1 //===- Local.cpp - Functions to perform local transformations -------------===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This family of functions perform various local transformations to the 10 // program. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/Analysis/Utils/Local.h" 15 #include "llvm/ADT/Twine.h" 16 #include "llvm/IR/DataLayout.h" 17 #include "llvm/IR/GetElementPtrTypeIterator.h" 18 #include "llvm/IR/IRBuilder.h" 19 20 using namespace llvm; 21 22 Value *llvm::emitGEPOffset(IRBuilderBase *Builder, const DataLayout &DL, 23 User *GEP, bool NoAssumptions) { 24 GEPOperator *GEPOp = cast<GEPOperator>(GEP); 25 Type *IntIdxTy = DL.getIndexType(GEP->getType()); 26 Value *Result = nullptr; 27 28 // If the GEP is inbounds, we know that none of the addressing operations will 29 // overflow in a signed sense. 30 bool isInBounds = GEPOp->isInBounds() && !NoAssumptions; 31 auto AddOffset = [&](Value *Offset) { 32 if (Result) 33 Result = Builder->CreateAdd(Result, Offset, GEP->getName() + ".offs", 34 false /*NUW*/, isInBounds /*NSW*/); 35 else 36 Result = Offset; 37 }; 38 39 gep_type_iterator GTI = gep_type_begin(GEP); 40 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e; 41 ++i, ++GTI) { 42 Value *Op = *i; 43 if (Constant *OpC = dyn_cast<Constant>(Op)) { 44 if (OpC->isZeroValue()) 45 continue; 46 47 // Handle a struct index, which adds its field offset to the pointer. 48 if (StructType *STy = GTI.getStructTypeOrNull()) { 49 uint64_t OpValue = OpC->getUniqueInteger().getZExtValue(); 50 uint64_t Size = DL.getStructLayout(STy)->getElementOffset(OpValue); 51 if (!Size) 52 continue; 53 54 AddOffset(ConstantInt::get(IntIdxTy, Size)); 55 continue; 56 } 57 } 58 59 // Splat the index if needed. 60 if (IntIdxTy->isVectorTy() && !Op->getType()->isVectorTy()) 61 Op = Builder->CreateVectorSplat( 62 cast<VectorType>(IntIdxTy)->getElementCount(), Op); 63 64 // Convert to correct type. 65 if (Op->getType() != IntIdxTy) 66 Op = Builder->CreateIntCast(Op, IntIdxTy, true, Op->getName() + ".c"); 67 TypeSize TSize = GTI.getSequentialElementStride(DL); 68 if (TSize != TypeSize::getFixed(1)) { 69 Value *Scale = Builder->CreateTypeSize(IntIdxTy->getScalarType(), TSize); 70 if (IntIdxTy->isVectorTy()) 71 Scale = Builder->CreateVectorSplat( 72 cast<VectorType>(IntIdxTy)->getElementCount(), Scale); 73 // We'll let instcombine(mul) convert this to a shl if possible. 74 Op = Builder->CreateMul(Op, Scale, GEP->getName() + ".idx", false /*NUW*/, 75 isInBounds /*NSW*/); 76 } 77 AddOffset(Op); 78 } 79 return Result ? Result : Constant::getNullValue(IntIdxTy); 80 } 81