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8cdecd4d3a
This implements the `nusw` and `nuw` flags for `getelementptr` as proposed at https://discourse.llvm.org/t/rfc-add-nusw-and-nuw-flags-for-getelementptr/78672. The three possible flags are encapsulated in the new `GEPNoWrapFlags` class. Currently this class has a ctor from bool, interpreted as the InBounds flag. This ctor should be removed in the future, as code gets migrated to handle all flags. There are a few places annotated with `TODO(gep_nowrap)`, where I've had to touch code but opted to not infer or precisely preserve the new flags, so as to keep this as NFC as possible and make sure any changes of that kind get test coverage when they are made.
281 lines
9.9 KiB
C++
281 lines
9.9 KiB
C++
//===-- Operator.cpp - Implement the LLVM operators -----------------------===//
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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 file implements the non-inline methods for the LLVM Operator classes.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/IR/Operator.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/Instructions.h"
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#include "ConstantsContext.h"
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namespace llvm {
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bool Operator::hasPoisonGeneratingFlags() const {
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switch (getOpcode()) {
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case Instruction::Add:
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case Instruction::Sub:
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case Instruction::Mul:
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case Instruction::Shl: {
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auto *OBO = cast<OverflowingBinaryOperator>(this);
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return OBO->hasNoUnsignedWrap() || OBO->hasNoSignedWrap();
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}
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case Instruction::Trunc: {
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if (auto *TI = dyn_cast<TruncInst>(this))
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return TI->hasNoUnsignedWrap() || TI->hasNoSignedWrap();
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return false;
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}
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case Instruction::UDiv:
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case Instruction::SDiv:
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case Instruction::AShr:
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case Instruction::LShr:
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return cast<PossiblyExactOperator>(this)->isExact();
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case Instruction::Or:
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return cast<PossiblyDisjointInst>(this)->isDisjoint();
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case Instruction::GetElementPtr: {
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auto *GEP = cast<GEPOperator>(this);
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// Note: inrange exists on constexpr only
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return GEP->getNoWrapFlags() != GEPNoWrapFlags::none() ||
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GEP->getInRange() != std::nullopt;
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}
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case Instruction::UIToFP:
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case Instruction::ZExt:
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if (auto *NNI = dyn_cast<PossiblyNonNegInst>(this))
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return NNI->hasNonNeg();
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return false;
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default:
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if (const auto *FP = dyn_cast<FPMathOperator>(this))
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return FP->hasNoNaNs() || FP->hasNoInfs();
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return false;
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}
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}
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bool Operator::hasPoisonGeneratingAnnotations() const {
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if (hasPoisonGeneratingFlags())
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return true;
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auto *I = dyn_cast<Instruction>(this);
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return I && (I->hasPoisonGeneratingReturnAttributes() ||
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I->hasPoisonGeneratingMetadata());
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}
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Type *GEPOperator::getSourceElementType() const {
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if (auto *I = dyn_cast<GetElementPtrInst>(this))
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return I->getSourceElementType();
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return cast<GetElementPtrConstantExpr>(this)->getSourceElementType();
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}
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Type *GEPOperator::getResultElementType() const {
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if (auto *I = dyn_cast<GetElementPtrInst>(this))
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return I->getResultElementType();
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return cast<GetElementPtrConstantExpr>(this)->getResultElementType();
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}
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std::optional<ConstantRange> GEPOperator::getInRange() const {
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if (auto *CE = dyn_cast<GetElementPtrConstantExpr>(this))
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return CE->getInRange();
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return std::nullopt;
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}
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Align GEPOperator::getMaxPreservedAlignment(const DataLayout &DL) const {
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/// compute the worse possible offset for every level of the GEP et accumulate
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/// the minimum alignment into Result.
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Align Result = Align(llvm::Value::MaximumAlignment);
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for (gep_type_iterator GTI = gep_type_begin(this), GTE = gep_type_end(this);
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GTI != GTE; ++GTI) {
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uint64_t Offset;
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ConstantInt *OpC = dyn_cast<ConstantInt>(GTI.getOperand());
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if (StructType *STy = GTI.getStructTypeOrNull()) {
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const StructLayout *SL = DL.getStructLayout(STy);
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Offset = SL->getElementOffset(OpC->getZExtValue());
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} else {
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assert(GTI.isSequential() && "should be sequencial");
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/// If the index isn't known, we take 1 because it is the index that will
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/// give the worse alignment of the offset.
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const uint64_t ElemCount = OpC ? OpC->getZExtValue() : 1;
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Offset = GTI.getSequentialElementStride(DL) * ElemCount;
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}
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Result = Align(MinAlign(Offset, Result.value()));
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}
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return Result;
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}
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bool GEPOperator::accumulateConstantOffset(
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const DataLayout &DL, APInt &Offset,
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function_ref<bool(Value &, APInt &)> ExternalAnalysis) const {
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assert(Offset.getBitWidth() ==
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DL.getIndexSizeInBits(getPointerAddressSpace()) &&
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"The offset bit width does not match DL specification.");
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SmallVector<const Value *> Index(llvm::drop_begin(operand_values()));
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return GEPOperator::accumulateConstantOffset(getSourceElementType(), Index,
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DL, Offset, ExternalAnalysis);
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}
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bool GEPOperator::accumulateConstantOffset(
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Type *SourceType, ArrayRef<const Value *> Index, const DataLayout &DL,
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APInt &Offset, function_ref<bool(Value &, APInt &)> ExternalAnalysis) {
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// Fast path for canonical getelementptr i8 form.
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if (SourceType->isIntegerTy(8) && !ExternalAnalysis) {
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if (auto *CI = dyn_cast<ConstantInt>(Index.front())) {
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Offset += CI->getValue().sextOrTrunc(Offset.getBitWidth());
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return true;
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}
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return false;
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}
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bool UsedExternalAnalysis = false;
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auto AccumulateOffset = [&](APInt Index, uint64_t Size) -> bool {
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Index = Index.sextOrTrunc(Offset.getBitWidth());
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APInt IndexedSize = APInt(Offset.getBitWidth(), Size);
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// For array or vector indices, scale the index by the size of the type.
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if (!UsedExternalAnalysis) {
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Offset += Index * IndexedSize;
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} else {
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// External Analysis can return a result higher/lower than the value
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// represents. We need to detect overflow/underflow.
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bool Overflow = false;
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APInt OffsetPlus = Index.smul_ov(IndexedSize, Overflow);
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if (Overflow)
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return false;
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Offset = Offset.sadd_ov(OffsetPlus, Overflow);
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if (Overflow)
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return false;
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}
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return true;
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};
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auto begin = generic_gep_type_iterator<decltype(Index.begin())>::begin(
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SourceType, Index.begin());
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auto end = generic_gep_type_iterator<decltype(Index.end())>::end(Index.end());
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for (auto GTI = begin, GTE = end; GTI != GTE; ++GTI) {
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// Scalable vectors are multiplied by a runtime constant.
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bool ScalableType = GTI.getIndexedType()->isScalableTy();
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Value *V = GTI.getOperand();
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StructType *STy = GTI.getStructTypeOrNull();
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// Handle ConstantInt if possible.
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if (auto ConstOffset = dyn_cast<ConstantInt>(V)) {
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if (ConstOffset->isZero())
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continue;
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// if the type is scalable and the constant is not zero (vscale * n * 0 =
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// 0) bailout.
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if (ScalableType)
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return false;
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// Handle a struct index, which adds its field offset to the pointer.
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if (STy) {
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unsigned ElementIdx = ConstOffset->getZExtValue();
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const StructLayout *SL = DL.getStructLayout(STy);
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// Element offset is in bytes.
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if (!AccumulateOffset(
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APInt(Offset.getBitWidth(), SL->getElementOffset(ElementIdx)),
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1))
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return false;
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continue;
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}
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if (!AccumulateOffset(ConstOffset->getValue(),
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GTI.getSequentialElementStride(DL)))
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return false;
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continue;
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}
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// The operand is not constant, check if an external analysis was provided.
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// External analsis is not applicable to a struct type.
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if (!ExternalAnalysis || STy || ScalableType)
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return false;
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APInt AnalysisIndex;
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if (!ExternalAnalysis(*V, AnalysisIndex))
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return false;
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UsedExternalAnalysis = true;
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if (!AccumulateOffset(AnalysisIndex, GTI.getSequentialElementStride(DL)))
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return false;
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}
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return true;
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}
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bool GEPOperator::collectOffset(
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const DataLayout &DL, unsigned BitWidth,
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MapVector<Value *, APInt> &VariableOffsets,
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APInt &ConstantOffset) const {
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assert(BitWidth == DL.getIndexSizeInBits(getPointerAddressSpace()) &&
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"The offset bit width does not match DL specification.");
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auto CollectConstantOffset = [&](APInt Index, uint64_t Size) {
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Index = Index.sextOrTrunc(BitWidth);
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APInt IndexedSize = APInt(BitWidth, Size);
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ConstantOffset += Index * IndexedSize;
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};
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for (gep_type_iterator GTI = gep_type_begin(this), GTE = gep_type_end(this);
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GTI != GTE; ++GTI) {
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// Scalable vectors are multiplied by a runtime constant.
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bool ScalableType = GTI.getIndexedType()->isScalableTy();
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Value *V = GTI.getOperand();
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StructType *STy = GTI.getStructTypeOrNull();
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// Handle ConstantInt if possible.
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if (auto ConstOffset = dyn_cast<ConstantInt>(V)) {
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if (ConstOffset->isZero())
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continue;
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// If the type is scalable and the constant is not zero (vscale * n * 0 =
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// 0) bailout.
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// TODO: If the runtime value is accessible at any point before DWARF
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// emission, then we could potentially keep a forward reference to it
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// in the debug value to be filled in later.
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if (ScalableType)
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return false;
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// Handle a struct index, which adds its field offset to the pointer.
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if (STy) {
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unsigned ElementIdx = ConstOffset->getZExtValue();
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const StructLayout *SL = DL.getStructLayout(STy);
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// Element offset is in bytes.
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CollectConstantOffset(APInt(BitWidth, SL->getElementOffset(ElementIdx)),
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1);
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continue;
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}
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CollectConstantOffset(ConstOffset->getValue(),
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GTI.getSequentialElementStride(DL));
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continue;
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}
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if (STy || ScalableType)
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return false;
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APInt IndexedSize = APInt(BitWidth, GTI.getSequentialElementStride(DL));
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// Insert an initial offset of 0 for V iff none exists already, then
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// increment the offset by IndexedSize.
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if (!IndexedSize.isZero()) {
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auto *It = VariableOffsets.insert({V, APInt(BitWidth, 0)}).first;
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It->second += IndexedSize;
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}
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}
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return true;
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}
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void FastMathFlags::print(raw_ostream &O) const {
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if (all())
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O << " fast";
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else {
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if (allowReassoc())
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O << " reassoc";
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if (noNaNs())
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O << " nnan";
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if (noInfs())
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O << " ninf";
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if (noSignedZeros())
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O << " nsz";
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if (allowReciprocal())
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O << " arcp";
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if (allowContract())
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O << " contract";
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if (approxFunc())
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O << " afn";
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}
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}
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} // namespace llvm
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