| //===- GVN.cpp - Eliminate redundant values and loads ------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This pass performs global value numbering to eliminate fully redundant |
| // instructions. It also performs simple dead load elimination. |
| // |
| // Note that this pass does the value numbering itself, it does not use the |
| // ValueNumbering analysis passes. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #define DEBUG_TYPE "gvn" |
| #include "llvm/Transforms/Scalar.h" |
| #include "llvm/BasicBlock.h" |
| #include "llvm/Constants.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/Function.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/Value.h" |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/DepthFirstIterator.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/Analysis/Dominators.h" |
| #include "llvm/Analysis/AliasAnalysis.h" |
| #include "llvm/Analysis/MemoryDependenceAnalysis.h" |
| #include "llvm/Support/CFG.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Compiler.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| using namespace llvm; |
| |
| STATISTIC(NumGVNInstr, "Number of instructions deleted"); |
| STATISTIC(NumGVNLoad, "Number of loads deleted"); |
| STATISTIC(NumGVNPRE, "Number of instructions PRE'd"); |
| |
| static cl::opt<bool> EnablePRE("enable-pre", |
| cl::init(true), cl::Hidden); |
| |
| //===----------------------------------------------------------------------===// |
| // ValueTable Class |
| //===----------------------------------------------------------------------===// |
| |
| /// This class holds the mapping between values and value numbers. It is used |
| /// as an efficient mechanism to determine the expression-wise equivalence of |
| /// two values. |
| namespace { |
| struct VISIBILITY_HIDDEN Expression { |
| enum ExpressionOpcode { ADD, SUB, MUL, UDIV, SDIV, FDIV, UREM, SREM, |
| FREM, SHL, LSHR, ASHR, AND, OR, XOR, ICMPEQ, |
| ICMPNE, ICMPUGT, ICMPUGE, ICMPULT, ICMPULE, |
| ICMPSGT, ICMPSGE, ICMPSLT, ICMPSLE, FCMPOEQ, |
| FCMPOGT, FCMPOGE, FCMPOLT, FCMPOLE, FCMPONE, |
| FCMPORD, FCMPUNO, FCMPUEQ, FCMPUGT, FCMPUGE, |
| FCMPULT, FCMPULE, FCMPUNE, EXTRACT, INSERT, |
| SHUFFLE, SELECT, TRUNC, ZEXT, SEXT, FPTOUI, |
| FPTOSI, UITOFP, SITOFP, FPTRUNC, FPEXT, |
| PTRTOINT, INTTOPTR, BITCAST, GEP, CALL, CONSTANT, |
| EMPTY, TOMBSTONE }; |
| |
| ExpressionOpcode opcode; |
| const Type* type; |
| uint32_t firstVN; |
| uint32_t secondVN; |
| uint32_t thirdVN; |
| SmallVector<uint32_t, 4> varargs; |
| Value* function; |
| |
| Expression() { } |
| Expression(ExpressionOpcode o) : opcode(o) { } |
| |
| bool operator==(const Expression &other) const { |
| if (opcode != other.opcode) |
| return false; |
| else if (opcode == EMPTY || opcode == TOMBSTONE) |
| return true; |
| else if (type != other.type) |
| return false; |
| else if (function != other.function) |
| return false; |
| else if (firstVN != other.firstVN) |
| return false; |
| else if (secondVN != other.secondVN) |
| return false; |
| else if (thirdVN != other.thirdVN) |
| return false; |
| else { |
| if (varargs.size() != other.varargs.size()) |
| return false; |
| |
| for (size_t i = 0; i < varargs.size(); ++i) |
| if (varargs[i] != other.varargs[i]) |
| return false; |
| |
| return true; |
| } |
| } |
| |
| bool operator!=(const Expression &other) const { |
| if (opcode != other.opcode) |
| return true; |
| else if (opcode == EMPTY || opcode == TOMBSTONE) |
| return false; |
| else if (type != other.type) |
| return true; |
| else if (function != other.function) |
| return true; |
| else if (firstVN != other.firstVN) |
| return true; |
| else if (secondVN != other.secondVN) |
| return true; |
| else if (thirdVN != other.thirdVN) |
| return true; |
| else { |
| if (varargs.size() != other.varargs.size()) |
| return true; |
| |
| for (size_t i = 0; i < varargs.size(); ++i) |
| if (varargs[i] != other.varargs[i]) |
| return true; |
| |
| return false; |
| } |
| } |
| }; |
| |
| class VISIBILITY_HIDDEN ValueTable { |
| private: |
| DenseMap<Value*, uint32_t> valueNumbering; |
| DenseMap<Expression, uint32_t> expressionNumbering; |
| AliasAnalysis* AA; |
| MemoryDependenceAnalysis* MD; |
| DominatorTree* DT; |
| |
| uint32_t nextValueNumber; |
| |
| Expression::ExpressionOpcode getOpcode(BinaryOperator* BO); |
| Expression::ExpressionOpcode getOpcode(CmpInst* C); |
| Expression::ExpressionOpcode getOpcode(CastInst* C); |
| Expression create_expression(BinaryOperator* BO); |
| Expression create_expression(CmpInst* C); |
| Expression create_expression(ShuffleVectorInst* V); |
| Expression create_expression(ExtractElementInst* C); |
| Expression create_expression(InsertElementInst* V); |
| Expression create_expression(SelectInst* V); |
| Expression create_expression(CastInst* C); |
| Expression create_expression(GetElementPtrInst* G); |
| Expression create_expression(CallInst* C); |
| Expression create_expression(Constant* C); |
| public: |
| ValueTable() : nextValueNumber(1) { } |
| uint32_t lookup_or_add(Value* V); |
| uint32_t lookup(Value* V) const; |
| void add(Value* V, uint32_t num); |
| void clear(); |
| void erase(Value* v); |
| unsigned size(); |
| void setAliasAnalysis(AliasAnalysis* A) { AA = A; } |
| void setMemDep(MemoryDependenceAnalysis* M) { MD = M; } |
| void setDomTree(DominatorTree* D) { DT = D; } |
| }; |
| } |
| |
| namespace llvm { |
| template <> struct DenseMapInfo<Expression> { |
| static inline Expression getEmptyKey() { |
| return Expression(Expression::EMPTY); |
| } |
| |
| static inline Expression getTombstoneKey() { |
| return Expression(Expression::TOMBSTONE); |
| } |
| |
| static unsigned getHashValue(const Expression e) { |
| unsigned hash = e.opcode; |
| |
| hash = e.firstVN + hash * 37; |
| hash = e.secondVN + hash * 37; |
| hash = e.thirdVN + hash * 37; |
| |
| hash = ((unsigned)((uintptr_t)e.type >> 4) ^ |
| (unsigned)((uintptr_t)e.type >> 9)) + |
| hash * 37; |
| |
| for (SmallVector<uint32_t, 4>::const_iterator I = e.varargs.begin(), |
| E = e.varargs.end(); I != E; ++I) |
| hash = *I + hash * 37; |
| |
| hash = ((unsigned)((uintptr_t)e.function >> 4) ^ |
| (unsigned)((uintptr_t)e.function >> 9)) + |
| hash * 37; |
| |
| return hash; |
| } |
| static bool isEqual(const Expression &LHS, const Expression &RHS) { |
| return LHS == RHS; |
| } |
| static bool isPod() { return true; } |
| }; |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // ValueTable Internal Functions |
| //===----------------------------------------------------------------------===// |
| Expression::ExpressionOpcode ValueTable::getOpcode(BinaryOperator* BO) { |
| switch(BO->getOpcode()) { |
| default: // THIS SHOULD NEVER HAPPEN |
| assert(0 && "Binary operator with unknown opcode?"); |
| case Instruction::Add: return Expression::ADD; |
| case Instruction::Sub: return Expression::SUB; |
| case Instruction::Mul: return Expression::MUL; |
| case Instruction::UDiv: return Expression::UDIV; |
| case Instruction::SDiv: return Expression::SDIV; |
| case Instruction::FDiv: return Expression::FDIV; |
| case Instruction::URem: return Expression::UREM; |
| case Instruction::SRem: return Expression::SREM; |
| case Instruction::FRem: return Expression::FREM; |
| case Instruction::Shl: return Expression::SHL; |
| case Instruction::LShr: return Expression::LSHR; |
| case Instruction::AShr: return Expression::ASHR; |
| case Instruction::And: return Expression::AND; |
| case Instruction::Or: return Expression::OR; |
| case Instruction::Xor: return Expression::XOR; |
| } |
| } |
| |
| Expression::ExpressionOpcode ValueTable::getOpcode(CmpInst* C) { |
| if (isa<ICmpInst>(C) || isa<VICmpInst>(C)) { |
| switch (C->getPredicate()) { |
| default: // THIS SHOULD NEVER HAPPEN |
| assert(0 && "Comparison with unknown predicate?"); |
| case ICmpInst::ICMP_EQ: return Expression::ICMPEQ; |
| case ICmpInst::ICMP_NE: return Expression::ICMPNE; |
| case ICmpInst::ICMP_UGT: return Expression::ICMPUGT; |
| case ICmpInst::ICMP_UGE: return Expression::ICMPUGE; |
| case ICmpInst::ICMP_ULT: return Expression::ICMPULT; |
| case ICmpInst::ICMP_ULE: return Expression::ICMPULE; |
| case ICmpInst::ICMP_SGT: return Expression::ICMPSGT; |
| case ICmpInst::ICMP_SGE: return Expression::ICMPSGE; |
| case ICmpInst::ICMP_SLT: return Expression::ICMPSLT; |
| case ICmpInst::ICMP_SLE: return Expression::ICMPSLE; |
| } |
| } |
| assert((isa<FCmpInst>(C) || isa<VFCmpInst>(C)) && "Unknown compare"); |
| switch (C->getPredicate()) { |
| default: // THIS SHOULD NEVER HAPPEN |
| assert(0 && "Comparison with unknown predicate?"); |
| case FCmpInst::FCMP_OEQ: return Expression::FCMPOEQ; |
| case FCmpInst::FCMP_OGT: return Expression::FCMPOGT; |
| case FCmpInst::FCMP_OGE: return Expression::FCMPOGE; |
| case FCmpInst::FCMP_OLT: return Expression::FCMPOLT; |
| case FCmpInst::FCMP_OLE: return Expression::FCMPOLE; |
| case FCmpInst::FCMP_ONE: return Expression::FCMPONE; |
| case FCmpInst::FCMP_ORD: return Expression::FCMPORD; |
| case FCmpInst::FCMP_UNO: return Expression::FCMPUNO; |
| case FCmpInst::FCMP_UEQ: return Expression::FCMPUEQ; |
| case FCmpInst::FCMP_UGT: return Expression::FCMPUGT; |
| case FCmpInst::FCMP_UGE: return Expression::FCMPUGE; |
| case FCmpInst::FCMP_ULT: return Expression::FCMPULT; |
| case FCmpInst::FCMP_ULE: return Expression::FCMPULE; |
| case FCmpInst::FCMP_UNE: return Expression::FCMPUNE; |
| } |
| } |
| |
| Expression::ExpressionOpcode ValueTable::getOpcode(CastInst* C) { |
| switch(C->getOpcode()) { |
| default: // THIS SHOULD NEVER HAPPEN |
| assert(0 && "Cast operator with unknown opcode?"); |
| case Instruction::Trunc: return Expression::TRUNC; |
| case Instruction::ZExt: return Expression::ZEXT; |
| case Instruction::SExt: return Expression::SEXT; |
| case Instruction::FPToUI: return Expression::FPTOUI; |
| case Instruction::FPToSI: return Expression::FPTOSI; |
| case Instruction::UIToFP: return Expression::UITOFP; |
| case Instruction::SIToFP: return Expression::SITOFP; |
| case Instruction::FPTrunc: return Expression::FPTRUNC; |
| case Instruction::FPExt: return Expression::FPEXT; |
| case Instruction::PtrToInt: return Expression::PTRTOINT; |
| case Instruction::IntToPtr: return Expression::INTTOPTR; |
| case Instruction::BitCast: return Expression::BITCAST; |
| } |
| } |
| |
| Expression ValueTable::create_expression(CallInst* C) { |
| Expression e; |
| |
| e.type = C->getType(); |
| e.firstVN = 0; |
| e.secondVN = 0; |
| e.thirdVN = 0; |
| e.function = C->getCalledFunction(); |
| e.opcode = Expression::CALL; |
| |
| for (CallInst::op_iterator I = C->op_begin()+1, E = C->op_end(); |
| I != E; ++I) |
| e.varargs.push_back(lookup_or_add(*I)); |
| |
| return e; |
| } |
| |
| Expression ValueTable::create_expression(BinaryOperator* BO) { |
| Expression e; |
| |
| e.firstVN = lookup_or_add(BO->getOperand(0)); |
| e.secondVN = lookup_or_add(BO->getOperand(1)); |
| e.thirdVN = 0; |
| e.function = 0; |
| e.type = BO->getType(); |
| e.opcode = getOpcode(BO); |
| |
| return e; |
| } |
| |
| Expression ValueTable::create_expression(CmpInst* C) { |
| Expression e; |
| |
| e.firstVN = lookup_or_add(C->getOperand(0)); |
| e.secondVN = lookup_or_add(C->getOperand(1)); |
| e.thirdVN = 0; |
| e.function = 0; |
| e.type = C->getType(); |
| e.opcode = getOpcode(C); |
| |
| return e; |
| } |
| |
| Expression ValueTable::create_expression(CastInst* C) { |
| Expression e; |
| |
| e.firstVN = lookup_or_add(C->getOperand(0)); |
| e.secondVN = 0; |
| e.thirdVN = 0; |
| e.function = 0; |
| e.type = C->getType(); |
| e.opcode = getOpcode(C); |
| |
| return e; |
| } |
| |
| Expression ValueTable::create_expression(ShuffleVectorInst* S) { |
| Expression e; |
| |
| e.firstVN = lookup_or_add(S->getOperand(0)); |
| e.secondVN = lookup_or_add(S->getOperand(1)); |
| e.thirdVN = lookup_or_add(S->getOperand(2)); |
| e.function = 0; |
| e.type = S->getType(); |
| e.opcode = Expression::SHUFFLE; |
| |
| return e; |
| } |
| |
| Expression ValueTable::create_expression(ExtractElementInst* E) { |
| Expression e; |
| |
| e.firstVN = lookup_or_add(E->getOperand(0)); |
| e.secondVN = lookup_or_add(E->getOperand(1)); |
| e.thirdVN = 0; |
| e.function = 0; |
| e.type = E->getType(); |
| e.opcode = Expression::EXTRACT; |
| |
| return e; |
| } |
| |
| Expression ValueTable::create_expression(InsertElementInst* I) { |
| Expression e; |
| |
| e.firstVN = lookup_or_add(I->getOperand(0)); |
| e.secondVN = lookup_or_add(I->getOperand(1)); |
| e.thirdVN = lookup_or_add(I->getOperand(2)); |
| e.function = 0; |
| e.type = I->getType(); |
| e.opcode = Expression::INSERT; |
| |
| return e; |
| } |
| |
| Expression ValueTable::create_expression(SelectInst* I) { |
| Expression e; |
| |
| e.firstVN = lookup_or_add(I->getCondition()); |
| e.secondVN = lookup_or_add(I->getTrueValue()); |
| e.thirdVN = lookup_or_add(I->getFalseValue()); |
| e.function = 0; |
| e.type = I->getType(); |
| e.opcode = Expression::SELECT; |
| |
| return e; |
| } |
| |
| Expression ValueTable::create_expression(GetElementPtrInst* G) { |
| Expression e; |
| |
| e.firstVN = lookup_or_add(G->getPointerOperand()); |
| e.secondVN = 0; |
| e.thirdVN = 0; |
| e.function = 0; |
| e.type = G->getType(); |
| e.opcode = Expression::GEP; |
| |
| for (GetElementPtrInst::op_iterator I = G->idx_begin(), E = G->idx_end(); |
| I != E; ++I) |
| e.varargs.push_back(lookup_or_add(*I)); |
| |
| return e; |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // ValueTable External Functions |
| //===----------------------------------------------------------------------===// |
| |
| /// add - Insert a value into the table with a specified value number. |
| void ValueTable::add(Value* V, uint32_t num) { |
| valueNumbering.insert(std::make_pair(V, num)); |
| } |
| |
| /// lookup_or_add - Returns the value number for the specified value, assigning |
| /// it a new number if it did not have one before. |
| uint32_t ValueTable::lookup_or_add(Value* V) { |
| DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V); |
| if (VI != valueNumbering.end()) |
| return VI->second; |
| |
| if (CallInst* C = dyn_cast<CallInst>(V)) { |
| if (AA->doesNotAccessMemory(C)) { |
| Expression e = create_expression(C); |
| |
| DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); |
| if (EI != expressionNumbering.end()) { |
| valueNumbering.insert(std::make_pair(V, EI->second)); |
| return EI->second; |
| } else { |
| expressionNumbering.insert(std::make_pair(e, nextValueNumber)); |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| |
| return nextValueNumber++; |
| } |
| } else if (AA->onlyReadsMemory(C)) { |
| Expression e = create_expression(C); |
| |
| if (expressionNumbering.find(e) == expressionNumbering.end()) { |
| expressionNumbering.insert(std::make_pair(e, nextValueNumber)); |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| return nextValueNumber++; |
| } |
| |
| Instruction* local_dep = MD->getDependency(C); |
| |
| if (local_dep == MemoryDependenceAnalysis::None) { |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| return nextValueNumber++; |
| } else if (local_dep != MemoryDependenceAnalysis::NonLocal) { |
| if (!isa<CallInst>(local_dep)) { |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| return nextValueNumber++; |
| } |
| |
| CallInst* local_cdep = cast<CallInst>(local_dep); |
| |
| if (local_cdep->getCalledFunction() != C->getCalledFunction() || |
| local_cdep->getNumOperands() != C->getNumOperands()) { |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| return nextValueNumber++; |
| } else if (!C->getCalledFunction()) { |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| return nextValueNumber++; |
| } else { |
| for (unsigned i = 1; i < C->getNumOperands(); ++i) { |
| uint32_t c_vn = lookup_or_add(C->getOperand(i)); |
| uint32_t cd_vn = lookup_or_add(local_cdep->getOperand(i)); |
| if (c_vn != cd_vn) { |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| return nextValueNumber++; |
| } |
| } |
| |
| uint32_t v = lookup_or_add(local_cdep); |
| valueNumbering.insert(std::make_pair(V, v)); |
| return v; |
| } |
| } |
| |
| |
| DenseMap<BasicBlock*, Value*> deps; |
| MD->getNonLocalDependency(C, deps); |
| CallInst* cdep = 0; |
| |
| for (DenseMap<BasicBlock*, Value*>::iterator I = deps.begin(), |
| E = deps.end(); I != E; ++I) { |
| if (I->second == MemoryDependenceAnalysis::None) { |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| |
| return nextValueNumber++; |
| } else if (I->second != MemoryDependenceAnalysis::NonLocal) { |
| if (DT->properlyDominates(I->first, C->getParent())) { |
| if (CallInst* CD = dyn_cast<CallInst>(I->second)) |
| cdep = CD; |
| else { |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| return nextValueNumber++; |
| } |
| } else { |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| return nextValueNumber++; |
| } |
| } |
| } |
| |
| if (!cdep) { |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| return nextValueNumber++; |
| } |
| |
| if (cdep->getCalledFunction() != C->getCalledFunction() || |
| cdep->getNumOperands() != C->getNumOperands()) { |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| return nextValueNumber++; |
| } else if (!C->getCalledFunction()) { |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| return nextValueNumber++; |
| } else { |
| for (unsigned i = 1; i < C->getNumOperands(); ++i) { |
| uint32_t c_vn = lookup_or_add(C->getOperand(i)); |
| uint32_t cd_vn = lookup_or_add(cdep->getOperand(i)); |
| if (c_vn != cd_vn) { |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| return nextValueNumber++; |
| } |
| } |
| |
| uint32_t v = lookup_or_add(cdep); |
| valueNumbering.insert(std::make_pair(V, v)); |
| return v; |
| } |
| |
| } else { |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| return nextValueNumber++; |
| } |
| } else if (BinaryOperator* BO = dyn_cast<BinaryOperator>(V)) { |
| Expression e = create_expression(BO); |
| |
| DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); |
| if (EI != expressionNumbering.end()) { |
| valueNumbering.insert(std::make_pair(V, EI->second)); |
| return EI->second; |
| } else { |
| expressionNumbering.insert(std::make_pair(e, nextValueNumber)); |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| |
| return nextValueNumber++; |
| } |
| } else if (CmpInst* C = dyn_cast<CmpInst>(V)) { |
| Expression e = create_expression(C); |
| |
| DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); |
| if (EI != expressionNumbering.end()) { |
| valueNumbering.insert(std::make_pair(V, EI->second)); |
| return EI->second; |
| } else { |
| expressionNumbering.insert(std::make_pair(e, nextValueNumber)); |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| |
| return nextValueNumber++; |
| } |
| } else if (ShuffleVectorInst* U = dyn_cast<ShuffleVectorInst>(V)) { |
| Expression e = create_expression(U); |
| |
| DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); |
| if (EI != expressionNumbering.end()) { |
| valueNumbering.insert(std::make_pair(V, EI->second)); |
| return EI->second; |
| } else { |
| expressionNumbering.insert(std::make_pair(e, nextValueNumber)); |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| |
| return nextValueNumber++; |
| } |
| } else if (ExtractElementInst* U = dyn_cast<ExtractElementInst>(V)) { |
| Expression e = create_expression(U); |
| |
| DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); |
| if (EI != expressionNumbering.end()) { |
| valueNumbering.insert(std::make_pair(V, EI->second)); |
| return EI->second; |
| } else { |
| expressionNumbering.insert(std::make_pair(e, nextValueNumber)); |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| |
| return nextValueNumber++; |
| } |
| } else if (InsertElementInst* U = dyn_cast<InsertElementInst>(V)) { |
| Expression e = create_expression(U); |
| |
| DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); |
| if (EI != expressionNumbering.end()) { |
| valueNumbering.insert(std::make_pair(V, EI->second)); |
| return EI->second; |
| } else { |
| expressionNumbering.insert(std::make_pair(e, nextValueNumber)); |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| |
| return nextValueNumber++; |
| } |
| } else if (SelectInst* U = dyn_cast<SelectInst>(V)) { |
| Expression e = create_expression(U); |
| |
| DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); |
| if (EI != expressionNumbering.end()) { |
| valueNumbering.insert(std::make_pair(V, EI->second)); |
| return EI->second; |
| } else { |
| expressionNumbering.insert(std::make_pair(e, nextValueNumber)); |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| |
| return nextValueNumber++; |
| } |
| } else if (CastInst* U = dyn_cast<CastInst>(V)) { |
| Expression e = create_expression(U); |
| |
| DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); |
| if (EI != expressionNumbering.end()) { |
| valueNumbering.insert(std::make_pair(V, EI->second)); |
| return EI->second; |
| } else { |
| expressionNumbering.insert(std::make_pair(e, nextValueNumber)); |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| |
| return nextValueNumber++; |
| } |
| } else if (GetElementPtrInst* U = dyn_cast<GetElementPtrInst>(V)) { |
| Expression e = create_expression(U); |
| |
| DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); |
| if (EI != expressionNumbering.end()) { |
| valueNumbering.insert(std::make_pair(V, EI->second)); |
| return EI->second; |
| } else { |
| expressionNumbering.insert(std::make_pair(e, nextValueNumber)); |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| |
| return nextValueNumber++; |
| } |
| } else { |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| return nextValueNumber++; |
| } |
| } |
| |
| /// lookup - Returns the value number of the specified value. Fails if |
| /// the value has not yet been numbered. |
| uint32_t ValueTable::lookup(Value* V) const { |
| DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V); |
| assert(VI != valueNumbering.end() && "Value not numbered?"); |
| return VI->second; |
| } |
| |
| /// clear - Remove all entries from the ValueTable |
| void ValueTable::clear() { |
| valueNumbering.clear(); |
| expressionNumbering.clear(); |
| nextValueNumber = 1; |
| } |
| |
| /// erase - Remove a value from the value numbering |
| void ValueTable::erase(Value* V) { |
| valueNumbering.erase(V); |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // GVN Pass |
| //===----------------------------------------------------------------------===// |
| |
| namespace llvm { |
| template<> struct DenseMapInfo<uint32_t> { |
| static inline uint32_t getEmptyKey() { return ~0; } |
| static inline uint32_t getTombstoneKey() { return ~0 - 1; } |
| static unsigned getHashValue(const uint32_t& Val) { return Val * 37; } |
| static bool isPod() { return true; } |
| static bool isEqual(const uint32_t& LHS, const uint32_t& RHS) { |
| return LHS == RHS; |
| } |
| }; |
| } |
| |
| namespace { |
| struct VISIBILITY_HIDDEN ValueNumberScope { |
| ValueNumberScope* parent; |
| DenseMap<uint32_t, Value*> table; |
| |
| ValueNumberScope(ValueNumberScope* p) : parent(p) { } |
| }; |
| } |
| |
| namespace { |
| |
| class VISIBILITY_HIDDEN GVN : public FunctionPass { |
| bool runOnFunction(Function &F); |
| public: |
| static char ID; // Pass identification, replacement for typeid |
| GVN() : FunctionPass((intptr_t)&ID) { } |
| |
| private: |
| ValueTable VN; |
| DenseMap<BasicBlock*, ValueNumberScope*> localAvail; |
| |
| typedef DenseMap<Value*, SmallPtrSet<Instruction*, 4> > PhiMapType; |
| PhiMapType phiMap; |
| |
| |
| // This transformation requires dominator postdominator info |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addRequired<DominatorTree>(); |
| AU.addRequired<MemoryDependenceAnalysis>(); |
| AU.addRequired<AliasAnalysis>(); |
| |
| AU.addPreserved<DominatorTree>(); |
| AU.addPreserved<AliasAnalysis>(); |
| AU.addPreserved<MemoryDependenceAnalysis>(); |
| } |
| |
| // Helper fuctions |
| // FIXME: eliminate or document these better |
| bool processLoad(LoadInst* L, |
| DenseMap<Value*, LoadInst*> &lastLoad, |
| SmallVectorImpl<Instruction*> &toErase); |
| bool processInstruction(Instruction* I, |
| DenseMap<Value*, LoadInst*>& lastSeenLoad, |
| SmallVectorImpl<Instruction*> &toErase); |
| bool processNonLocalLoad(LoadInst* L, |
| SmallVectorImpl<Instruction*> &toErase); |
| bool processBlock(DomTreeNode* DTN); |
| Value *GetValueForBlock(BasicBlock *BB, LoadInst* orig, |
| DenseMap<BasicBlock*, Value*> &Phis, |
| bool top_level = false); |
| void dump(DenseMap<uint32_t, Value*>& d); |
| bool iterateOnFunction(Function &F); |
| Value* CollapsePhi(PHINode* p); |
| bool isSafeReplacement(PHINode* p, Instruction* inst); |
| bool performPRE(Function& F); |
| Value* lookupNumber(BasicBlock* BB, uint32_t num); |
| }; |
| |
| char GVN::ID = 0; |
| } |
| |
| // createGVNPass - The public interface to this file... |
| FunctionPass *llvm::createGVNPass() { return new GVN(); } |
| |
| static RegisterPass<GVN> X("gvn", |
| "Global Value Numbering"); |
| |
| void GVN::dump(DenseMap<uint32_t, Value*>& d) { |
| printf("{\n"); |
| for (DenseMap<uint32_t, Value*>::iterator I = d.begin(), |
| E = d.end(); I != E; ++I) { |
| printf("%d\n", I->first); |
| I->second->dump(); |
| } |
| printf("}\n"); |
| } |
| |
| Value* GVN::CollapsePhi(PHINode* p) { |
| DominatorTree &DT = getAnalysis<DominatorTree>(); |
| Value* constVal = p->hasConstantValue(); |
| |
| if (!constVal) return 0; |
| |
| Instruction* inst = dyn_cast<Instruction>(constVal); |
| if (!inst) |
| return constVal; |
| |
| if (DT.dominates(inst, p)) |
| if (isSafeReplacement(p, inst)) |
| return inst; |
| return 0; |
| } |
| |
| bool GVN::isSafeReplacement(PHINode* p, Instruction* inst) { |
| if (!isa<PHINode>(inst)) |
| return true; |
| |
| for (Instruction::use_iterator UI = p->use_begin(), E = p->use_end(); |
| UI != E; ++UI) |
| if (PHINode* use_phi = dyn_cast<PHINode>(UI)) |
| if (use_phi->getParent() == inst->getParent()) |
| return false; |
| |
| return true; |
| } |
| |
| /// GetValueForBlock - Get the value to use within the specified basic block. |
| /// available values are in Phis. |
| Value *GVN::GetValueForBlock(BasicBlock *BB, LoadInst* orig, |
| DenseMap<BasicBlock*, Value*> &Phis, |
| bool top_level) { |
| |
| // If we have already computed this value, return the previously computed val. |
| DenseMap<BasicBlock*, Value*>::iterator V = Phis.find(BB); |
| if (V != Phis.end() && !top_level) return V->second; |
| |
| BasicBlock* singlePred = BB->getSinglePredecessor(); |
| if (singlePred) { |
| Value *ret = GetValueForBlock(singlePred, orig, Phis); |
| Phis[BB] = ret; |
| return ret; |
| } |
| |
| // Otherwise, the idom is the loop, so we need to insert a PHI node. Do so |
| // now, then get values to fill in the incoming values for the PHI. |
| PHINode *PN = PHINode::Create(orig->getType(), orig->getName()+".rle", |
| BB->begin()); |
| PN->reserveOperandSpace(std::distance(pred_begin(BB), pred_end(BB))); |
| |
| if (Phis.count(BB) == 0) |
| Phis.insert(std::make_pair(BB, PN)); |
| |
| // Fill in the incoming values for the block. |
| for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) { |
| Value* val = GetValueForBlock(*PI, orig, Phis); |
| PN->addIncoming(val, *PI); |
| } |
| |
| AliasAnalysis& AA = getAnalysis<AliasAnalysis>(); |
| AA.copyValue(orig, PN); |
| |
| // Attempt to collapse PHI nodes that are trivially redundant |
| Value* v = CollapsePhi(PN); |
| if (!v) { |
| // Cache our phi construction results |
| phiMap[orig->getPointerOperand()].insert(PN); |
| return PN; |
| } |
| |
| MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>(); |
| |
| MD.removeInstruction(PN); |
| PN->replaceAllUsesWith(v); |
| |
| for (DenseMap<BasicBlock*, Value*>::iterator I = Phis.begin(), |
| E = Phis.end(); I != E; ++I) |
| if (I->second == PN) |
| I->second = v; |
| |
| PN->eraseFromParent(); |
| |
| Phis[BB] = v; |
| return v; |
| } |
| |
| /// processNonLocalLoad - Attempt to eliminate a load whose dependencies are |
| /// non-local by performing PHI construction. |
| bool GVN::processNonLocalLoad(LoadInst* L, |
| SmallVectorImpl<Instruction*> &toErase) { |
| MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>(); |
| |
| // Find the non-local dependencies of the load |
| DenseMap<BasicBlock*, Value*> deps; |
| MD.getNonLocalDependency(L, deps); |
| |
| DenseMap<BasicBlock*, Value*> repl; |
| |
| // Filter out useless results (non-locals, etc) |
| for (DenseMap<BasicBlock*, Value*>::iterator I = deps.begin(), E = deps.end(); |
| I != E; ++I) { |
| if (I->second == MemoryDependenceAnalysis::None) |
| return false; |
| |
| if (I->second == MemoryDependenceAnalysis::NonLocal) |
| continue; |
| |
| if (StoreInst* S = dyn_cast<StoreInst>(I->second)) { |
| if (S->getPointerOperand() != L->getPointerOperand()) |
| return false; |
| repl[I->first] = S->getOperand(0); |
| } else if (LoadInst* LD = dyn_cast<LoadInst>(I->second)) { |
| if (LD->getPointerOperand() != L->getPointerOperand()) |
| return false; |
| repl[I->first] = LD; |
| } else { |
| return false; |
| } |
| } |
| |
| // Use cached PHI construction information from previous runs |
| SmallPtrSet<Instruction*, 4>& p = phiMap[L->getPointerOperand()]; |
| for (SmallPtrSet<Instruction*, 4>::iterator I = p.begin(), E = p.end(); |
| I != E; ++I) { |
| if ((*I)->getParent() == L->getParent()) { |
| MD.removeInstruction(L); |
| L->replaceAllUsesWith(*I); |
| toErase.push_back(L); |
| NumGVNLoad++; |
| return true; |
| } |
| |
| repl.insert(std::make_pair((*I)->getParent(), *I)); |
| } |
| |
| // Perform PHI construction |
| SmallPtrSet<BasicBlock*, 4> visited; |
| Value* v = GetValueForBlock(L->getParent(), L, repl, true); |
| |
| MD.removeInstruction(L); |
| L->replaceAllUsesWith(v); |
| toErase.push_back(L); |
| NumGVNLoad++; |
| |
| return true; |
| } |
| |
| /// processLoad - Attempt to eliminate a load, first by eliminating it |
| /// locally, and then attempting non-local elimination if that fails. |
| bool GVN::processLoad(LoadInst *L, DenseMap<Value*, LoadInst*> &lastLoad, |
| SmallVectorImpl<Instruction*> &toErase) { |
| if (L->isVolatile()) { |
| lastLoad[L->getPointerOperand()] = L; |
| return false; |
| } |
| |
| Value* pointer = L->getPointerOperand(); |
| LoadInst*& last = lastLoad[pointer]; |
| |
| // ... to a pointer that has been loaded from before... |
| MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>(); |
| bool removedNonLocal = false; |
| Instruction* dep = MD.getDependency(L); |
| if (dep == MemoryDependenceAnalysis::NonLocal && |
| L->getParent() != &L->getParent()->getParent()->getEntryBlock()) { |
| removedNonLocal = processNonLocalLoad(L, toErase); |
| |
| if (!removedNonLocal) |
| last = L; |
| |
| return removedNonLocal; |
| } |
| |
| |
| bool deletedLoad = false; |
| |
| // Walk up the dependency chain until we either find |
| // a dependency we can use, or we can't walk any further |
| while (dep != MemoryDependenceAnalysis::None && |
| dep != MemoryDependenceAnalysis::NonLocal && |
| (isa<LoadInst>(dep) || isa<StoreInst>(dep))) { |
| // ... that depends on a store ... |
| if (StoreInst* S = dyn_cast<StoreInst>(dep)) { |
| if (S->getPointerOperand() == pointer) { |
| // Remove it! |
| MD.removeInstruction(L); |
| |
| L->replaceAllUsesWith(S->getOperand(0)); |
| toErase.push_back(L); |
| deletedLoad = true; |
| NumGVNLoad++; |
| } |
| |
| // Whether we removed it or not, we can't |
| // go any further |
| break; |
| } else if (!last) { |
| // If we don't depend on a store, and we haven't |
| // been loaded before, bail. |
| break; |
| } else if (dep == last) { |
| // Remove it! |
| MD.removeInstruction(L); |
| |
| L->replaceAllUsesWith(last); |
| toErase.push_back(L); |
| deletedLoad = true; |
| NumGVNLoad++; |
| |
| break; |
| } else { |
| dep = MD.getDependency(L, dep); |
| } |
| } |
| |
| if (dep != MemoryDependenceAnalysis::None && |
| dep != MemoryDependenceAnalysis::NonLocal && |
| isa<AllocationInst>(dep)) { |
| // Check that this load is actually from the |
| // allocation we found |
| Value* v = L->getOperand(0); |
| while (true) { |
| if (BitCastInst *BC = dyn_cast<BitCastInst>(v)) |
| v = BC->getOperand(0); |
| else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(v)) |
| v = GEP->getOperand(0); |
| else |
| break; |
| } |
| if (v == dep) { |
| // If this load depends directly on an allocation, there isn't |
| // anything stored there; therefore, we can optimize this load |
| // to undef. |
| MD.removeInstruction(L); |
| |
| L->replaceAllUsesWith(UndefValue::get(L->getType())); |
| toErase.push_back(L); |
| deletedLoad = true; |
| NumGVNLoad++; |
| } |
| } |
| |
| if (!deletedLoad) |
| last = L; |
| |
| return deletedLoad; |
| } |
| |
| Value* GVN::lookupNumber(BasicBlock* BB, uint32_t num) { |
| DenseMap<BasicBlock*, ValueNumberScope*>::iterator I = localAvail.find(BB); |
| if (I == localAvail.end()) |
| return 0; |
| |
| ValueNumberScope* locals = I->second; |
| |
| while (locals) { |
| DenseMap<uint32_t, Value*>::iterator I = locals->table.find(num); |
| if (I != locals->table.end()) |
| return I->second; |
| else |
| locals = locals->parent; |
| } |
| |
| return 0; |
| } |
| |
| /// processInstruction - When calculating availability, handle an instruction |
| /// by inserting it into the appropriate sets |
| bool GVN::processInstruction(Instruction *I, |
| DenseMap<Value*, LoadInst*> &lastSeenLoad, |
| SmallVectorImpl<Instruction*> &toErase) { |
| if (LoadInst* L = dyn_cast<LoadInst>(I)) { |
| bool changed = processLoad(L, lastSeenLoad, toErase); |
| |
| if (!changed) { |
| unsigned num = VN.lookup_or_add(L); |
| localAvail[I->getParent()]->table.insert(std::make_pair(num, L)); |
| } |
| |
| return changed; |
| } |
| |
| unsigned num = VN.lookup_or_add(I); |
| |
| // Allocations are always uniquely numbered, so we can save time and memory |
| // by fast failing them. |
| if (isa<AllocationInst>(I)) { |
| localAvail[I->getParent()]->table.insert(std::make_pair(num, I)); |
| return false; |
| } |
| |
| // Collapse PHI nodes |
| if (PHINode* p = dyn_cast<PHINode>(I)) { |
| Value* constVal = CollapsePhi(p); |
| |
| if (constVal) { |
| for (PhiMapType::iterator PI = phiMap.begin(), PE = phiMap.end(); |
| PI != PE; ++PI) |
| if (PI->second.count(p)) |
| PI->second.erase(p); |
| |
| p->replaceAllUsesWith(constVal); |
| toErase.push_back(p); |
| } else { |
| localAvail[I->getParent()]->table.insert(std::make_pair(num, I)); |
| } |
| // Perform value-number based elimination |
| } else if (Value* repl = lookupNumber(I->getParent(), num)) { |
| // Remove it! |
| MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>(); |
| MD.removeInstruction(I); |
| |
| VN.erase(I); |
| I->replaceAllUsesWith(repl); |
| toErase.push_back(I); |
| return true; |
| } else if (!I->isTerminator()) { |
| localAvail[I->getParent()]->table.insert(std::make_pair(num, I)); |
| } |
| |
| return false; |
| } |
| |
| // GVN::runOnFunction - This is the main transformation entry point for a |
| // function. |
| // |
| bool GVN::runOnFunction(Function& F) { |
| VN.setAliasAnalysis(&getAnalysis<AliasAnalysis>()); |
| VN.setMemDep(&getAnalysis<MemoryDependenceAnalysis>()); |
| VN.setDomTree(&getAnalysis<DominatorTree>()); |
| |
| bool changed = false; |
| bool shouldContinue = true; |
| |
| while (shouldContinue) { |
| shouldContinue = iterateOnFunction(F); |
| changed |= shouldContinue; |
| } |
| |
| return changed; |
| } |
| |
| |
| bool GVN::processBlock(DomTreeNode* DTN) { |
| BasicBlock* BB = DTN->getBlock(); |
| |
| SmallVector<Instruction*, 8> toErase; |
| DenseMap<Value*, LoadInst*> lastSeenLoad; |
| bool changed_function = false; |
| |
| if (DTN->getIDom()) |
| localAvail[BB] = |
| new ValueNumberScope(localAvail[DTN->getIDom()->getBlock()]); |
| else |
| localAvail[BB] = new ValueNumberScope(0); |
| |
| for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); |
| BI != BE;) { |
| changed_function |= processInstruction(BI, lastSeenLoad, toErase); |
| if (toErase.empty()) { |
| ++BI; |
| continue; |
| } |
| |
| // If we need some instructions deleted, do it now. |
| NumGVNInstr += toErase.size(); |
| |
| // Avoid iterator invalidation. |
| bool AtStart = BI == BB->begin(); |
| if (!AtStart) |
| --BI; |
| |
| for (SmallVector<Instruction*, 4>::iterator I = toErase.begin(), |
| E = toErase.end(); I != E; ++I) |
| (*I)->eraseFromParent(); |
| |
| if (AtStart) |
| BI = BB->begin(); |
| else |
| ++BI; |
| |
| toErase.clear(); |
| } |
| |
| return changed_function; |
| } |
| |
| /// performPRE - Perform a purely local form of PRE that looks for diamond |
| /// control flow patterns and attempts to perform simple PRE at the join point. |
| bool GVN::performPRE(Function& F) { |
| bool changed = false; |
| SmallVector<std::pair<TerminatorInst*, unsigned>, 4> toSplit; |
| for (df_iterator<BasicBlock*> DI = df_begin(&F.getEntryBlock()), |
| DE = df_end(&F.getEntryBlock()); DI != DE; ++DI) { |
| BasicBlock* CurrentBlock = *DI; |
| |
| // Nothing to PRE in the entry block. |
| if (CurrentBlock == &F.getEntryBlock()) continue; |
| |
| for (BasicBlock::iterator BI = CurrentBlock->begin(), |
| BE = CurrentBlock->end(); BI != BE; ) { |
| if (isa<AllocationInst>(BI) || isa<TerminatorInst>(BI) || |
| isa<PHINode>(BI) || BI->mayReadFromMemory() || |
| BI->mayWriteToMemory()) { |
| BI++; |
| continue; |
| } |
| |
| uint32_t valno = VN.lookup(BI); |
| |
| // Look for the predecessors for PRE opportunities. We're |
| // only trying to solve the basic diamond case, where |
| // a value is computed in the successor and one predecessor, |
| // but not the other. We also explicitly disallow cases |
| // where the successor is its own predecessor, because they're |
| // more complicated to get right. |
| unsigned numWith = 0; |
| unsigned numWithout = 0; |
| BasicBlock* PREPred = 0; |
| DenseMap<BasicBlock*, Value*> predMap; |
| for (pred_iterator PI = pred_begin(CurrentBlock), |
| PE = pred_end(CurrentBlock); PI != PE; ++PI) { |
| // We're not interested in PRE where the block is its |
| // own predecessor, on in blocks with predecessors |
| // that are not reachable. |
| if (*PI == CurrentBlock) { |
| numWithout = 2; |
| break; |
| } else if (!localAvail.count(*PI)) { |
| numWithout = 2; |
| break; |
| } |
| |
| DenseMap<uint32_t, Value*>::iterator predV = |
| localAvail[*PI]->table.find(valno); |
| if (predV == localAvail[*PI]->table.end()) { |
| PREPred = *PI; |
| numWithout++; |
| } else if (predV->second == BI) { |
| numWithout = 2; |
| } else { |
| predMap[*PI] = predV->second; |
| numWith++; |
| } |
| } |
| |
| // Don't do PRE when it might increase code size, i.e. when |
| // we would need to insert instructions in more than one pred. |
| if (numWithout != 1 || numWith == 0) { |
| BI++; |
| continue; |
| } |
| |
| // We can't do PRE safely on a critical edge, so instead we schedule |
| // the edge to be split and perform the PRE the next time we iterate |
| // on the function. |
| unsigned succNum = 0; |
| for (unsigned i = 0, e = PREPred->getTerminator()->getNumSuccessors(); |
| i != e; ++i) |
| if (PREPred->getTerminator()->getSuccessor(i) == PREPred) { |
| succNum = i; |
| break; |
| } |
| |
| if (isCriticalEdge(PREPred->getTerminator(), succNum)) { |
| toSplit.push_back(std::make_pair(PREPred->getTerminator(), succNum)); |
| changed = true; |
| BI++; |
| continue; |
| } |
| |
| // Instantiate the expression the in predecessor that lacked it. |
| // Because we are going top-down through the block, all value numbers |
| // will be available in the predecessor by the time we need them. Any |
| // that weren't original present will have been instantiated earlier |
| // in this loop. |
| Instruction* PREInstr = BI->clone(); |
| bool success = true; |
| for (unsigned i = 0; i < BI->getNumOperands(); ++i) { |
| Value* op = BI->getOperand(i); |
| if (isa<Argument>(op) || isa<Constant>(op) || isa<GlobalValue>(op)) |
| PREInstr->setOperand(i, op); |
| else if (!lookupNumber(PREPred, VN.lookup(op))) { |
| success = false; |
| break; |
| } else |
| PREInstr->setOperand(i, lookupNumber(PREPred, VN.lookup(op))); |
| } |
| |
| // Fail out if we encounter an operand that is not available in |
| // the PRE predecessor. This is typically because of loads which |
| // are not value numbered precisely. |
| if (!success) { |
| delete PREInstr; |
| BI++; |
| continue; |
| } |
| |
| PREInstr->insertBefore(PREPred->getTerminator()); |
| PREInstr->setName(BI->getName() + ".pre"); |
| predMap[PREPred] = PREInstr; |
| VN.add(PREInstr, valno); |
| NumGVNPRE++; |
| |
| // Update the availability map to include the new instruction. |
| localAvail[PREPred]->table.insert(std::make_pair(valno, PREInstr)); |
| |
| // Create a PHI to make the value available in this block. |
| PHINode* Phi = PHINode::Create(BI->getType(), |
| BI->getName() + ".pre-phi", |
| CurrentBlock->begin()); |
| for (pred_iterator PI = pred_begin(CurrentBlock), |
| PE = pred_end(CurrentBlock); PI != PE; ++PI) |
| Phi->addIncoming(predMap[*PI], *PI); |
| |
| VN.add(Phi, valno); |
| localAvail[CurrentBlock]->table[valno] = Phi; |
| |
| BI->replaceAllUsesWith(Phi); |
| VN.erase(BI); |
| |
| Instruction* erase = BI; |
| BI++; |
| erase->eraseFromParent(); |
| |
| changed = true; |
| } |
| } |
| |
| for (SmallVector<std::pair<TerminatorInst*, unsigned>, 4>::iterator |
| I = toSplit.begin(), E = toSplit.end(); I != E; ++I) |
| SplitCriticalEdge(I->first, I->second, this); |
| |
| return changed; |
| } |
| |
| // GVN::iterateOnFunction - Executes one iteration of GVN |
| bool GVN::iterateOnFunction(Function &F) { |
| // Clean out global sets from any previous functions |
| VN.clear(); |
| phiMap.clear(); |
| |
| for (DenseMap<BasicBlock*, ValueNumberScope*>::iterator |
| I = localAvail.begin(), E = localAvail.end(); I != E; ++I) |
| delete I->second; |
| localAvail.clear(); |
| |
| DominatorTree &DT = getAnalysis<DominatorTree>(); |
| |
| // Top-down walk of the dominator tree |
| bool changed = false; |
| for (df_iterator<DomTreeNode*> DI = df_begin(DT.getRootNode()), |
| DE = df_end(DT.getRootNode()); DI != DE; ++DI) |
| changed |= processBlock(*DI); |
| |
| if (EnablePRE) |
| changed |= performPRE(F); |
| |
| return changed; |
| } |