return 0; 271295011Sandrew } 272295011Sandrew 273295011Sandrew case Instruction::Shl: { 274295011Sandrew ConstantInt *Amt = dyn_cast<ConstantInt>(CE->getOperand(1)); 275295011Sandrew if (Amt == 0) 276295011Sandrew return 0; 277295011Sandrew unsigned ShAmt = Amt->getZExtValue(); 278295011Sandrew // Cannot analyze non-byte shifts. 279295011Sandrew if ((ShAmt & 7) != 0) 280295011Sandrew return 0; 281295011Sandrew ShAmt >>= 3; 282295011Sandrew 283295011Sandrew // If the extract is known to be all zeros, return zero. 284295011Sandrew if (ByteStart+ByteSize <= ShAmt) 285295011Sandrew return Constant::getNullValue(IntegerType::get(CE->getContext(), 286295011Sandrew ByteSize*8)); 287295011Sandrew // If the extract is known to be fully in the input, extract it. 288295011Sandrew if (ByteStart >= ShAmt) 289295011Sandrew return ExtractConstantBytes(CE->getOperand(0), ByteStart-ShAmt, ByteSize); 290295011Sandrew 291295011Sandrew // TODO: Handle the 'partially zero' case. 292295011Sandrew return 0; 293295011Sandrew } 294295011Sandrew 295295011Sandrew case Instruction::ZExt: { 296295011Sandrew unsigned SrcBitSize = 297295011Sandrew cast<IntegerType>(CE->getOperand(0)->getType())->getBitWidth(); 298295011Sandrew 299295011Sandrew // If extracting something that is completely zero, return 0. 300295011Sandrew if (ByteStart*8 >= SrcBitSize) 301295011Sandrew return Constant::getNullValue(IntegerType::get(CE->getContext(), 302295011Sandrew ByteSize*8)); 303295011Sandrew 304295011Sandrew // If exactly extracting the input, return it. 305295011Sandrew if (ByteStart == 0 && ByteSize*8 == SrcBitSize) 306295011Sandrew return CE->getOperand(0); 307295011Sandrew 308295011Sandrew // If extracting something completely in the input, if if the input is a 309295011Sandrew // multiple of 8 bits, recurse. 310295011Sandrew if ((SrcBitSize&7) == 0 && (ByteStart+ByteSize)*8 <= SrcBitSize) 311295011Sandrew return ExtractConstantBytes(CE->getOperand(0), ByteStart, ByteSize); 312295011Sandrew 313295011Sandrew // Otherwise, if extracting a subset of the input, which is not multiple of 314295011Sandrew // 8 bits, do a shift and trunc to get the bits. 315295011Sandrew if ((ByteStart+ByteSize)*8 < SrcBitSize) { 316295011Sandrew assert((SrcBitSize&7) && "Shouldn't get byte sized case here"); 317295011Sandrew Constant *Res = CE->getOperand(0); 318295011Sandrew if (ByteStart) 319295011Sandrew Res = ConstantExpr::getLShr(Res, 320295011Sandrew ConstantInt::get(Res->getType(), ByteStart*8)); 321295011Sandrew return ConstantExpr::getTrunc(Res, IntegerType::get(C->getContext(), 322295011Sandrew ByteSize*8)); 323295011Sandrew } 324295011Sandrew 325295011Sandrew // TODO: Handle the 'partially zero' case. 326295011Sandrew return 0; 327295011Sandrew } 328295011Sandrew } 329295011Sandrew} 330295011Sandrew 331295011Sandrew/// getFoldedSizeOf - Return a ConstantExpr with type DestTy for sizeof 332295011Sandrew/// on Ty, with any known factors factored out. If Folded is false, 333295011Sandrew/// return null if no factoring was possible, to avoid endlessly 334295011Sandrew/// bouncing an unfoldable expression back into the top-level folder. 335295011Sandrew/// 336295011Sandrewstatic Constant *getFoldedSizeOf(Type *Ty, Type *DestTy, 337295011Sandrew bool Folded) { 338295011Sandrew if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 339295011Sandrew Constant *N = ConstantInt::get(DestTy, ATy->getNumElements()); 340295011Sandrew Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true); 341295011Sandrew return ConstantExpr::getNUWMul(E, N); 342295011Sandrew } 343295011Sandrew 344295011Sandrew if (StructType *STy = dyn_cast<StructType>(Ty)) 345295011Sandrew if (!STy->isPacked()) { 346295011Sandrew unsigned NumElems = STy->getNumElements(); 347295011Sandrew // An empty struct has size zero. 348295011Sandrew if (NumElems == 0) 349295011Sandrew return ConstantExpr::getNullValue(DestTy); 350295011Sandrew // Check for a struct with all members having the same size. 351295011Sandrew Constant *MemberSize = 352295011Sandrew getFoldedSizeOf(STy->getElementType(0), DestTy, true); 353295011Sandrew bool AllSame = true; 354295011Sandrew for (unsigned i = 1; i != NumElems; ++i) 355295011Sandrew if (MemberSize != 356295011Sandrew getFoldedSizeOf(STy->getElementType(i), DestTy, true)) { 357295011Sandrew AllSame = false; 358295011Sandrew break; 359295011Sandrew } 360295011Sandrew if (AllSame) { 361295011Sandrew Constant *N = ConstantInt::get(DestTy, NumElems); 362295011Sandrew return ConstantExpr::getNUWMul(MemberSize, N); 363295011Sandrew } 364295011Sandrew } 365295011Sandrew 366295011Sandrew // Pointer size doesn't depend on the pointee type, so canonicalize them 367295011Sandrew // to an arbitrary pointee. 368295011Sandrew if (PointerType *PTy = dyn_cast<PointerType>(Ty)) 369295011Sandrew if (!PTy->getElementType()->isIntegerTy(1)) 370295011Sandrew return 371295011Sandrew getFoldedSizeOf(PointerType::get(IntegerType::get(PTy->getContext(), 1), 372295011Sandrew PTy->getAddressSpace()), 373295011Sandrew DestTy, true); 374295011Sandrew 375295011Sandrew // If there's no interesting folding happening, bail so that we don't create 376295011Sandrew // a constant that looks like it needs folding but really doesn't. 377295011Sandrew if (!Folded) 378295011Sandrew return 0; 379295011Sandrew 380295011Sandrew // Base case: Get a regular sizeof expression. 381295011Sandrew Constant *C = ConstantExpr::getSizeOf(Ty); 382295011Sandrew C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 383295011Sandrew DestTy, false), 384295011Sandrew C, DestTy); 385295011Sandrew return C; 386295011Sandrew} 387295011Sandrew 388295011Sandrew/// getFoldedAlignOf - Return a ConstantExpr with type DestTy for alignof 389295011Sandrew/// on Ty, with any known factors factored out. If Folded is false, 390295011Sandrew/// return null if no factoring was possible, to avoid endlessly 391295011Sandrew/// bouncing an unfoldable expression back into the top-level folder. 392295011Sandrew/// 393295011Sandrewstatic Constant *getFoldedAlignOf(Type *Ty, Type *DestTy, 394295011Sandrew bool Folded) { 395295011Sandrew // The alignment of an array is equal to the alignment of the 396295011Sandrew // array element. Note that this is not always true for vectors. 397295011Sandrew if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 398295011Sandrew Constant *C = ConstantExpr::getAlignOf(ATy->getElementType()); 399295011Sandrew C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 400295011Sandrew DestTy, 401295011Sandrew false), 402295011Sandrew C, DestTy); 403295011Sandrew return C; 404295011Sandrew } 405295011Sandrew 406295011Sandrew if (StructType *STy = dyn_cast<StructType>(Ty)) { 407295011Sandrew // Packed structs always have an alignment of 1. 408295011Sandrew if (STy->isPacked()) 409295011Sandrew return ConstantInt::get(DestTy, 1); 410295011Sandrew 411295011Sandrew // Otherwise, struct alignment is the maximum alignment of any member. 412295011Sandrew // Without target data, we can't compare much, but we can check to see 413295011Sandrew // if all the members have the same alignment. 414295011Sandrew unsigned NumElems = STy->getNumElements(); 415295011Sandrew // An empty struct has minimal alignment. 416295011Sandrew if (NumElems == 0) 417295011Sandrew return ConstantInt::get(DestTy, 1); 418295011Sandrew // Check for a struct with all members having the same alignment. 419295011Sandrew Constant *MemberAlign = 420295011Sandrew getFoldedAlignOf(STy->getElementType(0), DestTy, true); 421295011Sandrew bool AllSame = true; 422295011Sandrew for (unsigned i = 1; i != NumElems; ++i) 423295011Sandrew if (MemberAlign != getFoldedAlignOf(STy->getElementType(i), DestTy, true)) { 424295011Sandrew AllSame = false; 425295011Sandrew break; 426295011Sandrew } 427295011Sandrew if (AllSame) 428295011Sandrew return MemberAlign; 429295011Sandrew } 430295011Sandrew 431295011Sandrew // Pointer alignment doesn't depend on the pointee type, so canonicalize them 432295011Sandrew // to an arbitrary pointee. 433295011Sandrew if (PointerType *PTy = dyn_cast<PointerType>(Ty)) 434295011Sandrew if (!PTy->getElementType()->isIntegerTy(1)) 435295011Sandrew return 436295011Sandrew getFoldedAlignOf(PointerType::get(IntegerType::get(PTy->getContext(), 437295011Sandrew 1), 438295011Sandrew PTy->getAddressSpace()), 439295011Sandrew DestTy, true); 440295011Sandrew 441295011Sandrew // If there's no interesting folding happening, bail so that we don't create 442295011Sandrew // a constant that looks like it needs folding but really doesn't. 443295011Sandrew if (!Folded) 444295011Sandrew return 0; 445295011Sandrew 446295011Sandrew // Base case: Get a regular alignof expression. 447295011Sandrew Constant *C = ConstantExpr::getAlignOf(Ty); 448295011Sandrew C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 449295011Sandrew DestTy, false), 450295011Sandrew C, DestTy); 451295011Sandrew return C; 452295011Sandrew} 453295011Sandrew 454295011Sandrew/// getFoldedOffsetOf - Return a ConstantExpr with type DestTy for offsetof 455295011Sandrew/// on Ty and FieldNo, with any known factors factored out. If Folded is false, 456295011Sandrew/// return null if no factoring was possible, to avoid endlessly 457295011Sandrew/// bouncing an unfoldable expression back into the top-level folder. 458295011Sandrew/// 459295011Sandrewstatic Constant *getFoldedOffsetOf(Type *Ty, Constant *FieldNo, 460295011Sandrew Type *DestTy, 461295011Sandrew bool Folded) { 462295011Sandrew if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 463295011Sandrew Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, false, 464295011Sandrew DestTy, false), 465295011Sandrew FieldNo, DestTy); 466295011Sandrew Constant *E = getFoldedSizeOf(ATy->getElementType(), DestTy, true); 467295011Sandrew return ConstantExpr::getNUWMul(E, N); 468295011Sandrew } 469295011Sandrew 470295011Sandrew if (StructType *STy = dyn_cast<StructType>(Ty)) 471295011Sandrew if (!STy->isPacked()) { 472295011Sandrew unsigned NumElems = STy->getNumElements(); 473295011Sandrew // An empty struct has no members. 474295011Sandrew if (NumElems == 0) 475295011Sandrew return 0; 476295011Sandrew // Check for a struct with all members having the same size. 477295011Sandrew Constant *MemberSize = 478295011Sandrew getFoldedSizeOf(STy->getElementType(0), DestTy, true); 479295011Sandrew bool AllSame = true; 480295011Sandrew for (unsigned i = 1; i != NumElems; ++i) 481295011Sandrew if (MemberSize != 482295011Sandrew getFoldedSizeOf(STy->getElementType(i), DestTy, true)) { 483295011Sandrew AllSame = false; 484295011Sandrew break; 485295011Sandrew } 486295011Sandrew if (AllSame) { 487295011Sandrew Constant *N = ConstantExpr::getCast(CastInst::getCastOpcode(FieldNo, 488295011Sandrew false, 489295011Sandrew DestTy, 490295011Sandrew false), 491295011Sandrew FieldNo, DestTy); 492295011Sandrew return ConstantExpr::getNUWMul(MemberSize, N); 493295011Sandrew } 494295011Sandrew } 495295011Sandrew 496295011Sandrew // If there's no interesting folding happening, bail so that we don't create 497295011Sandrew // a constant that looks like it needs folding but really doesn't. 498295011Sandrew if (!Folded) 499295011Sandrew return 0; 500295011Sandrew 501295011Sandrew // Base case: Get a regular offsetof expression. 502295011Sandrew Constant *C = ConstantExpr::getOffsetOf(Ty, FieldNo); 503295011Sandrew C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, 504295011Sandrew DestTy, false), 505295011Sandrew C, DestTy); 506295011Sandrew return C; 507295011Sandrew} 508295011Sandrew 509295011SandrewConstant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V, 510295011Sandrew Type *DestTy) { 511295011Sandrew if (isa<UndefValue>(V)) { 512295011Sandrew // zext(undef) = 0, because the top bits will be zero. 513295011Sandrew // sext(undef) = 0, because the top bits will all be the same. 514295011Sandrew // [us]itofp(undef) = 0, because the result value is bounded. 515295011Sandrew if (opc == Instruction::ZExt || opc == Instruction::SExt || 516295011Sandrew opc == Instruction::UIToFP || opc == Instruction::SIToFP) 517295011Sandrew return Constant::getNullValue(DestTy); 518295011Sandrew return UndefValue::get(DestTy); 519295011Sandrew } 520295011Sandrew 521295011Sandrew if (V->isNullValue() && !DestTy->isX86_MMXTy()) 522295011Sandrew return Constant::getNullValue(DestTy); 523295011Sandrew 524295011Sandrew // If the cast operand is a constant expression, there's a few things we can 525295011Sandrew // do to try to simplify it. 526295011Sandrew if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { 527295011Sandrew if (CE->isCast()) { 528295011Sandrew // Try hard to fold cast of cast because they are often eliminable. 529295011Sandrew if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy)) 530295011Sandrew return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy); 531295011Sandrew } else if (CE->getOpcode() == Instruction::GetElementPtr) { 532295011Sandrew // If all of the indexes in the GEP are null values, there is no pointer 533295011Sandrew // adjustment going on. We might as well cast the source pointer. 534295011Sandrew bool isAllNull = true; 535295011Sandrew for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) 536295011Sandrew if (!CE->getOperand(i)->isNullValue()) { 537295011Sandrew isAllNull = false; 538295011Sandrew break; 539295011Sandrew } 540295011Sandrew if (isAllNull) 541295011Sandrew // This is casting one pointer type to another, always BitCast 542295011Sandrew return ConstantExpr::getPointerCast(CE->getOperand(0), DestTy); 543295011Sandrew } 544295011Sandrew } 545295011Sandrew 546295011Sandrew // If the cast operand is a constant vector, perform the cast by 547295011Sandrew // operating on each element. In the cast of bitcasts, the element 548295011Sandrew // count may be mismatched; don't attempt to handle that here. 549295011Sandrew if ((isa<ConstantVector>(V) || isa<ConstantDataVector>(V)) && 550295011Sandrew DestTy->isVectorTy() && 551295011Sandrew DestTy->getVectorNumElements() == V->getType()->getVectorNumElements()) { 552295011Sandrew SmallVector<Constant*, 16> res; 553295011Sandrew VectorType *DestVecTy = cast<VectorType>(DestTy); 554295011Sandrew Type *DstEltTy = DestVecTy->getElementType(); 555295011Sandrew Type *Ty = IntegerType::get(V->getContext(), 32); 556295011Sandrew for (unsigned i = 0, e = V->getType()->getVectorNumElements(); i != e; ++i) { 557295011Sandrew Constant *C = 558295011Sandrew ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i)); 559295011Sandrew res.push_back(ConstantExpr::getCast(opc, C, DstEltTy)); 560295011Sandrew } 561295011Sandrew return ConstantVector::get(res); 562295011Sandrew } 563295011Sandrew 564295011Sandrew // We actually have to do a cast now. Perform the cast according to the 565295011Sandrew // opcode specified. 566295011Sandrew switch (opc) { 567295011Sandrew default: 568295011Sandrew llvm_unreachable("Failed to cast constant expression"); 569295011Sandrew case Instruction::FPTrunc: 570295011Sandrew case Instruction::FPExt: 571295011Sandrew if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { 572295011Sandrew bool ignored; 573295011Sandrew APFloat Val = FPC->getValueAPF(); 574295011Sandrew Val.convert(DestTy->isHalfTy() ? APFloat::IEEEhalf : 575295011Sandrew DestTy->isFloatTy() ? APFloat::IEEEsingle : 576295011Sandrew DestTy->isDoubleTy() ? APFloat::IEEEdouble : 577295011Sandrew DestTy->isX86_FP80Ty() ? APFloat::x87DoubleExtended : 578295011Sandrew DestTy->isFP128Ty() ? APFloat::IEEEquad : 579295011Sandrew DestTy->isPPC_FP128Ty() ? APFloat::PPCDoubleDouble : 580295011Sandrew APFloat::Bogus, 581295011Sandrew APFloat::rmNearestTiesToEven, &ignored); 582295011Sandrew return ConstantFP::get(V->getContext(), Val); 583295011Sandrew } 584295011Sandrew return 0; // Can't fold. 585295011Sandrew case Instruction::FPToUI: 586295011Sandrew case Instruction::FPToSI: 587295011Sandrew if (ConstantFP *FPC = dyn_cast<ConstantFP>(V)) { 588295011Sandrew const APFloat &V = FPC->getValueAPF(); 589295011Sandrew bool ignored; 590295011Sandrew uint64_t x[2]; 591295011Sandrew uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 592295011Sandrew (void) V.convertToInteger(x, DestBitWidth, opc==Instruction::FPToSI, 593295011Sandrew APFloat::rmTowardZero, &ignored); 594295011Sandrew APInt Val(DestBitWidth, x); 595295011Sandrew return ConstantInt::get(FPC->getContext(), Val); 596295011Sandrew } 597295011Sandrew return 0; // Can't fold. 598295011Sandrew case Instruction::IntToPtr: //always treated as unsigned 599295011Sandrew if (V->isNullValue()) // Is it an integral null value? 600295011Sandrew return ConstantPointerNull::get(cast<PointerType>(DestTy)); 601295011Sandrew return 0; // Other pointer types cannot be casted 602295011Sandrew case Instruction::PtrToInt: // always treated as unsigned 603295011Sandrew // Is it a null pointer value? 604295011Sandrew if (V->isNullValue()) 605295011Sandrew return ConstantInt::get(DestTy, 0); 606295011Sandrew // If this is a sizeof-like expression, pull out multiplications by 607295011Sandrew // known factors to expose them to subsequent folding. If it's an 608295011Sandrew // alignof-like expression, factor out known factors. 609295011Sandrew if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 610295011Sandrew if (CE->getOpcode() == Instruction::GetElementPtr && 611295011Sandrew CE->getOperand(0)->isNullValue()) { 612295011Sandrew Type *Ty = 613295011Sandrew cast<PointerType>(CE->getOperand(0)->getType())->getElementType(); 614295011Sandrew if (CE->getNumOperands() == 2) { 615295011Sandrew // Handle a sizeof-like expression. 616295011Sandrew Constant *Idx = CE->getOperand(1); 617295011Sandrew bool isOne = isa<ConstantInt>(Idx) && cast<ConstantInt>(Idx)->isOne(); 618295011Sandrew if (Constant *C = getFoldedSizeOf(Ty, DestTy, !isOne)) { 619295011Sandrew Idx = ConstantExpr::getCast(CastInst::getCastOpcode(Idx, true, 620295011Sandrew DestTy, false), 621295011Sandrew Idx, DestTy); 622295011Sandrew return ConstantExpr::getMul(C, Idx); 623295011Sandrew } 624295011Sandrew } else if (CE->getNumOperands() == 3 && 625295011Sandrew CE->getOperand(1)->isNullValue()) { 626295011Sandrew // Handle an alignof-like expression. 627295011Sandrew if (StructType *STy = dyn_cast<StructType>(Ty)) 628295011Sandrew if (!STy->isPacked()) { 629295011Sandrew ConstantInt *CI = cast<ConstantInt>(CE->getOperand(2)); 630295011Sandrew if (CI->isOne() && 631295011Sandrew STy->getNumElements() == 2 && 632295011Sandrew STy->getElementType(0)->isIntegerTy(1)) { 633295011Sandrew return getFoldedAlignOf(STy->getElementType(1), DestTy, false); 634295011Sandrew } 635295011Sandrew } 636295011Sandrew // Handle an offsetof-like expression. 637295011Sandrew if (Ty->isStructTy() || Ty->isArrayTy()) { 638295011Sandrew if (Constant *C = getFoldedOffsetOf(Ty, CE->getOperand(2), 639295011Sandrew DestTy, false)) 640295011Sandrew return C; 641295011Sandrew } 642295011Sandrew } 643295011Sandrew } 644295011Sandrew // Other pointer types cannot be casted 645295011Sandrew return 0; 646295011Sandrew case Instruction::UIToFP: 647295011Sandrew case Instruction::SIToFP: 648295011Sandrew if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 649295011Sandrew APInt api = CI->getValue(); 650295011Sandrew APFloat apf(DestTy->getFltSemantics(), 651295011Sandrew APInt::getNullValue(DestTy->getPrimitiveSizeInBits())); 652295011Sandrew (void)apf.convertFromAPInt(api, 653295011Sandrew opc==Instruction::SIToFP, 654295011Sandrew APFloat::rmNearestTiesToEven); 655295011Sandrew return ConstantFP::get(V->getContext(), apf); 656295011Sandrew } 657295011Sandrew return 0; 658295011Sandrew case Instruction::ZExt: 659295011Sandrew if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 660295011Sandrew uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 661295011Sandrew return ConstantInt::get(V->getContext(), 662295011Sandrew CI->getValue().zext(BitWidth)); 663295011Sandrew } 664295011Sandrew return 0; 665295011Sandrew case Instruction::SExt: 666295011Sandrew if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 667295011Sandrew uint32_t BitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 668295011Sandrew return ConstantInt::get(V->getContext(), 669295011Sandrew CI->getValue().sext(BitWidth)); 670295011Sandrew } 671295011Sandrew return 0; 672295011Sandrew case Instruction::Trunc: { 673295011Sandrew uint32_t DestBitWidth = cast<IntegerType>(DestTy)->getBitWidth(); 674295011Sandrew if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) { 675295011Sandrew return ConstantInt::get(V->getContext(), 676295011Sandrew CI->getValue().trunc(DestBitWidth)); 677295011Sandrew } 678295011Sandrew 679295011Sandrew // The input must be a constantexpr. See if we can simplify this based on 680295011Sandrew // the bytes we are demanding. Only do this if the source and dest are an 681295011Sandrew // even multiple of a byte. 682295011Sandrew if ((DestBitWidth & 7) == 0 && 683295011Sandrew (cast<IntegerType>(V->getType())->getBitWidth() & 7) == 0) 684295011Sandrew if (Constant *Res = ExtractConstantBytes(V, 0, DestBitWidth / 8)) 685295011Sandrew return Res; 686295011Sandrew 687295011Sandrew return 0; 688295011Sandrew } 689295011Sandrew case Instruction::BitCast: 690295011Sandrew return FoldBitCast(V, DestTy); 691295011Sandrew } 692295011Sandrew} 693295011Sandrew 694295011SandrewConstant *llvm::ConstantFoldSelectInstruction(Constant *Cond, 695295011Sandrew Constant *V1, Constant *V2) { 696295011Sandrew // Check for i1 and vector true/false conditions. 697295011Sandrew if (Cond->isNullValue()) return V2; 698295011Sandrew if (Cond->isAllOnesValue()) return V1; 699295011Sandrew 700295011Sandrew // If the condition is a vector constant, fold the result elementwise. 701295011Sandrew if (ConstantVector *CondV = dyn_cast<ConstantVector>(Cond)) { 702295011Sandrew SmallVector<Constant*, 16> Result; 703295011Sandrew Type *Ty = IntegerType::get(CondV->getContext(), 32); 704295011Sandrew for (unsigned i = 0, e = V1->getType()->getVectorNumElements(); i != e;++i){ 705295011Sandrew ConstantInt *Cond = dyn_cast<ConstantInt>(CondV->getOperand(i)); 706295011Sandrew if (Cond == 0) break; 707295011Sandrew 708295011Sandrew Constant *V = Cond->isNullValue() ? V2 : V1; 709295011Sandrew Constant *Res = ConstantExpr::getExtractElement(V, ConstantInt::get(Ty, i)); 710295011Sandrew Result.push_back(Res); 711295011Sandrew } 712295011Sandrew 713295011Sandrew // If we were able to build the vector, return it. 714295011Sandrew if (Result.size() == V1->getType()->getVectorNumElements()) 715295011Sandrew return ConstantVector::get(Result); 716295011Sandrew } 717295011Sandrew 718295011Sandrew if (isa<UndefValue>(Cond)) { 719295011Sandrew if (isa<UndefValue>(V1)) return V1; 720295011Sandrew return V2; 721295011Sandrew } 722295011Sandrew if (isa<UndefValue>(V1)) return V2; 723295011Sandrew if (isa<UndefValue>(V2)) return V1; 724295011Sandrew if (V1 == V2) return V1; 725295011Sandrew 726295011Sandrew if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) { 727295011Sandrew if (TrueVal->getOpcode() == Instruction::Select) 728295011Sandrew if (TrueVal->getOperand(0) == Cond) 729295011Sandrew return ConstantExpr::getSelect(Cond, TrueVal->getOperand(1), V2); 730295011Sandrew } 731295011Sandrew if (ConstantExpr *FalseVal = dyn_cast<ConstantExpr>(V2)) { 732295011Sandrew if (FalseVal->getOpcode() == Instruction::Select) 733295011Sandrew if (FalseVal->getOperand(0) == Cond) 734295011Sandrew return ConstantExpr::getSelect(Cond, V1, FalseVal->getOperand(2)); 735295011Sandrew } 736295011Sandrew 737295011Sandrew return 0; 738295011Sandrew} 739295011Sandrew 740295011SandrewConstant *llvm::ConstantFoldExtractElementInstruction(Constant *Val, 741295011Sandrew Constant *Idx) { 742295011Sandrew if (isa<UndefValue>(Val)) // ee(undef, x) -> undef 743295011Sandrew return UndefValue::get(Val->getType()->getVectorElementType()); 744295011Sandrew if (Val->isNullValue()) // ee(zero, x) -> zero 745295011Sandrew return Constant::getNullValue(Val->getType()->getVectorElementType()); 746295011Sandrew // ee({w,x,y,z}, undef) -> undef 747295011Sandrew if (isa<UndefValue>(Idx)) 748295011Sandrew return UndefValue::get(Val->getType()->getVectorElementType()); 749295011Sandrew 750295011Sandrew if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) { 751295011Sandrew uint64_t Index = CIdx->getZExtValue(); 752295011Sandrew // ee({w,x,y,z}, wrong_value) -> undef 753295011Sandrew if (Index >= Val->getType()->getVectorNumElements()) 754295011Sandrew return UndefValue::get(Val->getType()->getVectorElementType()); 755295011Sandrew return Val->getAggregateElement(Index); 756295011Sandrew } 757295011Sandrew return 0; 758295011Sandrew} 759295011Sandrew 760295011SandrewConstant *llvm::ConstantFoldInsertElementInstruction(Constant *Val, 761295011Sandrew Constant *Elt, 762295011Sandrew Constant *Idx) { 763295011Sandrew ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx); 764295011Sandrew if (!CIdx) return 0; 765295011Sandrew const APInt &IdxVal = CIdx->getValue(); 766295011Sandrew 767295011Sandrew SmallVector<Constant*, 16> Result; 768295011Sandrew Type *Ty = IntegerType::get(Val->getContext(), 32); 769295011Sandrew for (unsigned i = 0, e = Val->getType()->getVectorNumElements(); i != e; ++i){ 770295011Sandrew if (i == IdxVal) { 771295011Sandrew Result.push_back(Elt); 772295011Sandrew continue; 773295011Sandrew } 774295011Sandrew 775295011Sandrew Constant *C = 776295011Sandrew ConstantExpr::getExtractElement(Val, ConstantInt::get(Ty, i)); 777295011Sandrew Result.push_back(C); 778295011Sandrew } 779295011Sandrew 780295011Sandrew return ConstantVector::get(Result); 781295011Sandrew} 782295011Sandrew 783295011SandrewConstant *llvm::ConstantFoldShuffleVectorInstruction(Constant *V1, 784295011Sandrew Constant *V2, 785295011Sandrew Constant *Mask) { 786295011Sandrew unsigned MaskNumElts = Mask->getType()->getVectorNumElements(); 787295011Sandrew Type *EltTy = V1->getType()->getVectorElementType(); 788295011Sandrew 789295011Sandrew // Undefined shuffle mask -> undefined value. 790295011Sandrew if (isa<UndefValue>(Mask)) 791295011Sandrew return UndefValue::get(VectorType::get(EltTy, MaskNumElts)); 792295011Sandrew 793295011Sandrew // Don't break the bitcode reader hack. 794295011Sandrew if (isa<ConstantExpr>(Mask)) return 0; 795295011Sandrew 796295011Sandrew unsigned SrcNumElts = V1->getType()->getVectorNumElements(); 797295011Sandrew 798295011Sandrew // Loop over the shuffle mask, evaluating each element. 799295011Sandrew SmallVector<Constant*, 32> Result; 800295011Sandrew for (unsigned i = 0; i != MaskNumElts; ++i) { 801295011Sandrew int Elt = ShuffleVectorInst::getMaskValue(Mask, i); 802295011Sandrew if (Elt == -1) { 803295011Sandrew Result.push_back(UndefValue::get(EltTy)); 804295011Sandrew continue; 805295011Sandrew } 806295011Sandrew Constant *InElt; 807295011Sandrew if (unsigned(Elt) >= SrcNumElts*2) 808295011Sandrew InElt = UndefValue::get(EltTy); 809295011Sandrew else if (unsigned(Elt) >= SrcNumElts) { 810295011Sandrew Type *Ty = IntegerType::get(V2->getContext(), 32); 811295011Sandrew InElt = 812295011Sandrew ConstantExpr::getExtractElement(V2, 813295011Sandrew ConstantInt::get(Ty, Elt - SrcNumElts)); 814295011Sandrew } else { 815295011Sandrew Type *Ty = IntegerType::get(V1->getContext(), 32); 816295011Sandrew InElt = ConstantExpr::getExtractElement(V1, ConstantInt::get(Ty, Elt)); 817295011Sandrew } 818295011Sandrew Result.push_back(InElt); 819295011Sandrew } 820295011Sandrew 821295011Sandrew return ConstantVector::get(Result); 822295011Sandrew} 823295011Sandrew 824295011SandrewConstant *llvm::ConstantFoldExtractValueInstruction(Constant *Agg, 825295011Sandrew ArrayRef<unsigned> Idxs) { 826295011Sandrew // Base case: no indices, so return the entire value. 827295011Sandrew if (Idxs.empty()) 828295011Sandrew return Agg; 829295011Sandrew 830295011Sandrew if (Constant *C = Agg->getAggregateElement(Idxs[0])) 831295011Sandrew return ConstantFoldExtractValueInstruction(C, Idxs.slice(1)); 832295011Sandrew 833295011Sandrew return 0; 834295011Sandrew} 835295011Sandrew 836295011SandrewConstant *llvm::ConstantFoldInsertValueInstruction(Constant *Agg, 837295011Sandrew Constant *Val, 838295011Sandrew ArrayRef<unsigned> Idxs) { 839295011Sandrew // Base case: no indices, so replace the entire value. 840295011Sandrew if (Idxs.empty()) 841295011Sandrew return Val; 842295011Sandrew 843295011Sandrew unsigned NumElts; 844295011Sandrew if (StructType *ST = dyn_cast<StructType>(Agg->getType())) 845295011Sandrew NumElts = ST->getNumElements(); 846295011Sandrew else if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType())) 847295011Sandrew NumElts = AT->getNumElements(); 848295011Sandrew else 849295011Sandrew NumElts = Agg->getType()->getVectorNumElements(); 850295011Sandrew 851295011Sandrew SmallVector<Constant*, 32> Result; 852295011Sandrew for (unsigned i = 0; i != NumElts; ++i) { 853295011Sandrew Constant *C = Agg->getAggregateElement(i); 854295011Sandrew if (C == 0) return 0; 855295011Sandrew 856295011Sandrew if (Idxs[0] == i) 857295011Sandrew C = ConstantFoldInsertValueInstruction(C, Val, Idxs.slice(1)); 858295011Sandrew 859295011Sandrew Result.push_back(C); 860295011Sandrew } 861295011Sandrew 862295011Sandrew if (StructType *ST = dyn_cast<StructType>(Agg->getType())) 863295011Sandrew return ConstantStruct::get(ST, Result); 864295011Sandrew if (ArrayType *AT = dyn_cast<ArrayType>(Agg->getType())) 865295011Sandrew return ConstantArray::get(AT, Result); 866295011Sandrew return ConstantVector::get(Result); 867295011Sandrew} 868295011Sandrew 869295011Sandrew 870295011SandrewConstant *llvm::ConstantFoldBinaryInstruction(unsigned Opcode, 871295011Sandrew Constant *C1, Constant *C2) { 872295011Sandrew // Handle UndefValue up front. 873295011Sandrew if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { 874 switch (Opcode) { 875 case Instruction::Xor: 876 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) 877 // Handle undef ^ undef -> 0 special case. This is a common 878 // idiom (misuse). 879 return Constant::getNullValue(C1->getType()); 880 // Fallthrough 881 case Instruction::Add: 882 case Instruction::Sub: 883 return UndefValue::get(C1->getType()); 884 case Instruction::And: 885 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef & undef -> undef 886 return C1; 887 return Constant::getNullValue(C1->getType()); // undef & X -> 0 888 case Instruction::Mul: { 889 ConstantInt *CI; 890 // X * undef -> undef if X is odd or undef 891 if (((CI = dyn_cast<ConstantInt>(C1)) && CI->getValue()[0]) || 892 ((CI = dyn_cast<ConstantInt>(C2)) && CI->getValue()[0]) || 893 (isa<UndefValue>(C1) && isa<UndefValue>(C2))) 894 return UndefValue::get(C1->getType()); 895 896 // X * undef -> 0 otherwise 897 return Constant::getNullValue(C1->getType()); 898 } 899 case Instruction::UDiv: 900 case Instruction::SDiv: 901 // undef / 1 -> undef 902 if (Opcode == Instruction::UDiv || Opcode == Instruction::SDiv) 903 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) 904 if (CI2->isOne()) 905 return C1; 906 // FALL THROUGH 907 case Instruction::URem: 908 case Instruction::SRem: 909 if (!isa<UndefValue>(C2)) // undef / X -> 0 910 return Constant::getNullValue(C1->getType()); 911 return C2; // X / undef -> undef 912 case Instruction::Or: // X | undef -> -1 913 if (isa<UndefValue>(C1) && isa<UndefValue>(C2)) // undef | undef -> undef 914 return C1; 915 return Constant::getAllOnesValue(C1->getType()); // undef | X -> ~0 916 case Instruction::LShr: 917 if (isa<UndefValue>(C2) && isa<UndefValue>(C1)) 918 return C1; // undef lshr undef -> undef 919 return Constant::getNullValue(C1->getType()); // X lshr undef -> 0 920 // undef lshr X -> 0 921 case Instruction::AShr: 922 if (!isa<UndefValue>(C2)) // undef ashr X --> all ones 923 return Constant::getAllOnesValue(C1->getType()); 924 else if (isa<UndefValue>(C1)) 925 return C1; // undef ashr undef -> undef 926 else 927 return C1; // X ashr undef --> X 928 case Instruction::Shl: 929 if (isa<UndefValue>(C2) && isa<UndefValue>(C1)) 930 return C1; // undef shl undef -> undef 931 // undef << X -> 0 or X << undef -> 0 932 return Constant::getNullValue(C1->getType()); 933 } 934 } 935 936 // Handle simplifications when the RHS is a constant int. 937 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 938 switch (Opcode) { 939 case Instruction::Add: 940 if (CI2->equalsInt(0)) return C1; // X + 0 == X 941 break; 942 case Instruction::Sub: 943 if (CI2->equalsInt(0)) return C1; // X - 0 == X 944 break; 945 case Instruction::Mul: 946 if (CI2->equalsInt(0)) return C2; // X * 0 == 0 947 if (CI2->equalsInt(1)) 948 return C1; // X * 1 == X 949 break; 950 case Instruction::UDiv: 951 case Instruction::SDiv: 952 if (CI2->equalsInt(1)) 953 return C1; // X / 1 == X 954 if (CI2->equalsInt(0)) 955 return UndefValue::get(CI2->getType()); // X / 0 == undef 956 break; 957 case Instruction::URem: 958 case Instruction::SRem: 959 if (CI2->equalsInt(1)) 960 return Constant::getNullValue(CI2->getType()); // X % 1 == 0 961 if (CI2->equalsInt(0)) 962 return UndefValue::get(CI2->getType()); // X % 0 == undef 963 break; 964 case Instruction::And: 965 if (CI2->isZero()) return C2; // X & 0 == 0 966 if (CI2->isAllOnesValue()) 967 return C1; // X & -1 == X 968 969 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 970 // (zext i32 to i64) & 4294967295 -> (zext i32 to i64) 971 if (CE1->getOpcode() == Instruction::ZExt) { 972 unsigned DstWidth = CI2->getType()->getBitWidth(); 973 unsigned SrcWidth = 974 CE1->getOperand(0)->getType()->getPrimitiveSizeInBits(); 975 APInt PossiblySetBits(APInt::getLowBitsSet(DstWidth, SrcWidth)); 976 if ((PossiblySetBits & CI2->getValue()) == PossiblySetBits) 977 return C1; 978 } 979 980 // If and'ing the address of a global with a constant, fold it. 981 if (CE1->getOpcode() == Instruction::PtrToInt && 982 isa<GlobalValue>(CE1->getOperand(0))) { 983 GlobalValue *GV = cast<GlobalValue>(CE1->getOperand(0)); 984 985 // Functions are at least 4-byte aligned. 986 unsigned GVAlign = GV->getAlignment(); 987 if (isa<Function>(GV)) 988 GVAlign = std::max(GVAlign, 4U); 989 990 if (GVAlign > 1) { 991 unsigned DstWidth = CI2->getType()->getBitWidth(); 992 unsigned SrcWidth = std::min(DstWidth, Log2_32(GVAlign)); 993 APInt BitsNotSet(APInt::getLowBitsSet(DstWidth, SrcWidth)); 994 995 // If checking bits we know are clear, return zero. 996 if ((CI2->getValue() & BitsNotSet) == CI2->getValue()) 997 return Constant::getNullValue(CI2->getType()); 998 } 999 } 1000 } 1001 break; 1002 case Instruction::Or: 1003 if (CI2->equalsInt(0)) return C1; // X | 0 == X 1004 if (CI2->isAllOnesValue()) 1005 return C2; // X | -1 == -1 1006 break; 1007 case Instruction::Xor: 1008 if (CI2->equalsInt(0)) return C1; // X ^ 0 == X 1009 1010 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 1011 switch (CE1->getOpcode()) { 1012 default: break; 1013 case Instruction::ICmp: 1014 case Instruction::FCmp: 1015 // cmp pred ^ true -> cmp !pred 1016 assert(CI2->equalsInt(1)); 1017 CmpInst::Predicate pred = (CmpInst::Predicate)CE1->getPredicate(); 1018 pred = CmpInst::getInversePredicate(pred); 1019 return ConstantExpr::getCompare(pred, CE1->getOperand(0), 1020 CE1->getOperand(1)); 1021 } 1022 } 1023 break; 1024 case Instruction::AShr: 1025 // ashr (zext C to Ty), C2 -> lshr (zext C, CSA), C2 1026 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) 1027 if (CE1->getOpcode() == Instruction::ZExt) // Top bits known zero. 1028 return ConstantExpr::getLShr(C1, C2); 1029 break; 1030 } 1031 } else if (isa<ConstantInt>(C1)) { 1032 // If C1 is a ConstantInt and C2 is not, swap the operands. 1033 if (Instruction::isCommutative(Opcode)) 1034 return ConstantExpr::get(Opcode, C2, C1); 1035 } 1036 1037 // At this point we know neither constant is an UndefValue. 1038 if (ConstantInt *CI1 = dyn_cast<ConstantInt>(C1)) { 1039 if (ConstantInt *CI2 = dyn_cast<ConstantInt>(C2)) { 1040 const APInt &C1V = CI1->getValue(); 1041 const APInt &C2V = CI2->getValue(); 1042 switch (Opcode) { 1043 default: 1044 break; 1045 case Instruction::Add: 1046 return ConstantInt::get(CI1->getContext(), C1V + C2V); 1047 case Instruction::Sub: 1048 return ConstantInt::get(CI1->getContext(), C1V - C2V); 1049 case Instruction::Mul: 1050 return ConstantInt::get(CI1->getContext(), C1V * C2V); 1051 case Instruction::UDiv: 1052 assert(!CI2->isNullValue() && "Div by zero handled above"); 1053 return ConstantInt::get(CI1->getContext(), C1V.udiv(C2V)); 1054 case Instruction::SDiv: 1055 assert(!CI2->isNullValue() && "Div by zero handled above"); 1056 if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) 1057 return UndefValue::get(CI1->getType()); // MIN_INT / -1 -> undef 1058 return ConstantInt::get(CI1->getContext(), C1V.sdiv(C2V)); 1059 case Instruction::URem: 1060 assert(!CI2->isNullValue() && "Div by zero handled above"); 1061 return ConstantInt::get(CI1->getContext(), C1V.urem(C2V)); 1062 case Instruction::SRem: 1063 assert(!CI2->isNullValue() && "Div by zero handled above"); 1064 if (C2V.isAllOnesValue() && C1V.isMinSignedValue()) 1065 return UndefValue::get(CI1->getType()); // MIN_INT % -1 -> undef 1066 return ConstantInt::get(CI1->getContext(), C1V.srem(C2V)); 1067 case Instruction::And: 1068 return ConstantInt::get(CI1->getContext(), C1V & C2V); 1069 case Instruction::Or: 1070 return ConstantInt::get(CI1->getContext(), C1V | C2V); 1071 case Instruction::Xor: 1072 return ConstantInt::get(CI1->getContext(), C1V ^ C2V); 1073 case Instruction::Shl: { 1074 uint32_t shiftAmt = C2V.getZExtValue(); 1075 if (shiftAmt < C1V.getBitWidth()) 1076 return ConstantInt::get(CI1->getContext(), C1V.shl(shiftAmt)); 1077 else 1078 return UndefValue::get(C1->getType()); // too big shift is undef 1079 } 1080 case Instruction::LShr: { 1081 uint32_t shiftAmt = C2V.getZExtValue(); 1082 if (shiftAmt < C1V.getBitWidth()) 1083 return ConstantInt::get(CI1->getContext(), C1V.lshr(shiftAmt)); 1084 else 1085 return UndefValue::get(C1->getType()); // too big shift is undef 1086 } 1087 case Instruction::AShr: { 1088 uint32_t shiftAmt = C2V.getZExtValue(); 1089 if (shiftAmt < C1V.getBitWidth()) 1090 return ConstantInt::get(CI1->getContext(), C1V.ashr(shiftAmt)); 1091 else 1092 return UndefValue::get(C1->getType()); // too big shift is undef 1093 } 1094 } 1095 } 1096 1097 switch (Opcode) { 1098 case Instruction::SDiv: 1099 case Instruction::UDiv: 1100 case Instruction::URem: 1101 case Instruction::SRem: 1102 case Instruction::LShr: 1103 case Instruction::AShr: 1104 case Instruction::Shl: 1105 if (CI1->equalsInt(0)) return C1; 1106 break; 1107 default: 1108 break; 1109 } 1110 } else if (ConstantFP *CFP1 = dyn_cast<ConstantFP>(C1)) { 1111 if (ConstantFP *CFP2 = dyn_cast<ConstantFP>(C2)) { 1112 APFloat C1V = CFP1->getValueAPF(); 1113 APFloat C2V = CFP2->getValueAPF(); 1114 APFloat C3V = C1V; // copy for modification 1115 switch (Opcode) { 1116 default: 1117 break; 1118 case Instruction::FAdd: 1119 (void)C3V.add(C2V, APFloat::rmNearestTiesToEven); 1120 return ConstantFP::get(C1->getContext(), C3V); 1121 case Instruction::FSub: 1122 (void)C3V.subtract(C2V, APFloat::rmNearestTiesToEven); 1123 return ConstantFP::get(C1->getContext(), C3V); 1124 case Instruction::FMul: 1125 (void)C3V.multiply(C2V, APFloat::rmNearestTiesToEven); 1126 return ConstantFP::get(C1->getContext(), C3V); 1127 case Instruction::FDiv: 1128 (void)C3V.divide(C2V, APFloat::rmNearestTiesToEven); 1129 return ConstantFP::get(C1->getContext(), C3V); 1130 case Instruction::FRem: 1131 (void)C3V.mod(C2V, APFloat::rmNearestTiesToEven); 1132 return ConstantFP::get(C1->getContext(), C3V); 1133 } 1134 } 1135 } else if (VectorType *VTy = dyn_cast<VectorType>(C1->getType())) { 1136 // Perform elementwise folding. 1137 SmallVector<Constant*, 16> Result; 1138 Type *Ty = IntegerType::get(VTy->getContext(), 32); 1139 for (unsigned i = 0, e = VTy->getNumElements(); i != e; ++i) { 1140 Constant *LHS = 1141 ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i)); 1142 Constant *RHS = 1143 ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i)); 1144 1145 Result.push_back(ConstantExpr::get(Opcode, LHS, RHS)); 1146 } 1147 1148 return ConstantVector::get(Result); 1149 } 1150 1151 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 1152 // There are many possible foldings we could do here. We should probably 1153 // at least fold add of a pointer with an integer into the appropriate 1154 // getelementptr. This will improve alias analysis a bit. 1155 1156 // Given ((a + b) + c), if (b + c) folds to something interesting, return 1157 // (a + (b + c)). 1158 if (Instruction::isAssociative(Opcode) && CE1->getOpcode() == Opcode) { 1159 Constant *T = ConstantExpr::get(Opcode, CE1->getOperand(1), C2); 1160 if (!isa<ConstantExpr>(T) || cast<ConstantExpr>(T)->getOpcode() != Opcode) 1161 return ConstantExpr::get(Opcode, CE1->getOperand(0), T); 1162 } 1163 } else if (isa<ConstantExpr>(C2)) { 1164 // If C2 is a constant expr and C1 isn't, flop them around and fold the 1165 // other way if possible. 1166 if (Instruction::isCommutative(Opcode)) 1167 return ConstantFoldBinaryInstruction(Opcode, C2, C1); 1168 } 1169 1170 // i1 can be simplified in many cases. 1171 if (C1->getType()->isIntegerTy(1)) { 1172 switch (Opcode) { 1173 case Instruction::Add: 1174 case Instruction::Sub: 1175 return ConstantExpr::getXor(C1, C2); 1176 case Instruction::Mul: 1177 return ConstantExpr::getAnd(C1, C2); 1178 case Instruction::Shl: 1179 case Instruction::LShr: 1180 case Instruction::AShr: 1181 // We can assume that C2 == 0. If it were one the result would be 1182 // undefined because the shift value is as large as the bitwidth. 1183 return C1; 1184 case Instruction::SDiv: 1185 case Instruction::UDiv: 1186 // We can assume that C2 == 1. If it were zero the result would be 1187 // undefined through division by zero. 1188 return C1; 1189 case Instruction::URem: 1190 case Instruction::SRem: 1191 // We can assume that C2 == 1. If it were zero the result would be 1192 // undefined through division by zero. 1193 return ConstantInt::getFalse(C1->getContext()); 1194 default: 1195 break; 1196 } 1197 } 1198 1199 // We don't know how to fold this. 1200 return 0; 1201} 1202 1203/// isZeroSizedType - This type is zero sized if its an array or structure of 1204/// zero sized types. The only leaf zero sized type is an empty structure. 1205static bool isMaybeZeroSizedType(Type *Ty) { 1206 if (StructType *STy = dyn_cast<StructType>(Ty)) { 1207 if (STy->isOpaque()) return true; // Can't say. 1208 1209 // If all of elements have zero size, this does too. 1210 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) 1211 if (!isMaybeZeroSizedType(STy->getElementType(i))) return false; 1212 return true; 1213 1214 } else if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) { 1215 return isMaybeZeroSizedType(ATy->getElementType()); 1216 } 1217 return false; 1218} 1219 1220/// IdxCompare - Compare the two constants as though they were getelementptr 1221/// indices. This allows coersion of the types to be the same thing. 1222/// 1223/// If the two constants are the "same" (after coersion), return 0. If the 1224/// first is less than the second, return -1, if the second is less than the 1225/// first, return 1. If the constants are not integral, return -2. 1226/// 1227static int IdxCompare(Constant *C1, Constant *C2, Type *ElTy) { 1228 if (C1 == C2) return 0; 1229 1230 // Ok, we found a different index. If they are not ConstantInt, we can't do 1231 // anything with them. 1232 if (!isa<ConstantInt>(C1) || !isa<ConstantInt>(C2)) 1233 return -2; // don't know! 1234 1235 // Ok, we have two differing integer indices. Sign extend them to be the same 1236 // type. Long is always big enough, so we use it. 1237 if (!C1->getType()->isIntegerTy(64)) 1238 C1 = ConstantExpr::getSExt(C1, Type::getInt64Ty(C1->getContext())); 1239 1240 if (!C2->getType()->isIntegerTy(64)) 1241 C2 = ConstantExpr::getSExt(C2, Type::getInt64Ty(C1->getContext())); 1242 1243 if (C1 == C2) return 0; // They are equal 1244 1245 // If the type being indexed over is really just a zero sized type, there is 1246 // no pointer difference being made here. 1247 if (isMaybeZeroSizedType(ElTy)) 1248 return -2; // dunno. 1249 1250 // If they are really different, now that they are the same type, then we 1251 // found a difference! 1252 if (cast<ConstantInt>(C1)->getSExtValue() < 1253 cast<ConstantInt>(C2)->getSExtValue()) 1254 return -1; 1255 else 1256 return 1; 1257} 1258 1259/// evaluateFCmpRelation - This function determines if there is anything we can 1260/// decide about the two constants provided. This doesn't need to handle simple 1261/// things like ConstantFP comparisons, but should instead handle ConstantExprs. 1262/// If we can determine that the two constants have a particular relation to 1263/// each other, we should return the corresponding FCmpInst predicate, 1264/// otherwise return FCmpInst::BAD_FCMP_PREDICATE. This is used below in 1265/// ConstantFoldCompareInstruction. 1266/// 1267/// To simplify this code we canonicalize the relation so that the first 1268/// operand is always the most "complex" of the two. We consider ConstantFP 1269/// to be the simplest, and ConstantExprs to be the most complex. 1270static FCmpInst::Predicate evaluateFCmpRelation(Constant *V1, Constant *V2) { 1271 assert(V1->getType() == V2->getType() && 1272 "Cannot compare values of different types!"); 1273 1274 // Handle degenerate case quickly 1275 if (V1 == V2) return FCmpInst::FCMP_OEQ; 1276 1277 if (!isa<ConstantExpr>(V1)) { 1278 if (!isa<ConstantExpr>(V2)) { 1279 // We distilled thisUse the standard constant folder for a few cases 1280 ConstantInt *R = 0; 1281 R = dyn_cast<ConstantInt>( 1282 ConstantExpr::getFCmp(FCmpInst::FCMP_OEQ, V1, V2)); 1283 if (R && !R->isZero()) 1284 return FCmpInst::FCMP_OEQ; 1285 R = dyn_cast<ConstantInt>( 1286 ConstantExpr::getFCmp(FCmpInst::FCMP_OLT, V1, V2)); 1287 if (R && !R->isZero()) 1288 return FCmpInst::FCMP_OLT; 1289 R = dyn_cast<ConstantInt>( 1290 ConstantExpr::getFCmp(FCmpInst::FCMP_OGT, V1, V2)); 1291 if (R && !R->isZero()) 1292 return FCmpInst::FCMP_OGT; 1293 1294 // Nothing more we can do 1295 return FCmpInst::BAD_FCMP_PREDICATE; 1296 } 1297 1298 // If the first operand is simple and second is ConstantExpr, swap operands. 1299 FCmpInst::Predicate SwappedRelation = evaluateFCmpRelation(V2, V1); 1300 if (SwappedRelation != FCmpInst::BAD_FCMP_PREDICATE) 1301 return FCmpInst::getSwappedPredicate(SwappedRelation); 1302 } else { 1303 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 1304 // constantexpr or a simple constant. 1305 ConstantExpr *CE1 = cast<ConstantExpr>(V1); 1306 switch (CE1->getOpcode()) { 1307 case Instruction::FPTrunc: 1308 case Instruction::FPExt: 1309 case Instruction::UIToFP: 1310 case Instruction::SIToFP: 1311 // We might be able to do something with these but we don't right now. 1312 break; 1313 default: 1314 break; 1315 } 1316 } 1317 // There are MANY other foldings that we could perform here. They will 1318 // probably be added on demand, as they seem needed. 1319 return FCmpInst::BAD_FCMP_PREDICATE; 1320} 1321 1322/// evaluateICmpRelation - This function determines if there is anything we can 1323/// decide about the two constants provided. This doesn't need to handle simple 1324/// things like integer comparisons, but should instead handle ConstantExprs 1325/// and GlobalValues. If we can determine that the two constants have a 1326/// particular relation to each other, we should return the corresponding ICmp 1327/// predicate, otherwise return ICmpInst::BAD_ICMP_PREDICATE. 1328/// 1329/// To simplify this code we canonicalize the relation so that the first 1330/// operand is always the most "complex" of the two. We consider simple 1331/// constants (like ConstantInt) to be the simplest, followed by 1332/// GlobalValues, followed by ConstantExpr's (the most complex). 1333/// 1334static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2, 1335 bool isSigned) { 1336 assert(V1->getType() == V2->getType() && 1337 "Cannot compare different types of values!"); 1338 if (V1 == V2) return ICmpInst::ICMP_EQ; 1339 1340 if (!isa<ConstantExpr>(V1) && !isa<GlobalValue>(V1) && 1341 !isa<BlockAddress>(V1)) { 1342 if (!isa<GlobalValue>(V2) && !isa<ConstantExpr>(V2) && 1343 !isa<BlockAddress>(V2)) { 1344 // We distilled this down to a simple case, use the standard constant 1345 // folder. 1346 ConstantInt *R = 0; 1347 ICmpInst::Predicate pred = ICmpInst::ICMP_EQ; 1348 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); 1349 if (R && !R->isZero()) 1350 return pred; 1351 pred = isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1352 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); 1353 if (R && !R->isZero()) 1354 return pred; 1355 pred = isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1356 R = dyn_cast<ConstantInt>(ConstantExpr::getICmp(pred, V1, V2)); 1357 if (R && !R->isZero()) 1358 return pred; 1359 1360 // If we couldn't figure it out, bail. 1361 return ICmpInst::BAD_ICMP_PREDICATE; 1362 } 1363 1364 // If the first operand is simple, swap operands. 1365 ICmpInst::Predicate SwappedRelation = 1366 evaluateICmpRelation(V2, V1, isSigned); 1367 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1368 return ICmpInst::getSwappedPredicate(SwappedRelation); 1369 1370 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(V1)) { 1371 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 1372 ICmpInst::Predicate SwappedRelation = 1373 evaluateICmpRelation(V2, V1, isSigned); 1374 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1375 return ICmpInst::getSwappedPredicate(SwappedRelation); 1376 return ICmpInst::BAD_ICMP_PREDICATE; 1377 } 1378 1379 // Now we know that the RHS is a GlobalValue, BlockAddress or simple 1380 // constant (which, since the types must match, means that it's a 1381 // ConstantPointerNull). 1382 if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) { 1383 // Don't try to decide equality of aliases. 1384 if (!isa<GlobalAlias>(GV) && !isa<GlobalAlias>(GV2)) 1385 if (!GV->hasExternalWeakLinkage() || !GV2->hasExternalWeakLinkage()) 1386 return ICmpInst::ICMP_NE; 1387 } else if (isa<BlockAddress>(V2)) { 1388 return ICmpInst::ICMP_NE; // Globals never equal labels. 1389 } else { 1390 assert(isa<ConstantPointerNull>(V2) && "Canonicalization guarantee!"); 1391 // GlobalVals can never be null unless they have external weak linkage. 1392 // We don't try to evaluate aliases here. 1393 if (!GV->hasExternalWeakLinkage() && !isa<GlobalAlias>(GV)) 1394 return ICmpInst::ICMP_NE; 1395 } 1396 } else if (const BlockAddress *BA = dyn_cast<BlockAddress>(V1)) { 1397 if (isa<ConstantExpr>(V2)) { // Swap as necessary. 1398 ICmpInst::Predicate SwappedRelation = 1399 evaluateICmpRelation(V2, V1, isSigned); 1400 if (SwappedRelation != ICmpInst::BAD_ICMP_PREDICATE) 1401 return ICmpInst::getSwappedPredicate(SwappedRelation); 1402 return ICmpInst::BAD_ICMP_PREDICATE; 1403 } 1404 1405 // Now we know that the RHS is a GlobalValue, BlockAddress or simple 1406 // constant (which, since the types must match, means that it is a 1407 // ConstantPointerNull). 1408 if (const BlockAddress *BA2 = dyn_cast<BlockAddress>(V2)) { 1409 // Block address in another function can't equal this one, but block 1410 // addresses in the current function might be the same if blocks are 1411 // empty. 1412 if (BA2->getFunction() != BA->getFunction()) 1413 return ICmpInst::ICMP_NE; 1414 } else { 1415 // Block addresses aren't null, don't equal the address of globals. 1416 assert((isa<ConstantPointerNull>(V2) || isa<GlobalValue>(V2)) && 1417 "Canonicalization guarantee!"); 1418 return ICmpInst::ICMP_NE; 1419 } 1420 } else { 1421 // Ok, the LHS is known to be a constantexpr. The RHS can be any of a 1422 // constantexpr, a global, block address, or a simple constant. 1423 ConstantExpr *CE1 = cast<ConstantExpr>(V1); 1424 Constant *CE1Op0 = CE1->getOperand(0); 1425 1426 switch (CE1->getOpcode()) { 1427 case Instruction::Trunc: 1428 case Instruction::FPTrunc: 1429 case Instruction::FPExt: 1430 case Instruction::FPToUI: 1431 case Instruction::FPToSI: 1432 break; // We can't evaluate floating point casts or truncations. 1433 1434 case Instruction::UIToFP: 1435 case Instruction::SIToFP: 1436 case Instruction::BitCast: 1437 case Instruction::ZExt: 1438 case Instruction::SExt: 1439 // If the cast is not actually changing bits, and the second operand is a 1440 // null pointer, do the comparison with the pre-casted value. 1441 if (V2->isNullValue() && 1442 (CE1->getType()->isPointerTy() || CE1->getType()->isIntegerTy())) { 1443 if (CE1->getOpcode() == Instruction::ZExt) isSigned = false; 1444 if (CE1->getOpcode() == Instruction::SExt) isSigned = true; 1445 return evaluateICmpRelation(CE1Op0, 1446 Constant::getNullValue(CE1Op0->getType()), 1447 isSigned); 1448 } 1449 break; 1450 1451 case Instruction::GetElementPtr: 1452 // Ok, since this is a getelementptr, we know that the constant has a 1453 // pointer type. Check the various cases. 1454 if (isa<ConstantPointerNull>(V2)) { 1455 // If we are comparing a GEP to a null pointer, check to see if the base 1456 // of the GEP equals the null pointer. 1457 if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { 1458 if (GV->hasExternalWeakLinkage()) 1459 // Weak linkage GVals could be zero or not. We're comparing that 1460 // to null pointer so its greater-or-equal 1461 return isSigned ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE; 1462 else 1463 // If its not weak linkage, the GVal must have a non-zero address 1464 // so the result is greater-than 1465 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1466 } else if (isa<ConstantPointerNull>(CE1Op0)) { 1467 // If we are indexing from a null pointer, check to see if we have any 1468 // non-zero indices. 1469 for (unsigned i = 1, e = CE1->getNumOperands(); i != e; ++i) 1470 if (!CE1->getOperand(i)->isNullValue()) 1471 // Offsetting from null, must not be equal. 1472 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1473 // Only zero indexes from null, must still be zero. 1474 return ICmpInst::ICMP_EQ; 1475 } 1476 // Otherwise, we can't really say if the first operand is null or not. 1477 } else if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) { 1478 if (isa<ConstantPointerNull>(CE1Op0)) { 1479 if (GV2->hasExternalWeakLinkage()) 1480 // Weak linkage GVals could be zero or not. We're comparing it to 1481 // a null pointer, so its less-or-equal 1482 return isSigned ? ICmpInst::ICMP_SLE : ICmpInst::ICMP_ULE; 1483 else 1484 // If its not weak linkage, the GVal must have a non-zero address 1485 // so the result is less-than 1486 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1487 } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(CE1Op0)) { 1488 if (GV == GV2) { 1489 // If this is a getelementptr of the same global, then it must be 1490 // different. Because the types must match, the getelementptr could 1491 // only have at most one index, and because we fold getelementptr's 1492 // with a single zero index, it must be nonzero. 1493 assert(CE1->getNumOperands() == 2 && 1494 !CE1->getOperand(1)->isNullValue() && 1495 "Surprising getelementptr!"); 1496 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1497 } else { 1498 // If they are different globals, we don't know what the value is. 1499 return ICmpInst::BAD_ICMP_PREDICATE; 1500 } 1501 } 1502 } else { 1503 ConstantExpr *CE2 = cast<ConstantExpr>(V2); 1504 Constant *CE2Op0 = CE2->getOperand(0); 1505 1506 // There are MANY other foldings that we could perform here. They will 1507 // probably be added on demand, as they seem needed. 1508 switch (CE2->getOpcode()) { 1509 default: break; 1510 case Instruction::GetElementPtr: 1511 // By far the most common case to handle is when the base pointers are 1512 // obviously to the same global. 1513 if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { 1514 if (CE1Op0 != CE2Op0) // Don't know relative ordering. 1515 return ICmpInst::BAD_ICMP_PREDICATE; 1516 // Ok, we know that both getelementptr instructions are based on the 1517 // same global. From this, we can precisely determine the relative 1518 // ordering of the resultant pointers. 1519 unsigned i = 1; 1520 1521 // The logic below assumes that the result of the comparison 1522 // can be determined by finding the first index that differs. 1523 // This doesn't work if there is over-indexing in any 1524 // subsequent indices, so check for that case first. 1525 if (!CE1->isGEPWithNoNotionalOverIndexing() || 1526 !CE2->isGEPWithNoNotionalOverIndexing()) 1527 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1528 1529 // Compare all of the operands the GEP's have in common. 1530 gep_type_iterator GTI = gep_type_begin(CE1); 1531 for (;i != CE1->getNumOperands() && i != CE2->getNumOperands(); 1532 ++i, ++GTI) 1533 switch (IdxCompare(CE1->getOperand(i), 1534 CE2->getOperand(i), GTI.getIndexedType())) { 1535 case -1: return isSigned ? ICmpInst::ICMP_SLT:ICmpInst::ICMP_ULT; 1536 case 1: return isSigned ? ICmpInst::ICMP_SGT:ICmpInst::ICMP_UGT; 1537 case -2: return ICmpInst::BAD_ICMP_PREDICATE; 1538 } 1539 1540 // Ok, we ran out of things they have in common. If any leftovers 1541 // are non-zero then we have a difference, otherwise we are equal. 1542 for (; i < CE1->getNumOperands(); ++i) 1543 if (!CE1->getOperand(i)->isNullValue()) { 1544 if (isa<ConstantInt>(CE1->getOperand(i))) 1545 return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; 1546 else 1547 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1548 } 1549 1550 for (; i < CE2->getNumOperands(); ++i) 1551 if (!CE2->getOperand(i)->isNullValue()) { 1552 if (isa<ConstantInt>(CE2->getOperand(i))) 1553 return isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT; 1554 else 1555 return ICmpInst::BAD_ICMP_PREDICATE; // Might be equal. 1556 } 1557 return ICmpInst::ICMP_EQ; 1558 } 1559 } 1560 } 1561 default: 1562 break; 1563 } 1564 } 1565 1566 return ICmpInst::BAD_ICMP_PREDICATE; 1567} 1568 1569Constant *llvm::ConstantFoldCompareInstruction(unsigned short pred, 1570 Constant *C1, Constant *C2) { 1571 Type *ResultTy; 1572 if (VectorType *VT = dyn_cast<VectorType>(C1->getType())) 1573 ResultTy = VectorType::get(Type::getInt1Ty(C1->getContext()), 1574 VT->getNumElements()); 1575 else 1576 ResultTy = Type::getInt1Ty(C1->getContext()); 1577 1578 // Fold FCMP_FALSE/FCMP_TRUE unconditionally. 1579 if (pred == FCmpInst::FCMP_FALSE) 1580 return Constant::getNullValue(ResultTy); 1581 1582 if (pred == FCmpInst::FCMP_TRUE) 1583 return Constant::getAllOnesValue(ResultTy); 1584 1585 // Handle some degenerate cases first 1586 if (isa<UndefValue>(C1) || isa<UndefValue>(C2)) { 1587 // For EQ and NE, we can always pick a value for the undef to make the 1588 // predicate pass or fail, so we can return undef. 1589 // Also, if both operands are undef, we can return undef. 1590 if (ICmpInst::isEquality(ICmpInst::Predicate(pred)) || 1591 (isa<UndefValue>(C1) && isa<UndefValue>(C2))) 1592 return UndefValue::get(ResultTy); 1593 // Otherwise, pick the same value as the non-undef operand, and fold 1594 // it to true or false. 1595 return ConstantInt::get(ResultTy, CmpInst::isTrueWhenEqual(pred)); 1596 } 1597 1598 // icmp eq/ne(null,GV) -> false/true 1599 if (C1->isNullValue()) { 1600 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C2)) 1601 // Don't try to evaluate aliases. External weak GV can be null. 1602 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { 1603 if (pred == ICmpInst::ICMP_EQ) 1604 return ConstantInt::getFalse(C1->getContext()); 1605 else if (pred == ICmpInst::ICMP_NE) 1606 return ConstantInt::getTrue(C1->getContext()); 1607 } 1608 // icmp eq/ne(GV,null) -> false/true 1609 } else if (C2->isNullValue()) { 1610 if (const GlobalValue *GV = dyn_cast<GlobalValue>(C1)) 1611 // Don't try to evaluate aliases. External weak GV can be null. 1612 if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage()) { 1613 if (pred == ICmpInst::ICMP_EQ) 1614 return ConstantInt::getFalse(C1->getContext()); 1615 else if (pred == ICmpInst::ICMP_NE) 1616 return ConstantInt::getTrue(C1->getContext()); 1617 } 1618 } 1619 1620 // If the comparison is a comparison between two i1's, simplify it. 1621 if (C1->getType()->isIntegerTy(1)) { 1622 switch(pred) { 1623 case ICmpInst::ICMP_EQ: 1624 if (isa<ConstantInt>(C2)) 1625 return ConstantExpr::getXor(C1, ConstantExpr::getNot(C2)); 1626 return ConstantExpr::getXor(ConstantExpr::getNot(C1), C2); 1627 case ICmpInst::ICMP_NE: 1628 return ConstantExpr::getXor(C1, C2); 1629 default: 1630 break; 1631 } 1632 } 1633 1634 if (isa<ConstantInt>(C1) && isa<ConstantInt>(C2)) { 1635 APInt V1 = cast<ConstantInt>(C1)->getValue(); 1636 APInt V2 = cast<ConstantInt>(C2)->getValue(); 1637 switch (pred) { 1638 default: llvm_unreachable("Invalid ICmp Predicate"); 1639 case ICmpInst::ICMP_EQ: return ConstantInt::get(ResultTy, V1 == V2); 1640 case ICmpInst::ICMP_NE: return ConstantInt::get(ResultTy, V1 != V2); 1641 case ICmpInst::ICMP_SLT: return ConstantInt::get(ResultTy, V1.slt(V2)); 1642 case ICmpInst::ICMP_SGT: return ConstantInt::get(ResultTy, V1.sgt(V2)); 1643 case ICmpInst::ICMP_SLE: return ConstantInt::get(ResultTy, V1.sle(V2)); 1644 case ICmpInst::ICMP_SGE: return ConstantInt::get(ResultTy, V1.sge(V2)); 1645 case ICmpInst::ICMP_ULT: return ConstantInt::get(ResultTy, V1.ult(V2)); 1646 case ICmpInst::ICMP_UGT: return ConstantInt::get(ResultTy, V1.ugt(V2)); 1647 case ICmpInst::ICMP_ULE: return ConstantInt::get(ResultTy, V1.ule(V2)); 1648 case ICmpInst::ICMP_UGE: return ConstantInt::get(ResultTy, V1.uge(V2)); 1649 } 1650 } else if (isa<ConstantFP>(C1) && isa<ConstantFP>(C2)) { 1651 APFloat C1V = cast<ConstantFP>(C1)->getValueAPF(); 1652 APFloat C2V = cast<ConstantFP>(C2)->getValueAPF(); 1653 APFloat::cmpResult R = C1V.compare(C2V); 1654 switch (pred) { 1655 default: llvm_unreachable("Invalid FCmp Predicate"); 1656 case FCmpInst::FCMP_FALSE: return Constant::getNullValue(ResultTy); 1657 case FCmpInst::FCMP_TRUE: return Constant::getAllOnesValue(ResultTy); 1658 case FCmpInst::FCMP_UNO: 1659 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered); 1660 case FCmpInst::FCMP_ORD: 1661 return ConstantInt::get(ResultTy, R!=APFloat::cmpUnordered); 1662 case FCmpInst::FCMP_UEQ: 1663 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || 1664 R==APFloat::cmpEqual); 1665 case FCmpInst::FCMP_OEQ: 1666 return ConstantInt::get(ResultTy, R==APFloat::cmpEqual); 1667 case FCmpInst::FCMP_UNE: 1668 return ConstantInt::get(ResultTy, R!=APFloat::cmpEqual); 1669 case FCmpInst::FCMP_ONE: 1670 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan || 1671 R==APFloat::cmpGreaterThan); 1672 case FCmpInst::FCMP_ULT: 1673 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || 1674 R==APFloat::cmpLessThan); 1675 case FCmpInst::FCMP_OLT: 1676 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan); 1677 case FCmpInst::FCMP_UGT: 1678 return ConstantInt::get(ResultTy, R==APFloat::cmpUnordered || 1679 R==APFloat::cmpGreaterThan); 1680 case FCmpInst::FCMP_OGT: 1681 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan); 1682 case FCmpInst::FCMP_ULE: 1683 return ConstantInt::get(ResultTy, R!=APFloat::cmpGreaterThan); 1684 case FCmpInst::FCMP_OLE: 1685 return ConstantInt::get(ResultTy, R==APFloat::cmpLessThan || 1686 R==APFloat::cmpEqual); 1687 case FCmpInst::FCMP_UGE: 1688 return ConstantInt::get(ResultTy, R!=APFloat::cmpLessThan); 1689 case FCmpInst::FCMP_OGE: 1690 return ConstantInt::get(ResultTy, R==APFloat::cmpGreaterThan || 1691 R==APFloat::cmpEqual); 1692 } 1693 } else if (C1->getType()->isVectorTy()) { 1694 // If we can constant fold the comparison of each element, constant fold 1695 // the whole vector comparison. 1696 SmallVector<Constant*, 4> ResElts; 1697 Type *Ty = IntegerType::get(C1->getContext(), 32); 1698 // Compare the elements, producing an i1 result or constant expr. 1699 for (unsigned i = 0, e = C1->getType()->getVectorNumElements(); i != e;++i){ 1700 Constant *C1E = 1701 ConstantExpr::getExtractElement(C1, ConstantInt::get(Ty, i)); 1702 Constant *C2E = 1703 ConstantExpr::getExtractElement(C2, ConstantInt::get(Ty, i)); 1704 1705 ResElts.push_back(ConstantExpr::getCompare(pred, C1E, C2E)); 1706 } 1707 1708 return ConstantVector::get(ResElts); 1709 } 1710 1711 if (C1->getType()->isFloatingPointTy()) { 1712 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. 1713 switch (evaluateFCmpRelation(C1, C2)) { 1714 default: llvm_unreachable("Unknown relation!"); 1715 case FCmpInst::FCMP_UNO: 1716 case FCmpInst::FCMP_ORD: 1717 case FCmpInst::FCMP_UEQ: 1718 case FCmpInst::FCMP_UNE: 1719 case FCmpInst::FCMP_ULT: 1720 case FCmpInst::FCMP_UGT: 1721 case FCmpInst::FCMP_ULE: 1722 case FCmpInst::FCMP_UGE: 1723 case FCmpInst::FCMP_TRUE: 1724 case FCmpInst::FCMP_FALSE: 1725 case FCmpInst::BAD_FCMP_PREDICATE: 1726 break; // Couldn't determine anything about these constants. 1727 case FCmpInst::FCMP_OEQ: // We know that C1 == C2 1728 Result = (pred == FCmpInst::FCMP_UEQ || pred == FCmpInst::FCMP_OEQ || 1729 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE || 1730 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1731 break; 1732 case FCmpInst::FCMP_OLT: // We know that C1 < C2 1733 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1734 pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT || 1735 pred == FCmpInst::FCMP_ULE || pred == FCmpInst::FCMP_OLE); 1736 break; 1737 case FCmpInst::FCMP_OGT: // We know that C1 > C2 1738 Result = (pred == FCmpInst::FCMP_UNE || pred == FCmpInst::FCMP_ONE || 1739 pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT || 1740 pred == FCmpInst::FCMP_UGE || pred == FCmpInst::FCMP_OGE); 1741 break; 1742 case FCmpInst::FCMP_OLE: // We know that C1 <= C2 1743 // We can only partially decide this relation. 1744 if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1745 Result = 0; 1746 else if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1747 Result = 1; 1748 break; 1749 case FCmpInst::FCMP_OGE: // We known that C1 >= C2 1750 // We can only partially decide this relation. 1751 if (pred == FCmpInst::FCMP_ULT || pred == FCmpInst::FCMP_OLT) 1752 Result = 0; 1753 else if (pred == FCmpInst::FCMP_UGT || pred == FCmpInst::FCMP_OGT) 1754 Result = 1; 1755 break; 1756 case FCmpInst::FCMP_ONE: // We know that C1 != C2 1757 // We can only partially decide this relation. 1758 if (pred == FCmpInst::FCMP_OEQ || pred == FCmpInst::FCMP_UEQ) 1759 Result = 0; 1760 else if (pred == FCmpInst::FCMP_ONE || pred == FCmpInst::FCMP_UNE) 1761 Result = 1; 1762 break; 1763 } 1764 1765 // If we evaluated the result, return it now. 1766 if (Result != -1) 1767 return ConstantInt::get(ResultTy, Result); 1768 1769 } else { 1770 // Evaluate the relation between the two constants, per the predicate. 1771 int Result = -1; // -1 = unknown, 0 = known false, 1 = known true. 1772 switch (evaluateICmpRelation(C1, C2, CmpInst::isSigned(pred))) { 1773 default: llvm_unreachable("Unknown relational!"); 1774 case ICmpInst::BAD_ICMP_PREDICATE: 1775 break; // Couldn't determine anything about these constants. 1776 case ICmpInst::ICMP_EQ: // We know the constants are equal! 1777 // If we know the constants are equal, we can decide the result of this 1778 // computation precisely. 1779 Result = ICmpInst::isTrueWhenEqual((ICmpInst::Predicate)pred); 1780 break; 1781 case ICmpInst::ICMP_ULT: 1782 switch (pred) { 1783 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_ULE: 1784 Result = 1; break; 1785 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_UGE: 1786 Result = 0; break; 1787 } 1788 break; 1789 case ICmpInst::ICMP_SLT: 1790 switch (pred) { 1791 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SLE: 1792 Result = 1; break; 1793 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SGE: 1794 Result = 0; break; 1795 } 1796 break; 1797 case ICmpInst::ICMP_UGT: 1798 switch (pred) { 1799 case ICmpInst::ICMP_UGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_UGE: 1800 Result = 1; break; 1801 case ICmpInst::ICMP_ULT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_ULE: 1802 Result = 0; break; 1803 } 1804 break; 1805 case ICmpInst::ICMP_SGT: 1806 switch (pred) { 1807 case ICmpInst::ICMP_SGT: case ICmpInst::ICMP_NE: case ICmpInst::ICMP_SGE: 1808 Result = 1; break; 1809 case ICmpInst::ICMP_SLT: case ICmpInst::ICMP_EQ: case ICmpInst::ICMP_SLE: 1810 Result = 0; break; 1811 } 1812 break; 1813 case ICmpInst::ICMP_ULE: 1814 if (pred == ICmpInst::ICMP_UGT) Result = 0; 1815 if (pred == ICmpInst::ICMP_ULT || pred == ICmpInst::ICMP_ULE) Result = 1; 1816 break; 1817 case ICmpInst::ICMP_SLE: 1818 if (pred == ICmpInst::ICMP_SGT) Result = 0; 1819 if (pred == ICmpInst::ICMP_SLT || pred == ICmpInst::ICMP_SLE) Result = 1; 1820 break; 1821 case ICmpInst::ICMP_UGE: 1822 if (pred == ICmpInst::ICMP_ULT) Result = 0; 1823 if (pred == ICmpInst::ICMP_UGT || pred == ICmpInst::ICMP_UGE) Result = 1; 1824 break; 1825 case ICmpInst::ICMP_SGE: 1826 if (pred == ICmpInst::ICMP_SLT) Result = 0; 1827 if (pred == ICmpInst::ICMP_SGT || pred == ICmpInst::ICMP_SGE) Result = 1; 1828 break; 1829 case ICmpInst::ICMP_NE: 1830 if (pred == ICmpInst::ICMP_EQ) Result = 0; 1831 if (pred == ICmpInst::ICMP_NE) Result = 1; 1832 break; 1833 } 1834 1835 // If we evaluated the result, return it now. 1836 if (Result != -1) 1837 return ConstantInt::get(ResultTy, Result); 1838 1839 // If the right hand side is a bitcast, try using its inverse to simplify 1840 // it by moving it to the left hand side. We can't do this if it would turn 1841 // a vector compare into a scalar compare or visa versa. 1842 if (ConstantExpr *CE2 = dyn_cast<ConstantExpr>(C2)) { 1843 Constant *CE2Op0 = CE2->getOperand(0); 1844 if (CE2->getOpcode() == Instruction::BitCast && 1845 CE2->getType()->isVectorTy() == CE2Op0->getType()->isVectorTy()) { 1846 Constant *Inverse = ConstantExpr::getBitCast(C1, CE2Op0->getType()); 1847 return ConstantExpr::getICmp(pred, Inverse, CE2Op0); 1848 } 1849 } 1850 1851 // If the left hand side is an extension, try eliminating it. 1852 if (ConstantExpr *CE1 = dyn_cast<ConstantExpr>(C1)) { 1853 if ((CE1->getOpcode() == Instruction::SExt && ICmpInst::isSigned(pred)) || 1854 (CE1->getOpcode() == Instruction::ZExt && !ICmpInst::isSigned(pred))){ 1855 Constant *CE1Op0 = CE1->getOperand(0); 1856 Constant *CE1Inverse = ConstantExpr::getTrunc(CE1, CE1Op0->getType()); 1857 if (CE1Inverse == CE1Op0) { 1858 // Check whether we can safely truncate the right hand side. 1859 Constant *C2Inverse = ConstantExpr::getTrunc(C2, CE1Op0->getType()); 1860 if (ConstantExpr::getZExt(C2Inverse, C2->getType()) == C2) { 1861 return ConstantExpr::getICmp(pred, CE1Inverse, C2Inverse); 1862 } 1863 } 1864 } 1865 } 1866 1867 if ((!isa<ConstantExpr>(C1) && isa<ConstantExpr>(C2)) || 1868 (C1->isNullValue() && !C2->isNullValue())) { 1869 // If C2 is a constant expr and C1 isn't, flip them around and fold the 1870 // other way if possible. 1871 // Also, if C1 is null and C2 isn't, flip them around. 1872 pred = ICmpInst::getSwappedPredicate((ICmpInst::Predicate)pred); 1873 return ConstantExpr::getICmp(pred, C2, C1); 1874 } 1875 } 1876 return 0; 1877} 1878 1879/// isInBoundsIndices - Test whether the given sequence of *normalized* indices 1880/// is "inbounds". 1881template<typename IndexTy> 1882static bool isInBoundsIndices(ArrayRef<IndexTy> Idxs) { 1883 // No indices means nothing that could be out of bounds. 1884 if (Idxs.empty()) return true; 1885 1886 // If the first index is zero, it's in bounds. 1887 if (cast<Constant>(Idxs[0])->isNullValue()) return true; 1888 1889 // If the first index is one and all the rest are zero, it's in bounds, 1890 // by the one-past-the-end rule. 1891 if (!cast<ConstantInt>(Idxs[0])->isOne()) 1892 return false; 1893 for (unsigned i = 1, e = Idxs.size(); i != e; ++i) 1894 if (!cast<Constant>(Idxs[i])->isNullValue()) 1895 return false; 1896 return true; 1897} 1898 1899template<typename IndexTy> 1900static Constant *ConstantFoldGetElementPtrImpl(Constant *C, 1901 bool inBounds, 1902 ArrayRef<IndexTy> Idxs) { 1903 if (Idxs.empty()) return C; 1904 Constant *Idx0 = cast<Constant>(Idxs[0]); 1905 if ((Idxs.size() == 1 && Idx0->isNullValue())) 1906 return C; 1907 1908 if (isa<UndefValue>(C)) { 1909 PointerType *Ptr = cast<PointerType>(C->getType()); 1910 Type *Ty = GetElementPtrInst::getIndexedType(Ptr, Idxs); 1911 assert(Ty != 0 && "Invalid indices for GEP!"); 1912 return UndefValue::get(PointerType::get(Ty, Ptr->getAddressSpace())); 1913 } 1914 1915 if (C->isNullValue()) { 1916 bool isNull = true; 1917 for (unsigned i = 0, e = Idxs.size(); i != e; ++i) 1918 if (!cast<Constant>(Idxs[i])->isNullValue()) { 1919 isNull = false; 1920 break; 1921 } 1922 if (isNull) { 1923 PointerType *Ptr = cast<PointerType>(C->getType()); 1924 Type *Ty = GetElementPtrInst::getIndexedType(Ptr, Idxs); 1925 assert(Ty != 0 && "Invalid indices for GEP!"); 1926 return ConstantPointerNull::get(PointerType::get(Ty, 1927 Ptr->getAddressSpace())); 1928 } 1929 } 1930 1931 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) { 1932 // Combine Indices - If the source pointer to this getelementptr instruction 1933 // is a getelementptr instruction, combine the indices of the two 1934 // getelementptr instructions into a single instruction. 1935 // 1936 if (CE->getOpcode() == Instruction::GetElementPtr) { 1937 Type *LastTy = 0; 1938 for (gep_type_iterator I = gep_type_begin(CE), E = gep_type_end(CE); 1939 I != E; ++I) 1940 LastTy = *I; 1941 1942 if ((LastTy && isa<SequentialType>(LastTy)) || Idx0->isNullValue()) { 1943 SmallVector<Value*, 16> NewIndices; 1944 NewIndices.reserve(Idxs.size() + CE->getNumOperands()); 1945 for (unsigned i = 1, e = CE->getNumOperands()-1; i != e; ++i) 1946 NewIndices.push_back(CE->getOperand(i)); 1947 1948 // Add the last index of the source with the first index of the new GEP. 1949 // Make sure to handle the case when they are actually different types. 1950 Constant *Combined = CE->getOperand(CE->getNumOperands()-1); 1951 // Otherwise it must be an array. 1952 if (!Idx0->isNullValue()) { 1953 Type *IdxTy = Combined->getType(); 1954 if (IdxTy != Idx0->getType()) { 1955 Type *Int64Ty = Type::getInt64Ty(IdxTy->getContext()); 1956 Constant *C1 = ConstantExpr::getSExtOrBitCast(Idx0, Int64Ty); 1957 Constant *C2 = ConstantExpr::getSExtOrBitCast(Combined, Int64Ty); 1958 Combined = ConstantExpr::get(Instruction::Add, C1, C2); 1959 } else { 1960 Combined = 1961 ConstantExpr::get(Instruction::Add, Idx0, Combined); 1962 } 1963 } 1964 1965 NewIndices.push_back(Combined); 1966 NewIndices.append(Idxs.begin() + 1, Idxs.end()); 1967 return 1968 ConstantExpr::getGetElementPtr(CE->getOperand(0), NewIndices, 1969 inBounds && 1970 cast<GEPOperator>(CE)->isInBounds()); 1971 } 1972 } 1973 1974 // Attempt to fold casts to the same type away. For example, folding: 1975 // 1976 // i32* getelementptr ([2 x i32]* bitcast ([3 x i32]* %X to [2 x i32]*), 1977 // i64 0, i64 0) 1978 // into: 1979 // 1980 // i32* getelementptr ([3 x i32]* %X, i64 0, i64 0) 1981 // 1982 // Don't fold if the cast is changing address spaces. 1983 if (CE->isCast() && Idxs.size() > 1 && Idx0->isNullValue()) { 1984 PointerType *SrcPtrTy = 1985 dyn_cast<PointerType>(CE->getOperand(0)->getType()); 1986 PointerType *DstPtrTy = dyn_cast<PointerType>(CE->getType()); 1987 if (SrcPtrTy && DstPtrTy) { 1988 ArrayType *SrcArrayTy = 1989 dyn_cast<ArrayType>(SrcPtrTy->getElementType()); 1990 ArrayType *DstArrayTy = 1991 dyn_cast<ArrayType>(DstPtrTy->getElementType()); 1992 if (SrcArrayTy && DstArrayTy 1993 && SrcArrayTy->getElementType() == DstArrayTy->getElementType() 1994 && SrcPtrTy->getAddressSpace() == DstPtrTy->getAddressSpace()) 1995 return ConstantExpr::getGetElementPtr((Constant*)CE->getOperand(0), 1996 Idxs, inBounds); 1997 } 1998 } 1999 } 2000 2001 // Check to see if any array indices are not within the corresponding 2002 // notional array bounds. If so, try to determine if they can be factored 2003 // out into preceding dimensions. 2004 bool Unknown = false; 2005 SmallVector<Constant *, 8> NewIdxs; 2006 Type *Ty = C->getType(); 2007 Type *Prev = 0; 2008 for (unsigned i = 0, e = Idxs.size(); i != e; 2009 Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]), ++i) { 2010 if (ConstantInt *CI = dyn_cast<ConstantInt>(Idxs[i])) { 2011 if (ArrayType *ATy = dyn_cast<ArrayType>(Ty)) 2012 if (ATy->getNumElements() <= INT64_MAX && 2013 ATy->getNumElements() != 0 && 2014 CI->getSExtValue() >= (int64_t)ATy->getNumElements()) { 2015 if (isa<SequentialType>(Prev)) { 2016 // It's out of range, but we can factor it into the prior 2017 // dimension. 2018 NewIdxs.resize(Idxs.size()); 2019 ConstantInt *Factor = ConstantInt::get(CI->getType(), 2020 ATy->getNumElements()); 2021 NewIdxs[i] = ConstantExpr::getSRem(CI, Factor); 2022 2023 Constant *PrevIdx = cast<Constant>(Idxs[i-1]); 2024 Constant *Div = ConstantExpr::getSDiv(CI, Factor); 2025 2026 // Before adding, extend both operands to i64 to avoid 2027 // overflow trouble. 2028 if (!PrevIdx->getType()->isIntegerTy(64)) 2029 PrevIdx = ConstantExpr::getSExt(PrevIdx, 2030 Type::getInt64Ty(Div->getContext())); 2031 if (!Div->getType()->isIntegerTy(64)) 2032 Div = ConstantExpr::getSExt(Div, 2033 Type::getInt64Ty(Div->getContext())); 2034 2035 NewIdxs[i-1] = ConstantExpr::getAdd(PrevIdx, Div); 2036 } else { 2037 // It's out of range, but the prior dimension is a struct 2038 // so we can't do anything about it. 2039 Unknown = true; 2040 } 2041 } 2042 } else { 2043 // We don't know if it's in range or not. 2044 Unknown = true; 2045 } 2046 } 2047 2048 // If we did any factoring, start over with the adjusted indices. 2049 if (!NewIdxs.empty()) { 2050 for (unsigned i = 0, e = Idxs.size(); i != e; ++i) 2051 if (!NewIdxs[i]) NewIdxs[i] = cast<Constant>(Idxs[i]); 2052 return ConstantExpr::getGetElementPtr(C, NewIdxs, inBounds); 2053 } 2054 2055 // If all indices are known integers and normalized, we can do a simple 2056 // check for the "inbounds" property. 2057 if (!Unknown && !inBounds && 2058 isa<GlobalVariable>(C) && isInBoundsIndices(Idxs)) 2059 return ConstantExpr::getInBoundsGetElementPtr(C, Idxs); 2060 2061 return 0; 2062} 2063 2064Constant *llvm::ConstantFoldGetElementPtr(Constant *C, 2065 bool inBounds, 2066 ArrayRef<Constant *> Idxs) { 2067 return ConstantFoldGetElementPtrImpl(C, inBounds, Idxs); 2068} 2069 2070Constant *llvm::ConstantFoldGetElementPtr(Constant *C, 2071 bool inBounds, 2072 ArrayRef<Value *> Idxs) { 2073 return ConstantFoldGetElementPtrImpl(C, inBounds, Idxs); 2074} 2075