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must be called in the pass's constructor. This function uses static dependency declarations to recursively initialize the pass's dependencies. Clients that only create passes through the createFooPass() APIs will require no changes. Clients that want to use the CommandLine options for passes will need to manually call the appropriate initialization functions in PassInitialization.h before parsing commandline arguments. I have tested this with all standard configurations of clang and llvm-gcc on Darwin. It is possible that there are problems with the static dependencies that will only be visible with non-standard options. If you encounter any crash in pass registration/creation, please send the testcase to me directly. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116820 91177308-0d34-0410-b5e6-96231b3b80d8
135 lines
4.6 KiB
C++
135 lines
4.6 KiB
C++
//===- Reg2Mem.cpp - Convert registers to allocas -------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file demotes all registers to memory references. It is intented to be
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// the inverse of PromoteMemoryToRegister. By converting to loads, the only
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// values live accross basic blocks are allocas and loads before phi nodes.
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// It is intended that this should make CFG hacking much easier.
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// To make later hacking easier, the entry block is split into two, such that
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// all introduced allocas and nothing else are in the entry block.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "reg2mem"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include "llvm/Pass.h"
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#include "llvm/Function.h"
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#include "llvm/LLVMContext.h"
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#include "llvm/Module.h"
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#include "llvm/BasicBlock.h"
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#include "llvm/Instructions.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Support/CFG.h"
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#include <list>
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using namespace llvm;
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STATISTIC(NumRegsDemoted, "Number of registers demoted");
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STATISTIC(NumPhisDemoted, "Number of phi-nodes demoted");
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namespace {
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struct RegToMem : public FunctionPass {
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static char ID; // Pass identification, replacement for typeid
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RegToMem() : FunctionPass(ID) {
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initializeRegToMemPass(*PassRegistry::getPassRegistry());
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}
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequiredID(BreakCriticalEdgesID);
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AU.addPreservedID(BreakCriticalEdgesID);
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}
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bool valueEscapes(const Instruction *Inst) const {
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const BasicBlock *BB = Inst->getParent();
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for (Value::const_use_iterator UI = Inst->use_begin(),E = Inst->use_end();
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UI != E; ++UI) {
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const Instruction *I = cast<Instruction>(*UI);
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if (I->getParent() != BB || isa<PHINode>(I))
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return true;
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}
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return false;
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}
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virtual bool runOnFunction(Function &F);
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};
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}
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char RegToMem::ID = 0;
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INITIALIZE_PASS_BEGIN(RegToMem, "reg2mem", "Demote all values to stack slots",
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false, false)
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INITIALIZE_PASS_DEPENDENCY(BreakCriticalEdges)
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INITIALIZE_PASS_END(RegToMem, "reg2mem", "Demote all values to stack slots",
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false, false)
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bool RegToMem::runOnFunction(Function &F) {
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if (F.isDeclaration())
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return false;
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// Insert all new allocas into entry block.
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BasicBlock *BBEntry = &F.getEntryBlock();
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assert(pred_begin(BBEntry) == pred_end(BBEntry) &&
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"Entry block to function must not have predecessors!");
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// Find first non-alloca instruction and create insertion point. This is
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// safe if block is well-formed: it always have terminator, otherwise
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// we'll get and assertion.
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BasicBlock::iterator I = BBEntry->begin();
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while (isa<AllocaInst>(I)) ++I;
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CastInst *AllocaInsertionPoint =
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new BitCastInst(Constant::getNullValue(Type::getInt32Ty(F.getContext())),
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Type::getInt32Ty(F.getContext()),
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"reg2mem alloca point", I);
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// Find the escaped instructions. But don't create stack slots for
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// allocas in entry block.
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std::list<Instruction*> WorkList;
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for (Function::iterator ibb = F.begin(), ibe = F.end();
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ibb != ibe; ++ibb)
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for (BasicBlock::iterator iib = ibb->begin(), iie = ibb->end();
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iib != iie; ++iib) {
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if (!(isa<AllocaInst>(iib) && iib->getParent() == BBEntry) &&
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valueEscapes(iib)) {
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WorkList.push_front(&*iib);
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}
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}
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// Demote escaped instructions
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NumRegsDemoted += WorkList.size();
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for (std::list<Instruction*>::iterator ilb = WorkList.begin(),
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ile = WorkList.end(); ilb != ile; ++ilb)
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DemoteRegToStack(**ilb, false, AllocaInsertionPoint);
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WorkList.clear();
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// Find all phi's
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for (Function::iterator ibb = F.begin(), ibe = F.end();
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ibb != ibe; ++ibb)
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for (BasicBlock::iterator iib = ibb->begin(), iie = ibb->end();
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iib != iie; ++iib)
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if (isa<PHINode>(iib))
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WorkList.push_front(&*iib);
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// Demote phi nodes
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NumPhisDemoted += WorkList.size();
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for (std::list<Instruction*>::iterator ilb = WorkList.begin(),
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ile = WorkList.end(); ilb != ile; ++ilb)
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DemotePHIToStack(cast<PHINode>(*ilb), AllocaInsertionPoint);
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return true;
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}
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// createDemoteRegisterToMemory - Provide an entry point to create this pass.
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//
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char &llvm::DemoteRegisterToMemoryID = RegToMem::ID;
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FunctionPass *llvm::createDemoteRegisterToMemoryPass() {
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return new RegToMem();
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}
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