Loads.cpp | Explore in Territory

//===- Loads.cpp - Local load analysis ------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines simple local analyses for load instructions.
//
//===----------------------------------------------------------------------===//

#include "llvm/Analysis/Loads.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AssumeBundleQueries.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/MemoryLocation.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Operator.h"

usingnamespacellvm;

static bool isAligned(const Value *Base, const APInt &Offset, Align Alignment,
                      const DataLayout &DL) { … }

/// Test if V is always a pointer to allocated and suitably aligned memory for
/// a simple load or store.
static bool isDereferenceableAndAlignedPointer(
    const Value *V, Align Alignment, const APInt &Size, const DataLayout &DL,
    const Instruction *CtxI, AssumptionCache *AC, const DominatorTree *DT,
    const TargetLibraryInfo *TLI, SmallPtrSetImpl<const Value *> &Visited,
    unsigned MaxDepth) { … }

bool llvm::isDereferenceableAndAlignedPointer(
    const Value *V, Align Alignment, const APInt &Size, const DataLayout &DL,
    const Instruction *CtxI, AssumptionCache *AC, const DominatorTree *DT,
    const TargetLibraryInfo *TLI) { … }

bool llvm::isDereferenceableAndAlignedPointer(
    const Value *V, Type *Ty, Align Alignment, const DataLayout &DL,
    const Instruction *CtxI, AssumptionCache *AC, const DominatorTree *DT,
    const TargetLibraryInfo *TLI) { … }

bool llvm::isDereferenceablePointer(const Value *V, Type *Ty,
                                    const DataLayout &DL,
                                    const Instruction *CtxI,
                                    AssumptionCache *AC,
                                    const DominatorTree *DT,
                                    const TargetLibraryInfo *TLI) { … }

/// Test if A and B will obviously have the same value.
///
/// This includes recognizing that %t0 and %t1 will have the same
/// value in code like this:
/// \code
///   %t0 = getelementptr \@a, 0, 3
///   store i32 0, i32* %t0
///   %t1 = getelementptr \@a, 0, 3
///   %t2 = load i32* %t1
/// \endcode
///
static bool AreEquivalentAddressValues(const Value *A, const Value *B) { … }

bool llvm::isDereferenceableAndAlignedInLoop(
    LoadInst *LI, Loop *L, ScalarEvolution &SE, DominatorTree &DT,
    AssumptionCache *AC, SmallVectorImpl<const SCEVPredicate *> *Predicates) { … }

static bool suppressSpeculativeLoadForSanitizers(const Instruction &CtxI) { … }

bool llvm::mustSuppressSpeculation(const LoadInst &LI) { … }

/// Check if executing a load of this pointer value cannot trap.
///
/// If DT and ScanFrom are specified this method performs context-sensitive
/// analysis and returns true if it is safe to load immediately before ScanFrom.
///
/// If it is not obviously safe to load from the specified pointer, we do
/// a quick local scan of the basic block containing \c ScanFrom, to determine
/// if the address is already accessed.
///
/// This uses the pointee type to determine how many bytes need to be safe to
/// load from the pointer.
bool llvm::isSafeToLoadUnconditionally(Value *V, Align Alignment, const APInt &Size,
                                       const DataLayout &DL,
                                       Instruction *ScanFrom,
                                       AssumptionCache *AC,
                                       const DominatorTree *DT,
                                       const TargetLibraryInfo *TLI) { … }

bool llvm::isSafeToLoadUnconditionally(Value *V, Type *Ty, Align Alignment,
                                       const DataLayout &DL,
                                       Instruction *ScanFrom,
                                       AssumptionCache *AC,
                                       const DominatorTree *DT,
                                       const TargetLibraryInfo *TLI) { … }

/// DefMaxInstsToScan - the default number of maximum instructions
/// to scan in the block, used by FindAvailableLoadedValue().
/// FindAvailableLoadedValue() was introduced in r60148, to improve jump
/// threading in part by eliminating partially redundant loads.
/// At that point, the value of MaxInstsToScan was already set to '6'
/// without documented explanation.
cl::opt<unsigned>
llvm::DefMaxInstsToScan("available-load-scan-limit", cl::init(6), cl::Hidden,
  cl::desc("Use this to specify the default maximum number of instructions "
           "to scan backward from a given instruction, when searching for "
           "available loaded value"));

Value *llvm::FindAvailableLoadedValue(LoadInst *Load, BasicBlock *ScanBB,
                                      BasicBlock::iterator &ScanFrom,
                                      unsigned MaxInstsToScan,
                                      BatchAAResults *AA, bool *IsLoad,
                                      unsigned *NumScanedInst) { … }

// Check if the load and the store have the same base, constant offsets and
// non-overlapping access ranges.
static bool areNonOverlapSameBaseLoadAndStore(const Value *LoadPtr,
                                              Type *LoadTy,
                                              const Value *StorePtr,
                                              Type *StoreTy,
                                              const DataLayout &DL) { … }

static Value *getAvailableLoadStore(Instruction *Inst, const Value *Ptr,
                                    Type *AccessTy, bool AtLeastAtomic,
                                    const DataLayout &DL, bool *IsLoadCSE) { … }

Value *llvm::findAvailablePtrLoadStore(
    const MemoryLocation &Loc, Type *AccessTy, bool AtLeastAtomic,
    BasicBlock *ScanBB, BasicBlock::iterator &ScanFrom, unsigned MaxInstsToScan,
    BatchAAResults *AA, bool *IsLoadCSE, unsigned *NumScanedInst) { … }

Value *llvm::FindAvailableLoadedValue(LoadInst *Load, BatchAAResults &AA,
                                      bool *IsLoadCSE,
                                      unsigned MaxInstsToScan) { … }

// Returns true if a use is either in an ICmp/PtrToInt or a Phi/Select that only
// feeds into them.
static bool isPointerUseReplacable(const Use &U) { … }

// Returns true if `To` is a null pointer, constant dereferenceable pointer or
// both pointers have the same underlying objects.
static bool isPointerAlwaysReplaceable(const Value *From, const Value *To,
                                       const DataLayout &DL) { … }

bool llvm::canReplacePointersInUseIfEqual(const Use &U, const Value *To,
                                          const DataLayout &DL) { … }

bool llvm::canReplacePointersIfEqual(const Value *From, const Value *To,
                                     const DataLayout &DL) { … }

bool llvm::isDereferenceableReadOnlyLoop(
    Loop *L, ScalarEvolution *SE, DominatorTree *DT, AssumptionCache *AC,
    SmallVectorImpl<const SCEVPredicate *> *Predicates) { … }
llvm/llvm/lib/Analysis/Loads.cpp
