diff options
Diffstat (limited to 'lib/Transforms/Utils')
| -rw-r--r-- | lib/Transforms/Utils/AddrModeMatcher.cpp | 2 | ||||
| -rw-r--r-- | lib/Transforms/Utils/BasicBlockUtils.cpp | 4 | ||||
| -rw-r--r-- | lib/Transforms/Utils/BypassSlowDivision.cpp | 253 | ||||
| -rw-r--r-- | lib/Transforms/Utils/CMakeLists.txt | 1 | ||||
| -rw-r--r-- | lib/Transforms/Utils/Local.cpp | 36 | ||||
| -rw-r--r-- | lib/Transforms/Utils/SimplifyCFG.cpp | 777 | ||||
| -rw-r--r-- | lib/Transforms/Utils/SimplifyInstructions.cpp | 2 |
7 files changed, 887 insertions, 188 deletions
diff --git a/lib/Transforms/Utils/AddrModeMatcher.cpp b/lib/Transforms/Utils/AddrModeMatcher.cpp index d831452..1e6586b 100644 --- a/lib/Transforms/Utils/AddrModeMatcher.cpp +++ b/lib/Transforms/Utils/AddrModeMatcher.cpp @@ -55,10 +55,12 @@ void ExtAddrMode::print(raw_ostream &OS) const { OS << ']'; } +#ifndef NDEBUG void ExtAddrMode::dump() const { print(dbgs()); dbgs() << '\n'; } +#endif /// MatchScaledValue - Try adding ScaleReg*Scale to the current addressing mode. diff --git a/lib/Transforms/Utils/BasicBlockUtils.cpp b/lib/Transforms/Utils/BasicBlockUtils.cpp index 2679b93..75a7817 100644 --- a/lib/Transforms/Utils/BasicBlockUtils.cpp +++ b/lib/Transforms/Utils/BasicBlockUtils.cpp @@ -94,7 +94,7 @@ void llvm::FoldSingleEntryPHINodes(BasicBlock *BB, Pass *P) { /// is dead. Also recursively delete any operands that become dead as /// a result. This includes tracing the def-use list from the PHI to see if /// it is ultimately unused or if it reaches an unused cycle. -bool llvm::DeleteDeadPHIs(BasicBlock *BB) { +bool llvm::DeleteDeadPHIs(BasicBlock *BB, const TargetLibraryInfo *TLI) { // Recursively deleting a PHI may cause multiple PHIs to be deleted // or RAUW'd undef, so use an array of WeakVH for the PHIs to delete. SmallVector<WeakVH, 8> PHIs; @@ -105,7 +105,7 @@ bool llvm::DeleteDeadPHIs(BasicBlock *BB) { bool Changed = false; for (unsigned i = 0, e = PHIs.size(); i != e; ++i) if (PHINode *PN = dyn_cast_or_null<PHINode>(PHIs[i].operator Value*())) - Changed |= RecursivelyDeleteDeadPHINode(PN); + Changed |= RecursivelyDeleteDeadPHINode(PN, TLI); return Changed; } diff --git a/lib/Transforms/Utils/BypassSlowDivision.cpp b/lib/Transforms/Utils/BypassSlowDivision.cpp new file mode 100644 index 0000000..30d60be --- /dev/null +++ b/lib/Transforms/Utils/BypassSlowDivision.cpp @@ -0,0 +1,253 @@ +//===-- BypassSlowDivision.cpp - Bypass slow division ---------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file contains an optimization for div and rem on architectures that +// execute short instructions significantly faster than longer instructions. +// For example, on Intel Atom 32-bit divides are slow enough that during +// runtime it is profitable to check the value of the operands, and if they are +// positive and less than 256 use an unsigned 8-bit divide. +// +//===----------------------------------------------------------------------===// + +#define DEBUG_TYPE "bypass-slow-division" +#include "llvm/Instructions.h" +#include "llvm/Function.h" +#include "llvm/IRBuilder.h" +#include "llvm/ADT/DenseMap.h" +#include "llvm/Transforms/Utils/BypassSlowDivision.h" + +using namespace llvm; + +namespace { + struct DivOpInfo { + bool SignedOp; + Value *Dividend; + Value *Divisor; + + DivOpInfo(bool InSignedOp, Value *InDividend, Value *InDivisor) + : SignedOp(InSignedOp), Dividend(InDividend), Divisor(InDivisor) {} + }; + + struct DivPhiNodes { + PHINode *Quotient; + PHINode *Remainder; + + DivPhiNodes(PHINode *InQuotient, PHINode *InRemainder) + : Quotient(InQuotient), Remainder(InRemainder) {} + }; +} + +namespace llvm { + template<> + struct DenseMapInfo<DivOpInfo> { + static bool isEqual(const DivOpInfo &Val1, const DivOpInfo &Val2) { + return Val1.SignedOp == Val2.SignedOp && + Val1.Dividend == Val2.Dividend && + Val1.Divisor == Val2.Divisor; + } + + static DivOpInfo getEmptyKey() { + return DivOpInfo(false, 0, 0); + } + + static DivOpInfo getTombstoneKey() { + return DivOpInfo(true, 0, 0); + } + + static unsigned getHashValue(const DivOpInfo &Val) { + return (unsigned)(reinterpret_cast<uintptr_t>(Val.Dividend) ^ + reinterpret_cast<uintptr_t>(Val.Divisor)) ^ + (unsigned)Val.SignedOp; + } + }; + + typedef DenseMap<DivOpInfo, DivPhiNodes> DivCacheTy; +} + +// insertFastDiv - Substitutes the div/rem instruction with code that checks the +// value of the operands and uses a shorter-faster div/rem instruction when +// possible and the longer-slower div/rem instruction otherwise. +static bool insertFastDiv(Function &F, + Function::iterator &I, + BasicBlock::iterator &J, + IntegerType *BypassType, + bool UseDivOp, + bool UseSignedOp, + DivCacheTy &PerBBDivCache) { + // Get instruction operands + Instruction *Instr = J; + Value *Dividend = Instr->getOperand(0); + Value *Divisor = Instr->getOperand(1); + + if (isa<ConstantInt>(Divisor) || + (isa<ConstantInt>(Dividend) && isa<ConstantInt>(Divisor))) { + // Operations with immediate values should have + // been solved and replaced during compile time. + return false; + } + + // Basic Block is split before divide + BasicBlock *MainBB = I; + BasicBlock *SuccessorBB = I->splitBasicBlock(J); + ++I; //advance iterator I to successorBB + + // Add new basic block for slow divide operation + BasicBlock *SlowBB = BasicBlock::Create(F.getContext(), "", + MainBB->getParent(), SuccessorBB); + SlowBB->moveBefore(SuccessorBB); + IRBuilder<> SlowBuilder(SlowBB, SlowBB->begin()); + Value *SlowQuotientV; + Value *SlowRemainderV; + if (UseSignedOp) { + SlowQuotientV = SlowBuilder.CreateSDiv(Dividend, Divisor); + SlowRemainderV = SlowBuilder.CreateSRem(Dividend, Divisor); + } else { + SlowQuotientV = SlowBuilder.CreateUDiv(Dividend, Divisor); + SlowRemainderV = SlowBuilder.CreateURem(Dividend, Divisor); + } + SlowBuilder.CreateBr(SuccessorBB); + + // Add new basic block for fast divide operation + BasicBlock *FastBB = BasicBlock::Create(F.getContext(), "", + MainBB->getParent(), SuccessorBB); + FastBB->moveBefore(SlowBB); + IRBuilder<> FastBuilder(FastBB, FastBB->begin()); + Value *ShortDivisorV = FastBuilder.CreateCast(Instruction::Trunc, Divisor, + BypassType); + Value *ShortDividendV = FastBuilder.CreateCast(Instruction::Trunc, Dividend, + BypassType); + + // udiv/urem because optimization only handles positive numbers + Value *ShortQuotientV = FastBuilder.CreateExactUDiv(ShortDividendV, + ShortDivisorV); + Value *ShortRemainderV = FastBuilder.CreateURem(ShortDividendV, + ShortDivisorV); + Value *FastQuotientV = FastBuilder.CreateCast(Instruction::ZExt, + ShortQuotientV, + Dividend->getType()); + Value *FastRemainderV = FastBuilder.CreateCast(Instruction::ZExt, + ShortRemainderV, + Dividend->getType()); + FastBuilder.CreateBr(SuccessorBB); + + // Phi nodes for result of div and rem + IRBuilder<> SuccessorBuilder(SuccessorBB, SuccessorBB->begin()); + PHINode *QuoPhi = SuccessorBuilder.CreatePHI(Instr->getType(), 2); + QuoPhi->addIncoming(SlowQuotientV, SlowBB); + QuoPhi->addIncoming(FastQuotientV, FastBB); + PHINode *RemPhi = SuccessorBuilder.CreatePHI(Instr->getType(), 2); + RemPhi->addIncoming(SlowRemainderV, SlowBB); + RemPhi->addIncoming(FastRemainderV, FastBB); + + // Replace Instr with appropriate phi node + if (UseDivOp) + Instr->replaceAllUsesWith(QuoPhi); + else + Instr->replaceAllUsesWith(RemPhi); + Instr->eraseFromParent(); + + // Combine operands into a single value with OR for value testing below + MainBB->getInstList().back().eraseFromParent(); + IRBuilder<> MainBuilder(MainBB, MainBB->end()); + Value *OrV = MainBuilder.CreateOr(Dividend, Divisor); + + // BitMask is inverted to check if the operands are + // larger than the bypass type + uint64_t BitMask = ~BypassType->getBitMask(); + Value *AndV = MainBuilder.CreateAnd(OrV, BitMask); + + // Compare operand values and branch + Value *ZeroV = MainBuilder.getInt32(0); + Value *CmpV = MainBuilder.CreateICmpEQ(AndV, ZeroV); + MainBuilder.CreateCondBr(CmpV, FastBB, SlowBB); + + // point iterator J at first instruction of successorBB + J = I->begin(); + + // Cache phi nodes to be used later in place of other instances + // of div or rem with the same sign, dividend, and divisor + DivOpInfo Key(UseSignedOp, Dividend, Divisor); + DivPhiNodes Value(QuoPhi, RemPhi); + PerBBDivCache.insert(std::pair<DivOpInfo, DivPhiNodes>(Key, Value)); + return true; +} + +// reuseOrInsertFastDiv - Reuses previously computed dividend or remainder if +// operands and operation are identical. Otherwise call insertFastDiv to perform +// the optimization and cache the resulting dividend and remainder. +static bool reuseOrInsertFastDiv(Function &F, + Function::iterator &I, + BasicBlock::iterator &J, + IntegerType *BypassType, + bool UseDivOp, + bool UseSignedOp, + DivCacheTy &PerBBDivCache) { + // Get instruction operands + Instruction *Instr = J; + DivOpInfo Key(UseSignedOp, Instr->getOperand(0), Instr->getOperand(1)); + DivCacheTy::iterator CacheI = PerBBDivCache.find(Key); + + if (CacheI == PerBBDivCache.end()) { + // If previous instance does not exist, insert fast div + return insertFastDiv(F, I, J, BypassType, UseDivOp, UseSignedOp, + PerBBDivCache); + } + + // Replace operation value with previously generated phi node + DivPhiNodes &Value = CacheI->second; + if (UseDivOp) { + // Replace all uses of div instruction with quotient phi node + J->replaceAllUsesWith(Value.Quotient); + } else { + // Replace all uses of rem instruction with remainder phi node + J->replaceAllUsesWith(Value.Remainder); + } + + // Advance to next operation + ++J; + + // Remove redundant operation + Instr->eraseFromParent(); + return true; +} + +// bypassSlowDivision - This optimization identifies DIV instructions that can +// be profitably bypassed and carried out with a shorter, faster divide. +bool llvm::bypassSlowDivision(Function &F, + Function::iterator &I, + const DenseMap<Type *, Type *> &BypassTypeMap) { + DivCacheTy DivCache; + + bool MadeChange = false; + for (BasicBlock::iterator J = I->begin(); J != I->end(); J++) { + + // Get instruction details + unsigned Opcode = J->getOpcode(); + bool UseDivOp = Opcode == Instruction::SDiv || Opcode == Instruction::UDiv; + bool UseRemOp = Opcode == Instruction::SRem || Opcode == Instruction::URem; + bool UseSignedOp = Opcode == Instruction::SDiv || + Opcode == Instruction::SRem; + + // Only optimize div or rem ops + if (!UseDivOp && !UseRemOp) + continue; + + // Continue if div/rem type is not bypassed + DenseMap<Type *, Type *>::const_iterator BT = + BypassTypeMap.find(J->getType()); + if (BT == BypassTypeMap.end()) + continue; + + IntegerType *BypassType = cast<IntegerType>(BT->second); + MadeChange |= reuseOrInsertFastDiv(F, I, J, BypassType, UseDivOp, + UseSignedOp, DivCache); + } + + return MadeChange; +} diff --git a/lib/Transforms/Utils/CMakeLists.txt b/lib/Transforms/Utils/CMakeLists.txt index 4ff31ca..215a16f 100644 --- a/lib/Transforms/Utils/CMakeLists.txt +++ b/lib/Transforms/Utils/CMakeLists.txt @@ -3,6 +3,7 @@ add_llvm_library(LLVMTransformUtils BasicBlockUtils.cpp BreakCriticalEdges.cpp BuildLibCalls.cpp + BypassSlowDivision.cpp CloneFunction.cpp CloneModule.cpp CmpInstAnalysis.cpp diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp index bed7d72..0601433 100644 --- a/lib/Transforms/Utils/Local.cpp +++ b/lib/Transforms/Utils/Local.cpp @@ -52,7 +52,8 @@ using namespace llvm; /// Also calls RecursivelyDeleteTriviallyDeadInstructions() on any branch/switch /// conditions and indirectbr addresses this might make dead if /// DeleteDeadConditions is true. -bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions) { +bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions, + const TargetLibraryInfo *TLI) { TerminatorInst *T = BB->getTerminator(); IRBuilder<> Builder(T); @@ -96,7 +97,7 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions) { Value *Cond = BI->getCondition(); BI->eraseFromParent(); if (DeleteDeadConditions) - RecursivelyDeleteTriviallyDeadInstructions(Cond); + RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI); return true; } return false; @@ -161,7 +162,7 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions) { Value *Cond = SI->getCondition(); SI->eraseFromParent(); if (DeleteDeadConditions) - RecursivelyDeleteTriviallyDeadInstructions(Cond); + RecursivelyDeleteTriviallyDeadInstructions(Cond, TLI); return true; } @@ -205,7 +206,7 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions) { Value *Address = IBI->getAddress(); IBI->eraseFromParent(); if (DeleteDeadConditions) - RecursivelyDeleteTriviallyDeadInstructions(Address); + RecursivelyDeleteTriviallyDeadInstructions(Address, TLI); // If we didn't find our destination in the IBI successor list, then we // have undefined behavior. Replace the unconditional branch with an @@ -230,7 +231,8 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions) { /// isInstructionTriviallyDead - Return true if the result produced by the /// instruction is not used, and the instruction has no side effects. /// -bool llvm::isInstructionTriviallyDead(Instruction *I) { +bool llvm::isInstructionTriviallyDead(Instruction *I, + const TargetLibraryInfo *TLI) { if (!I->use_empty() || isa<TerminatorInst>(I)) return false; // We don't want the landingpad instruction removed by anything this general. @@ -265,9 +267,9 @@ bool llvm::isInstructionTriviallyDead(Instruction *I) { return isa<UndefValue>(II->getArgOperand(1)); } - if (isAllocLikeFn(I)) return true; + if (isAllocLikeFn(I, TLI)) return true; - if (CallInst *CI = isFreeCall(I)) + if (CallInst *CI = isFreeCall(I, TLI)) if (Constant *C = dyn_cast<Constant>(CI->getArgOperand(0))) return C->isNullValue() || isa<UndefValue>(C); @@ -278,9 +280,11 @@ bool llvm::isInstructionTriviallyDead(Instruction *I) { /// trivially dead instruction, delete it. If that makes any of its operands /// trivially dead, delete them too, recursively. Return true if any /// instructions were deleted. -bool llvm::RecursivelyDeleteTriviallyDeadInstructions(Value *V) { +bool +llvm::RecursivelyDeleteTriviallyDeadInstructions(Value *V, + const TargetLibraryInfo *TLI) { Instruction *I = dyn_cast<Instruction>(V); - if (!I || !I->use_empty() || !isInstructionTriviallyDead(I)) + if (!I || !I->use_empty() || !isInstructionTriviallyDead(I, TLI)) return false; SmallVector<Instruction*, 16> DeadInsts; @@ -301,7 +305,7 @@ bool llvm::RecursivelyDeleteTriviallyDeadInstructions(Value *V) { // operand, and if it is 'trivially' dead, delete it in a future loop // iteration. if (Instruction *OpI = dyn_cast<Instruction>(OpV)) - if (isInstructionTriviallyDead(OpI)) + if (isInstructionTriviallyDead(OpI, TLI)) DeadInsts.push_back(OpI); } @@ -334,19 +338,20 @@ static bool areAllUsesEqual(Instruction *I) { /// either forms a cycle or is terminated by a trivially dead instruction, /// delete it. If that makes any of its operands trivially dead, delete them /// too, recursively. Return true if a change was made. -bool llvm::RecursivelyDeleteDeadPHINode(PHINode *PN) { +bool llvm::RecursivelyDeleteDeadPHINode(PHINode *PN, + const TargetLibraryInfo *TLI) { SmallPtrSet<Instruction*, 4> Visited; for (Instruction *I = PN; areAllUsesEqual(I) && !I->mayHaveSideEffects(); I = cast<Instruction>(*I->use_begin())) { if (I->use_empty()) - return RecursivelyDeleteTriviallyDeadInstructions(I); + return RecursivelyDeleteTriviallyDeadInstructions(I, TLI); // If we find an instruction more than once, we're on a cycle that // won't prove fruitful. if (!Visited.insert(I)) { // Break the cycle and delete the instruction and its operands. I->replaceAllUsesWith(UndefValue::get(I->getType())); - (void)RecursivelyDeleteTriviallyDeadInstructions(I); + (void)RecursivelyDeleteTriviallyDeadInstructions(I, TLI); return true; } } @@ -358,7 +363,8 @@ bool llvm::RecursivelyDeleteDeadPHINode(PHINode *PN) { /// /// This returns true if it changed the code, note that it can delete /// instructions in other blocks as well in this block. -bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB, const TargetData *TD) { +bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB, const TargetData *TD, + const TargetLibraryInfo *TLI) { bool MadeChange = false; #ifndef NDEBUG @@ -381,7 +387,7 @@ bool llvm::SimplifyInstructionsInBlock(BasicBlock *BB, const TargetData *TD) { continue; } - MadeChange |= RecursivelyDeleteTriviallyDeadInstructions(Inst); + MadeChange |= RecursivelyDeleteTriviallyDeadInstructions(Inst, TLI); if (BIHandle != BI) BI = BB->begin(); } diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp index 518df7c..32d7fa1 100644 --- a/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/lib/Transforms/Utils/SimplifyCFG.cpp @@ -22,6 +22,7 @@ #include "llvm/LLVMContext.h" #include "llvm/MDBuilder.h" #include "llvm/Metadata.h" +#include "llvm/Module.h" #include "llvm/Operator.h" #include "llvm/Type.h" #include "llvm/ADT/DenseMap.h" @@ -54,6 +55,7 @@ DupRet("simplifycfg-dup-ret", cl::Hidden, cl::init(false), cl::desc("Duplicate return instructions into unconditional branches")); STATISTIC(NumSpeculations, "Number of speculative executed instructions"); +STATISTIC(NumLookupTables, "Number of switch instructions turned into lookup tables"); namespace { /// ValueEqualityComparisonCase - Represents a case of a switch. @@ -101,14 +103,14 @@ public: /// static bool SafeToMergeTerminators(TerminatorInst *SI1, TerminatorInst *SI2) { if (SI1 == SI2) return false; // Can't merge with self! - + // It is not safe to merge these two switch instructions if they have a common // successor, and if that successor has a PHI node, and if *that* PHI node has // conflicting incoming values from the two switch blocks. BasicBlock *SI1BB = SI1->getParent(); BasicBlock *SI2BB = SI2->getParent(); SmallPtrSet<BasicBlock*, 16> SI1Succs(succ_begin(SI1BB), succ_end(SI1BB)); - + for (succ_iterator I = succ_begin(SI2BB), E = succ_end(SI2BB); I != E; ++I) if (SI1Succs.count(*I)) for (BasicBlock::iterator BBI = (*I)->begin(); @@ -118,7 +120,7 @@ static bool SafeToMergeTerminators(TerminatorInst *SI1, TerminatorInst *SI2) { PN->getIncomingValueForBlock(SI2BB)) return false; } - + return true; } @@ -135,7 +137,7 @@ static bool isProfitableToFoldUnconditional(BranchInst *SI1, assert(SI1->isUnconditional() && SI2->isConditional()); // We fold the unconditional branch if we can easily update all PHI nodes in - // common successors: + // common successors: // 1> We have a constant incoming value for the conditional branch; // 2> We have "Cond" as the incoming value for the unconditional branch; // 3> SI2->getCondition() and Cond have same operands. @@ -170,7 +172,7 @@ static bool isProfitableToFoldUnconditional(BranchInst *SI1, static void AddPredecessorToBlock(BasicBlock *Succ, BasicBlock *NewPred, BasicBlock *ExistPred) { if (!isa<PHINode>(Succ->begin())) return; // Quick exit if nothing to do - + PHINode *PN; for (BasicBlock::iterator I = Succ->begin(); (PN = dyn_cast<PHINode>(I)); ++I) @@ -222,7 +224,7 @@ static Value *GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue, // doesn't dominate BB. if (Pred2->getSinglePredecessor() == 0) return 0; - + // If we found a conditional branch predecessor, make sure that it branches // to BB and Pred2Br. If it doesn't, this isn't an "if statement". if (Pred1Br->getSuccessor(0) == BB && @@ -252,7 +254,7 @@ static Value *GetIfCondition(BasicBlock *BB, BasicBlock *&IfTrue, // Otherwise, if this is a conditional branch, then we can use it! BranchInst *BI = dyn_cast<BranchInst>(CommonPred->getTerminator()); if (BI == 0) return 0; - + assert(BI->isConditional() && "Two successors but not conditional?"); if (BI->getSuccessor(0) == Pred1) { IfTrue = Pred1; @@ -345,7 +347,7 @@ static bool DominatesMergePoint(Value *V, BasicBlock *BB, // If we aren't allowing aggressive promotion anymore, then don't consider // instructions in the 'if region'. if (AggressiveInsts == 0) return false; - + // If we have seen this instruction before, don't count it again. if (AggressiveInsts->count(I)) return true; @@ -411,7 +413,7 @@ GatherConstantCompares(Value *V, std::vector<ConstantInt*> &Vals, Value *&Extra, const TargetData *TD, bool isEQ, unsigned &UsedICmps) { Instruction *I = dyn_cast<Instruction>(V); if (I == 0) return 0; - + // If this is an icmp against a constant, handle this as one of the cases. if (ICmpInst *ICI = dyn_cast<ICmpInst>(I)) { if (ConstantInt *C = GetConstantInt(I->getOperand(1), TD)) { @@ -420,21 +422,21 @@ GatherConstantCompares(Value *V, std::vector<ConstantInt*> &Vals, Value *&Extra, Vals.push_back(C); return I->getOperand(0); } - + // If we have "x ult 3" comparison, for example, then we can add 0,1,2 to // the set. ConstantRange Span = ConstantRange::makeICmpRegion(ICI->getPredicate(), C->getValue()); - + // If this is an and/!= check then we want to optimize "x ugt 2" into // x != 0 && x != 1. if (!isEQ) Span = Span.inverse(); - + // If there are a ton of values, we don't want to make a ginormous switch. if (Span.getSetSize().ugt(8) || Span.isEmptySet()) return 0; - + for (APInt Tmp = Span.getLower(); Tmp != Span.getUpper(); ++Tmp) Vals.push_back(ConstantInt::get(V->getContext(), Tmp)); UsedICmps++; @@ -442,11 +444,11 @@ GatherConstantCompares(Value *V, std::vector<ConstantInt*> &Vals, Value *&Extra, } return 0; } - + // Otherwise, we can only handle an | or &, depending on isEQ. if (I->getOpcode() != (isEQ ? Instruction::Or : Instruction::And)) return 0; - + unsigned NumValsBeforeLHS = Vals.size(); unsigned UsedICmpsBeforeLHS = UsedICmps; if (Value *LHS = GatherConstantCompares(I->getOperand(0), Vals, Extra, TD, @@ -467,12 +469,12 @@ GatherConstantCompares(Value *V, std::vector<ConstantInt*> &Vals, Value *&Extra, Extra = I->getOperand(1); return LHS; } - + Vals.resize(NumValsBeforeLHS); UsedICmps = UsedICmpsBeforeLHS; return 0; } - + // If the LHS can't be folded in, but Extra is available and RHS can, try to // use LHS as Extra. if (Extra == 0 || Extra == I->getOperand(0)) { @@ -484,7 +486,7 @@ GatherConstantCompares(Value *V, std::vector<ConstantInt*> &Vals, Value *&Extra, assert(Vals.size() == NumValsBeforeLHS); Extra = OldExtra; } - + return 0; } @@ -615,6 +617,9 @@ SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI, assert(ThisVal && "This isn't a value comparison!!"); if (ThisVal != PredVal) return false; // Different predicates. + // TODO: Preserve branch weight metadata, similarly to how + // FoldValueComparisonIntoPredecessors preserves it. + // Find out information about when control will move from Pred to TI's block. std::vector<ValueEqualityComparisonCase> PredCases; BasicBlock *PredDef = GetValueEqualityComparisonCases(Pred->getTerminator(), @@ -634,7 +639,7 @@ SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI, // can simplify TI. if (!ValuesOverlap(PredCases, ThisCases)) return false; - + if (isa<BranchInst>(TI)) { // Okay, one of the successors of this condbr is dead. Convert it to a // uncond br. @@ -652,7 +657,7 @@ SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI, EraseTerminatorInstAndDCECond(TI); return true; } - + SwitchInst *SI = cast<SwitchInst>(TI); // Okay, TI has cases that are statically dead, prune them away. SmallPtrSet<Constant*, 16> DeadCases; @@ -673,7 +678,7 @@ SimplifyEqualityComparisonWithOnlyPredecessor(TerminatorInst *TI, DEBUG(dbgs() << "Leaving: " << *TI << "\n"); return true; } - + // Otherwise, TI's block must correspond to some matched value. Find out // which value (or set of values) this is. ConstantInt *TIV = 0; @@ -729,8 +734,8 @@ namespace { } static int ConstantIntSortPredicate(const void *P1, const void *P2) { - const ConstantInt *LHS = *(const ConstantInt**)P1; - const ConstantInt *RHS = *(const ConstantInt**)P2; + const ConstantInt *LHS = *(const ConstantInt*const*)P1; + const ConstantInt *RHS = *(const ConstantInt*const*)P2; if (LHS->getValue().ult(RHS->getValue())) return 1; if (LHS->getValue() == RHS->getValue()) @@ -738,6 +743,67 @@ static int ConstantIntSortPredicate(const void *P1, const void *P2) { return -1; } +static inline bool HasBranchWeights(const Instruction* I) { + MDNode* ProfMD = I->getMetadata(LLVMContext::MD_prof); + if (ProfMD && ProfMD->getOperand(0)) + if (MDString* MDS = dyn_cast<MDString>(ProfMD->getOperand(0))) + return MDS->getString().equals("branch_weights"); + + return false; +} + +/// Tries to get a branch weight for the given instruction, returns NULL if it +/// can't. Pos starts at 0. +static ConstantInt* GetWeight(Instruction* I, int Pos) { + MDNode* ProfMD = I->getMetadata(LLVMContext::MD_prof); + if (ProfMD && ProfMD->getOperand(0)) { + if (MDString* MDS = dyn_cast<MDString>(ProfMD->getOperand(0))) { + if (MDS->getString().equals("branch_weights")) { + assert(ProfMD->getNumOperands() >= 3); + return dyn_cast<ConstantInt>(ProfMD->getOperand(1 + Pos)); + } + } + } + + return 0; +} + +/// Scale the given weights based on the successor TI's metadata. Scaling is +/// done by multiplying every weight by the sum of the successor's weights. +static void ScaleWeights(Instruction* STI, MutableArrayRef<uint64_t> Weights) { + // Sum the successor's weights + assert(HasBranchWeights(STI)); + unsigned Scale = 0; + MDNode* ProfMD = STI->getMetadata(LLVMContext::MD_prof); + for (unsigned i = 1; i < ProfMD->getNumOperands(); ++i) { + ConstantInt* CI = dyn_cast<ConstantInt>(ProfMD->getOperand(i)); + assert(CI); + Scale += CI->getValue().getZExtValue(); + } + + // Skip default, as it's replaced during the folding + for (unsigned i = 1; i < Weights.size(); ++i) { + Weights[i] *= Scale; + } +} + +/// Sees if any of the weights are too big for a uint32_t, and halves all the +/// weights if any are. +static void FitWeights(MutableArrayRef<uint64_t> Weights) { + bool Halve = false; + for (unsigned i = 0; i < Weights.size(); ++i) + if (Weights[i] > UINT_MAX) { + Halve = true; + break; + } + + if (! Halve) + return; + + for (unsigned i = 0; i < Weights.size(); ++i) + Weights[i] /= 2; +} + /// FoldValueComparisonIntoPredecessors - The specified terminator is a value /// equality comparison instruction (either a switch or a branch on "X == c"). /// See if any of the predecessors of the terminator block are value comparisons @@ -770,6 +836,55 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI, // build. SmallVector<BasicBlock*, 8> NewSuccessors; + // Update the branch weight metadata along the way + SmallVector<uint64_t, 8> Weights; + uint64_t PredDefaultWeight = 0; + bool PredHasWeights = HasBranchWeights(PTI); + bool SuccHasWeights = HasBranchWeights(TI); + + if (PredHasWeights) { + MDNode* MD = PTI->getMetadata(LLVMContext::MD_prof); + assert(MD); + for (unsigned i = 1, e = MD->getNumOperands(); i < e; ++i) { + ConstantInt* CI = dyn_cast<ConstantInt>(MD->getOperand(i)); + assert(CI); + Weights.push_back(CI->getValue().getZExtValue()); + } + + // If the predecessor is a conditional eq, then swap the default weight + // to be the first entry. + if (BranchInst* BI = dyn_cast<BranchInst>(PTI)) { + assert(Weights.size() == 2); + ICmpInst *ICI = cast<ICmpInst>(BI->getCondition()); + + if (ICI->getPredicate() == ICmpInst::ICMP_EQ) { + std::swap(Weights.front(), Weights.back()); + } + } + + PredDefaultWeight = Weights.front(); + } else if (SuccHasWeights) { + // If there are no predecessor weights but there are successor weights, + // populate Weights with 1, which will later be scaled to the sum of + // successor's weights + Weights.assign(1 + PredCases.size(), 1); + PredDefaultWeight = 1; + } + + uint64_t SuccDefaultWeight = 0; + if (SuccHasWeights) { + int Index = 0; + if (BranchInst* BI = dyn_cast<BranchInst>(TI)) { + ICmpInst* ICI = dyn_cast<ICmpInst>(BI->getCondition()); + assert(ICI); + + if (ICI->getPredicate() == ICmpInst::ICMP_EQ) + Index = 1; + } + + SuccDefaultWeight = GetWeight(TI, Index)->getValue().getZExtValue(); + } + if (PredDefault == BB) { // If this is the default destination from PTI, only the edges in TI // that don't occur in PTI, or that branch to BB will be activated. @@ -780,6 +895,12 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI, else { // The default destination is BB, we don't need explicit targets. std::swap(PredCases[i], PredCases.back()); + + if (PredHasWeights) { + std::swap(Weights[i+1], Weights.back()); + Weights.pop_back(); + } + PredCases.pop_back(); --i; --e; } @@ -790,14 +911,34 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI, PredDefault = BBDefault; NewSuccessors.push_back(BBDefault); } + + if (SuccHasWeights) { + ScaleWeights(TI, Weights); + Weights.front() *= SuccDefaultWeight; + } else if (PredHasWeights) { + Weights.front() /= (1 + BBCases.size()); + } + for (unsigned i = 0, e = BBCases.size(); i != e; ++i) if (!PTIHandled.count(BBCases[i].Value) && BBCases[i].Dest != BBDefault) { PredCases.push_back(BBCases[i]); NewSuccessors.push_back(BBCases[i].Dest); + if (SuccHasWeights) { + Weights.push_back(PredDefaultWeight * + GetWeight(TI, i)->getValue().getZExtValue()); + } else if (PredHasWeights) { + // Split the old default's weight amongst the children + Weights.push_back(PredDefaultWeight / (1 + BBCases.size())); + } } } else { + // FIXME: preserve branch weight metadata, similarly to the 'then' + // above. For now, drop it. + PredHasWeights = false; + SuccHasWeights = false; + // If this is not the default destination from PSI, only the edges // in SI that occur in PSI with a destination of BB will be // activated. @@ -822,7 +963,7 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI, // If there are any constants vectored to BB that TI doesn't handle, // they must go to the default destination of TI. - for (std::set<ConstantInt*, ConstantIntOrdering>::iterator I = + for (std::set<ConstantInt*, ConstantIntOrdering>::iterator I = PTIHandled.begin(), E = PTIHandled.end(); I != E; ++I) { PredCases.push_back(ValueEqualityComparisonCase(*I, BBDefault)); @@ -851,6 +992,17 @@ bool SimplifyCFGOpt::FoldValueComparisonIntoPredecessors(TerminatorInst *TI, for (unsigned i = 0, e = PredCases.size(); i != e; ++i) NewSI->addCase(PredCases[i].Value, PredCases[i].Dest); + if (PredHasWeights || SuccHasWeights) { + // Halve the weights if any of them cannot fit in an uint32_t + FitWeights(Weights); + + SmallVector<uint32_t, 8> MDWeights(Weights.begin(), Weights.end()); + + NewSI->setMetadata(LLVMContext::MD_prof, + MDBuilder(BB->getContext()). + createBranchWeights(MDWeights)); + } + EraseTerminatorInstAndDCECond(PTI); // Okay, last check. If BB is still a successor of PSI, then we must @@ -984,11 +1136,11 @@ HoistTerminator: Value *BB1V = PN->getIncomingValueForBlock(BB1); Value *BB2V = PN->getIncomingValueForBlock(BB2); if (BB1V == BB2V) continue; - + // These values do not agree. Insert a select instruction before NT // that determines the right value. SelectInst *&SI = InsertedSelects[std::make_pair(BB1V, BB2V)]; - if (SI == 0) + if (SI == 0) SI = cast<SelectInst> (Builder.CreateSelect(BI->getCondition(), BB1V, BB2V, BB1V->getName()+"."+BB2V->getName())); @@ -1056,7 +1208,7 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) { // Do not hoist the instruction if any of its operands are defined but not // used in this BB. The transformation will prevent the operand from // being sunk into the use block. - for (User::op_iterator i = HInst->op_begin(), e = HInst->op_end(); + for (User::op_iterator i = HInst->op_begin(), e = HInst->op_end(); i != e; ++i) { Instruction *OpI = dyn_cast<Instruction>(*i); if (OpI && OpI->getParent() == BIParent && @@ -1112,7 +1264,7 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) { // as well. if (PHIs.empty()) return false; - + // If we get here, we can hoist the instruction and if-convert. DEBUG(dbgs() << "SPECULATIVELY EXECUTING BB" << *BB1 << "\n";); @@ -1162,13 +1314,13 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *BB1) { static bool BlockIsSimpleEnoughToThreadThrough(BasicBlock *BB) { BranchInst *BI = cast<BranchInst>(BB->getTerminator()); unsigned Size = 0; - + for (BasicBlock::iterator BBI = BB->begin(); &*BBI != BI; ++BBI) { if (isa<DbgInfoIntrinsic>(BBI)) continue; if (Size > 10) return false; // Don't clone large BB's. ++Size; - + // We can only support instructions that do not define values that are // live outside of the current basic block. for (Value::use_iterator UI = BBI->use_begin(), E = BBI->use_end(); @@ -1176,7 +1328,7 @@ static bool BlockIsSimpleEnoughToThreadThrough(BasicBlock *BB) { Instruction *U = cast<Instruction>(*UI); if (U->getParent() != BB || isa<PHINode>(U)) return false; } - + // Looks ok, continue checking. } @@ -1194,31 +1346,31 @@ static bool FoldCondBranchOnPHI(BranchInst *BI, const TargetData *TD) { // outside of the block. if (!PN || PN->getParent() != BB || !PN->hasOneUse()) return false; - + // Degenerate case of a single entry PHI. if (PN->getNumIncomingValues() == 1) { FoldSingleEntryPHINodes(PN->getParent()); - return true; + return true; } // Now we know that this block has multiple preds and two succs. if (!BlockIsSimpleEnoughToThreadThrough(BB)) return false; - + // Okay, this is a simple enough basic block. See if any phi values are // constants. for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { ConstantInt *CB = dyn_cast<ConstantInt>(PN->getIncomingValue(i)); if (CB == 0 || !CB->getType()->isIntegerTy(1)) continue; - + // Okay, we now know that all edges from PredBB should be revectored to // branch to RealDest. BasicBlock *PredBB = PN->getIncomingBlock(i); BasicBlock *RealDest = BI->getSuccessor(!CB->getZExtValue()); - + if (RealDest == BB) continue; // Skip self loops. // Skip if the predecessor's terminator is an indirect branch. if (isa<IndirectBrInst>(PredBB->getTerminator())) continue; - + // The dest block might have PHI nodes, other predecessors and other // difficult cases. Instead of being smart about this, just insert a new // block that jumps to the destination block, effectively splitting @@ -1227,7 +1379,7 @@ static bool FoldCondBranchOnPHI(BranchInst *BI, const TargetData *TD) { RealDest->getName()+".critedge", RealDest->getParent(), RealDest); BranchInst::Create(RealDest, EdgeBB); - + // Update PHI nodes. AddPredecessorToBlock(RealDest, EdgeBB, BB); @@ -1244,7 +1396,7 @@ static bool FoldCondBranchOnPHI(BranchInst *BI, const TargetData *TD) { // Clone the instruction. Instruction *N = BBI->clone(); if (BBI->hasName()) N->setName(BBI->getName()+".c"); - + // Update operands due to translation. for (User::op_iterator i = N->op_begin(), e = N->op_end(); i != e; ++i) { @@ -1252,7 +1404,7 @@ static bool FoldCondBranchOnPHI(BranchInst *BI, const TargetData *TD) { if (PI != TranslateMap.end()) *i = PI->second; } - + // Check for trivial simplification. if (Value *V = SimplifyInstruction(N, TD)) { TranslateMap[BBI] = V; @@ -1297,7 +1449,7 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { // Don't bother if the branch will be constant folded trivially. isa<ConstantInt>(IfCond)) return false; - + // Okay, we found that we can merge this two-entry phi node into a select. // Doing so would require us to fold *all* two entry phi nodes in this block. // At some point this becomes non-profitable (particularly if the target @@ -1307,14 +1459,14 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++NumPhis, ++I) if (NumPhis > 2) return false; - + // Loop over the PHI's seeing if we can promote them all to select // instructions. While we are at it, keep track of the instructions // that need to be moved to the dominating block. SmallPtrSet<Instruction*, 4> AggressiveInsts; unsigned MaxCostVal0 = PHINodeFoldingThreshold, MaxCostVal1 = PHINodeFoldingThreshold; - + for (BasicBlock::iterator II = BB->begin(); isa<PHINode>(II);) { PHINode *PN = cast<PHINode>(II++); if (Value *V = SimplifyInstruction(PN, TD)) { @@ -1322,19 +1474,19 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { PN->eraseFromParent(); continue; } - + if (!DominatesMergePoint(PN->getIncomingValue(0), BB, &AggressiveInsts, MaxCostVal0) || !DominatesMergePoint(PN->getIncomingValue(1), BB, &AggressiveInsts, MaxCostVal1)) return false; } - + // If we folded the first phi, PN dangles at this point. Refresh it. If // we ran out of PHIs then we simplified them all. PN = dyn_cast<PHINode>(BB->begin()); if (PN == 0) return true; - + // Don't fold i1 branches on PHIs which contain binary operators. These can // often be turned into switches and other things. if (PN->getType()->isIntegerTy(1) && @@ -1342,7 +1494,7 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { isa<BinaryOperator>(PN->getIncomingValue(1)) || isa<BinaryOperator>(IfCond))) return false; - + // If we all PHI nodes are promotable, check to make sure that all // instructions in the predecessor blocks can be promoted as well. If // not, we won't be able to get rid of the control flow, so it's not @@ -1362,7 +1514,7 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { return false; } } - + if (cast<BranchInst>(IfBlock2->getTerminator())->isConditional()) { IfBlock2 = 0; } else { @@ -1375,15 +1527,15 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { return false; } } - + DEBUG(dbgs() << "FOUND IF CONDITION! " << *IfCond << " T: " << IfTrue->getName() << " F: " << IfFalse->getName() << "\n"); - + // If we can still promote the PHI nodes after this gauntlet of tests, // do all of the PHI's now. Instruction *InsertPt = DomBlock->getTerminator(); IRBuilder<true, NoFolder> Builder(InsertPt); - + // Move all 'aggressive' instructions, which are defined in the // conditional parts of the if's up to the dominating block. if (IfBlock1) @@ -1394,19 +1546,19 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { DomBlock->getInstList().splice(InsertPt, IfBlock2->getInstList(), IfBlock2->begin(), IfBlock2->getTerminator()); - + while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) { // Change the PHI node into a select instruction. Value *TrueVal = PN->getIncomingValue(PN->getIncomingBlock(0) == IfFalse); Value *FalseVal = PN->getIncomingValue(PN->getIncomingBlock(0) == IfTrue); - - SelectInst *NV = + + SelectInst *NV = cast<SelectInst>(Builder.CreateSelect(IfCond, TrueVal, FalseVal, "")); PN->replaceAllUsesWith(NV); NV->takeName(PN); PN->eraseFromParent(); } - + // At this point, IfBlock1 and IfBlock2 are both empty, so our if statement // has been flattened. Change DomBlock to jump directly to our new block to // avoid other simplifycfg's kicking in on the diamond. @@ -1420,14 +1572,14 @@ static bool FoldTwoEntryPHINode(PHINode *PN, const TargetData *TD) { /// SimplifyCondBranchToTwoReturns - If we found a conditional branch that goes /// to two returning blocks, try to merge them together into one return, /// introducing a select if the return values disagree. -static bool SimplifyCondBranchToTwoReturns(BranchInst *BI, +static bool SimplifyCondBranchToTwoReturns(BranchInst *BI, IRBuilder<> &Builder) { assert(BI->isConditional() && "Must be a conditional branch"); BasicBlock *TrueSucc = BI->getSuccessor(0); BasicBlock *FalseSucc = BI->getSuccessor(1); ReturnInst *TrueRet = cast<ReturnInst>(TrueSucc->getTerminator()); ReturnInst *FalseRet = cast<ReturnInst>(FalseSucc->getTerminator()); - + // Check to ensure both blocks are empty (just a return) or optionally empty // with PHI nodes. If there are other instructions, merging would cause extra // computation on one path or the other. @@ -1447,12 +1599,12 @@ static bool SimplifyCondBranchToTwoReturns(BranchInst *BI, EraseTerminatorInstAndDCECond(BI); return true; } - + // Otherwise, figure out what the true and false return values are // so we can insert a new select instruction. Value *TrueValue = TrueRet->getReturnValue(); Value *FalseValue = FalseRet->getReturnValue(); - + // Unwrap any PHI nodes in the return blocks. if (PHINode *TVPN = dyn_cast_or_null<PHINode>(TrueValue)) if (TVPN->getParent() == TrueSucc) @@ -1460,7 +1612,7 @@ static bool SimplifyCondBranchToTwoReturns(BranchInst *BI, if (PHINode *FVPN = dyn_cast_or_null<PHINode>(FalseValue)) if (FVPN->getParent() == FalseSucc) FalseValue = FVPN->getIncomingValueForBlock(BI->getParent()); - + // In order for this transformation to be safe, we must be able to // unconditionally execute both operands to the return. This is // normally the case, but we could have a potentially-trapping @@ -1472,12 +1624,12 @@ static bool SimplifyCondBranchToTwoReturns(BranchInst *BI, if (ConstantExpr *FCV = dyn_cast_or_null<ConstantExpr>(FalseValue)) if (FCV->canTrap()) return false; - + // Okay, we collected all the mapped values and checked them for sanity, and // defined to really do this transformation. First, update the CFG. TrueSucc->removePredecessor(BI->getParent()); FalseSucc->removePredecessor(BI->getParent()); - + // Insert select instructions where needed. Value *BrCond = BI->getCondition(); if (TrueValue) { @@ -1491,15 +1643,15 @@ static bool SimplifyCondBranchToTwoReturns(BranchInst *BI, } } - Value *RI = !TrueValue ? + Value *RI = !TrueValue ? Builder.CreateRetVoid() : Builder.CreateRet(TrueValue); (void) RI; - + DEBUG(dbgs() << "\nCHANGING BRANCH TO TWO RETURNS INTO SELECT:" << "\n " << *BI << "NewRet = " << *RI << "TRUEBLOCK: " << *TrueSucc << "FALSEBLOCK: "<< *FalseSucc); - + EraseTerminatorInstAndDCECond(BI); return true; @@ -1600,7 +1752,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { if (Cond == 0) return false; } - + if (Cond == 0 || (!isa<CmpInst>(Cond) && !isa<BinaryOperator>(Cond)) || Cond->getParent() != BB || !Cond->hasOneUse()) return false; @@ -1623,7 +1775,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { isSafeToSpeculativelyExecute(FrontIt)) { BonusInst = &*FrontIt; ++FrontIt; - + // Ignore dbg intrinsics. while (isa<DbgInfoIntrinsic>(FrontIt)) ++FrontIt; } @@ -1631,13 +1783,13 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { // Only a single bonus inst is allowed. if (&*FrontIt != Cond) return false; - + // Make sure the instruction after the condition is the cond branch. BasicBlock::iterator CondIt = Cond; ++CondIt; // Ingore dbg intrinsics. while (isa<DbgInfoIntrinsic>(CondIt)) ++CondIt; - + if (&*CondIt != BI) return false; @@ -1649,7 +1801,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Cond->getOperand(1))) if (CE->canTrap()) return false; - + // Finally, don't infinitely unroll conditional loops. BasicBlock *TrueDest = BI->getSuccessor(0); BasicBlock *FalseDest = (BI->isConditional()) ? BI->getSuccessor(1) : 0; @@ -1659,22 +1811,22 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) { BasicBlock *PredBlock = *PI; BranchInst *PBI = dyn_cast<BranchInst>(PredBlock->getTerminator()); - + // Check that we have two conditional branches. If there is a PHI node in // the common successor, verify that the same value flows in from both // blocks. SmallVector<PHINode*, 4> PHIs; if (PBI == 0 || PBI->isUnconditional() || - (BI->isConditional() && + (BI->isConditional() && !SafeToMergeTerminators(BI, PBI)) || (!BI->isConditional() && !isProfitableToFoldUnconditional(BI, PBI, Cond, PHIs))) continue; - + // Determine if the two branches share a common destination. Instruction::BinaryOps Opc; bool InvertPredCond = false; - + if (BI->isConditional()) { if (PBI->getSuccessor(0) == TrueDest) Opc = Instruction::Or; @@ -1693,7 +1845,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { // Ensure that any values used in the bonus instruction are also used // by the terminator of the predecessor. This means that those values - // must already have been resolved, so we won't be inhibiting the + // must already have been resolved, so we won't be inhibiting the // out-of-order core by speculating them earlier. if (BonusInst) { // Collect the values used by the bonus inst @@ -1707,47 +1859,47 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { SmallVector<std::pair<Value*, unsigned>, 4> Worklist; Worklist.push_back(std::make_pair(PBI->getOperand(0), 0)); - + // Walk up to four levels back up the use-def chain of the predecessor's // terminator to see if all those values were used. The choice of four // levels is arbitrary, to provide a compile-time-cost bound. while (!Worklist.empty()) { std::pair<Value*, unsigned> Pair = Worklist.back(); Worklist.pop_back(); - + if (Pair.second >= 4) continue; UsedValues.erase(Pair.first); if (UsedValues.empty()) break; - + if (Instruction *I = dyn_cast<Instruction>(Pair.first)) { for (Instruction::op_iterator OI = I->op_begin(), OE = I->op_end(); OI != OE; ++OI) Worklist.push_back(std::make_pair(OI->get(), Pair.second+1)); - } + } } - + if (!UsedValues.empty()) return false; } DEBUG(dbgs() << "FOLDING BRANCH TO COMMON DEST:\n" << *PBI << *BB); - IRBuilder<> Builder(PBI); + IRBuilder<> Builder(PBI); // If we need to invert the condition in the pred block to match, do so now. if (InvertPredCond) { Value *NewCond = PBI->getCondition(); - + if (NewCond->hasOneUse() && isa<CmpInst>(NewCond)) { CmpInst *CI = cast<CmpInst>(NewCond); CI->setPredicate(CI->getInversePredicate()); } else { - NewCond = Builder.CreateNot(NewCond, + NewCond = Builder.CreateNot(NewCond, PBI->getCondition()->getName()+".not"); } - + PBI->setCondition(NewCond); PBI->swapSuccessors(); } - + // If we have a bonus inst, clone it into the predecessor block. Instruction *NewBonus = 0; if (BonusInst) { @@ -1756,7 +1908,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { NewBonus->takeName(BonusInst); BonusInst->setName(BonusInst->getName()+".old"); } - + // Clone Cond into the predecessor basic block, and or/and the // two conditions together. Instruction *New = Cond->clone(); @@ -1764,9 +1916,9 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { PredBlock->getInstList().insert(PBI, New); New->takeName(Cond); Cond->setName(New->getName()+".old"); - + if (BI->isConditional()) { - Instruction *NewCond = + Instruction *NewCond = cast<Instruction>(Builder.CreateBinOp(Opc, PBI->getCondition(), New, "or.cond")); PBI->setCondition(NewCond); @@ -1806,7 +1958,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { // Create (PBI_Cond and BI_Value) or (!PBI_Cond and PBI_C) // PBI_C is true: (PBI_Cond and BI_Value) or (!PBI_Cond) // is false: PBI_Cond and BI_Value - MergedCond = + MergedCond = cast<Instruction>(Builder.CreateBinOp(Instruction::And, PBI->getCondition(), New, "and.cond")); @@ -1814,7 +1966,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { Instruction *NotCond = cast<Instruction>(Builder.CreateNot(PBI->getCondition(), "not.cond")); - MergedCond = + MergedCond = cast<Instruction>(Builder.CreateBinOp(Instruction::Or, NotCond, MergedCond, "or.cond")); @@ -1921,7 +2073,7 @@ bool llvm::FoldBranchToCommonDest(BranchInst *BI) { for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) if (isa<DbgInfoIntrinsic>(*I)) I->clone()->insertBefore(PBI); - + return true; } return false; @@ -1936,7 +2088,7 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) { BasicBlock *BB = BI->getParent(); // If this block ends with a branch instruction, and if there is a - // predecessor that ends on a branch of the same condition, make + // predecessor that ends on a branch of the same condition, make // this conditional branch redundant. if (PBI->getCondition() == BI->getCondition() && PBI->getSuccessor(0) != PBI->getSuccessor(1)) { @@ -1945,11 +2097,11 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) { if (BB->getSinglePredecessor()) { // Turn this into a branch on constant. bool CondIsTrue = PBI->getSuccessor(0) == BB; - BI->setCondition(ConstantInt::get(Type::getInt1Ty(BB->getContext()), + BI->setCondition(ConstantInt::get(Type::getInt1Ty(BB->getContext()), CondIsTrue)); return true; // Nuke the branch on constant. } - + // Otherwise, if there are multiple predecessors, insert a PHI that merges // in the constant and simplify the block result. Subsequent passes of // simplifycfg will thread the block. @@ -1969,18 +2121,18 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) { PBI->getCondition() == BI->getCondition() && PBI->getSuccessor(0) != PBI->getSuccessor(1)) { bool CondIsTrue = PBI->getSuccessor(0) == BB; - NewPN->addIncoming(ConstantInt::get(Type::getInt1Ty(BB->getContext()), + NewPN->addIncoming(ConstantInt::get(Type::getInt1Ty(BB->getContext()), CondIsTrue), P); } else { NewPN->addIncoming(BI->getCondition(), P); } } - + BI->setCondition(NewPN); return true; } } - + // If this is a conditional branch in an empty block, and if any // predecessors is a conditional branch to one of our destinations, // fold the conditions into logical ops and one cond br. @@ -1991,11 +2143,11 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) { if (&*BBI != BI) return false; - + if (ConstantExpr *CE = dyn_cast<ConstantExpr>(BI->getCondition())) if (CE->canTrap()) return false; - + int PBIOp, BIOp; if (PBI->getSuccessor(0) == BI->getSuccessor(0)) PBIOp = BIOp = 0; @@ -2007,31 +2159,31 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) { PBIOp = BIOp = 1; else return false; - + // Check to make sure that the other destination of this branch // isn't BB itself. If so, this is an infinite loop that will // keep getting unwound. if (PBI->getSuccessor(PBIOp) == BB) return false; - - // Do not perform this transformation if it would require + + // Do not perform this transformation if it would require // insertion of a large number of select instructions. For targets // without predication/cmovs, this is a big pessimization. BasicBlock *CommonDest = PBI->getSuccessor(PBIOp); - + unsigned NumPhis = 0; for (BasicBlock::iterator II = CommonDest->begin(); isa<PHINode>(II); ++II, ++NumPhis) if (NumPhis > 2) // Disable this xform. return false; - + // Finally, if everything is ok, fold the branches to logical ops. BasicBlock *OtherDest = BI->getSuccessor(BIOp ^ 1); - + DEBUG(dbgs() << "FOLDING BRs:" << *PBI->getParent() << "AND: " << *BI->getParent()); - - + + // If OtherDest *is* BB, then BB is a basic block with a single conditional // branch in it, where one edge (OtherDest) goes back to itself but the other // exits. We don't *know* that the program avoids the infinite loop @@ -2046,13 +2198,13 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) { "infloop", BB->getParent()); BranchInst::Create(InfLoopBlock, InfLoopBlock); OtherDest = InfLoopBlock; - } - + } + DEBUG(dbgs() << *PBI->getParent()->getParent()); // BI may have other predecessors. Because of this, we leave // it alone, but modify PBI. - + // Make sure we get to CommonDest on True&True directions. Value *PBICond = PBI->getCondition(); IRBuilder<true, NoFolder> Builder(PBI); @@ -2065,16 +2217,16 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) { // Merge the conditions. Value *Cond = Builder.CreateOr(PBICond, BICond, "brmerge"); - + // Modify PBI to branch on the new condition to the new dests. PBI->setCondition(Cond); PBI->setSuccessor(0, CommonDest); PBI->setSuccessor(1, OtherDest); - + // OtherDest may have phi nodes. If so, add an entry from PBI's // block that are identical to the entries for BI's block. AddPredecessorToBlock(OtherDest, PBI->getParent(), BB); - + // We know that the CommonDest already had an edge from PBI to // it. If it has PHIs though, the PHIs may have different // entries for BB and PBI's BB. If so, insert a select to make @@ -2092,10 +2244,10 @@ static bool SimplifyCondBranchToCondBranch(BranchInst *PBI, BranchInst *BI) { PN->setIncomingValue(PBBIdx, NV); } } - + DEBUG(dbgs() << "INTO: " << *PBI->getParent()); DEBUG(dbgs() << *PBI->getParent()->getParent()); - + // This basic block is probably dead. We know it has at least // one fewer predecessor. return true; @@ -2214,7 +2366,7 @@ static bool SimplifyIndirectBrOnSelect(IndirectBrInst *IBI, SelectInst *SI) { /// br label %end /// end: /// ... = phi i1 [ true, %entry ], [ %tmp, %DEFAULT ], [ true, %entry ] -/// +/// /// We prefer to split the edge to 'end' so that there is a true/false entry to /// the PHI, merging the third icmp into the switch. static bool TryToSimplifyUncondBranchWithICmpInIt(ICmpInst *ICI, @@ -2228,17 +2380,17 @@ static bool TryToSimplifyUncondBranchWithICmpInIt(ICmpInst *ICI, Value *V = ICI->getOperand(0); ConstantInt *Cst = cast<ConstantInt>(ICI->getOperand(1)); - + // The pattern we're looking for is where our only predecessor is a switch on // 'V' and this block is the default case for the switch. In this case we can // fold the compared value into the switch to simplify things. BasicBlock *Pred = BB->getSinglePredecessor(); if (Pred == 0 || !isa<SwitchInst>(Pred->getTerminator())) return false; - + SwitchInst *SI = cast<SwitchInst>(Pred->getTerminator()); if (SI->getCondition() != V) return false; - + // If BB is reachable on a non-default case, then we simply know the value of // V in this block. Substitute it and constant fold the icmp instruction // away. @@ -2246,7 +2398,7 @@ static bool TryToSimplifyUncondBranchWithICmpInIt(ICmpInst *ICI, ConstantInt *VVal = SI->findCaseDest(BB); assert(VVal && "Should have a unique destination value"); ICI->setOperand(0, VVal); - + if (Value *V = SimplifyInstruction(ICI, TD)) { ICI->replaceAllUsesWith(V); ICI->eraseFromParent(); @@ -2254,7 +2406,7 @@ static bool TryToSimplifyUncondBranchWithICmpInIt(ICmpInst *ICI, // BB is now empty, so it is likely to simplify away. return SimplifyCFG(BB) | true; } - + // Ok, the block is reachable from the default dest. If the constant we're // comparing exists in one of the other edges, then we can constant fold ICI // and zap it. @@ -2264,13 +2416,13 @@ static bool TryToSimplifyUncondBranchWithICmpInIt(ICmpInst *ICI, V = ConstantInt::getFalse(BB->getContext()); else V = ConstantInt::getTrue(BB->getContext()); - + ICI->replaceAllUsesWith(V); ICI->eraseFromParent(); // BB is now empty, so it is likely to simplify away. return SimplifyCFG(BB) | true; } - + // The use of the icmp has to be in the 'end' block, by the only PHI node in // the block. BasicBlock *SuccBlock = BB->getTerminator()->getSuccessor(0); @@ -2297,7 +2449,7 @@ static bool TryToSimplifyUncondBranchWithICmpInIt(ICmpInst *ICI, BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), "switch.edge", BB->getParent(), BB); SI->addCase(Cst, NewBB); - + // NewBB branches to the phi block, add the uncond branch and the phi entry. Builder.SetInsertPoint(NewBB); Builder.SetCurrentDebugLocation(SI->getDebugLoc()); @@ -2313,8 +2465,8 @@ static bool SimplifyBranchOnICmpChain(BranchInst *BI, const TargetData *TD, IRBuilder<> &Builder) { Instruction *Cond = dyn_cast<Instruction>(BI->getCondition()); if (Cond == 0) return false; - - + + // Change br (X == 0 | X == 1), T, F into a switch instruction. // If this is a bunch of seteq's or'd together, or if it's a bunch of // 'setne's and'ed together, collect them. @@ -2323,7 +2475,7 @@ static bool SimplifyBranchOnICmpChain(BranchInst *BI, const TargetData *TD, bool TrueWhenEqual = true; Value *ExtraCase = 0; unsigned UsedICmps = 0; - + if (Cond->getOpcode() == Instruction::Or) { CompVal = GatherConstantCompares(Cond, Values, ExtraCase, TD, true, UsedICmps); @@ -2332,7 +2484,7 @@ static bool SimplifyBranchOnICmpChain(BranchInst *BI, const TargetData *TD, UsedICmps); TrueWhenEqual = false; } - + // If we didn't have a multiply compared value, fail. if (CompVal == 0) return false; @@ -2344,21 +2496,24 @@ static bool SimplifyBranchOnICmpChain(BranchInst *BI, const TargetData *TD, // instruction can't handle, remove them now. array_pod_sort(Values.begin(), Values.end(), ConstantIntSortPredicate); Values.erase(std::unique(Values.begin(), Values.end()), Values.end()); - + // If Extra was used, we require at least two switch values to do the // transformation. A switch with one value is just an cond branch. if (ExtraCase && Values.size() < 2) return false; - + + // TODO: Preserve branch weight metadata, similarly to how + // FoldValueComparisonIntoPredecessors preserves it. + // Figure out which block is which destination. BasicBlock *DefaultBB = BI->getSuccessor(1); BasicBlock *EdgeBB = BI->getSuccessor(0); if (!TrueWhenEqual) std::swap(DefaultBB, EdgeBB); - + BasicBlock *BB = BI->getParent(); - + DEBUG(dbgs() << "Converting 'icmp' chain with " << Values.size() << " cases into SWITCH. BB is:\n" << *BB); - + // If there are any extra values that couldn't be folded into the switch // then we evaluate them with an explicit branch first. Split the block // right before the condbr to handle it. @@ -2372,13 +2527,13 @@ static bool SimplifyBranchOnICmpChain(BranchInst *BI, const TargetData *TD, Builder.CreateCondBr(ExtraCase, EdgeBB, NewBB); else Builder.CreateCondBr(ExtraCase, NewBB, EdgeBB); - + OldTI->eraseFromParent(); - + // If there are PHI nodes in EdgeBB, then we need to add a new entry to them // for the edge we just added. AddPredecessorToBlock(EdgeBB, BB, NewBB); - + DEBUG(dbgs() << " ** 'icmp' chain unhandled condition: " << *ExtraCase << "\nEXTRABB = " << *BB); BB = NewBB; @@ -2392,14 +2547,14 @@ static bool SimplifyBranchOnICmpChain(BranchInst *BI, const TargetData *TD, TD->getIntPtrType(CompVal->getContext()), "magicptr"); } - + // Create the new switch instruction now. SwitchInst *New = Builder.CreateSwitch(CompVal, DefaultBB, Values.size()); // Add all of the 'cases' to the switch instruction. for (unsigned i = 0, e = Values.size(); i != e; ++i) New->addCase(Values[i], EdgeBB); - + // We added edges from PI to the EdgeBB. As such, if there were any // PHI nodes in EdgeBB, they need entries to be added corresponding to // the number of edges added. @@ -2410,10 +2565,10 @@ static bool SimplifyBranchOnICmpChain(BranchInst *BI, const TargetData *TD, for (unsigned i = 0, e = Values.size()-1; i != e; ++i) PN->addIncoming(InVal, BB); } - + // Erase the old branch instruction. EraseTerminatorInstAndDCECond(BI); - + DEBUG(dbgs() << " ** 'icmp' chain result is:\n" << *BB << '\n'); return true; } @@ -2467,7 +2622,7 @@ bool SimplifyCFGOpt::SimplifyResume(ResumeInst *RI, IRBuilder<> &Builder) { bool SimplifyCFGOpt::SimplifyReturn(ReturnInst *RI, IRBuilder<> &Builder) { BasicBlock *BB = RI->getParent(); if (!BB->getFirstNonPHIOrDbg()->isTerminator()) return false; - + // Find predecessors that end with branches. SmallVector<BasicBlock*, 8> UncondBranchPreds; SmallVector<BranchInst*, 8> CondBranchPreds; @@ -2481,7 +2636,7 @@ bool SimplifyCFGOpt::SimplifyReturn(ReturnInst *RI, IRBuilder<> &Builder) { CondBranchPreds.push_back(BI); } } - + // If we found some, do the transformation! if (!UncondBranchPreds.empty() && DupRet) { while (!UncondBranchPreds.empty()) { @@ -2490,21 +2645,21 @@ bool SimplifyCFGOpt::SimplifyReturn(ReturnInst *RI, IRBuilder<> &Builder) { << "INTO UNCOND BRANCH PRED: " << *Pred); (void)FoldReturnIntoUncondBranch(RI, BB, Pred); } - + // If we eliminated all predecessors of the block, delete the block now. if (pred_begin(BB) == pred_end(BB)) // We know there are no successors, so just nuke the block. BB->eraseFromParent(); - + return true; } - + // Check out all of the conditional branches going to this return // instruction. If any of them just select between returns, change the // branch itself into a select/return pair. while (!CondBranchPreds.empty()) { BranchInst *BI = CondBranchPreds.pop_back_val(); - + // Check to see if the non-BB successor is also a return block. if (isa<ReturnInst>(BI->getSuccessor(0)->getTerminator()) && isa<ReturnInst>(BI->getSuccessor(1)->getTerminator()) && @@ -2516,9 +2671,9 @@ bool SimplifyCFGOpt::SimplifyReturn(ReturnInst *RI, IRBuilder<> &Builder) { bool SimplifyCFGOpt::SimplifyUnreachable(UnreachableInst *UI) { BasicBlock *BB = UI->getParent(); - + bool Changed = false; - + // If there are any instructions immediately before the unreachable that can // be removed, do so. while (UI != BB->begin()) { @@ -2558,11 +2713,11 @@ bool SimplifyCFGOpt::SimplifyUnreachable(UnreachableInst *UI) { BBI->eraseFromParent(); Changed = true; } - + // If the unreachable instruction is the first in the block, take a gander // at all of the predecessors of this instruction, and simplify them. if (&BB->front() != UI) return Changed; - + SmallVector<BasicBlock*, 8> Preds(pred_begin(BB), pred_end(BB)); for (unsigned i = 0, e = Preds.size(); i != e; ++i) { TerminatorInst *TI = Preds[i]->getTerminator(); @@ -2615,7 +2770,7 @@ bool SimplifyCFGOpt::SimplifyUnreachable(UnreachableInst *UI) { BasicBlock *MaxBlock = 0; for (std::map<BasicBlock*, std::pair<unsigned, unsigned> >::iterator I = Popularity.begin(), E = Popularity.end(); I != E; ++I) { - if (I->second.first > MaxPop || + if (I->second.first > MaxPop || (I->second.first == MaxPop && MaxIndex > I->second.second)) { MaxPop = I->second.first; MaxIndex = I->second.second; @@ -2627,13 +2782,13 @@ bool SimplifyCFGOpt::SimplifyUnreachable(UnreachableInst *UI) { // edges to it. SI->setDefaultDest(MaxBlock); Changed = true; - + // If MaxBlock has phinodes in it, remove MaxPop-1 entries from // it. if (isa<PHINode>(MaxBlock->begin())) for (unsigned i = 0; i != MaxPop-1; ++i) MaxBlock->removePredecessor(SI->getParent()); - + for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end(); i != e; ++i) if (i.getCaseSuccessor() == MaxBlock) { @@ -2648,7 +2803,7 @@ bool SimplifyCFGOpt::SimplifyUnreachable(UnreachableInst *UI) { // place to note that the call does not throw though. BranchInst *BI = Builder.CreateBr(II->getNormalDest()); II->removeFromParent(); // Take out of symbol table - + // Insert the call now... SmallVector<Value*, 8> Args(II->op_begin(), II->op_end()-3); Builder.SetInsertPoint(BI); @@ -2663,7 +2818,7 @@ bool SimplifyCFGOpt::SimplifyUnreachable(UnreachableInst *UI) { } } } - + // If this block is now dead, remove it. if (pred_begin(BB) == pred_end(BB) && BB != &BB->getParent()->getEntryBlock()) { @@ -2823,6 +2978,285 @@ static bool ForwardSwitchConditionToPHI(SwitchInst *SI) { return Changed; } +/// ValidLookupTableConstant - Return true if the backend will be able to handle +/// initializing an array of constants like C. +static bool ValidLookupTableConstant(Constant *C) { + if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) + return CE->isGEPWithNoNotionalOverIndexing(); + + return isa<ConstantFP>(C) || + isa<ConstantInt>(C) || + isa<ConstantPointerNull>(C) || + isa<GlobalValue>(C) || + isa<UndefValue>(C); +} + +/// GetCaseResulsts - Try to determine the resulting constant values in phi +/// nodes at the common destination basic block for one of the case +/// destinations of a switch instruction. +static bool GetCaseResults(SwitchInst *SI, + BasicBlock *CaseDest, + BasicBlock **CommonDest, + SmallVector<std::pair<PHINode*,Constant*>, 4> &Res) { + // The block from which we enter the common destination. + BasicBlock *Pred = SI->getParent(); + + // If CaseDest is empty, continue to its successor. + if (CaseDest->getFirstNonPHIOrDbg() == CaseDest->getTerminator() && + !isa<PHINode>(CaseDest->begin())) { + + TerminatorInst *Terminator = CaseDest->getTerminator(); + if (Terminator->getNumSuccessors() != 1) + return false; + + Pred = CaseDest; + CaseDest = Terminator->getSuccessor(0); + } + + // If we did not have a CommonDest before, use the current one. + if (!*CommonDest) + *CommonDest = CaseDest; + // If the destination isn't the common one, abort. + if (CaseDest != *CommonDest) + return false; + + // Get the values for this case from phi nodes in the destination block. + BasicBlock::iterator I = (*CommonDest)->begin(); + while (PHINode *PHI = dyn_cast<PHINode>(I++)) { + int Idx = PHI->getBasicBlockIndex(Pred); + if (Idx == -1) + continue; + + Constant *ConstVal = dyn_cast<Constant>(PHI->getIncomingValue(Idx)); + if (!ConstVal) + return false; + + // Be conservative about which kinds of constants we support. + if (!ValidLookupTableConstant(ConstVal)) + return false; + + Res.push_back(std::make_pair(PHI, ConstVal)); + } + + return true; +} + +/// BuildLookupTable - Build a lookup table with the contents of Results, using +/// DefaultResult to fill the holes in the table. If the table ends up +/// containing the same result in each element, set *SingleResult to that value +/// and return NULL. +static GlobalVariable *BuildLookupTable(Module &M, + uint64_t TableSize, + ConstantInt *Offset, + const SmallVector<std::pair<ConstantInt*, Constant*>, 4>& Results, + Constant *DefaultResult, + Constant **SingleResult) { + assert(Results.size() && "Need values to build lookup table"); + assert(TableSize >= Results.size() && "Table needs to hold all values"); + + // If all values in the table are equal, this is that value. + Constant *SameResult = Results.begin()->second; + + // Build up the table contents. + std::vector<Constant*> TableContents(TableSize); + for (size_t I = 0, E = Results.size(); I != E; ++I) { + ConstantInt *CaseVal = Results[I].first; + Constant *CaseRes = Results[I].second; + + uint64_t Idx = (CaseVal->getValue() - Offset->getValue()).getLimitedValue(); + TableContents[Idx] = CaseRes; + + if (CaseRes != SameResult) + SameResult = NULL; + } + + // Fill in any holes in the table with the default result. + if (Results.size() < TableSize) { + for (unsigned i = 0; i < TableSize; ++i) { + if (!TableContents[i]) + TableContents[i] = DefaultResult; + } + + if (DefaultResult != SameResult) + SameResult = NULL; + } + + // Same result was used in the entire table; just return that. + if (SameResult) { + *SingleResult = SameResult; + return NULL; + } + + ArrayType *ArrayTy = ArrayType::get(DefaultResult->getType(), TableSize); + Constant *Initializer = ConstantArray::get(ArrayTy, TableContents); + + GlobalVariable *GV = new GlobalVariable(M, ArrayTy, /*constant=*/ true, + GlobalVariable::PrivateLinkage, + Initializer, + "switch.table"); + GV->setUnnamedAddr(true); + return GV; +} + +/// SwitchToLookupTable - If the switch is only used to initialize one or more +/// phi nodes in a common successor block with different constant values, +/// replace the switch with lookup tables. +static bool SwitchToLookupTable(SwitchInst *SI, + IRBuilder<> &Builder) { + assert(SI->getNumCases() > 1 && "Degenerate switch?"); + // FIXME: Handle unreachable cases. + + // FIXME: If the switch is too sparse for a lookup table, perhaps we could + // split off a dense part and build a lookup table for that. + + // FIXME: If the results are all integers and the lookup table would fit in a + // target-legal register, we should store them as a bitmap and use shift/mask + // to look up the result. + + // FIXME: This creates arrays of GEPs to constant strings, which means each + // GEP needs a runtime relocation in PIC code. We should just build one big + // string and lookup indices into that. + + // Ignore the switch if the number of cases are too small. + // This is similar to the check when building jump tables in + // SelectionDAGBuilder::handleJTSwitchCase. + // FIXME: Determine the best cut-off. + if (SI->getNumCases() < 4) + return false; + + // Figure out the corresponding result for each case value and phi node in the + // common destination, as well as the the min and max case values. + assert(SI->case_begin() != SI->case_end()); + SwitchInst::CaseIt CI = SI->case_begin(); + ConstantInt *MinCaseVal = CI.getCaseValue(); + ConstantInt *MaxCaseVal = CI.getCaseValue(); + + BasicBlock *CommonDest = NULL; + typedef SmallVector<std::pair<ConstantInt*, Constant*>, 4> ResultListTy; + SmallDenseMap<PHINode*, ResultListTy> ResultLists; + SmallDenseMap<PHINode*, Constant*> DefaultResults; + SmallDenseMap<PHINode*, Type*> ResultTypes; + SmallVector<PHINode*, 4> PHIs; + + for (SwitchInst::CaseIt E = SI->case_end(); CI != E; ++CI) { + ConstantInt *CaseVal = CI.getCaseValue(); + if (CaseVal->getValue().slt(MinCaseVal->getValue())) + MinCaseVal = CaseVal; + if (CaseVal->getValue().sgt(MaxCaseVal->getValue())) + MaxCaseVal = CaseVal; + + // Resulting value at phi nodes for this case value. + typedef SmallVector<std::pair<PHINode*, Constant*>, 4> ResultsTy; + ResultsTy Results; + if (!GetCaseResults(SI, CI.getCaseSuccessor(), &CommonDest, Results)) + return false; + + // Append the result from this case to the list for each phi. + for (ResultsTy::iterator I = Results.begin(), E = Results.end(); I!=E; ++I) { + if (!ResultLists.count(I->first)) + PHIs.push_back(I->first); + ResultLists[I->first].push_back(std::make_pair(CaseVal, I->second)); + } + } + + // Get the resulting values for the default case. + SmallVector<std::pair<PHINode*, Constant*>, 4> DefaultResultsList; + if (!GetCaseResults(SI, SI->getDefaultDest(), &CommonDest, DefaultResultsList)) + return false; + for (size_t I = 0, E = DefaultResultsList.size(); I != E; ++I) { + PHINode *PHI = DefaultResultsList[I].first; + Constant *Result = DefaultResultsList[I].second; + DefaultResults[PHI] = Result; + ResultTypes[PHI] = Result->getType(); + } + + APInt RangeSpread = MaxCaseVal->getValue() - MinCaseVal->getValue(); + // The table density should be at lest 40%. This is the same criterion as for + // jump tables, see SelectionDAGBuilder::handleJTSwitchCase. + // FIXME: Find the best cut-off. + // Be careful to avoid overlow in the density computation. + if (RangeSpread.zextOrSelf(64).ugt(UINT64_MAX / 4 - 1)) + return false; + uint64_t TableSize = RangeSpread.getLimitedValue() + 1; + if (SI->getNumCases() * 10 < TableSize * 4) + return false; + + // Build the lookup tables. + SmallDenseMap<PHINode*, GlobalVariable*> LookupTables; + SmallDenseMap<PHINode*, Constant*> SingleResults; + + Module &Mod = *CommonDest->getParent()->getParent(); + for (SmallVector<PHINode*, 4>::iterator I = PHIs.begin(), E = PHIs.end(); + I != E; ++I) { + PHINode *PHI = *I; + + Constant *SingleResult = NULL; + LookupTables[PHI] = BuildLookupTable(Mod, TableSize, MinCaseVal, + ResultLists[PHI], DefaultResults[PHI], + &SingleResult); + SingleResults[PHI] = SingleResult; + } + + // Create the BB that does the lookups. + BasicBlock *LookupBB = BasicBlock::Create(Mod.getContext(), + "switch.lookup", + CommonDest->getParent(), + CommonDest); + + // Check whether the condition value is within the case range, and branch to + // the new BB. + Builder.SetInsertPoint(SI); + Value *TableIndex = Builder.CreateSub(SI->getCondition(), MinCaseVal, + "switch.tableidx"); + Value *Cmp = Builder.CreateICmpULT(TableIndex, ConstantInt::get( + MinCaseVal->getType(), TableSize)); + Builder.CreateCondBr(Cmp, LookupBB, SI->getDefaultDest()); + + // Populate the BB that does the lookups. + Builder.SetInsertPoint(LookupBB); + bool ReturnedEarly = false; + for (SmallVector<PHINode*, 4>::iterator I = PHIs.begin(), E = PHIs.end(); + I != E; ++I) { + PHINode *PHI = *I; + // There was a single result for this phi; just use that. + if (Constant *SingleResult = SingleResults[PHI]) { + PHI->addIncoming(SingleResult, LookupBB); + continue; + } + + Value *GEPIndices[] = { Builder.getInt32(0), TableIndex }; + Value *GEP = Builder.CreateInBoundsGEP(LookupTables[PHI], GEPIndices, + "switch.gep"); + Value *Result = Builder.CreateLoad(GEP, "switch.load"); + + // If the result is only going to be used to return from the function, + // we want to do that right here. + if (PHI->hasOneUse() && isa<ReturnInst>(*PHI->use_begin())) { + if (CommonDest->getFirstNonPHIOrDbg() == CommonDest->getTerminator()) { + Builder.CreateRet(Result); + ReturnedEarly = true; + } + } + + if (!ReturnedEarly) + PHI->addIncoming(Result, LookupBB); + } + + if (!ReturnedEarly) + Builder.CreateBr(CommonDest); + + // Remove the switch. + for (unsigned i = 0; i < SI->getNumSuccessors(); ++i) { + BasicBlock *Succ = SI->getSuccessor(i); + if (Succ == SI->getDefaultDest()) continue; + Succ->removePredecessor(SI->getParent()); + } + SI->eraseFromParent(); + + ++NumLookupTables; + return true; +} + bool SimplifyCFGOpt::SimplifySwitch(SwitchInst *SI, IRBuilder<> &Builder) { // If this switch is too complex to want to look at, ignore it. if (!isValueEqualityComparison(SI)) @@ -2862,13 +3296,16 @@ bool SimplifyCFGOpt::SimplifySwitch(SwitchInst *SI, IRBuilder<> &Builder) { if (ForwardSwitchConditionToPHI(SI)) return SimplifyCFG(BB) | true; + if (SwitchToLookupTable(SI, Builder)) + return SimplifyCFG(BB) | true; + return false; } bool SimplifyCFGOpt::SimplifyIndirectBr(IndirectBrInst *IBI) { BasicBlock *BB = IBI->getParent(); bool Changed = false; - + // Eliminate redundant destinations. SmallPtrSet<Value *, 8> Succs; for (unsigned i = 0, e = IBI->getNumDestinations(); i != e; ++i) { @@ -2879,7 +3316,7 @@ bool SimplifyCFGOpt::SimplifyIndirectBr(IndirectBrInst *IBI) { --i; --e; Changed = true; } - } + } if (IBI->getNumDestinations() == 0) { // If the indirectbr has no successors, change it to unreachable. @@ -2887,14 +3324,14 @@ bool SimplifyCFGOpt::SimplifyIndirectBr(IndirectBrInst *IBI) { EraseTerminatorInstAndDCECond(IBI); return true; } - + if (IBI->getNumDestinations() == 1) { // If the indirectbr has one successor, change it to a direct branch. BranchInst::Create(IBI->getDestination(0), IBI); EraseTerminatorInstAndDCECond(IBI); return true; } - + if (SelectInst *SI = dyn_cast<SelectInst>(IBI->getAddress())) { if (SimplifyIndirectBrOnSelect(IBI, SI)) return SimplifyCFG(BB) | true; @@ -2904,13 +3341,13 @@ bool SimplifyCFGOpt::SimplifyIndirectBr(IndirectBrInst *IBI) { bool SimplifyCFGOpt::SimplifyUncondBranch(BranchInst *BI, IRBuilder<> &Builder){ BasicBlock *BB = BI->getParent(); - + // If the Terminator is the only non-phi instruction, simplify the block. BasicBlock::iterator I = BB->getFirstNonPHIOrDbgOrLifetime(); if (I->isTerminator() && BB != &BB->getParent()->getEntryBlock() && TryToSimplifyUncondBranchFromEmptyBlock(BB)) return true; - + // If the only instruction in the block is a seteq/setne comparison // against a constant, try to simplify the block. if (ICmpInst *ICI = dyn_cast<ICmpInst>(I)) @@ -2921,7 +3358,7 @@ bool SimplifyCFGOpt::SimplifyUncondBranch(BranchInst *BI, IRBuilder<> &Builder){ TryToSimplifyUncondBranchWithICmpInIt(ICI, TD, Builder)) return true; } - + // If this basic block is ONLY a compare and a branch, and if a predecessor // branches to us and our successor, fold the comparison into the // predecessor and use logical operations to update the incoming value @@ -2934,7 +3371,7 @@ bool SimplifyCFGOpt::SimplifyUncondBranch(BranchInst *BI, IRBuilder<> &Builder){ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { BasicBlock *BB = BI->getParent(); - + // Conditional branch if (isValueEqualityComparison(BI)) { // If we only have one predecessor, and if it is a branch on this value, @@ -2943,7 +3380,7 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { if (BasicBlock *OnlyPred = BB->getSinglePredecessor()) if (SimplifyEqualityComparisonWithOnlyPredecessor(BI, OnlyPred, Builder)) return SimplifyCFG(BB) | true; - + // This block must be empty, except for the setcond inst, if it exists. // Ignore dbg intrinsics. BasicBlock::iterator I = BB->begin(); @@ -2962,17 +3399,17 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { return SimplifyCFG(BB) | true; } } - + // Try to turn "br (X == 0 | X == 1), T, F" into a switch instruction. if (SimplifyBranchOnICmpChain(BI, TD, Builder)) return true; - + // If this basic block is ONLY a compare and a branch, and if a predecessor // branches to us and one of our successors, fold the comparison into the // predecessor and use logical operations to pick the right destination. if (FoldBranchToCommonDest(BI)) return SimplifyCFG(BB) | true; - + // We have a conditional branch to two blocks that are only reachable // from BI. We know that the condbr dominates the two blocks, so see if // there is any identical code in the "then" and "else" blocks. If so, we @@ -2999,14 +3436,14 @@ bool SimplifyCFGOpt::SimplifyCondBranch(BranchInst *BI, IRBuilder<> &Builder) { if (SpeculativelyExecuteBB(BI, BI->getSuccessor(1))) return SimplifyCFG(BB) | true; } - + // If this is a branch on a phi node in the current block, thread control // through this block if any PHI node entries are constants. if (PHINode *PN = dyn_cast<PHINode>(BI->getCondition())) if (PN->getParent() == BI->getParent()) if (FoldCondBranchOnPHI(BI, TD)) return SimplifyCFG(BB) | true; - + // Scan predecessor blocks for conditional branches. for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) if (BranchInst *PBI = dyn_cast<BranchInst>((*PI)->getTerminator())) @@ -3114,7 +3551,7 @@ bool SimplifyCFGOpt::run(BasicBlock *BB) { // if (MergeBlockIntoPredecessor(BB)) return true; - + IRBuilder<> Builder(BB); // If there is a trivial two-entry PHI node in this basic block, and we can diff --git a/lib/Transforms/Utils/SimplifyInstructions.cpp b/lib/Transforms/Utils/SimplifyInstructions.cpp index 81eb9e0..528e6a1 100644 --- a/lib/Transforms/Utils/SimplifyInstructions.cpp +++ b/lib/Transforms/Utils/SimplifyInstructions.cpp @@ -72,7 +72,7 @@ namespace { ++NumSimplified; Changed = true; } - Changed |= RecursivelyDeleteTriviallyDeadInstructions(I); + Changed |= RecursivelyDeleteTriviallyDeadInstructions(I, TLI); } // Place the list of instructions to simplify on the next loop iteration |