| //===- 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/IntrinsicInst.h" |
| #include "llvm/LLVMContext.h" |
| #include "llvm/Value.h" |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/DepthFirstIterator.h" |
| #include "llvm/ADT/PostOrderIterator.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/Support/ErrorHandling.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| #include <cstdio> |
| using namespace llvm; |
| |
| STATISTIC(NumGVNInstr, "Number of instructions deleted"); |
| STATISTIC(NumGVNLoad, "Number of loads deleted"); |
| STATISTIC(NumGVNPRE, "Number of instructions PRE'd"); |
| STATISTIC(NumGVNBlocks, "Number of blocks merged"); |
| STATISTIC(NumPRELoad, "Number of loads PRE'd"); |
| |
| static cl::opt<bool> EnablePRE("enable-pre", |
| cl::init(true), cl::Hidden); |
| static cl::opt<bool> EnableLoadPRE("enable-load-pre", cl::init(true)); |
| |
| //===----------------------------------------------------------------------===// |
| // 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, FADD, SUB, FSUB, MUL, FMUL, |
| 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 { |
| return !(*this == other); |
| } |
| }; |
| |
| 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; } |
| AliasAnalysis *getAliasAnalysis() const { return AA; } |
| void setMemDep(MemoryDependenceAnalysis* M) { MD = M; } |
| void setDomTree(DominatorTree* D) { DT = D; } |
| uint32_t getNextUnusedValueNumber() { return nextValueNumber; } |
| void verifyRemoved(const Value *) const; |
| }; |
| } |
| |
| 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 |
| llvm_unreachable("Binary operator with unknown opcode?"); |
| case Instruction::Add: return Expression::ADD; |
| case Instruction::FAdd: return Expression::FADD; |
| case Instruction::Sub: return Expression::SUB; |
| case Instruction::FSub: return Expression::FSUB; |
| case Instruction::Mul: return Expression::MUL; |
| case Instruction::FMul: return Expression::FMUL; |
| 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)) { |
| switch (C->getPredicate()) { |
| default: // THIS SHOULD NEVER HAPPEN |
| llvm_unreachable("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; |
| } |
| } else { |
| switch (C->getPredicate()) { |
| default: // THIS SHOULD NEVER HAPPEN |
| llvm_unreachable("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 |
| llvm_unreachable("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++; |
| } |
| |
| MemDepResult local_dep = MD->getDependency(C); |
| |
| if (!local_dep.isDef() && !local_dep.isNonLocal()) { |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| return nextValueNumber++; |
| } |
| |
| if (local_dep.isDef()) { |
| CallInst* local_cdep = cast<CallInst>(local_dep.getInst()); |
| |
| if (local_cdep->getNumOperands() != C->getNumOperands()) { |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| return nextValueNumber++; |
| } |
| |
| 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; |
| } |
| |
| // Non-local case. |
| const MemoryDependenceAnalysis::NonLocalDepInfo &deps = |
| MD->getNonLocalCallDependency(CallSite(C)); |
| // FIXME: call/call dependencies for readonly calls should return def, not |
| // clobber! Move the checking logic to MemDep! |
| CallInst* cdep = 0; |
| |
| // Check to see if we have a single dominating call instruction that is |
| // identical to C. |
| for (unsigned i = 0, e = deps.size(); i != e; ++i) { |
| const MemoryDependenceAnalysis::NonLocalDepEntry *I = &deps[i]; |
| // Ignore non-local dependencies. |
| if (I->second.isNonLocal()) |
| continue; |
| |
| // We don't handle non-depedencies. If we already have a call, reject |
| // instruction dependencies. |
| if (I->second.isClobber() || cdep != 0) { |
| cdep = 0; |
| break; |
| } |
| |
| CallInst *NonLocalDepCall = dyn_cast<CallInst>(I->second.getInst()); |
| // FIXME: All duplicated with non-local case. |
| if (NonLocalDepCall && DT->properlyDominates(I->first, C->getParent())){ |
| cdep = NonLocalDepCall; |
| continue; |
| } |
| |
| cdep = 0; |
| break; |
| } |
| |
| if (!cdep) { |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| return nextValueNumber++; |
| } |
| |
| if (cdep->getNumOperands() != C->getNumOperands()) { |
| valueNumbering.insert(std::make_pair(V, nextValueNumber)); |
| return nextValueNumber++; |
| } |
| 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); |
| } |
| |
| /// verifyRemoved - Verify that the value is removed from all internal data |
| /// structures. |
| void ValueTable::verifyRemoved(const Value *V) const { |
| for (DenseMap<Value*, uint32_t>::iterator |
| I = valueNumbering.begin(), E = valueNumbering.end(); I != E; ++I) { |
| assert(I->first != V && "Inst still occurs in value numbering map!"); |
| } |
| } |
| |
| //===----------------------------------------------------------------------===// |
| // GVN Pass |
| //===----------------------------------------------------------------------===// |
| |
| 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(&ID) { } |
| |
| private: |
| MemoryDependenceAnalysis *MD; |
| DominatorTree *DT; |
| |
| 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>(); |
| } |
| |
| // Helper fuctions |
| // FIXME: eliminate or document these better |
| bool processLoad(LoadInst* L, |
| SmallVectorImpl<Instruction*> &toErase); |
| bool processInstruction(Instruction* I, |
| SmallVectorImpl<Instruction*> &toErase); |
| bool processNonLocalLoad(LoadInst* L, |
| SmallVectorImpl<Instruction*> &toErase); |
| bool processBlock(BasicBlock* BB); |
| Value *GetValueForBlock(BasicBlock *BB, Instruction* 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); |
| bool mergeBlockIntoPredecessor(BasicBlock* BB); |
| Value* AttemptRedundancyElimination(Instruction* orig, unsigned valno); |
| void cleanupGlobalSets(); |
| void verifyRemoved(const Instruction *I) const; |
| }; |
| |
| 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) { |
| 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, Instruction* 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; |
| |
| // If the block is unreachable, just return undef, since this path |
| // can't actually occur at runtime. |
| if (!DT->isReachableFromEntry(BB)) |
| return Phis[BB] = UndefValue::get(orig->getType()); |
| |
| if (BasicBlock *Pred = BB->getSinglePredecessor()) { |
| Value *ret = GetValueForBlock(Pred, orig, Phis); |
| Phis[BB] = ret; |
| return ret; |
| } |
| |
| // Get the number of predecessors of this block so we can reserve space later. |
| // If there is already a PHI in it, use the #preds from it, otherwise count. |
| // Getting it from the PHI is constant time. |
| unsigned NumPreds; |
| if (PHINode *ExistingPN = dyn_cast<PHINode>(BB->begin())) |
| NumPreds = ExistingPN->getNumIncomingValues(); |
| else |
| NumPreds = std::distance(pred_begin(BB), pred_end(BB)); |
| |
| // 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(NumPreds); |
| |
| 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); |
| } |
| |
| VN.getAliasAnalysis()->copyValue(orig, PN); |
| |
| // Attempt to collapse PHI nodes that are trivially redundant |
| Value* v = CollapsePhi(PN); |
| if (!v) { |
| // Cache our phi construction results |
| if (LoadInst* L = dyn_cast<LoadInst>(orig)) |
| phiMap[L->getPointerOperand()].insert(PN); |
| else |
| phiMap[orig].insert(PN); |
| |
| return PN; |
| } |
| |
| PN->replaceAllUsesWith(v); |
| if (isa<PointerType>(v->getType())) |
| MD->invalidateCachedPointerInfo(v); |
| |
| for (DenseMap<BasicBlock*, Value*>::iterator I = Phis.begin(), |
| E = Phis.end(); I != E; ++I) |
| if (I->second == PN) |
| I->second = v; |
| |
| DEBUG(errs() << "GVN removed: " << *PN); |
| MD->removeInstruction(PN); |
| PN->eraseFromParent(); |
| DEBUG(verifyRemoved(PN)); |
| |
| Phis[BB] = v; |
| return v; |
| } |
| |
| /// IsValueFullyAvailableInBlock - Return true if we can prove that the value |
| /// we're analyzing is fully available in the specified block. As we go, keep |
| /// track of which blocks we know are fully alive in FullyAvailableBlocks. This |
| /// map is actually a tri-state map with the following values: |
| /// 0) we know the block *is not* fully available. |
| /// 1) we know the block *is* fully available. |
| /// 2) we do not know whether the block is fully available or not, but we are |
| /// currently speculating that it will be. |
| /// 3) we are speculating for this block and have used that to speculate for |
| /// other blocks. |
| static bool IsValueFullyAvailableInBlock(BasicBlock *BB, |
| DenseMap<BasicBlock*, char> &FullyAvailableBlocks) { |
| // Optimistically assume that the block is fully available and check to see |
| // if we already know about this block in one lookup. |
| std::pair<DenseMap<BasicBlock*, char>::iterator, char> IV = |
| FullyAvailableBlocks.insert(std::make_pair(BB, 2)); |
| |
| // If the entry already existed for this block, return the precomputed value. |
| if (!IV.second) { |
| // If this is a speculative "available" value, mark it as being used for |
| // speculation of other blocks. |
| if (IV.first->second == 2) |
| IV.first->second = 3; |
| return IV.first->second != 0; |
| } |
| |
| // Otherwise, see if it is fully available in all predecessors. |
| pred_iterator PI = pred_begin(BB), PE = pred_end(BB); |
| |
| // If this block has no predecessors, it isn't live-in here. |
| if (PI == PE) |
| goto SpeculationFailure; |
| |
| for (; PI != PE; ++PI) |
| // If the value isn't fully available in one of our predecessors, then it |
| // isn't fully available in this block either. Undo our previous |
| // optimistic assumption and bail out. |
| if (!IsValueFullyAvailableInBlock(*PI, FullyAvailableBlocks)) |
| goto SpeculationFailure; |
| |
| return true; |
| |
| // SpeculationFailure - If we get here, we found out that this is not, after |
| // all, a fully-available block. We have a problem if we speculated on this and |
| // used the speculation to mark other blocks as available. |
| SpeculationFailure: |
| char &BBVal = FullyAvailableBlocks[BB]; |
| |
| // If we didn't speculate on this, just return with it set to false. |
| if (BBVal == 2) { |
| BBVal = 0; |
| return false; |
| } |
| |
| // If we did speculate on this value, we could have blocks set to 1 that are |
| // incorrect. Walk the (transitive) successors of this block and mark them as |
| // 0 if set to one. |
| SmallVector<BasicBlock*, 32> BBWorklist; |
| BBWorklist.push_back(BB); |
| |
| while (!BBWorklist.empty()) { |
| BasicBlock *Entry = BBWorklist.pop_back_val(); |
| // Note that this sets blocks to 0 (unavailable) if they happen to not |
| // already be in FullyAvailableBlocks. This is safe. |
| char &EntryVal = FullyAvailableBlocks[Entry]; |
| if (EntryVal == 0) continue; // Already unavailable. |
| |
| // Mark as unavailable. |
| EntryVal = 0; |
| |
| for (succ_iterator I = succ_begin(Entry), E = succ_end(Entry); I != E; ++I) |
| BBWorklist.push_back(*I); |
| } |
| |
| return false; |
| } |
| |
| /// processNonLocalLoad - Attempt to eliminate a load whose dependencies are |
| /// non-local by performing PHI construction. |
| bool GVN::processNonLocalLoad(LoadInst *LI, |
| SmallVectorImpl<Instruction*> &toErase) { |
| // Find the non-local dependencies of the load. |
| SmallVector<MemoryDependenceAnalysis::NonLocalDepEntry, 64> Deps; |
| MD->getNonLocalPointerDependency(LI->getOperand(0), true, LI->getParent(), |
| Deps); |
| //DEBUG(errs() << "INVESTIGATING NONLOCAL LOAD: " << Deps.size() << *LI); |
| |
| // If we had to process more than one hundred blocks to find the |
| // dependencies, this load isn't worth worrying about. Optimizing |
| // it will be too expensive. |
| if (Deps.size() > 100) |
| return false; |
| |
| // If we had a phi translation failure, we'll have a single entry which is a |
| // clobber in the current block. Reject this early. |
| if (Deps.size() == 1 && Deps[0].second.isClobber()) { |
| DEBUG( |
| errs() << "GVN: non-local load "; |
| WriteAsOperand(errs(), LI); |
| errs() << " is clobbered by " << *Deps[0].second.getInst(); |
| ); |
| return false; |
| } |
| |
| // Filter out useless results (non-locals, etc). Keep track of the blocks |
| // where we have a value available in repl, also keep track of whether we see |
| // dependencies that produce an unknown value for the load (such as a call |
| // that could potentially clobber the load). |
| SmallVector<std::pair<BasicBlock*, Value*>, 16> ValuesPerBlock; |
| SmallVector<BasicBlock*, 16> UnavailableBlocks; |
| |
| for (unsigned i = 0, e = Deps.size(); i != e; ++i) { |
| BasicBlock *DepBB = Deps[i].first; |
| MemDepResult DepInfo = Deps[i].second; |
| |
| if (DepInfo.isClobber()) { |
| UnavailableBlocks.push_back(DepBB); |
| continue; |
| } |
| |
| Instruction *DepInst = DepInfo.getInst(); |
| |
| // Loading the allocation -> undef. |
| if (isa<AllocationInst>(DepInst)) { |
| ValuesPerBlock.push_back(std::make_pair(DepBB, |
| UndefValue::get(LI->getType()))); |
| continue; |
| } |
| |
| if (StoreInst* S = dyn_cast<StoreInst>(DepInst)) { |
| // Reject loads and stores that are to the same address but are of |
| // different types. |
| // NOTE: 403.gcc does have this case (e.g. in readonly_fields_p) because |
| // of bitfield access, it would be interesting to optimize for it at some |
| // point. |
| if (S->getOperand(0)->getType() != LI->getType()) { |
| UnavailableBlocks.push_back(DepBB); |
| continue; |
| } |
| |
| ValuesPerBlock.push_back(std::make_pair(DepBB, S->getOperand(0))); |
| |
| } else if (LoadInst* LD = dyn_cast<LoadInst>(DepInst)) { |
| if (LD->getType() != LI->getType()) { |
| UnavailableBlocks.push_back(DepBB); |
| continue; |
| } |
| ValuesPerBlock.push_back(std::make_pair(DepBB, LD)); |
| } else { |
| UnavailableBlocks.push_back(DepBB); |
| continue; |
| } |
| } |
| |
| // If we have no predecessors that produce a known value for this load, exit |
| // early. |
| if (ValuesPerBlock.empty()) return false; |
| |
| // If all of the instructions we depend on produce a known value for this |
| // load, then it is fully redundant and we can use PHI insertion to compute |
| // its value. Insert PHIs and remove the fully redundant value now. |
| if (UnavailableBlocks.empty()) { |
| // Use cached PHI construction information from previous runs |
| SmallPtrSet<Instruction*, 4> &p = phiMap[LI->getPointerOperand()]; |
| // FIXME: What does phiMap do? Are we positive it isn't getting invalidated? |
| for (SmallPtrSet<Instruction*, 4>::iterator I = p.begin(), E = p.end(); |
| I != E; ++I) { |
| if ((*I)->getParent() == LI->getParent()) { |
| DEBUG(errs() << "GVN REMOVING NONLOCAL LOAD #1: " << *LI); |
| LI->replaceAllUsesWith(*I); |
| if (isa<PointerType>((*I)->getType())) |
| MD->invalidateCachedPointerInfo(*I); |
| toErase.push_back(LI); |
| NumGVNLoad++; |
| return true; |
| } |
| |
| ValuesPerBlock.push_back(std::make_pair((*I)->getParent(), *I)); |
| } |
| |
| DEBUG(errs() << "GVN REMOVING NONLOCAL LOAD: " << *LI); |
| |
| DenseMap<BasicBlock*, Value*> BlockReplValues; |
| BlockReplValues.insert(ValuesPerBlock.begin(), ValuesPerBlock.end()); |
| // Perform PHI construction. |
| Value* v = GetValueForBlock(LI->getParent(), LI, BlockReplValues, true); |
| LI->replaceAllUsesWith(v); |
| |
| if (isa<PHINode>(v)) |
| v->takeName(LI); |
| if (isa<PointerType>(v->getType())) |
| MD->invalidateCachedPointerInfo(v); |
| toErase.push_back(LI); |
| NumGVNLoad++; |
| return true; |
| } |
| |
| if (!EnablePRE || !EnableLoadPRE) |
| return false; |
| |
| // Okay, we have *some* definitions of the value. This means that the value |
| // is available in some of our (transitive) predecessors. Lets think about |
| // doing PRE of this load. This will involve inserting a new load into the |
| // predecessor when it's not available. We could do this in general, but |
| // prefer to not increase code size. As such, we only do this when we know |
| // that we only have to insert *one* load (which means we're basically moving |
| // the load, not inserting a new one). |
| |
| SmallPtrSet<BasicBlock *, 4> Blockers; |
| for (unsigned i = 0, e = UnavailableBlocks.size(); i != e; ++i) |
| Blockers.insert(UnavailableBlocks[i]); |
| |
| // Lets find first basic block with more than one predecessor. Walk backwards |
| // through predecessors if needed. |
| BasicBlock *LoadBB = LI->getParent(); |
| BasicBlock *TmpBB = LoadBB; |
| |
| bool isSinglePred = false; |
| bool allSingleSucc = true; |
| while (TmpBB->getSinglePredecessor()) { |
| isSinglePred = true; |
| TmpBB = TmpBB->getSinglePredecessor(); |
| if (!TmpBB) // If haven't found any, bail now. |
| return false; |
| if (TmpBB == LoadBB) // Infinite (unreachable) loop. |
| return false; |
| if (Blockers.count(TmpBB)) |
| return false; |
| if (TmpBB->getTerminator()->getNumSuccessors() != 1) |
| allSingleSucc = false; |
| } |
| |
| assert(TmpBB); |
| LoadBB = TmpBB; |
| |
| // If we have a repl set with LI itself in it, this means we have a loop where |
| // at least one of the values is LI. Since this means that we won't be able |
| // to eliminate LI even if we insert uses in the other predecessors, we will |
| // end up increasing code size. Reject this by scanning for LI. |
| for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i) |
| if (ValuesPerBlock[i].second == LI) |
| return false; |
| |
| if (isSinglePred) { |
| bool isHot = false; |
| for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i) |
| if (Instruction *I = dyn_cast<Instruction>(ValuesPerBlock[i].second)) |
| // "Hot" Instruction is in some loop (because it dominates its dep. |
| // instruction). |
| if (DT->dominates(LI, I)) { |
| isHot = true; |
| break; |
| } |
| |
| // We are interested only in "hot" instructions. We don't want to do any |
| // mis-optimizations here. |
| if (!isHot) |
| return false; |
| } |
| |
| // Okay, we have some hope :). Check to see if the loaded value is fully |
| // available in all but one predecessor. |
| // FIXME: If we could restructure the CFG, we could make a common pred with |
| // all the preds that don't have an available LI and insert a new load into |
| // that one block. |
| BasicBlock *UnavailablePred = 0; |
| |
| DenseMap<BasicBlock*, char> FullyAvailableBlocks; |
| for (unsigned i = 0, e = ValuesPerBlock.size(); i != e; ++i) |
| FullyAvailableBlocks[ValuesPerBlock[i].first] = true; |
| for (unsigned i = 0, e = UnavailableBlocks.size(); i != e; ++i) |
| FullyAvailableBlocks[UnavailableBlocks[i]] = false; |
| |
| for (pred_iterator PI = pred_begin(LoadBB), E = pred_end(LoadBB); |
| PI != E; ++PI) { |
| if (IsValueFullyAvailableInBlock(*PI, FullyAvailableBlocks)) |
| continue; |
| |
| // If this load is not available in multiple predecessors, reject it. |
| if (UnavailablePred && UnavailablePred != *PI) |
| return false; |
| UnavailablePred = *PI; |
| } |
| |
| assert(UnavailablePred != 0 && |
| "Fully available value should be eliminated above!"); |
| |
| // If the loaded pointer is PHI node defined in this block, do PHI translation |
| // to get its value in the predecessor. |
| Value *LoadPtr = LI->getOperand(0)->DoPHITranslation(LoadBB, UnavailablePred); |
| |
| // Make sure the value is live in the predecessor. If it was defined by a |
| // non-PHI instruction in this block, we don't know how to recompute it above. |
| if (Instruction *LPInst = dyn_cast<Instruction>(LoadPtr)) |
| if (!DT->dominates(LPInst->getParent(), UnavailablePred)) { |
| DEBUG(errs() << "COULDN'T PRE LOAD BECAUSE PTR IS UNAVAILABLE IN PRED: " |
| << *LPInst << *LI << "\n"); |
| return false; |
| } |
| |
| // We don't currently handle critical edges :( |
| if (UnavailablePred->getTerminator()->getNumSuccessors() != 1) { |
| DEBUG(errs() << "COULD NOT PRE LOAD BECAUSE OF CRITICAL EDGE '" |
| << UnavailablePred->getName() << "': " << *LI); |
| return false; |
| } |
| |
| // Make sure it is valid to move this load here. We have to watch out for: |
| // @1 = getelementptr (i8* p, ... |
| // test p and branch if == 0 |
| // load @1 |
| // It is valid to have the getelementptr before the test, even if p can be 0, |
| // as getelementptr only does address arithmetic. |
| // If we are not pushing the value through any multiple-successor blocks |
| // we do not have this case. Otherwise, check that the load is safe to |
| // put anywhere; this can be improved, but should be conservatively safe. |
| if (!allSingleSucc && |
| !isSafeToLoadUnconditionally(LoadPtr, UnavailablePred->getTerminator())) |
| return false; |
| |
| // Okay, we can eliminate this load by inserting a reload in the predecessor |
| // and using PHI construction to get the value in the other predecessors, do |
| // it. |
| DEBUG(errs() << "GVN REMOVING PRE LOAD: " << *LI); |
| |
| Value *NewLoad = new LoadInst(LoadPtr, LI->getName()+".pre", false, |
| LI->getAlignment(), |
| UnavailablePred->getTerminator()); |
| |
| SmallPtrSet<Instruction*, 4> &p = phiMap[LI->getPointerOperand()]; |
| for (SmallPtrSet<Instruction*, 4>::iterator I = p.begin(), E = p.end(); |
| I != E; ++I) |
| ValuesPerBlock.push_back(std::make_pair((*I)->getParent(), *I)); |
| |
| DenseMap<BasicBlock*, Value*> BlockReplValues; |
| BlockReplValues.insert(ValuesPerBlock.begin(), ValuesPerBlock.end()); |
| BlockReplValues[UnavailablePred] = NewLoad; |
| |
| // Perform PHI construction. |
| Value* v = GetValueForBlock(LI->getParent(), LI, BlockReplValues, true); |
| LI->replaceAllUsesWith(v); |
| if (isa<PHINode>(v)) |
| v->takeName(LI); |
| if (isa<PointerType>(v->getType())) |
| MD->invalidateCachedPointerInfo(v); |
| toErase.push_back(LI); |
| NumPRELoad++; |
| 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, SmallVectorImpl<Instruction*> &toErase) { |
| if (L->isVolatile()) |
| return false; |
| |
| Value* pointer = L->getPointerOperand(); |
| |
| // ... to a pointer that has been loaded from before... |
| MemDepResult dep = MD->getDependency(L); |
| |
| // If the value isn't available, don't do anything! |
| if (dep.isClobber()) { |
| DEBUG( |
| // fast print dep, using operator<< on instruction would be too slow |
| errs() << "GVN: load "; |
| WriteAsOperand(errs(), L); |
| Instruction *I = dep.getInst(); |
| errs() << " is clobbered by " << *I; |
| ); |
| return false; |
| } |
| |
| // If it is defined in another block, try harder. |
| if (dep.isNonLocal()) |
| return processNonLocalLoad(L, toErase); |
| |
| Instruction *DepInst = dep.getInst(); |
| if (StoreInst *DepSI = dyn_cast<StoreInst>(DepInst)) { |
| // Only forward substitute stores to loads of the same type. |
| // FIXME: Could do better! |
| if (DepSI->getPointerOperand()->getType() != pointer->getType()) |
| return false; |
| |
| // Remove it! |
| L->replaceAllUsesWith(DepSI->getOperand(0)); |
| if (isa<PointerType>(DepSI->getOperand(0)->getType())) |
| MD->invalidateCachedPointerInfo(DepSI->getOperand(0)); |
| toErase.push_back(L); |
| NumGVNLoad++; |
| return true; |
| } |
| |
| if (LoadInst *DepLI = dyn_cast<LoadInst>(DepInst)) { |
| // Only forward substitute stores to loads of the same type. |
| // FIXME: Could do better! load i32 -> load i8 -> truncate on little endian. |
| if (DepLI->getType() != L->getType()) |
| return false; |
| |
| // Remove it! |
| L->replaceAllUsesWith(DepLI); |
| if (isa<PointerType>(DepLI->getType())) |
| MD->invalidateCachedPointerInfo(DepLI); |
| toErase.push_back(L); |
| NumGVNLoad++; |
| return true; |
| } |
| |
| // If this load really doesn't depend on anything, then we must be loading an |
| // undef value. This can happen when loading for a fresh allocation with no |
| // intervening stores, for example. |
| if (isa<AllocationInst>(DepInst)) { |
| L->replaceAllUsesWith(UndefValue::get(L->getType())); |
| toErase.push_back(L); |
| NumGVNLoad++; |
| return true; |
| } |
| |
| return false; |
| } |
| |
| 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; |
| } |
| |
| /// AttemptRedundancyElimination - If the "fast path" of redundancy elimination |
| /// by inheritance from the dominator fails, see if we can perform phi |
| /// construction to eliminate the redundancy. |
| Value* GVN::AttemptRedundancyElimination(Instruction* orig, unsigned valno) { |
| BasicBlock* BaseBlock = orig->getParent(); |
| |
| SmallPtrSet<BasicBlock*, 4> Visited; |
| SmallVector<BasicBlock*, 8> Stack; |
| Stack.push_back(BaseBlock); |
| |
| DenseMap<BasicBlock*, Value*> Results; |
| |
| // Walk backwards through our predecessors, looking for instances of the |
| // value number we're looking for. Instances are recorded in the Results |
| // map, which is then used to perform phi construction. |
| while (!Stack.empty()) { |
| BasicBlock* Current = Stack.back(); |
| Stack.pop_back(); |
| |
| // If we've walked all the way to a proper dominator, then give up. Cases |
| // where the instance is in the dominator will have been caught by the fast |
| // path, and any cases that require phi construction further than this are |
| // probably not worth it anyways. Note that this is a SIGNIFICANT compile |
| // time improvement. |
| if (DT->properlyDominates(Current, orig->getParent())) return 0; |
| |
| DenseMap<BasicBlock*, ValueNumberScope*>::iterator LA = |
| localAvail.find(Current); |
| if (LA == localAvail.end()) return 0; |
| DenseMap<uint32_t, Value*>::iterator V = LA->second->table.find(valno); |
| |
| if (V != LA->second->table.end()) { |
| // Found an instance, record it. |
| Results.insert(std::make_pair(Current, V->second)); |
| continue; |
| } |
| |
| // If we reach the beginning of the function, then give up. |
| if (pred_begin(Current) == pred_end(Current)) |
| return 0; |
| |
| for (pred_iterator PI = pred_begin(Current), PE = pred_end(Current); |
| PI != PE; ++PI) |
| if (Visited.insert(*PI)) |
| Stack.push_back(*PI); |
| } |
| |
| // If we didn't find instances, give up. Otherwise, perform phi construction. |
| if (Results.size() == 0) |
| return 0; |
| else |
| return GetValueForBlock(BaseBlock, orig, Results, true); |
| } |
| |
| /// processInstruction - When calculating availability, handle an instruction |
| /// by inserting it into the appropriate sets |
| bool GVN::processInstruction(Instruction *I, |
| SmallVectorImpl<Instruction*> &toErase) { |
| if (LoadInst* L = dyn_cast<LoadInst>(I)) { |
| bool changed = processLoad(L, toErase); |
| |
| if (!changed) { |
| unsigned num = VN.lookup_or_add(L); |
| localAvail[I->getParent()]->table.insert(std::make_pair(num, L)); |
| } |
| |
| return changed; |
| } |
| |
| uint32_t nextNum = VN.getNextUnusedValueNumber(); |
| unsigned num = VN.lookup_or_add(I); |
| |
| if (BranchInst* BI = dyn_cast<BranchInst>(I)) { |
| localAvail[I->getParent()]->table.insert(std::make_pair(num, I)); |
| |
| if (!BI->isConditional() || isa<Constant>(BI->getCondition())) |
| return false; |
| |
| Value* branchCond = BI->getCondition(); |
| uint32_t condVN = VN.lookup_or_add(branchCond); |
| |
| BasicBlock* trueSucc = BI->getSuccessor(0); |
| BasicBlock* falseSucc = BI->getSuccessor(1); |
| |
| if (trueSucc->getSinglePredecessor()) |
| localAvail[trueSucc]->table[condVN] = |
| ConstantInt::getTrue(trueSucc->getContext()); |
| if (falseSucc->getSinglePredecessor()) |
| localAvail[falseSucc]->table[condVN] = |
| ConstantInt::getFalse(trueSucc->getContext()); |
| |
| return false; |
| |
| // Allocations are always uniquely numbered, so we can save time and memory |
| // by fast failing them. |
| } else if (isa<AllocationInst>(I) || isa<TerminatorInst>(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) |
| PI->second.erase(p); |
| |
| p->replaceAllUsesWith(constVal); |
| if (isa<PointerType>(constVal->getType())) |
| MD->invalidateCachedPointerInfo(constVal); |
| VN.erase(p); |
| |
| toErase.push_back(p); |
| } else { |
| localAvail[I->getParent()]->table.insert(std::make_pair(num, I)); |
| } |
| |
| // If the number we were assigned was a brand new VN, then we don't |
| // need to do a lookup to see if the number already exists |
| // somewhere in the domtree: it can't! |
| } else if (num == nextNum) { |
| localAvail[I->getParent()]->table.insert(std::make_pair(num, I)); |
| |
| // Perform fast-path value-number based elimination of values inherited from |
| // dominators. |
| } else if (Value* repl = lookupNumber(I->getParent(), num)) { |
| // Remove it! |
| VN.erase(I); |
| I->replaceAllUsesWith(repl); |
| if (isa<PointerType>(repl->getType())) |
| MD->invalidateCachedPointerInfo(repl); |
| toErase.push_back(I); |
| return true; |
| |
| #if 0 |
| // Perform slow-pathvalue-number based elimination with phi construction. |
| } else if (Value* repl = AttemptRedundancyElimination(I, num)) { |
| // Remove it! |
| VN.erase(I); |
| I->replaceAllUsesWith(repl); |
| if (isa<PointerType>(repl->getType())) |
| MD->invalidateCachedPointerInfo(repl); |
| toErase.push_back(I); |
| return true; |
| #endif |
| } else { |
| localAvail[I->getParent()]->table.insert(std::make_pair(num, I)); |
| } |
| |
| return false; |
| } |
| |
| /// runOnFunction - This is the main transformation entry point for a function. |
| bool GVN::runOnFunction(Function& F) { |
| MD = &getAnalysis<MemoryDependenceAnalysis>(); |
| DT = &getAnalysis<DominatorTree>(); |
| VN.setAliasAnalysis(&getAnalysis<AliasAnalysis>()); |
| VN.setMemDep(MD); |
| VN.setDomTree(DT); |
| |
| bool changed = false; |
| bool shouldContinue = true; |
| |
| // Merge unconditional branches, allowing PRE to catch more |
| // optimization opportunities. |
| for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ) { |
| BasicBlock* BB = FI; |
| ++FI; |
| bool removedBlock = MergeBlockIntoPredecessor(BB, this); |
| if (removedBlock) NumGVNBlocks++; |
| |
| changed |= removedBlock; |
| } |
| |
| unsigned Iteration = 0; |
| |
| while (shouldContinue) { |
| DEBUG(errs() << "GVN iteration: " << Iteration << "\n"); |
| shouldContinue = iterateOnFunction(F); |
| changed |= shouldContinue; |
| ++Iteration; |
| } |
| |
| if (EnablePRE) { |
| bool PREChanged = true; |
| while (PREChanged) { |
| PREChanged = performPRE(F); |
| changed |= PREChanged; |
| } |
| } |
| // FIXME: Should perform GVN again after PRE does something. PRE can move |
| // computations into blocks where they become fully redundant. Note that |
| // we can't do this until PRE's critical edge splitting updates memdep. |
| // Actually, when this happens, we should just fully integrate PRE into GVN. |
| |
| cleanupGlobalSets(); |
| |
| return changed; |
| } |
| |
| |
| bool GVN::processBlock(BasicBlock* BB) { |
| // FIXME: Kill off toErase by doing erasing eagerly in a helper function (and |
| // incrementing BI before processing an instruction). |
| SmallVector<Instruction*, 8> toErase; |
| bool changed_function = false; |
| |
| for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); |
| BI != BE;) { |
| changed_function |= processInstruction(BI, 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) { |
| DEBUG(errs() << "GVN removed: " << **I); |
| MD->removeInstruction(*I); |
| (*I)->eraseFromParent(); |
| DEBUG(verifyRemoved(*I)); |
| } |
| toErase.clear(); |
| |
| if (AtStart) |
| BI = BB->begin(); |
| else |
| ++BI; |
| } |
| |
| 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; |
| DenseMap<BasicBlock*, Value*> predMap; |
| 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; ) { |
| Instruction *CurInst = BI++; |
| |
| if (isa<AllocationInst>(CurInst) || isa<TerminatorInst>(CurInst) || |
| isa<PHINode>(CurInst) || (CurInst->getType() == Type::VoidTy) || |
| CurInst->mayReadFromMemory() || CurInst->mayHaveSideEffects() || |
| isa<DbgInfoIntrinsic>(CurInst)) |
| continue; |
| |
| uint32_t valno = VN.lookup(CurInst); |
| |
| // 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; |
| predMap.clear(); |
| |
| 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 == CurInst) { |
| 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) |
| 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) == CurrentBlock) { |
| succNum = i; |
| break; |
| } |
| |
| if (isCriticalEdge(PREPred->getTerminator(), succNum)) { |
| toSplit.push_back(std::make_pair(PREPred->getTerminator(), succNum)); |
| 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 = CurInst->clone(CurInst->getContext()); |
| bool success = true; |
| for (unsigned i = 0, e = CurInst->getNumOperands(); i != e; ++i) { |
| Value *Op = PREInstr->getOperand(i); |
| if (isa<Argument>(Op) || isa<Constant>(Op) || isa<GlobalValue>(Op)) |
| continue; |
| |
| if (Value *V = lookupNumber(PREPred, VN.lookup(Op))) { |
| PREInstr->setOperand(i, V); |
| } else { |
| success = false; |
| break; |
| } |
| } |
| |
| // 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; |
| DEBUG(verifyRemoved(PREInstr)); |
| continue; |
| } |
| |
| PREInstr->insertBefore(PREPred->getTerminator()); |
| PREInstr->setName(CurInst->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(CurInst->getType(), |
| CurInst->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; |
| |
| CurInst->replaceAllUsesWith(Phi); |
| if (isa<PointerType>(Phi->getType())) |
| MD->invalidateCachedPointerInfo(Phi); |
| VN.erase(CurInst); |
| |
| DEBUG(errs() << "GVN PRE removed: " << *CurInst); |
| MD->removeInstruction(CurInst); |
| CurInst->eraseFromParent(); |
| DEBUG(verifyRemoved(CurInst)); |
| 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 || toSplit.size(); |
| } |
| |
| /// iterateOnFunction - Executes one iteration of GVN |
| bool GVN::iterateOnFunction(Function &F) { |
| cleanupGlobalSets(); |
| |
| for (df_iterator<DomTreeNode*> DI = df_begin(DT->getRootNode()), |
| DE = df_end(DT->getRootNode()); DI != DE; ++DI) { |
| if (DI->getIDom()) |
| localAvail[DI->getBlock()] = |
| new ValueNumberScope(localAvail[DI->getIDom()->getBlock()]); |
| else |
| localAvail[DI->getBlock()] = new ValueNumberScope(0); |
| } |
| |
| // Top-down walk of the dominator tree |
| bool changed = false; |
| #if 0 |
| // Needed for value numbering with phi construction to work. |
| ReversePostOrderTraversal<Function*> RPOT(&F); |
| for (ReversePostOrderTraversal<Function*>::rpo_iterator RI = RPOT.begin(), |
| RE = RPOT.end(); RI != RE; ++RI) |
| changed |= processBlock(*RI); |
| #else |
| for (df_iterator<DomTreeNode*> DI = df_begin(DT->getRootNode()), |
| DE = df_end(DT->getRootNode()); DI != DE; ++DI) |
| changed |= processBlock(DI->getBlock()); |
| #endif |
| |
| return changed; |
| } |
| |
| void GVN::cleanupGlobalSets() { |
| VN.clear(); |
| phiMap.clear(); |
| |
| for (DenseMap<BasicBlock*, ValueNumberScope*>::iterator |
| I = localAvail.begin(), E = localAvail.end(); I != E; ++I) |
| delete I->second; |
| localAvail.clear(); |
| } |
| |
| /// verifyRemoved - Verify that the specified instruction does not occur in our |
| /// internal data structures. |
| void GVN::verifyRemoved(const Instruction *Inst) const { |
| VN.verifyRemoved(Inst); |
| |
| // Walk through the PHI map to make sure the instruction isn't hiding in there |
| // somewhere. |
| for (PhiMapType::iterator |
| I = phiMap.begin(), E = phiMap.end(); I != E; ++I) { |
| assert(I->first != Inst && "Inst is still a key in PHI map!"); |
| |
| for (SmallPtrSet<Instruction*, 4>::iterator |
| II = I->second.begin(), IE = I->second.end(); II != IE; ++II) { |
| assert(*II != Inst && "Inst is still a value in PHI map!"); |
| } |
| } |
| |
| // Walk through the value number scope to make sure the instruction isn't |
| // ferreted away in it. |
| for (DenseMap<BasicBlock*, ValueNumberScope*>::iterator |
| I = localAvail.begin(), E = localAvail.end(); I != E; ++I) { |
| const ValueNumberScope *VNS = I->second; |
| |
| while (VNS) { |
| for (DenseMap<uint32_t, Value*>::iterator |
| II = VNS->table.begin(), IE = VNS->table.end(); II != IE; ++II) { |
| assert(II->second != Inst && "Inst still in value numbering scope!"); |
| } |
| |
| VNS = VNS->parent; |
| } |
| } |
| } |