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//===- Reg2Mem.cpp - Convert registers to allocas -------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file demotes all registers to memory references. It is intented to be
// the inverse of PromoteMemoryToRegister. By converting to loads, the only
// values live accross basic blocks are allocas and loads before phi nodes.
// It is intended that this should make CFG hacking much easier.
// To make later hacking easier, the entry block is split into two, such that
// all introduced allocas and nothing else are in the entry block.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "reg2mem"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Pass.h"
#include "llvm/Function.h"
#include "llvm/Module.h"
#include "llvm/BasicBlock.h"
#include "llvm/Instructions.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/Compiler.h"
#include <list>
using namespace llvm;
STATISTIC(NumDemoted, "Number of registers demoted");
namespace {
struct VISIBILITY_HIDDEN RegToMem : public FunctionPass {
static const char ID; // Pass identifcation, replacement for typeid
RegToMem() : FunctionPass((intptr_t)&ID) {}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequiredID(BreakCriticalEdgesID);
AU.addPreservedID(BreakCriticalEdgesID);
}
bool valueEscapes(Instruction* i) {
BasicBlock* bb = i->getParent();
for(Value::use_iterator ii = i->use_begin(), ie = i->use_end();
ii != ie; ++ii)
if (cast<Instruction>(*ii)->getParent() != bb ||
isa<PHINode>(*ii))
return true;
return false;
}
virtual bool runOnFunction(Function &F) {
if (!F.isDeclaration()) {
//give us a clean block
BasicBlock* bbold = &F.getEntryBlock();
BasicBlock* bbnew = new BasicBlock("allocablock", &F, &F.getEntryBlock());
new BranchInst(bbold, bbnew);
//find the instructions
std::list<Instruction*> worklist;
for (Function::iterator ibb = F.begin(), ibe = F.end();
ibb != ibe; ++ibb)
for (BasicBlock::iterator iib = ibb->begin(), iie = ibb->end();
iib != iie; ++iib) {
if(valueEscapes(iib))
worklist.push_front(&*iib);
}
//demote escaped instructions
NumDemoted += worklist.size();
for (std::list<Instruction*>::iterator ilb = worklist.begin(),
ile = worklist.end(); ilb != ile; ++ilb)
DemoteRegToStack(**ilb, false);
return true;
}
return false;
}
};
const char RegToMem::ID = 0;
RegisterPass<RegToMem> X("reg2mem", "Demote all values to stack slots");
}
// createDemoteRegisterToMemory - Provide an entry point to create this pass.
//
const PassInfo *llvm::DemoteRegisterToMemoryID = X.getPassInfo();
FunctionPass *llvm::createDemoteRegisterToMemoryPass() {
return new RegToMem();
}
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