X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FTransforms%2FUtils%2FLowerSwitch.cpp;h=35cd917330ab21e4322ba7a432d8e978e09bf952;hb=7478e275730f5b9fc0651b5600761c8e707e1897;hp=c24847858c2ffe3f3a0ef1f17d91b104d44835a2;hpb=6ddba2b933645d308428201e942abe1274fa5085;p=oota-llvm.git diff --git a/lib/Transforms/Utils/LowerSwitch.cpp b/lib/Transforms/Utils/LowerSwitch.cpp index c24847858c2..35cd917330a 100644 --- a/lib/Transforms/Utils/LowerSwitch.cpp +++ b/lib/Transforms/Utils/LowerSwitch.cpp @@ -14,34 +14,40 @@ //===----------------------------------------------------------------------===// #include "llvm/Transforms/Scalar.h" -#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h" -#include "llvm/Constants.h" -#include "llvm/Function.h" -#include "llvm/Instructions.h" -#include "llvm/Pass.h" +#include "llvm/Transforms/Utils/BasicBlockUtils.h" #include "llvm/ADT/STLExtras.h" -#include "llvm/Support/Debug.h" +#include "llvm/IR/Constants.h" +#include "llvm/IR/Function.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/LLVMContext.h" +#include "llvm/IR/CFG.h" +#include "llvm/Pass.h" #include "llvm/Support/Compiler.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h" #include using namespace llvm; +#define DEBUG_TYPE "lower-switch" + namespace { /// LowerSwitch Pass - Replace all SwitchInst instructions with chained branch - /// instructions. Note that this cannot be a BasicBlock pass because it - /// modifies the CFG! - class VISIBILITY_HIDDEN LowerSwitch : public FunctionPass { + /// instructions. + class LowerSwitch : public FunctionPass { public: static char ID; // Pass identification, replacement for typeid - LowerSwitch() : FunctionPass((intptr_t) &ID) {} + LowerSwitch() : FunctionPass(ID) { + initializeLowerSwitchPass(*PassRegistry::getPassRegistry()); + } - virtual bool runOnFunction(Function &F); - - virtual void getAnalysisUsage(AnalysisUsage &AU) const { + bool runOnFunction(Function &F) override; + + void getAnalysisUsage(AnalysisUsage &AU) const override { // This is a cluster of orthogonal Transforms AU.addPreserved(); - AU.addPreservedID(PromoteMemoryToRegisterID); + AU.addPreserved("mem2reg"); AU.addPreservedID(LowerInvokePassID); - AU.addPreservedID(LowerAllocationsID); } struct CaseRange { @@ -49,21 +55,23 @@ namespace { Constant* High; BasicBlock* BB; - CaseRange() : Low(0), High(0), BB(0) { } - CaseRange(Constant* low, Constant* high, BasicBlock* bb) : + CaseRange(Constant *low = nullptr, Constant *high = nullptr, + BasicBlock *bb = nullptr) : Low(low), High(high), BB(bb) { } }; - typedef std::vector CaseVector; + typedef std::vector CaseVector; typedef std::vector::iterator CaseItr; private: void processSwitchInst(SwitchInst *SI); - BasicBlock* switchConvert(CaseItr Begin, CaseItr End, Value* Val, - BasicBlock* OrigBlock, BasicBlock* Default); - BasicBlock* newLeafBlock(CaseRange& Leaf, Value* Val, - BasicBlock* OrigBlock, BasicBlock* Default); - unsigned Clusterify(CaseVector& Cases, SwitchInst *SI); + BasicBlock *switchConvert(CaseItr Begin, CaseItr End, + ConstantInt *LowerBound, ConstantInt *UpperBound, + Value *Val, BasicBlock *Predecessor, + BasicBlock *OrigBlock, BasicBlock *Default); + BasicBlock *newLeafBlock(CaseRange &Leaf, Value *Val, BasicBlock *OrigBlock, + BasicBlock *Default); + unsigned Clusterify(CaseVector &Cases, SwitchInst *SI); }; /// The comparison function for sorting the switch case values in the vector. @@ -80,11 +88,11 @@ namespace { } char LowerSwitch::ID = 0; -static RegisterPass -X("lowerswitch", "Lower SwitchInst's to branches"); +INITIALIZE_PASS(LowerSwitch, "lowerswitch", + "Lower SwitchInst's to branches", false, false) -// Publically exposed interface to pass... -const PassInfo *const llvm::LowerSwitchID = &X; +// Publicly exposed interface to pass... +char &llvm::LowerSwitchID = LowerSwitch::ID; // createLowerSwitchPass - Interface to this file... FunctionPass *llvm::createLowerSwitchPass() { return new LowerSwitch(); @@ -107,8 +115,11 @@ bool LowerSwitch::runOnFunction(Function &F) { // operator<< - Used for debugging purposes. // -static std::ostream& operator<<(std::ostream &O, - const LowerSwitch::CaseVector &C) { +static raw_ostream& operator<<(raw_ostream &O, + const LowerSwitch::CaseVector &C) + LLVM_ATTRIBUTE_USED; +static raw_ostream& operator<<(raw_ostream &O, + const LowerSwitch::CaseVector &C) { O << "["; for (LowerSwitch::CaseVector::const_iterator B = C.begin(), @@ -120,50 +131,136 @@ static std::ostream& operator<<(std::ostream &O, return O << "]"; } -static OStream& operator<<(OStream &O, const LowerSwitch::CaseVector &C) { - if (O.stream()) *O.stream() << C; - return O; +// \brief Update the first occurrence of the "switch statement" BB in the PHI +// node with the "new" BB. The other occurrences will: +// +// 1) Be updated by subsequent calls to this function. Switch statements may +// have more than one outcoming edge into the same BB if they all have the same +// value. When the switch statement is converted these incoming edges are now +// coming from multiple BBs. +// 2) Removed if subsequent incoming values now share the same case, i.e., +// multiple outcome edges are condensed into one. This is necessary to keep the +// number of phi values equal to the number of branches to SuccBB. +static void fixPhis(BasicBlock *SuccBB, BasicBlock *OrigBB, BasicBlock *NewBB, + unsigned NumMergedCases) { + for (BasicBlock::iterator I = SuccBB->begin(), IE = SuccBB->getFirstNonPHI(); + I != IE; ++I) { + PHINode *PN = cast(I); + + // Only update the first occurence. + unsigned Idx = 0, E = PN->getNumIncomingValues(); + unsigned LocalNumMergedCases = NumMergedCases; + for (; Idx != E; ++Idx) { + if (PN->getIncomingBlock(Idx) == OrigBB) { + PN->setIncomingBlock(Idx, NewBB); + break; + } + } + + // Remove additional occurences coming from condensed cases and keep the + // number of incoming values equal to the number of branches to SuccBB. + for (++Idx; LocalNumMergedCases > 0 && Idx < E; ++Idx) + if (PN->getIncomingBlock(Idx) == OrigBB) { + PN->removeIncomingValue(Idx); + LocalNumMergedCases--; + } + } } // switchConvert - Convert the switch statement into a binary lookup of // the case values. The function recursively builds this tree. -// -BasicBlock* LowerSwitch::switchConvert(CaseItr Begin, CaseItr End, - Value* Val, BasicBlock* OrigBlock, - BasicBlock* Default) -{ +// LowerBound and UpperBound are used to keep track of the bounds for Val +// that have already been checked by a block emitted by one of the previous +// calls to switchConvert in the call stack. +BasicBlock *LowerSwitch::switchConvert(CaseItr Begin, CaseItr End, + ConstantInt *LowerBound, + ConstantInt *UpperBound, Value *Val, + BasicBlock *Predecessor, + BasicBlock *OrigBlock, + BasicBlock *Default) { unsigned Size = End - Begin; - if (Size == 1) + if (Size == 1) { + // Check if the Case Range is perfectly squeezed in between + // already checked Upper and Lower bounds. If it is then we can avoid + // emitting the code that checks if the value actually falls in the range + // because the bounds already tell us so. + if (Begin->Low == LowerBound && Begin->High == UpperBound) { + unsigned NumMergedCases = 0; + if (LowerBound && UpperBound) + NumMergedCases = + UpperBound->getSExtValue() - LowerBound->getSExtValue(); + fixPhis(Begin->BB, OrigBlock, Predecessor, NumMergedCases); + return Begin->BB; + } return newLeafBlock(*Begin, Val, OrigBlock, Default); + } unsigned Mid = Size / 2; std::vector LHS(Begin, Begin + Mid); - DOUT << "LHS: " << LHS << "\n"; + DEBUG(dbgs() << "LHS: " << LHS << "\n"); std::vector RHS(Begin + Mid, End); - DOUT << "RHS: " << RHS << "\n"; - - CaseRange& Pivot = *(Begin + Mid); - DEBUG( DOUT << "Pivot ==> " - << cast(Pivot.Low)->getValue().toStringSigned(10) - << " -" - << cast(Pivot.High)->getValue().toStringSigned(10) - << "\n"); + DEBUG(dbgs() << "RHS: " << RHS << "\n"); + + CaseRange &Pivot = *(Begin + Mid); + DEBUG(dbgs() << "Pivot ==> " + << cast(Pivot.Low)->getValue() + << " -" << cast(Pivot.High)->getValue() << "\n"); + + // NewLowerBound here should never be the integer minimal value. + // This is because it is computed from a case range that is never + // the smallest, so there is always a case range that has at least + // a smaller value. + ConstantInt *NewLowerBound = cast(Pivot.Low); + ConstantInt *NewUpperBound; + + // If we don't have a Default block then it means that we can never + // have a value outside of a case range, so set the UpperBound to the highest + // value in the LHS part of the case ranges. + if (Default != nullptr) { + // Because NewLowerBound is never the smallest representable integer + // it is safe here to subtract one. + NewUpperBound = ConstantInt::get(NewLowerBound->getContext(), + NewLowerBound->getValue() - 1); + } else { + CaseItr LastLHS = LHS.begin() + LHS.size() - 1; + NewUpperBound = cast(LastLHS->High); + } - BasicBlock* LBranch = switchConvert(LHS.begin(), LHS.end(), Val, - OrigBlock, Default); - BasicBlock* RBranch = switchConvert(RHS.begin(), RHS.end(), Val, - OrigBlock, Default); + DEBUG(dbgs() << "LHS Bounds ==> "; + if (LowerBound) { + dbgs() << cast(LowerBound)->getSExtValue(); + } else { + dbgs() << "NONE"; + } + dbgs() << " - " << NewUpperBound->getSExtValue() << "\n"; + dbgs() << "RHS Bounds ==> "; + dbgs() << NewLowerBound->getSExtValue() << " - "; + if (UpperBound) { + dbgs() << cast(UpperBound)->getSExtValue() << "\n"; + } else { + dbgs() << "NONE\n"; + }); // Create a new node that checks if the value is < pivot. Go to the // left branch if it is and right branch if not. Function* F = OrigBlock->getParent(); - BasicBlock* NewNode = BasicBlock::Create("NodeBlock"); + BasicBlock* NewNode = BasicBlock::Create(Val->getContext(), "NodeBlock"); + + ICmpInst* Comp = new ICmpInst(ICmpInst::ICMP_SLT, + Val, Pivot.Low, "Pivot"); + + BasicBlock *LBranch = switchConvert(LHS.begin(), LHS.end(), LowerBound, + NewUpperBound, Val, NewNode, OrigBlock, + Default); + BasicBlock *RBranch = switchConvert(RHS.begin(), RHS.end(), NewLowerBound, + UpperBound, Val, NewNode, OrigBlock, + Default); + Function::iterator FI = OrigBlock; F->getBasicBlockList().insert(++FI, NewNode); - - ICmpInst* Comp = new ICmpInst(ICmpInst::ICMP_SLT, Val, Pivot.Low, "Pivot"); NewNode->getInstList().push_back(Comp); + BranchInst::Create(LBranch, RBranch, Comp, NewNode); return NewNode; } @@ -179,35 +276,35 @@ BasicBlock* LowerSwitch::newLeafBlock(CaseRange& Leaf, Value* Val, BasicBlock* Default) { Function* F = OrigBlock->getParent(); - BasicBlock* NewLeaf = BasicBlock::Create("LeafBlock"); + BasicBlock* NewLeaf = BasicBlock::Create(Val->getContext(), "LeafBlock"); Function::iterator FI = OrigBlock; F->getBasicBlockList().insert(++FI, NewLeaf); // Emit comparison - ICmpInst* Comp = NULL; + ICmpInst* Comp = nullptr; if (Leaf.Low == Leaf.High) { // Make the seteq instruction... - Comp = new ICmpInst(ICmpInst::ICMP_EQ, Val, Leaf.Low, - "SwitchLeaf", NewLeaf); + Comp = new ICmpInst(*NewLeaf, ICmpInst::ICMP_EQ, Val, + Leaf.Low, "SwitchLeaf"); } else { // Make range comparison if (cast(Leaf.Low)->isMinValue(true /*isSigned*/)) { // Val >= Min && Val <= Hi --> Val <= Hi - Comp = new ICmpInst(ICmpInst::ICMP_SLE, Val, Leaf.High, - "SwitchLeaf", NewLeaf); + Comp = new ICmpInst(*NewLeaf, ICmpInst::ICMP_SLE, Val, Leaf.High, + "SwitchLeaf"); } else if (cast(Leaf.Low)->isZero()) { // Val >= 0 && Val <= Hi --> Val <=u Hi - Comp = new ICmpInst(ICmpInst::ICMP_ULE, Val, Leaf.High, - "SwitchLeaf", NewLeaf); + Comp = new ICmpInst(*NewLeaf, ICmpInst::ICMP_ULE, Val, Leaf.High, + "SwitchLeaf"); } else { // Emit V-Lo <=u Hi-Lo Constant* NegLo = ConstantExpr::getNeg(Leaf.Low); - Instruction* Add = BinaryOperator::createAdd(Val, NegLo, + Instruction* Add = BinaryOperator::CreateAdd(Val, NegLo, Val->getName()+".off", NewLeaf); Constant *UpperBound = ConstantExpr::getAdd(NegLo, Leaf.High); - Comp = new ICmpInst(ICmpInst::ICMP_ULE, Add, UpperBound, - "SwitchLeaf", NewLeaf); + Comp = new ICmpInst(*NewLeaf, ICmpInst::ICMP_ULE, Add, UpperBound, + "SwitchLeaf"); } } @@ -239,15 +336,16 @@ unsigned LowerSwitch::Clusterify(CaseVector& Cases, SwitchInst *SI) { unsigned numCmps = 0; // Start with "simple" cases - for (unsigned i = 1; i < SI->getNumSuccessors(); ++i) - Cases.push_back(CaseRange(SI->getSuccessorValue(i), - SI->getSuccessorValue(i), - SI->getSuccessor(i))); + for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end(); i != e; ++i) + Cases.push_back(CaseRange(i.getCaseValue(), i.getCaseValue(), + i.getCaseSuccessor())); + std::sort(Cases.begin(), Cases.end(), CaseCmp()); // Merge case into clusters if (Cases.size()>=2) - for (CaseItr I=Cases.begin(), J=next(Cases.begin()); J!=Cases.end(); ) { + for (CaseItr I = Cases.begin(), J = std::next(Cases.begin()); + J != Cases.end();) { int64_t nextValue = cast(J->Low)->getSExtValue(); int64_t currentValue = cast(I->High)->getSExtValue(); BasicBlock* nextBB = J->BB; @@ -279,23 +377,29 @@ void LowerSwitch::processSwitchInst(SwitchInst *SI) { BasicBlock *CurBlock = SI->getParent(); BasicBlock *OrigBlock = CurBlock; Function *F = CurBlock->getParent(); - Value *Val = SI->getOperand(0); // The value we are switching on... + Value *Val = SI->getCondition(); // The value we are switching on... BasicBlock* Default = SI->getDefaultDest(); // If there is only the default destination, don't bother with the code below. - if (SI->getNumOperands() == 2) { + if (!SI->getNumCases()) { BranchInst::Create(SI->getDefaultDest(), CurBlock); CurBlock->getInstList().erase(SI); return; } + const bool DefaultIsUnreachable = + Default->size() == 1 && isa(Default->getTerminator()); // Create a new, empty default block so that the new hierarchy of // if-then statements go to this and the PHI nodes are happy. - BasicBlock* NewDefault = BasicBlock::Create("NewDefault"); - F->getBasicBlockList().insert(Default, NewDefault); - - BranchInst::Create(Default, NewDefault); - + // if the default block is set as an unreachable we avoid creating one + // because will never be a valid target. + BasicBlock *NewDefault = nullptr; + if (!DefaultIsUnreachable) { + NewDefault = BasicBlock::Create(SI->getContext(), "NewDefault"); + F->getBasicBlockList().insert(Default, NewDefault); + + BranchInst::Create(Default, NewDefault); + } // If there is an entry in any PHI nodes for the default edge, make sure // to update them as well. for (BasicBlock::iterator I = Default->begin(); isa(I); ++I) { @@ -309,16 +413,36 @@ void LowerSwitch::processSwitchInst(SwitchInst *SI) { CaseVector Cases; unsigned numCmps = Clusterify(Cases, SI); - DOUT << "Clusterify finished. Total clusters: " << Cases.size() - << ". Total compares: " << numCmps << "\n"; - DOUT << "Cases: " << Cases << "\n"; + DEBUG(dbgs() << "Clusterify finished. Total clusters: " << Cases.size() + << ". Total compares: " << numCmps << "\n"); + DEBUG(dbgs() << "Cases: " << Cases << "\n"); + (void)numCmps; - BasicBlock* SwitchBlock = switchConvert(Cases.begin(), Cases.end(), Val, - OrigBlock, NewDefault); + ConstantInt *UpperBound = nullptr; + ConstantInt *LowerBound = nullptr; + + // Optimize the condition where Default is an unreachable block. In this case + // we can make the bounds tightly fitted around the case value ranges, + // because we know that the value passed to the switch should always be + // exactly one of the case values. + if (DefaultIsUnreachable) { + CaseItr LastCase = Cases.begin() + Cases.size() - 1; + UpperBound = cast(LastCase->High); + LowerBound = cast(Cases.begin()->Low); + } + BasicBlock *SwitchBlock = + switchConvert(Cases.begin(), Cases.end(), LowerBound, UpperBound, Val, + OrigBlock, OrigBlock, NewDefault); // Branch to our shiny new if-then stuff... BranchInst::Create(SwitchBlock, OrigBlock); // We are now done with the switch instruction, delete it. CurBlock->getInstList().erase(SI); + + pred_iterator PI = pred_begin(Default), E = pred_end(Default); + // If the Default block has no more predecessors just remove it + if (PI == E) { + DeleteDeadBlock(Default); + } }