llvm/llvm/lib/Transforms/IPO/ConstantMerge.cpp

//===- ConstantMerge.cpp - Merge duplicate global constants ---------------===//
//
// 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 the interface to a pass that merges duplicate global
// constants together into a single constant that is shared.  This is useful
// because some passes (ie TraceValues) insert a lot of string constants into
// the program, regardless of whether or not an existing string is available.
//
// Algorithm: ConstantMerge is designed to build up a map of available constants
// and eliminate duplicates when it is initialized.
//
//===----------------------------------------------------------------------===//

#include "llvm/Transforms/IPO/ConstantMerge.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Debug.h"
#include "llvm/Transforms/IPO.h"
#include <algorithm>
#include <cassert>
#include <utility>

usingnamespacellvm;

#define DEBUG_TYPE …

STATISTIC(NumIdenticalMerged, "Number of identical global constants merged");

/// Find values that are marked as llvm.used.
static void FindUsedValues(GlobalVariable *LLVMUsed,
                           SmallPtrSetImpl<const GlobalValue*> &UsedValues) { … }

// True if A is better than B.
static bool IsBetterCanonical(const GlobalVariable &A,
                              const GlobalVariable &B) { … }

static bool hasMetadataOtherThanDebugLoc(const GlobalVariable *GV) { … }

static void copyDebugLocMetadata(const GlobalVariable *From,
                                 GlobalVariable *To) { … }

static Align getAlign(GlobalVariable *GV) { … }

static bool
isUnmergeableGlobal(GlobalVariable *GV,
                    const SmallPtrSetImpl<const GlobalValue *> &UsedGlobals) { … }

enum class CanMerge { … };
static CanMerge makeMergeable(GlobalVariable *Old, GlobalVariable *New) { … }

static void replace(Module &M, GlobalVariable *Old, GlobalVariable *New) { … }

static bool mergeConstants(Module &M) { … }

PreservedAnalyses ConstantMergePass::run(Module &M, ModuleAnalysisManager &) { … }