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
emitGEPOffset(IRBuilderBase * Builder,const DataLayout & DL,User * GEP,bool NoAssumptions)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