1//===- Reg2Mem.cpp - Convert registers to allocas -------------------------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 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. 16// 17//===----------------------------------------------------------------------===// 18 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/LLVMContext.h" 25#include "llvm/Module.h" 26#include "llvm/BasicBlock.h" 27#include "llvm/Instructions.h" 28#include "llvm/ADT/Statistic.h"
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29#include "llvm/Support/Compiler.h"
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29#include "llvm/Support/CFG.h" 30#include <list> 31using namespace llvm; 32 33STATISTIC(NumRegsDemoted, "Number of registers demoted"); 34STATISTIC(NumPhisDemoted, "Number of phi-nodes demoted"); 35 36namespace {
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38 struct VISIBILITY_HIDDEN RegToMem : public FunctionPass {
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37 struct RegToMem : public FunctionPass { |
38 static char ID; // Pass identification, replacement for typeid 39 RegToMem() : FunctionPass(&ID) {} 40 41 virtual void getAnalysisUsage(AnalysisUsage &AU) const { 42 AU.addRequiredID(BreakCriticalEdgesID); 43 AU.addPreservedID(BreakCriticalEdgesID); 44 } 45
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47 bool valueEscapes(Instruction* i) {
48 BasicBlock* bb = i->getParent();
49 for (Value::use_iterator ii = i->use_begin(), ie = i->use_end();
50 ii != ie; ++ii)
51 if (cast<Instruction>(*ii)->getParent() != bb ||
52 isa<PHINode>(*ii))
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46 bool valueEscapes(const Instruction *Inst) const { 47 const BasicBlock *BB = Inst->getParent(); 48 for (Value::use_const_iterator UI = Inst->use_begin(),E = Inst->use_end(); 49 UI != E; ++UI) 50 if (cast<Instruction>(*UI)->getParent() != BB || 51 isa<PHINode>(*UI)) |
52 return true; 53 return false; 54 } 55
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57 virtual bool runOnFunction(Function &F) {
58 if (!F.isDeclaration()) {
59 // Insert all new allocas into entry block.
60 BasicBlock* BBEntry = &F.getEntryBlock();
61 assert(pred_begin(BBEntry) == pred_end(BBEntry) &&
62 "Entry block to function must not have predecessors!");
63
64 // Find first non-alloca instruction and create insertion point. This is
65 // safe if block is well-formed: it always have terminator, otherwise
66 // we'll get and assertion.
67 BasicBlock::iterator I = BBEntry->begin();
68 while (isa<AllocaInst>(I)) ++I;
69
70 CastInst *AllocaInsertionPoint =
71 CastInst::Create(Instruction::BitCast,
72 Context->getNullValue(Type::Int32Ty), Type::Int32Ty,
73 "reg2mem alloca point", I);
74
75 // Find the escaped instructions. But don't create stack slots for
76 // allocas in entry block.
77 std::list<Instruction*> worklist;
78 for (Function::iterator ibb = F.begin(), ibe = F.end();
79 ibb != ibe; ++ibb)
80 for (BasicBlock::iterator iib = ibb->begin(), iie = ibb->end();
81 iib != iie; ++iib) {
82 if (!(isa<AllocaInst>(iib) && iib->getParent() == BBEntry) &&
83 valueEscapes(iib)) {
84 worklist.push_front(&*iib);
85 }
86 }
87
88 // Demote escaped instructions
89 NumRegsDemoted += worklist.size();
90 for (std::list<Instruction*>::iterator ilb = worklist.begin(),
91 ile = worklist.end(); ilb != ile; ++ilb)
92 DemoteRegToStack(**ilb, false, AllocaInsertionPoint);
93
94 worklist.clear();
95
96 // Find all phi's
97 for (Function::iterator ibb = F.begin(), ibe = F.end();
98 ibb != ibe; ++ibb)
99 for (BasicBlock::iterator iib = ibb->begin(), iie = ibb->end();
100 iib != iie; ++iib)
101 if (isa<PHINode>(iib))
102 worklist.push_front(&*iib);
103
104 // Demote phi nodes
105 NumPhisDemoted += worklist.size();
106 for (std::list<Instruction*>::iterator ilb = worklist.begin(),
107 ile = worklist.end(); ilb != ile; ++ilb)
108 DemotePHIToStack(cast<PHINode>(*ilb), AllocaInsertionPoint);
109
110 return true;
111 }
112 return false;
113 }
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56 virtual bool runOnFunction(Function &F); |
57 }; 58} 59 60char RegToMem::ID = 0; 61static RegisterPass<RegToMem> 62X("reg2mem", "Demote all values to stack slots"); 63
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64 65bool RegToMem::runOnFunction(Function &F) { 66 if (F.isDeclaration()) 67 return false; 68 69 // Insert all new allocas into entry block. 70 BasicBlock *BBEntry = &F.getEntryBlock(); 71 assert(pred_begin(BBEntry) == pred_end(BBEntry) && 72 "Entry block to function must not have predecessors!"); 73 74 // Find first non-alloca instruction and create insertion point. This is 75 // safe if block is well-formed: it always have terminator, otherwise 76 // we'll get and assertion. 77 BasicBlock::iterator I = BBEntry->begin(); 78 while (isa<AllocaInst>(I)) ++I; 79 80 CastInst *AllocaInsertionPoint = 81 new BitCastInst(Constant::getNullValue(Type::getInt32Ty(F.getContext())), 82 Type::getInt32Ty(F.getContext()), 83 "reg2mem alloca point", I); 84 85 // Find the escaped instructions. But don't create stack slots for 86 // allocas in entry block. 87 std::list<Instruction*> WorkList; 88 for (Function::iterator ibb = F.begin(), ibe = F.end(); 89 ibb != ibe; ++ibb) 90 for (BasicBlock::iterator iib = ibb->begin(), iie = ibb->end(); 91 iib != iie; ++iib) { 92 if (!(isa<AllocaInst>(iib) && iib->getParent() == BBEntry) && 93 valueEscapes(iib)) { 94 WorkList.push_front(&*iib); 95 } 96 } 97 98 // Demote escaped instructions 99 NumRegsDemoted += WorkList.size(); 100 for (std::list<Instruction*>::iterator ilb = WorkList.begin(), 101 ile = WorkList.end(); ilb != ile; ++ilb) 102 DemoteRegToStack(**ilb, false, AllocaInsertionPoint); 103 104 WorkList.clear(); 105 106 // Find all phi's 107 for (Function::iterator ibb = F.begin(), ibe = F.end(); 108 ibb != ibe; ++ibb) 109 for (BasicBlock::iterator iib = ibb->begin(), iie = ibb->end(); 110 iib != iie; ++iib) 111 if (isa<PHINode>(iib)) 112 WorkList.push_front(&*iib); 113 114 // Demote phi nodes 115 NumPhisDemoted += WorkList.size(); 116 for (std::list<Instruction*>::iterator ilb = WorkList.begin(), 117 ile = WorkList.end(); ilb != ile; ++ilb) 118 DemotePHIToStack(cast<PHINode>(*ilb), AllocaInsertionPoint); 119 120 return true; 121} 122 123 |
124// createDemoteRegisterToMemory - Provide an entry point to create this pass. 125// 126const PassInfo *const llvm::DemoteRegisterToMemoryID = &X; 127FunctionPass *llvm::createDemoteRegisterToMemoryPass() { 128 return new RegToMem(); 129}
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