83 lines
3.0 KiB
C++
83 lines
3.0 KiB
C++
//===- Local.cpp - Functions to perform local transformations -------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This family of functions perform various local transformations to the
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// program.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/Utils/Local.h"
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#include "llvm/ADT/Twine.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/GetElementPtrTypeIterator.h"
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#include "llvm/IR/IRBuilder.h"
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using namespace llvm;
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Value *llvm::emitGEPOffset(IRBuilderBase *Builder, const DataLayout &DL,
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User *GEP, bool NoAssumptions) {
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GEPOperator *GEPOp = cast<GEPOperator>(GEP);
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Type *IntIdxTy = DL.getIndexType(GEP->getType());
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Value *Result = nullptr;
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// If the GEP is inbounds, we know that none of the addressing operations will
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// overflow in a signed sense.
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bool isInBounds = GEPOp->isInBounds() && !NoAssumptions;
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auto AddOffset = [&](Value *Offset) {
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if (Result)
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Result = Builder->CreateAdd(Result, Offset, GEP->getName() + ".offs",
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false /*NUW*/, isInBounds /*NSW*/);
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else
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Result = Offset;
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};
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// Build a mask for high order bits.
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unsigned IntPtrWidth = IntIdxTy->getScalarType()->getIntegerBitWidth();
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uint64_t PtrSizeMask =
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std::numeric_limits<uint64_t>::max() >> (64 - IntPtrWidth);
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gep_type_iterator GTI = gep_type_begin(GEP);
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for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); i != e;
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++i, ++GTI) {
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Value *Op = *i;
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uint64_t Size = DL.getTypeAllocSize(GTI.getIndexedType()) & PtrSizeMask;
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if (Constant *OpC = dyn_cast<Constant>(Op)) {
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if (OpC->isZeroValue())
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continue;
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// Handle a struct index, which adds its field offset to the pointer.
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if (StructType *STy = GTI.getStructTypeOrNull()) {
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uint64_t OpValue = OpC->getUniqueInteger().getZExtValue();
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Size = DL.getStructLayout(STy)->getElementOffset(OpValue);
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if (!Size)
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continue;
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AddOffset(ConstantInt::get(IntIdxTy, Size));
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continue;
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}
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}
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// Splat the index if needed.
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if (IntIdxTy->isVectorTy() && !Op->getType()->isVectorTy())
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Op = Builder->CreateVectorSplat(
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cast<FixedVectorType>(IntIdxTy)->getNumElements(), Op);
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// Convert to correct type.
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if (Op->getType() != IntIdxTy)
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Op = Builder->CreateIntCast(Op, IntIdxTy, true, Op->getName() + ".c");
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if (Size != 1) {
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// We'll let instcombine(mul) convert this to a shl if possible.
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Op = Builder->CreateMul(Op, ConstantInt::get(IntIdxTy, Size),
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GEP->getName() + ".idx", false /*NUW*/,
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isInBounds /*NSW*/);
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}
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AddOffset(Op);
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}
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return Result ? Result : Constant::getNullValue(IntIdxTy);
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}
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