AlignmentFromAssumptions.cpp | Explore in Territory

//===----------------------- AlignmentFromAssumptions.cpp -----------------===//
//                  Set Load/Store Alignments From Assumptions
//
// 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 implements a ScalarEvolution-based transformation to set
// the alignments of load, stores and memory intrinsics based on the truth
// expressions of assume intrinsics. The primary motivation is to handle
// complex alignment assumptions that apply to vector loads and stores that
// appear after vectorization and unrolling.
//
//===----------------------------------------------------------------------===//

#include "llvm/Transforms/Scalar/AlignmentFromAssumptions.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/ScalarEvolutionExpressions.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"

#define DEBUG_TYPE …
usingnamespacellvm;

STATISTIC(NumLoadAlignChanged,
  "Number of loads changed by alignment assumptions");
STATISTIC(NumStoreAlignChanged,
  "Number of stores changed by alignment assumptions");
STATISTIC(NumMemIntAlignChanged,
  "Number of memory intrinsics changed by alignment assumptions");

// Given an expression for the (constant) alignment, AlignSCEV, and an
// expression for the displacement between a pointer and the aligned address,
// DiffSCEV, compute the alignment of the displaced pointer if it can be reduced
// to a constant. Using SCEV to compute alignment handles the case where
// DiffSCEV is a recurrence with constant start such that the aligned offset
// is constant. e.g. {16,+,32} % 32 -> 16.
static MaybeAlign getNewAlignmentDiff(const SCEV *DiffSCEV,
                                      const SCEV *AlignSCEV,
                                      ScalarEvolution *SE) { … }

// There is an address given by an offset OffSCEV from AASCEV which has an
// alignment AlignSCEV. Use that information, if possible, to compute a new
// alignment for Ptr.
static Align getNewAlignment(const SCEV *AASCEV, const SCEV *AlignSCEV,
                             const SCEV *OffSCEV, Value *Ptr,
                             ScalarEvolution *SE) { … }

bool AlignmentFromAssumptionsPass::extractAlignmentInfo(CallInst *I,
                                                        unsigned Idx,
                                                        Value *&AAPtr,
                                                        const SCEV *&AlignSCEV,
                                                        const SCEV *&OffSCEV) { … }

bool AlignmentFromAssumptionsPass::processAssumption(CallInst *ACall,
                                                     unsigned Idx) { … }

bool AlignmentFromAssumptionsPass::runImpl(Function &F, AssumptionCache &AC,
                                           ScalarEvolution *SE_,
                                           DominatorTree *DT_) { … }

PreservedAnalyses
AlignmentFromAssumptionsPass::run(Function &F, FunctionAnalysisManager &AM) { … }
llvm/llvm/lib/Transforms/Scalar/AlignmentFromAssumptions.cpp
