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Andrew Scull5e1ddfa2018-08-14 10:06:54 +01001//===- Local.h - Functions to perform local transformations -----*- C++ -*-===//
2//
Andrew Walbran16937d02019-10-22 13:54:20 +01003// 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
Andrew Scull5e1ddfa2018-08-14 10:06:54 +01006//
7//===----------------------------------------------------------------------===//
8//
9// This family of functions perform various local transformations to the
10// program.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_ANALYSIS_UTILS_LOCAL_H
15#define LLVM_ANALYSIS_UTILS_LOCAL_H
16
Olivier Deprezf4ef2d02021-04-20 13:36:24 +020017#include "llvm/ADT/StringRef.h"
Andrew Scull5e1ddfa2018-08-14 10:06:54 +010018#include "llvm/IR/DataLayout.h"
Andrew Scull5e1ddfa2018-08-14 10:06:54 +010019#include "llvm/IR/GetElementPtrTypeIterator.h"
Andrew Scull5e1ddfa2018-08-14 10:06:54 +010020
21namespace llvm {
22
Andrew Scull5e1ddfa2018-08-14 10:06:54 +010023/// Given a getelementptr instruction/constantexpr, emit the code necessary to
24/// compute the offset from the base pointer (without adding in the base
25/// pointer). Return the result as a signed integer of intptr size.
26/// When NoAssumptions is true, no assumptions about index computation not
27/// overflowing is made.
28template <typename IRBuilderTy>
29Value *EmitGEPOffset(IRBuilderTy *Builder, const DataLayout &DL, User *GEP,
30 bool NoAssumptions = false) {
31 GEPOperator *GEPOp = cast<GEPOperator>(GEP);
Olivier Deprezf4ef2d02021-04-20 13:36:24 +020032 Type *IntIdxTy = DL.getIndexType(GEP->getType());
33 Value *Result = nullptr;
Andrew Scull5e1ddfa2018-08-14 10:06:54 +010034
35 // If the GEP is inbounds, we know that none of the addressing operations will
Olivier Deprezf4ef2d02021-04-20 13:36:24 +020036 // overflow in a signed sense.
Andrew Scull5e1ddfa2018-08-14 10:06:54 +010037 bool isInBounds = GEPOp->isInBounds() && !NoAssumptions;
38
39 // Build a mask for high order bits.
Olivier Deprezf4ef2d02021-04-20 13:36:24 +020040 unsigned IntPtrWidth = IntIdxTy->getScalarType()->getIntegerBitWidth();
Andrew Scull5e1ddfa2018-08-14 10:06:54 +010041 uint64_t PtrSizeMask =
42 std::numeric_limits<uint64_t>::max() >> (64 - IntPtrWidth);
43
44 gep_type_iterator GTI = gep_type_begin(GEP);
45 for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e;
46 ++i, ++GTI) {
47 Value *Op = *i;
48 uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask;
Olivier Deprezf4ef2d02021-04-20 13:36:24 +020049 Value *Offset;
Andrew Scull5e1ddfa2018-08-14 10:06:54 +010050 if (Constant *OpC = dyn_cast<Constant>(Op)) {
51 if (OpC->isZeroValue())
52 continue;
53
54 // Handle a struct index, which adds its field offset to the pointer.
55 if (StructType *STy = GTI.getStructTypeOrNull()) {
Olivier Deprezf4ef2d02021-04-20 13:36:24 +020056 uint64_t OpValue = OpC->getUniqueInteger().getZExtValue();
Andrew Scull5e1ddfa2018-08-14 10:06:54 +010057 Size = DL.getStructLayout(STy)->getElementOffset(OpValue);
Olivier Deprezf4ef2d02021-04-20 13:36:24 +020058 if (!Size)
59 continue;
Andrew Scull5e1ddfa2018-08-14 10:06:54 +010060
Olivier Deprezf4ef2d02021-04-20 13:36:24 +020061 Offset = ConstantInt::get(IntIdxTy, Size);
62 } else {
63 // Splat the constant if needed.
64 if (IntIdxTy->isVectorTy() && !OpC->getType()->isVectorTy())
65 OpC = ConstantVector::getSplat(
66 cast<VectorType>(IntIdxTy)->getElementCount(), OpC);
67
68 Constant *Scale = ConstantInt::get(IntIdxTy, Size);
69 Constant *OC =
70 ConstantExpr::getIntegerCast(OpC, IntIdxTy, true /*SExt*/);
71 Offset =
72 ConstantExpr::getMul(OC, Scale, false /*NUW*/, isInBounds /*NSW*/);
Andrew Scull5e1ddfa2018-08-14 10:06:54 +010073 }
Olivier Deprezf4ef2d02021-04-20 13:36:24 +020074 } else {
75 // Splat the index if needed.
76 if (IntIdxTy->isVectorTy() && !Op->getType()->isVectorTy())
77 Op = Builder->CreateVectorSplat(
78 cast<FixedVectorType>(IntIdxTy)->getNumElements(), Op);
Andrew Scull5e1ddfa2018-08-14 10:06:54 +010079
Olivier Deprezf4ef2d02021-04-20 13:36:24 +020080 // Convert to correct type.
81 if (Op->getType() != IntIdxTy)
82 Op = Builder->CreateIntCast(Op, IntIdxTy, true, Op->getName().str()+".c");
83 if (Size != 1) {
84 // We'll let instcombine(mul) convert this to a shl if possible.
85 Op = Builder->CreateMul(Op, ConstantInt::get(IntIdxTy, Size),
86 GEP->getName().str() + ".idx", false /*NUW*/,
87 isInBounds /*NSW*/);
88 }
89 Offset = Op;
Andrew Scull5e1ddfa2018-08-14 10:06:54 +010090 }
91
Olivier Deprezf4ef2d02021-04-20 13:36:24 +020092 if (Result)
93 Result = Builder->CreateAdd(Result, Offset, GEP->getName().str()+".offs",
94 false /*NUW*/, isInBounds /*NSW*/);
95 else
96 Result = Offset;
Andrew Scull5e1ddfa2018-08-14 10:06:54 +010097 }
Olivier Deprezf4ef2d02021-04-20 13:36:24 +020098 return Result ? Result : Constant::getNullValue(IntIdxTy);
Andrew Scull5e1ddfa2018-08-14 10:06:54 +010099}
100
Andrew Scullcdfcccc2018-10-05 20:58:37 +0100101}
Andrew Scull5e1ddfa2018-08-14 10:06:54 +0100102
103#endif // LLVM_TRANSFORMS_UTILS_LOCAL_H