1 //===- Reg2Mem.cpp - Convert registers to allocas -------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file demotes all registers to memory references. It is intented to be
11 // the inverse of PromoteMemoryToRegister. By converting to loads, the only
12 // values live accross basic blocks are allocas and loads before phi nodes.
13 // It is intended that this should make CFG hacking much easier.
14 // To make later hacking easier, the entry block is split into two, such that
15 // all introduced allocas and nothing else are in the entry block.
17 //===----------------------------------------------------------------------===//
19 #define DEBUG_TYPE "reg2mem"
20 #include "llvm/Transforms/Scalar.h"
21 #include "llvm/Transforms/Utils/Local.h"
22 #include "llvm/Pass.h"
23 #include "llvm/Function.h"
24 #include "llvm/Module.h"
25 #include "llvm/BasicBlock.h"
26 #include "llvm/Instructions.h"
27 #include "llvm/ADT/Statistic.h"
31 STATISTIC(NumDemoted, "Number of registers demoted");
34 struct RegToMem : public FunctionPass {
36 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
37 AU.addRequiredID(BreakCriticalEdgesID);
38 AU.addPreservedID(BreakCriticalEdgesID);
41 bool valueEscapes(Instruction* i) {
42 BasicBlock* bb = i->getParent();
43 for(Value::use_iterator ii = i->use_begin(), ie = i->use_end();
45 if (cast<Instruction>(*ii)->getParent() != bb ||
51 virtual bool runOnFunction(Function &F) {
52 if (!F.isExternal()) {
53 //give us a clean block
54 BasicBlock* bbold = &F.getEntryBlock();
55 BasicBlock* bbnew = new BasicBlock("allocablock", &F, &F.getEntryBlock());
56 new BranchInst(bbold, bbnew);
58 //find the instructions
59 std::list<Instruction*> worklist;
60 for (Function::iterator ibb = F.begin(), ibe = F.end();
62 for (BasicBlock::iterator iib = ibb->begin(), iie = ibb->end();
65 worklist.push_front(&*iib);
67 //demote escaped instructions
68 NumDemoted += worklist.size();
69 for (std::list<Instruction*>::iterator ilb = worklist.begin(),
70 ile = worklist.end(); ilb != ile; ++ilb)
71 DemoteRegToStack(**ilb, false);
78 RegisterPass<RegToMem> X("reg2mem", "Demote all values to stack slots");
81 // createDemoteRegisterToMemory - Provide an entry point to create this pass.
83 const PassInfo *llvm::DemoteRegisterToMemoryID = X.getPassInfo();
84 FunctionPass *llvm::createDemoteRegisterToMemoryPass() {
85 return new RegToMem();