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"
28 #include "llvm/Support/Compiler.h"
32 STATISTIC(NumDemoted, "Number of registers demoted");
35 struct VISIBILITY_HIDDEN RegToMem : public FunctionPass {
36 static char ID; // Pass identifcation, replacement for typeid
37 RegToMem() : FunctionPass((intptr_t)&ID) {}
39 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
40 AU.addRequiredID(BreakCriticalEdgesID);
41 AU.addPreservedID(BreakCriticalEdgesID);
44 bool valueEscapes(Instruction* i) {
45 BasicBlock* bb = i->getParent();
46 for(Value::use_iterator ii = i->use_begin(), ie = i->use_end();
48 if (cast<Instruction>(*ii)->getParent() != bb ||
54 virtual bool runOnFunction(Function &F) {
55 if (!F.isDeclaration()) {
56 //give us a clean block
57 BasicBlock* bbold = &F.getEntryBlock();
58 BasicBlock* bbnew = new BasicBlock("allocablock", &F, &F.getEntryBlock());
59 new BranchInst(bbold, bbnew);
61 //find the instructions
62 std::list<Instruction*> worklist;
63 for (Function::iterator ibb = F.begin(), ibe = F.end();
65 for (BasicBlock::iterator iib = ibb->begin(), iie = ibb->end();
68 worklist.push_front(&*iib);
70 //demote escaped instructions
71 NumDemoted += worklist.size();
72 for (std::list<Instruction*>::iterator ilb = worklist.begin(),
73 ile = worklist.end(); ilb != ile; ++ilb)
74 DemoteRegToStack(**ilb, false);
81 char RegToMem::ID = 0;
82 RegisterPass<RegToMem> X("reg2mem", "Demote all values to stack slots");
85 // createDemoteRegisterToMemory - Provide an entry point to create this pass.
87 const PassInfo *llvm::DemoteRegisterToMemoryID = X.getPassInfo();
88 FunctionPass *llvm::createDemoteRegisterToMemoryPass() {
89 return new RegToMem();