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llvm-mirror/lib/Transforms/Utils/Mem2Reg.cpp
Reid Kleckner 68092989f3 Sink all InitializePasses.h includes
This file lists every pass in LLVM, and is included by Pass.h, which is
very popular. Every time we add, remove, or rename a pass in LLVM, it
caused lots of recompilation.

I found this fact by looking at this table, which is sorted by the
number of times a file was changed over the last 100,000 git commits
multiplied by the number of object files that depend on it in the
current checkout:
  recompiles    touches affected_files  header
  342380        95      3604    llvm/include/llvm/ADT/STLExtras.h
  314730        234     1345    llvm/include/llvm/InitializePasses.h
  307036        118     2602    llvm/include/llvm/ADT/APInt.h
  213049        59      3611    llvm/include/llvm/Support/MathExtras.h
  170422        47      3626    llvm/include/llvm/Support/Compiler.h
  162225        45      3605    llvm/include/llvm/ADT/Optional.h
  158319        63      2513    llvm/include/llvm/ADT/Triple.h
  140322        39      3598    llvm/include/llvm/ADT/StringRef.h
  137647        59      2333    llvm/include/llvm/Support/Error.h
  131619        73      1803    llvm/include/llvm/Support/FileSystem.h

Before this change, touching InitializePasses.h would cause 1345 files
to recompile. After this change, touching it only causes 550 compiles in
an incremental rebuild.

Reviewers: bkramer, asbirlea, bollu, jdoerfert

Differential Revision: https://reviews.llvm.org/D70211
2019-11-13 16:34:37 -08:00

117 lines
3.7 KiB
C++

//===- Mem2Reg.cpp - The -mem2reg pass, a wrapper around the Utils lib ----===//
//
// 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 pass is a simple pass wrapper around the PromoteMemToReg function call
// exposed by the Utils library.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Utils/Mem2Reg.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/PassManager.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Transforms/Utils.h"
#include "llvm/Transforms/Utils/PromoteMemToReg.h"
#include <vector>
using namespace llvm;
#define DEBUG_TYPE "mem2reg"
STATISTIC(NumPromoted, "Number of alloca's promoted");
static bool promoteMemoryToRegister(Function &F, DominatorTree &DT,
AssumptionCache &AC) {
std::vector<AllocaInst *> Allocas;
BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
bool Changed = false;
while (true) {
Allocas.clear();
// Find allocas that are safe to promote, by looking at all instructions in
// the entry node
for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
if (AllocaInst *AI = dyn_cast<AllocaInst>(I)) // Is it an alloca?
if (isAllocaPromotable(AI))
Allocas.push_back(AI);
if (Allocas.empty())
break;
PromoteMemToReg(Allocas, DT, &AC);
NumPromoted += Allocas.size();
Changed = true;
}
return Changed;
}
PreservedAnalyses PromotePass::run(Function &F, FunctionAnalysisManager &AM) {
auto &DT = AM.getResult<DominatorTreeAnalysis>(F);
auto &AC = AM.getResult<AssumptionAnalysis>(F);
if (!promoteMemoryToRegister(F, DT, AC))
return PreservedAnalyses::all();
PreservedAnalyses PA;
PA.preserveSet<CFGAnalyses>();
return PA;
}
namespace {
struct PromoteLegacyPass : public FunctionPass {
// Pass identification, replacement for typeid
static char ID;
PromoteLegacyPass() : FunctionPass(ID) {
initializePromoteLegacyPassPass(*PassRegistry::getPassRegistry());
}
// runOnFunction - To run this pass, first we calculate the alloca
// instructions that are safe for promotion, then we promote each one.
bool runOnFunction(Function &F) override {
if (skipFunction(F))
return false;
DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
AssumptionCache &AC =
getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
return promoteMemoryToRegister(F, DT, AC);
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<AssumptionCacheTracker>();
AU.addRequired<DominatorTreeWrapperPass>();
AU.setPreservesCFG();
}
};
} // end anonymous namespace
char PromoteLegacyPass::ID = 0;
INITIALIZE_PASS_BEGIN(PromoteLegacyPass, "mem2reg", "Promote Memory to "
"Register",
false, false)
INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
INITIALIZE_PASS_END(PromoteLegacyPass, "mem2reg", "Promote Memory to Register",
false, false)
// createPromoteMemoryToRegister - Provide an entry point to create this pass.
FunctionPass *llvm::createPromoteMemoryToRegisterPass() {
return new PromoteLegacyPass();
}