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//===- Mem2Reg.cpp - The -mem2reg pass, a wrapper around the Utils lib ----===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass is a simple pass wrapper around the PromoteMemToReg function call
// exposed by the Utils library.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "mem2reg"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/PromoteMemToReg.h"
#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Instructions.h"
#include "llvm/Function.h"
#include "llvm/ADT/Statistic.h"
using namespace llvm;
STATISTIC(NumPromoted, "Number of alloca's promoted");
namespace {
struct PromotePass : public FunctionPass {
static char ID; // Pass identification, replacement for typeid
PromotePass() : FunctionPass(ID) {}
// runOnFunction - To run this pass, first we calculate the alloca
// instructions that are safe for promotion, then we promote each one.
//
virtual bool runOnFunction(Function &F);
// getAnalysisUsage - We need dominance frontiers
//
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<DominatorTree>();
AU.addRequired<DominanceFrontier>();
AU.setPreservesCFG();
// This is a cluster of orthogonal Transforms
AU.addPreserved<UnifyFunctionExitNodes>();
AU.addPreservedID(LowerSwitchID);
AU.addPreservedID(LowerInvokePassID);
}
};
} // end of anonymous namespace
char PromotePass::ID = 0;
static RegisterPass<PromotePass> X("mem2reg", "Promote Memory to Register");
bool PromotePass::runOnFunction(Function &F) {
std::vector<AllocaInst*> Allocas;
BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
bool Changed = false;
DominatorTree &DT = getAnalysis<DominatorTree>();
DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
while (1) {
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, DF);
NumPromoted += Allocas.size();
Changed = true;
}
return Changed;
}
// createPromoteMemoryToRegister - Provide an entry point to create this pass.
//
FunctionPass *llvm::createPromoteMemoryToRegisterPass() {
return new PromotePass();
}
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