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
20using namespace llvm;
21
22Value *llvm::emitGEPOffset(IRBuilderBase *Builder, const DataLayout &DL,
23 User *GEP, bool NoAssumptions) {
24 GEPOperator *GEPOp = cast<GEPOperator>(Val: GEP);
25 Type *IntIdxTy = DL.getIndexType(PtrTy: GEP->getType());
26 Value *Result = nullptr;
27
28 // nusw implies nsw for the offset arithmetic.
29 bool NSW = GEPOp->hasNoUnsignedSignedWrap() && !NoAssumptions;
30 bool NUW = GEPOp->hasNoUnsignedWrap() && !NoAssumptions;
31 auto AddOffset = [&](Value *Offset) {
32 if (Result)
33 Result = Builder->CreateAdd(LHS: Result, RHS: Offset, Name: GEP->getName() + ".offs",
34 HasNUW: NUW, HasNSW: 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>(Val: 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(Ty: STy)->getElementOffset(Idx: OpValue);
51 if (!Size)
52 continue;
53
54 AddOffset(ConstantInt::get(Ty: IntIdxTy, V: Size));
55 continue;
56 }
57 }
58
59 // Splat the index if needed.
60 if (IntIdxTy->isVectorTy() && !Op->getType()->isVectorTy())
61 Op = Builder->CreateVectorSplat(
62 EC: cast<VectorType>(Val: IntIdxTy)->getElementCount(), V: Op);
63
64 // Convert to correct type.
65 if (Op->getType() != IntIdxTy)
66 Op = Builder->CreateIntCast(V: Op, DestTy: IntIdxTy, isSigned: true, Name: Op->getName() + ".c");
67 TypeSize TSize = GTI.getSequentialElementStride(DL);
68 if (TSize != TypeSize::getFixed(ExactSize: 1)) {
69 Value *Scale = Builder->CreateTypeSize(Ty: IntIdxTy->getScalarType(), Size: TSize);
70 if (IntIdxTy->isVectorTy())
71 Scale = Builder->CreateVectorSplat(
72 EC: cast<VectorType>(Val: IntIdxTy)->getElementCount(), V: Scale);
73 // We'll let instcombine(mul) convert this to a shl if possible.
74 Op = Builder->CreateMul(LHS: Op, RHS: Scale, Name: GEP->getName() + ".idx", HasNUW: NUW, HasNSW: NSW);
75 }
76 AddOffset(Op);
77 }
78 return Result ? Result : Constant::getNullValue(Ty: IntIdxTy);
79}
80