| //===- Reg2Mem.cpp - Convert registers to allocas -------------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file 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 intended to be |
| // the inverse of PromoteMemoryToRegister. By converting to loads, the only |
| // values live across 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/ADT/Statistic.h" |
| #include "llvm/IR/BasicBlock.h" |
| #include "llvm/IR/Function.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/LLVMContext.h" |
| #include "llvm/IR/Module.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Support/CFG.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| #include <list> |
| using namespace llvm; |
| |
| STATISTIC(NumRegsDemoted, "Number of registers demoted"); |
| STATISTIC(NumPhisDemoted, "Number of phi-nodes demoted"); |
| |
| namespace { |
| struct RegToMem : public FunctionPass { |
| static char ID; // Pass identification, replacement for typeid |
| RegToMem() : FunctionPass(ID) { |
| initializeRegToMemPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addRequiredID(BreakCriticalEdgesID); |
| AU.addPreservedID(BreakCriticalEdgesID); |
| } |
| |
| bool valueEscapes(const Instruction *Inst) const { |
| const BasicBlock *BB = Inst->getParent(); |
| for (Value::const_use_iterator UI = Inst->use_begin(),E = Inst->use_end(); |
| UI != E; ++UI) { |
| const Instruction *I = cast<Instruction>(*UI); |
| if (I->getParent() != BB || isa<PHINode>(I)) |
| return true; |
| } |
| return false; |
| } |
| |
| virtual bool runOnFunction(Function &F); |
| }; |
| } |
| |
| char RegToMem::ID = 0; |
| INITIALIZE_PASS_BEGIN(RegToMem, "reg2mem", "Demote all values to stack slots", |
| false, false) |
| INITIALIZE_PASS_DEPENDENCY(BreakCriticalEdges) |
| INITIALIZE_PASS_END(RegToMem, "reg2mem", "Demote all values to stack slots", |
| false, false) |
| |
| bool RegToMem::runOnFunction(Function &F) { |
| if (F.isDeclaration()) |
| return false; |
| |
| // Insert all new allocas into entry block. |
| BasicBlock *BBEntry = &F.getEntryBlock(); |
| assert(pred_begin(BBEntry) == pred_end(BBEntry) && |
| "Entry block to function must not have predecessors!"); |
| |
| // Find first non-alloca instruction and create insertion point. This is |
| // safe if block is well-formed: it always have terminator, otherwise |
| // we'll get and assertion. |
| BasicBlock::iterator I = BBEntry->begin(); |
| while (isa<AllocaInst>(I)) ++I; |
| |
| CastInst *AllocaInsertionPoint = |
| new BitCastInst(Constant::getNullValue(Type::getInt32Ty(F.getContext())), |
| Type::getInt32Ty(F.getContext()), |
| "reg2mem alloca point", I); |
| |
| // Find the escaped instructions. But don't create stack slots for |
| // allocas in entry block. |
| 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 (!(isa<AllocaInst>(iib) && iib->getParent() == BBEntry) && |
| valueEscapes(iib)) { |
| WorkList.push_front(&*iib); |
| } |
| } |
| |
| // Demote escaped instructions |
| NumRegsDemoted += WorkList.size(); |
| for (std::list<Instruction*>::iterator ilb = WorkList.begin(), |
| ile = WorkList.end(); ilb != ile; ++ilb) |
| DemoteRegToStack(**ilb, false, AllocaInsertionPoint); |
| |
| WorkList.clear(); |
| |
| // Find all phi's |
| 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 (isa<PHINode>(iib)) |
| WorkList.push_front(&*iib); |
| |
| // Demote phi nodes |
| NumPhisDemoted += WorkList.size(); |
| for (std::list<Instruction*>::iterator ilb = WorkList.begin(), |
| ile = WorkList.end(); ilb != ile; ++ilb) |
| DemotePHIToStack(cast<PHINode>(*ilb), AllocaInsertionPoint); |
| |
| return true; |
| } |
| |
| |
| // createDemoteRegisterToMemory - Provide an entry point to create this pass. |
| char &llvm::DemoteRegisterToMemoryID = RegToMem::ID; |
| FunctionPass *llvm::createDemoteRegisterToMemoryPass() { |
| return new RegToMem(); |
| } |