781 lines
38 KiB
C++
781 lines
38 KiB
C++
//===- llvm/Analysis/ValueTracking.h - Walk computations --------*- C++ -*-===//
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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 contains routines that help analyze properties that chains of
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// computations have.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_ANALYSIS_VALUETRACKING_H
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#define LLVM_ANALYSIS_VALUETRACKING_H
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#include "llvm/ADT/ArrayRef.h"
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#include "llvm/ADT/Optional.h"
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#include "llvm/ADT/SmallSet.h"
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#include "llvm/IR/Constants.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/InstrTypes.h"
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#include "llvm/IR/Intrinsics.h"
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#include "llvm/IR/Operator.h"
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#include <cassert>
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#include <cstdint>
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namespace llvm {
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class AddOperator;
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class AllocaInst;
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class APInt;
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class AssumptionCache;
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class DominatorTree;
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class GEPOperator;
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class IntrinsicInst;
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class LoadInst;
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class WithOverflowInst;
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struct KnownBits;
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class Loop;
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class LoopInfo;
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class MDNode;
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class OptimizationRemarkEmitter;
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class StringRef;
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class TargetLibraryInfo;
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class Value;
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constexpr unsigned MaxAnalysisRecursionDepth = 6;
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/// Determine which bits of V are known to be either zero or one and return
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/// them in the KnownZero/KnownOne bit sets.
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///
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/// This function is defined on values with integer type, values with pointer
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/// type, and vectors of integers. In the case
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/// where V is a vector, the known zero and known one values are the
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/// same width as the vector element, and the bit is set only if it is true
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/// for all of the elements in the vector.
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void computeKnownBits(const Value *V, KnownBits &Known,
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const DataLayout &DL, unsigned Depth = 0,
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AssumptionCache *AC = nullptr,
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const Instruction *CxtI = nullptr,
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const DominatorTree *DT = nullptr,
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OptimizationRemarkEmitter *ORE = nullptr,
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bool UseInstrInfo = true);
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/// Determine which bits of V are known to be either zero or one and return
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/// them in the KnownZero/KnownOne bit sets.
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///
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/// This function is defined on values with integer type, values with pointer
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/// type, and vectors of integers. In the case
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/// where V is a vector, the known zero and known one values are the
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/// same width as the vector element, and the bit is set only if it is true
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/// for all of the demanded elements in the vector.
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void computeKnownBits(const Value *V, const APInt &DemandedElts,
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KnownBits &Known, const DataLayout &DL,
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unsigned Depth = 0, AssumptionCache *AC = nullptr,
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const Instruction *CxtI = nullptr,
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const DominatorTree *DT = nullptr,
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OptimizationRemarkEmitter *ORE = nullptr,
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bool UseInstrInfo = true);
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/// Returns the known bits rather than passing by reference.
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KnownBits computeKnownBits(const Value *V, const DataLayout &DL,
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unsigned Depth = 0, AssumptionCache *AC = nullptr,
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const Instruction *CxtI = nullptr,
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const DominatorTree *DT = nullptr,
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OptimizationRemarkEmitter *ORE = nullptr,
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bool UseInstrInfo = true);
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/// Returns the known bits rather than passing by reference.
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KnownBits computeKnownBits(const Value *V, const APInt &DemandedElts,
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const DataLayout &DL, unsigned Depth = 0,
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AssumptionCache *AC = nullptr,
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const Instruction *CxtI = nullptr,
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const DominatorTree *DT = nullptr,
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OptimizationRemarkEmitter *ORE = nullptr,
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bool UseInstrInfo = true);
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/// Compute known bits from the range metadata.
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/// \p KnownZero the set of bits that are known to be zero
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/// \p KnownOne the set of bits that are known to be one
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void computeKnownBitsFromRangeMetadata(const MDNode &Ranges,
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KnownBits &Known);
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/// Return true if LHS and RHS have no common bits set.
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bool haveNoCommonBitsSet(const Value *LHS, const Value *RHS,
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const DataLayout &DL,
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AssumptionCache *AC = nullptr,
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const Instruction *CxtI = nullptr,
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const DominatorTree *DT = nullptr,
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bool UseInstrInfo = true);
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/// Return true if the given value is known to have exactly one bit set when
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/// defined. For vectors return true if every element is known to be a power
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/// of two when defined. Supports values with integer or pointer type and
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/// vectors of integers. If 'OrZero' is set, then return true if the given
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/// value is either a power of two or zero.
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bool isKnownToBeAPowerOfTwo(const Value *V, const DataLayout &DL,
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bool OrZero = false, unsigned Depth = 0,
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AssumptionCache *AC = nullptr,
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const Instruction *CxtI = nullptr,
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const DominatorTree *DT = nullptr,
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bool UseInstrInfo = true);
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bool isOnlyUsedInZeroEqualityComparison(const Instruction *CxtI);
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/// Return true if the given value is known to be non-zero when defined. For
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/// vectors, return true if every element is known to be non-zero when
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/// defined. For pointers, if the context instruction and dominator tree are
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/// specified, perform context-sensitive analysis and return true if the
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/// pointer couldn't possibly be null at the specified instruction.
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/// Supports values with integer or pointer type and vectors of integers.
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bool isKnownNonZero(const Value *V, const DataLayout &DL, unsigned Depth = 0,
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AssumptionCache *AC = nullptr,
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const Instruction *CxtI = nullptr,
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const DominatorTree *DT = nullptr,
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bool UseInstrInfo = true);
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/// Return true if the two given values are negation.
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/// Currently can recoginze Value pair:
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/// 1: <X, Y> if X = sub (0, Y) or Y = sub (0, X)
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/// 2: <X, Y> if X = sub (A, B) and Y = sub (B, A)
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bool isKnownNegation(const Value *X, const Value *Y, bool NeedNSW = false);
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/// Returns true if the give value is known to be non-negative.
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bool isKnownNonNegative(const Value *V, const DataLayout &DL,
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unsigned Depth = 0,
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AssumptionCache *AC = nullptr,
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const Instruction *CxtI = nullptr,
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const DominatorTree *DT = nullptr,
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bool UseInstrInfo = true);
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/// Returns true if the given value is known be positive (i.e. non-negative
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/// and non-zero).
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bool isKnownPositive(const Value *V, const DataLayout &DL, unsigned Depth = 0,
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AssumptionCache *AC = nullptr,
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const Instruction *CxtI = nullptr,
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const DominatorTree *DT = nullptr,
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bool UseInstrInfo = true);
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/// Returns true if the given value is known be negative (i.e. non-positive
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/// and non-zero).
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bool isKnownNegative(const Value *V, const DataLayout &DL, unsigned Depth = 0,
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AssumptionCache *AC = nullptr,
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const Instruction *CxtI = nullptr,
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const DominatorTree *DT = nullptr,
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bool UseInstrInfo = true);
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/// Return true if the given values are known to be non-equal when defined.
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/// Supports scalar integer types only.
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bool isKnownNonEqual(const Value *V1, const Value *V2, const DataLayout &DL,
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AssumptionCache *AC = nullptr,
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const Instruction *CxtI = nullptr,
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const DominatorTree *DT = nullptr,
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bool UseInstrInfo = true);
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/// Return true if 'V & Mask' is known to be zero. We use this predicate to
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/// simplify operations downstream. Mask is known to be zero for bits that V
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/// cannot have.
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///
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/// This function is defined on values with integer type, values with pointer
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/// type, and vectors of integers. In the case
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/// where V is a vector, the mask, known zero, and known one values are the
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/// same width as the vector element, and the bit is set only if it is true
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/// for all of the elements in the vector.
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bool MaskedValueIsZero(const Value *V, const APInt &Mask,
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const DataLayout &DL,
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unsigned Depth = 0, AssumptionCache *AC = nullptr,
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const Instruction *CxtI = nullptr,
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const DominatorTree *DT = nullptr,
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bool UseInstrInfo = true);
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/// Return the number of times the sign bit of the register is replicated into
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/// the other bits. We know that at least 1 bit is always equal to the sign
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/// bit (itself), but other cases can give us information. For example,
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/// immediately after an "ashr X, 2", we know that the top 3 bits are all
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/// equal to each other, so we return 3. For vectors, return the number of
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/// sign bits for the vector element with the mininum number of known sign
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/// bits.
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unsigned ComputeNumSignBits(const Value *Op, const DataLayout &DL,
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unsigned Depth = 0, AssumptionCache *AC = nullptr,
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const Instruction *CxtI = nullptr,
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const DominatorTree *DT = nullptr,
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bool UseInstrInfo = true);
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/// This function computes the integer multiple of Base that equals V. If
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/// successful, it returns true and returns the multiple in Multiple. If
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/// unsuccessful, it returns false. Also, if V can be simplified to an
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/// integer, then the simplified V is returned in Val. Look through sext only
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/// if LookThroughSExt=true.
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bool ComputeMultiple(Value *V, unsigned Base, Value *&Multiple,
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bool LookThroughSExt = false,
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unsigned Depth = 0);
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/// Map a call instruction to an intrinsic ID. Libcalls which have equivalent
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/// intrinsics are treated as-if they were intrinsics.
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Intrinsic::ID getIntrinsicForCallSite(const CallBase &CB,
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const TargetLibraryInfo *TLI);
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/// Return true if we can prove that the specified FP value is never equal to
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/// -0.0.
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bool CannotBeNegativeZero(const Value *V, const TargetLibraryInfo *TLI,
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unsigned Depth = 0);
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/// Return true if we can prove that the specified FP value is either NaN or
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/// never less than -0.0.
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///
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/// NaN --> true
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/// +0 --> true
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/// -0 --> true
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/// x > +0 --> true
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/// x < -0 --> false
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bool CannotBeOrderedLessThanZero(const Value *V, const TargetLibraryInfo *TLI);
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/// Return true if the floating-point scalar value is not an infinity or if
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/// the floating-point vector value has no infinities. Return false if a value
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/// could ever be infinity.
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bool isKnownNeverInfinity(const Value *V, const TargetLibraryInfo *TLI,
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unsigned Depth = 0);
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/// Return true if the floating-point scalar value is not a NaN or if the
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/// floating-point vector value has no NaN elements. Return false if a value
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/// could ever be NaN.
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bool isKnownNeverNaN(const Value *V, const TargetLibraryInfo *TLI,
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unsigned Depth = 0);
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/// Return true if we can prove that the specified FP value's sign bit is 0.
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///
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/// NaN --> true/false (depending on the NaN's sign bit)
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/// +0 --> true
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/// -0 --> false
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/// x > +0 --> true
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/// x < -0 --> false
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bool SignBitMustBeZero(const Value *V, const TargetLibraryInfo *TLI);
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/// If the specified value can be set by repeating the same byte in memory,
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/// return the i8 value that it is represented with. This is true for all i8
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/// values obviously, but is also true for i32 0, i32 -1, i16 0xF0F0, double
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/// 0.0 etc. If the value can't be handled with a repeated byte store (e.g.
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/// i16 0x1234), return null. If the value is entirely undef and padding,
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/// return undef.
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Value *isBytewiseValue(Value *V, const DataLayout &DL);
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/// Given an aggregate and an sequence of indices, see if the scalar value
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/// indexed is already around as a register, for example if it were inserted
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/// directly into the aggregate.
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///
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/// If InsertBefore is not null, this function will duplicate (modified)
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/// insertvalues when a part of a nested struct is extracted.
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Value *FindInsertedValue(Value *V,
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ArrayRef<unsigned> idx_range,
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Instruction *InsertBefore = nullptr);
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/// Analyze the specified pointer to see if it can be expressed as a base
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/// pointer plus a constant offset. Return the base and offset to the caller.
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///
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/// This is a wrapper around Value::stripAndAccumulateConstantOffsets that
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/// creates and later unpacks the required APInt.
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inline Value *GetPointerBaseWithConstantOffset(Value *Ptr, int64_t &Offset,
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const DataLayout &DL,
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bool AllowNonInbounds = true) {
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APInt OffsetAPInt(DL.getIndexTypeSizeInBits(Ptr->getType()), 0);
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Value *Base =
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Ptr->stripAndAccumulateConstantOffsets(DL, OffsetAPInt, AllowNonInbounds);
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Offset = OffsetAPInt.getSExtValue();
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return Base;
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}
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inline const Value *
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GetPointerBaseWithConstantOffset(const Value *Ptr, int64_t &Offset,
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const DataLayout &DL,
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bool AllowNonInbounds = true) {
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return GetPointerBaseWithConstantOffset(const_cast<Value *>(Ptr), Offset, DL,
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AllowNonInbounds);
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}
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/// Returns true if the GEP is based on a pointer to a string (array of
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// \p CharSize integers) and is indexing into this string.
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bool isGEPBasedOnPointerToString(const GEPOperator *GEP,
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unsigned CharSize = 8);
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/// Represents offset+length into a ConstantDataArray.
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struct ConstantDataArraySlice {
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/// ConstantDataArray pointer. nullptr indicates a zeroinitializer (a valid
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/// initializer, it just doesn't fit the ConstantDataArray interface).
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const ConstantDataArray *Array;
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/// Slice starts at this Offset.
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uint64_t Offset;
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/// Length of the slice.
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uint64_t Length;
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/// Moves the Offset and adjusts Length accordingly.
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void move(uint64_t Delta) {
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assert(Delta < Length);
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Offset += Delta;
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Length -= Delta;
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}
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/// Convenience accessor for elements in the slice.
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uint64_t operator[](unsigned I) const {
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return Array==nullptr ? 0 : Array->getElementAsInteger(I + Offset);
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}
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};
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/// Returns true if the value \p V is a pointer into a ConstantDataArray.
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/// If successful \p Slice will point to a ConstantDataArray info object
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/// with an appropriate offset.
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bool getConstantDataArrayInfo(const Value *V, ConstantDataArraySlice &Slice,
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unsigned ElementSize, uint64_t Offset = 0);
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/// This function computes the length of a null-terminated C string pointed to
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/// by V. If successful, it returns true and returns the string in Str. If
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/// unsuccessful, it returns false. This does not include the trailing null
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/// character by default. If TrimAtNul is set to false, then this returns any
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/// trailing null characters as well as any other characters that come after
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/// it.
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bool getConstantStringInfo(const Value *V, StringRef &Str,
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uint64_t Offset = 0, bool TrimAtNul = true);
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/// If we can compute the length of the string pointed to by the specified
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/// pointer, return 'len+1'. If we can't, return 0.
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uint64_t GetStringLength(const Value *V, unsigned CharSize = 8);
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/// This function returns call pointer argument that is considered the same by
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/// aliasing rules. You CAN'T use it to replace one value with another. If
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/// \p MustPreserveNullness is true, the call must preserve the nullness of
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/// the pointer.
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const Value *getArgumentAliasingToReturnedPointer(const CallBase *Call,
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bool MustPreserveNullness);
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inline Value *
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getArgumentAliasingToReturnedPointer(CallBase *Call,
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bool MustPreserveNullness) {
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return const_cast<Value *>(getArgumentAliasingToReturnedPointer(
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const_cast<const CallBase *>(Call), MustPreserveNullness));
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}
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/// {launder,strip}.invariant.group returns pointer that aliases its argument,
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/// and it only captures pointer by returning it.
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/// These intrinsics are not marked as nocapture, because returning is
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/// considered as capture. The arguments are not marked as returned neither,
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/// because it would make it useless. If \p MustPreserveNullness is true,
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/// the intrinsic must preserve the nullness of the pointer.
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bool isIntrinsicReturningPointerAliasingArgumentWithoutCapturing(
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const CallBase *Call, bool MustPreserveNullness);
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/// This method strips off any GEP address adjustments and pointer casts from
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/// the specified value, returning the original object being addressed. Note
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/// that the returned value has pointer type if the specified value does. If
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/// the MaxLookup value is non-zero, it limits the number of instructions to
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/// be stripped off.
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Value *getUnderlyingObject(Value *V, unsigned MaxLookup = 6);
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inline const Value *getUnderlyingObject(const Value *V,
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unsigned MaxLookup = 6) {
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return getUnderlyingObject(const_cast<Value *>(V), MaxLookup);
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}
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/// This method is similar to getUnderlyingObject except that it can
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/// look through phi and select instructions and return multiple objects.
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///
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/// If LoopInfo is passed, loop phis are further analyzed. If a pointer
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/// accesses different objects in each iteration, we don't look through the
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/// phi node. E.g. consider this loop nest:
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///
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/// int **A;
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/// for (i)
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/// for (j) {
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/// A[i][j] = A[i-1][j] * B[j]
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/// }
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///
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/// This is transformed by Load-PRE to stash away A[i] for the next iteration
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/// of the outer loop:
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///
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/// Curr = A[0]; // Prev_0
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/// for (i: 1..N) {
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/// Prev = Curr; // Prev = PHI (Prev_0, Curr)
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/// Curr = A[i];
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/// for (j: 0..N) {
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/// Curr[j] = Prev[j] * B[j]
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/// }
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/// }
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///
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/// Since A[i] and A[i-1] are independent pointers, getUnderlyingObjects
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/// should not assume that Curr and Prev share the same underlying object thus
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/// it shouldn't look through the phi above.
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void getUnderlyingObjects(const Value *V,
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SmallVectorImpl<const Value *> &Objects,
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LoopInfo *LI = nullptr, unsigned MaxLookup = 6);
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/// This is a wrapper around getUnderlyingObjects and adds support for basic
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/// ptrtoint+arithmetic+inttoptr sequences.
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bool getUnderlyingObjectsForCodeGen(const Value *V,
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SmallVectorImpl<Value *> &Objects);
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/// Returns unique alloca where the value comes from, or nullptr.
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/// If OffsetZero is true check that V points to the begining of the alloca.
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AllocaInst *findAllocaForValue(Value *V, bool OffsetZero = false);
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inline const AllocaInst *findAllocaForValue(const Value *V,
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bool OffsetZero = false) {
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return findAllocaForValue(const_cast<Value *>(V), OffsetZero);
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}
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/// Return true if the only users of this pointer are lifetime markers.
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bool onlyUsedByLifetimeMarkers(const Value *V);
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/// Return true if the only users of this pointer are lifetime markers or
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/// droppable instructions.
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bool onlyUsedByLifetimeMarkersOrDroppableInsts(const Value *V);
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/// Return true if speculation of the given load must be suppressed to avoid
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/// ordering or interfering with an active sanitizer. If not suppressed,
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/// dereferenceability and alignment must be proven separately. Note: This
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/// is only needed for raw reasoning; if you use the interface below
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/// (isSafeToSpeculativelyExecute), this is handled internally.
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bool mustSuppressSpeculation(const LoadInst &LI);
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/// Return true if the instruction does not have any effects besides
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/// calculating the result and does not have undefined behavior.
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///
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/// This method never returns true for an instruction that returns true for
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/// mayHaveSideEffects; however, this method also does some other checks in
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/// addition. It checks for undefined behavior, like dividing by zero or
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/// loading from an invalid pointer (but not for undefined results, like a
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/// shift with a shift amount larger than the width of the result). It checks
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/// for malloc and alloca because speculatively executing them might cause a
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/// memory leak. It also returns false for instructions related to control
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/// flow, specifically terminators and PHI nodes.
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///
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/// If the CtxI is specified this method performs context-sensitive analysis
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/// and returns true if it is safe to execute the instruction immediately
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/// before the CtxI.
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///
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/// If the CtxI is NOT specified this method only looks at the instruction
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/// itself and its operands, so if this method returns true, it is safe to
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/// move the instruction as long as the correct dominance relationships for
|
|
/// the operands and users hold.
|
|
///
|
|
/// This method can return true for instructions that read memory;
|
|
/// for such instructions, moving them may change the resulting value.
|
|
bool isSafeToSpeculativelyExecute(const Value *V,
|
|
const Instruction *CtxI = nullptr,
|
|
const DominatorTree *DT = nullptr);
|
|
|
|
/// Returns true if the result or effects of the given instructions \p I
|
|
/// depend on or influence global memory.
|
|
/// Memory dependence arises for example if the instruction reads from
|
|
/// memory or may produce effects or undefined behaviour. Memory dependent
|
|
/// instructions generally cannot be reorderd with respect to other memory
|
|
/// dependent instructions or moved into non-dominated basic blocks.
|
|
/// Instructions which just compute a value based on the values of their
|
|
/// operands are not memory dependent.
|
|
bool mayBeMemoryDependent(const Instruction &I);
|
|
|
|
/// Return true if it is an intrinsic that cannot be speculated but also
|
|
/// cannot trap.
|
|
bool isAssumeLikeIntrinsic(const Instruction *I);
|
|
|
|
/// Return true if it is valid to use the assumptions provided by an
|
|
/// assume intrinsic, I, at the point in the control-flow identified by the
|
|
/// context instruction, CxtI.
|
|
bool isValidAssumeForContext(const Instruction *I, const Instruction *CxtI,
|
|
const DominatorTree *DT = nullptr);
|
|
|
|
enum class OverflowResult {
|
|
/// Always overflows in the direction of signed/unsigned min value.
|
|
AlwaysOverflowsLow,
|
|
/// Always overflows in the direction of signed/unsigned max value.
|
|
AlwaysOverflowsHigh,
|
|
/// May or may not overflow.
|
|
MayOverflow,
|
|
/// Never overflows.
|
|
NeverOverflows,
|
|
};
|
|
|
|
OverflowResult computeOverflowForUnsignedMul(const Value *LHS,
|
|
const Value *RHS,
|
|
const DataLayout &DL,
|
|
AssumptionCache *AC,
|
|
const Instruction *CxtI,
|
|
const DominatorTree *DT,
|
|
bool UseInstrInfo = true);
|
|
OverflowResult computeOverflowForSignedMul(const Value *LHS, const Value *RHS,
|
|
const DataLayout &DL,
|
|
AssumptionCache *AC,
|
|
const Instruction *CxtI,
|
|
const DominatorTree *DT,
|
|
bool UseInstrInfo = true);
|
|
OverflowResult computeOverflowForUnsignedAdd(const Value *LHS,
|
|
const Value *RHS,
|
|
const DataLayout &DL,
|
|
AssumptionCache *AC,
|
|
const Instruction *CxtI,
|
|
const DominatorTree *DT,
|
|
bool UseInstrInfo = true);
|
|
OverflowResult computeOverflowForSignedAdd(const Value *LHS, const Value *RHS,
|
|
const DataLayout &DL,
|
|
AssumptionCache *AC = nullptr,
|
|
const Instruction *CxtI = nullptr,
|
|
const DominatorTree *DT = nullptr);
|
|
/// This version also leverages the sign bit of Add if known.
|
|
OverflowResult computeOverflowForSignedAdd(const AddOperator *Add,
|
|
const DataLayout &DL,
|
|
AssumptionCache *AC = nullptr,
|
|
const Instruction *CxtI = nullptr,
|
|
const DominatorTree *DT = nullptr);
|
|
OverflowResult computeOverflowForUnsignedSub(const Value *LHS, const Value *RHS,
|
|
const DataLayout &DL,
|
|
AssumptionCache *AC,
|
|
const Instruction *CxtI,
|
|
const DominatorTree *DT);
|
|
OverflowResult computeOverflowForSignedSub(const Value *LHS, const Value *RHS,
|
|
const DataLayout &DL,
|
|
AssumptionCache *AC,
|
|
const Instruction *CxtI,
|
|
const DominatorTree *DT);
|
|
|
|
/// Returns true if the arithmetic part of the \p WO 's result is
|
|
/// used only along the paths control dependent on the computation
|
|
/// not overflowing, \p WO being an <op>.with.overflow intrinsic.
|
|
bool isOverflowIntrinsicNoWrap(const WithOverflowInst *WO,
|
|
const DominatorTree &DT);
|
|
|
|
|
|
/// Determine the possible constant range of an integer or vector of integer
|
|
/// value. This is intended as a cheap, non-recursive check.
|
|
ConstantRange computeConstantRange(const Value *V, bool UseInstrInfo = true,
|
|
AssumptionCache *AC = nullptr,
|
|
const Instruction *CtxI = nullptr,
|
|
unsigned Depth = 0);
|
|
|
|
/// Return true if this function can prove that the instruction I will
|
|
/// always transfer execution to one of its successors (including the next
|
|
/// instruction that follows within a basic block). E.g. this is not
|
|
/// guaranteed for function calls that could loop infinitely.
|
|
///
|
|
/// In other words, this function returns false for instructions that may
|
|
/// transfer execution or fail to transfer execution in a way that is not
|
|
/// captured in the CFG nor in the sequence of instructions within a basic
|
|
/// block.
|
|
///
|
|
/// Undefined behavior is assumed not to happen, so e.g. division is
|
|
/// guaranteed to transfer execution to the following instruction even
|
|
/// though division by zero might cause undefined behavior.
|
|
bool isGuaranteedToTransferExecutionToSuccessor(const Instruction *I);
|
|
|
|
/// Returns true if this block does not contain a potential implicit exit.
|
|
/// This is equivelent to saying that all instructions within the basic block
|
|
/// are guaranteed to transfer execution to their successor within the basic
|
|
/// block. This has the same assumptions w.r.t. undefined behavior as the
|
|
/// instruction variant of this function.
|
|
bool isGuaranteedToTransferExecutionToSuccessor(const BasicBlock *BB);
|
|
|
|
/// Return true if this function can prove that the instruction I
|
|
/// is executed for every iteration of the loop L.
|
|
///
|
|
/// Note that this currently only considers the loop header.
|
|
bool isGuaranteedToExecuteForEveryIteration(const Instruction *I,
|
|
const Loop *L);
|
|
|
|
/// Return true if I yields poison or raises UB if any of its operands is
|
|
/// poison.
|
|
/// Formally, given I = `r = op v1 v2 .. vN`, propagatesPoison returns true
|
|
/// if, for all i, r is evaluated to poison or op raises UB if vi = poison.
|
|
/// To filter out operands that raise UB on poison, you can use
|
|
/// getGuaranteedNonPoisonOp.
|
|
bool propagatesPoison(const Operator *I);
|
|
|
|
/// Insert operands of I into Ops such that I will trigger undefined behavior
|
|
/// if I is executed and that operand has a poison value.
|
|
void getGuaranteedNonPoisonOps(const Instruction *I,
|
|
SmallPtrSetImpl<const Value *> &Ops);
|
|
|
|
/// Return true if the given instruction must trigger undefined behavior
|
|
/// when I is executed with any operands which appear in KnownPoison holding
|
|
/// a poison value at the point of execution.
|
|
bool mustTriggerUB(const Instruction *I,
|
|
const SmallSet<const Value *, 16>& KnownPoison);
|
|
|
|
/// Return true if this function can prove that if Inst is executed
|
|
/// and yields a poison value or undef bits, then that will trigger
|
|
/// undefined behavior.
|
|
///
|
|
/// Note that this currently only considers the basic block that is
|
|
/// the parent of Inst.
|
|
bool programUndefinedIfUndefOrPoison(const Instruction *Inst);
|
|
bool programUndefinedIfPoison(const Instruction *Inst);
|
|
|
|
/// canCreateUndefOrPoison returns true if Op can create undef or poison from
|
|
/// non-undef & non-poison operands.
|
|
/// For vectors, canCreateUndefOrPoison returns true if there is potential
|
|
/// poison or undef in any element of the result when vectors without
|
|
/// undef/poison poison are given as operands.
|
|
/// For example, given `Op = shl <2 x i32> %x, <0, 32>`, this function returns
|
|
/// true. If Op raises immediate UB but never creates poison or undef
|
|
/// (e.g. sdiv I, 0), canCreatePoison returns false.
|
|
///
|
|
/// canCreatePoison returns true if Op can create poison from non-poison
|
|
/// operands.
|
|
bool canCreateUndefOrPoison(const Operator *Op);
|
|
bool canCreatePoison(const Operator *Op);
|
|
|
|
/// Return true if V is poison given that ValAssumedPoison is already poison.
|
|
/// For example, if ValAssumedPoison is `icmp X, 10` and V is `icmp X, 5`,
|
|
/// impliesPoison returns true.
|
|
bool impliesPoison(const Value *ValAssumedPoison, const Value *V);
|
|
|
|
/// Return true if this function can prove that V does not have undef bits
|
|
/// and is never poison. If V is an aggregate value or vector, check whether
|
|
/// all elements (except padding) are not undef or poison.
|
|
/// Note that this is different from canCreateUndefOrPoison because the
|
|
/// function assumes Op's operands are not poison/undef.
|
|
///
|
|
/// If CtxI and DT are specified this method performs flow-sensitive analysis
|
|
/// and returns true if it is guaranteed to be never undef or poison
|
|
/// immediately before the CtxI.
|
|
bool isGuaranteedNotToBeUndefOrPoison(const Value *V,
|
|
AssumptionCache *AC = nullptr,
|
|
const Instruction *CtxI = nullptr,
|
|
const DominatorTree *DT = nullptr,
|
|
unsigned Depth = 0);
|
|
bool isGuaranteedNotToBePoison(const Value *V, AssumptionCache *AC = nullptr,
|
|
const Instruction *CtxI = nullptr,
|
|
const DominatorTree *DT = nullptr,
|
|
unsigned Depth = 0);
|
|
|
|
/// Specific patterns of select instructions we can match.
|
|
enum SelectPatternFlavor {
|
|
SPF_UNKNOWN = 0,
|
|
SPF_SMIN, /// Signed minimum
|
|
SPF_UMIN, /// Unsigned minimum
|
|
SPF_SMAX, /// Signed maximum
|
|
SPF_UMAX, /// Unsigned maximum
|
|
SPF_FMINNUM, /// Floating point minnum
|
|
SPF_FMAXNUM, /// Floating point maxnum
|
|
SPF_ABS, /// Absolute value
|
|
SPF_NABS /// Negated absolute value
|
|
};
|
|
|
|
/// Behavior when a floating point min/max is given one NaN and one
|
|
/// non-NaN as input.
|
|
enum SelectPatternNaNBehavior {
|
|
SPNB_NA = 0, /// NaN behavior not applicable.
|
|
SPNB_RETURNS_NAN, /// Given one NaN input, returns the NaN.
|
|
SPNB_RETURNS_OTHER, /// Given one NaN input, returns the non-NaN.
|
|
SPNB_RETURNS_ANY /// Given one NaN input, can return either (or
|
|
/// it has been determined that no operands can
|
|
/// be NaN).
|
|
};
|
|
|
|
struct SelectPatternResult {
|
|
SelectPatternFlavor Flavor;
|
|
SelectPatternNaNBehavior NaNBehavior; /// Only applicable if Flavor is
|
|
/// SPF_FMINNUM or SPF_FMAXNUM.
|
|
bool Ordered; /// When implementing this min/max pattern as
|
|
/// fcmp; select, does the fcmp have to be
|
|
/// ordered?
|
|
|
|
/// Return true if \p SPF is a min or a max pattern.
|
|
static bool isMinOrMax(SelectPatternFlavor SPF) {
|
|
return SPF != SPF_UNKNOWN && SPF != SPF_ABS && SPF != SPF_NABS;
|
|
}
|
|
};
|
|
|
|
/// Pattern match integer [SU]MIN, [SU]MAX and ABS idioms, returning the kind
|
|
/// and providing the out parameter results if we successfully match.
|
|
///
|
|
/// For ABS/NABS, LHS will be set to the input to the abs idiom. RHS will be
|
|
/// the negation instruction from the idiom.
|
|
///
|
|
/// If CastOp is not nullptr, also match MIN/MAX idioms where the type does
|
|
/// not match that of the original select. If this is the case, the cast
|
|
/// operation (one of Trunc,SExt,Zext) that must be done to transform the
|
|
/// type of LHS and RHS into the type of V is returned in CastOp.
|
|
///
|
|
/// For example:
|
|
/// %1 = icmp slt i32 %a, i32 4
|
|
/// %2 = sext i32 %a to i64
|
|
/// %3 = select i1 %1, i64 %2, i64 4
|
|
///
|
|
/// -> LHS = %a, RHS = i32 4, *CastOp = Instruction::SExt
|
|
///
|
|
SelectPatternResult matchSelectPattern(Value *V, Value *&LHS, Value *&RHS,
|
|
Instruction::CastOps *CastOp = nullptr,
|
|
unsigned Depth = 0);
|
|
|
|
inline SelectPatternResult
|
|
matchSelectPattern(const Value *V, const Value *&LHS, const Value *&RHS) {
|
|
Value *L = const_cast<Value *>(LHS);
|
|
Value *R = const_cast<Value *>(RHS);
|
|
auto Result = matchSelectPattern(const_cast<Value *>(V), L, R);
|
|
LHS = L;
|
|
RHS = R;
|
|
return Result;
|
|
}
|
|
|
|
/// Determine the pattern that a select with the given compare as its
|
|
/// predicate and given values as its true/false operands would match.
|
|
SelectPatternResult matchDecomposedSelectPattern(
|
|
CmpInst *CmpI, Value *TrueVal, Value *FalseVal, Value *&LHS, Value *&RHS,
|
|
Instruction::CastOps *CastOp = nullptr, unsigned Depth = 0);
|
|
|
|
/// Return the canonical comparison predicate for the specified
|
|
/// minimum/maximum flavor.
|
|
CmpInst::Predicate getMinMaxPred(SelectPatternFlavor SPF,
|
|
bool Ordered = false);
|
|
|
|
/// Return the inverse minimum/maximum flavor of the specified flavor.
|
|
/// For example, signed minimum is the inverse of signed maximum.
|
|
SelectPatternFlavor getInverseMinMaxFlavor(SelectPatternFlavor SPF);
|
|
|
|
/// Return the canonical inverse comparison predicate for the specified
|
|
/// minimum/maximum flavor.
|
|
CmpInst::Predicate getInverseMinMaxPred(SelectPatternFlavor SPF);
|
|
|
|
/// Check if the values in \p VL are select instructions that can be converted
|
|
/// to a min or max (vector) intrinsic. Returns the intrinsic ID, if such a
|
|
/// conversion is possible, together with a bool indicating whether all select
|
|
/// conditions are only used by the selects. Otherwise return
|
|
/// Intrinsic::not_intrinsic.
|
|
std::pair<Intrinsic::ID, bool>
|
|
canConvertToMinOrMaxIntrinsic(ArrayRef<Value *> VL);
|
|
|
|
/// Return true if RHS is known to be implied true by LHS. Return false if
|
|
/// RHS is known to be implied false by LHS. Otherwise, return None if no
|
|
/// implication can be made.
|
|
/// A & B must be i1 (boolean) values or a vector of such values. Note that
|
|
/// the truth table for implication is the same as <=u on i1 values (but not
|
|
/// <=s!). The truth table for both is:
|
|
/// | T | F (B)
|
|
/// T | T | F
|
|
/// F | T | T
|
|
/// (A)
|
|
Optional<bool> isImpliedCondition(const Value *LHS, const Value *RHS,
|
|
const DataLayout &DL, bool LHSIsTrue = true,
|
|
unsigned Depth = 0);
|
|
Optional<bool> isImpliedCondition(const Value *LHS,
|
|
CmpInst::Predicate RHSPred,
|
|
const Value *RHSOp0, const Value *RHSOp1,
|
|
const DataLayout &DL, bool LHSIsTrue = true,
|
|
unsigned Depth = 0);
|
|
|
|
/// Return the boolean condition value in the context of the given instruction
|
|
/// if it is known based on dominating conditions.
|
|
Optional<bool> isImpliedByDomCondition(const Value *Cond,
|
|
const Instruction *ContextI,
|
|
const DataLayout &DL);
|
|
Optional<bool> isImpliedByDomCondition(CmpInst::Predicate Pred,
|
|
const Value *LHS, const Value *RHS,
|
|
const Instruction *ContextI,
|
|
const DataLayout &DL);
|
|
|
|
/// If Ptr1 is provably equal to Ptr2 plus a constant offset, return that
|
|
/// offset. For example, Ptr1 might be &A[42], and Ptr2 might be &A[40]. In
|
|
/// this case offset would be -8.
|
|
Optional<int64_t> isPointerOffset(const Value *Ptr1, const Value *Ptr2,
|
|
const DataLayout &DL);
|
|
} // end namespace llvm
|
|
|
|
#endif // LLVM_ANALYSIS_VALUETRACKING_H
|