diff options
| -rw-r--r-- | lib/Transforms/Scalar/LoopIndexSplit.cpp | 153 |
1 files changed, 93 insertions, 60 deletions
diff --git a/lib/Transforms/Scalar/LoopIndexSplit.cpp b/lib/Transforms/Scalar/LoopIndexSplit.cpp index eb1a5b1..37adeef 100644 --- a/lib/Transforms/Scalar/LoopIndexSplit.cpp +++ b/lib/Transforms/Scalar/LoopIndexSplit.cpp @@ -46,6 +46,28 @@ namespace { } private: + + class SplitInfo { + public: + SplitInfo() : IndVar(NULL), SplitValue(NULL), ExitValue(NULL), + SplitCondition(NULL), ExitCondition(NULL) {} + // Induction variable whose range is being split by this transformation. + PHINode *IndVar; + + // Induction variable's range is split at this value. + Value *SplitValue; + + // Induction variable's final loop exit value. + Value *ExitValue; + + // This compare instruction compares IndVar against SplitValue. + ICmpInst *SplitCondition; + + // Loop exit condition. + ICmpInst *ExitCondition; + }; + + private: /// Find condition inside a loop that is suitable candidate for index split. void findSplitCondition(); @@ -54,17 +76,17 @@ namespace { /// entire (i.e. meaningful) loop body is dominated by this compare /// instruction then loop body is executed only for one iteration. In /// such case eliminate loop structure surrounding this loop body. For - bool processOneIterationLoop(LPPassManager &LPM); + bool processOneIterationLoop(SplitInfo &SD, LPPassManager &LPM); // If loop header includes loop variant instruction operands then // this loop may not be eliminated. - bool safeHeader(BasicBlock *BB); + bool safeHeader(SplitInfo &SD, BasicBlock *BB); // If Exit block includes loop variant instructions then this // loop may not be eliminated. - bool safeExitBlock(BasicBlock *BB); + bool safeExitBlock(SplitInfo &SD, BasicBlock *BB); - bool splitLoop(); + bool splitLoop(SplitInfo &SD); private: @@ -72,20 +94,7 @@ namespace { Loop *L; ScalarEvolution *SE; - // Induction variable whose range is being split by this transformation. - PHINode *IndVar; - - // Induction variable's range is split at this value. - Value *SplitValue; - - // Induction variable's final loop exit value. - Value *ExitValue; - - // This compare instruction compares IndVar against SplitValue. - ICmpInst *SplitCondition; - - // Loop exit condition. - ICmpInst *ExitCondition; + SmallVector<SplitInfo, 4> SplitData; }; char LoopIndexSplit::ID = 0; @@ -100,30 +109,51 @@ LoopPass *llvm::createLoopIndexSplitPass() { bool LoopIndexSplit::runOnLoop(Loop *IncomingLoop, LPPassManager &LPM) { bool Changed = false; L = IncomingLoop; - SplitCondition = NULL; + SE = &getAnalysis<ScalarEvolution>(); findSplitCondition(); - if (!SplitCondition) + if (SplitData.empty()) return false; - if (SplitCondition->getPredicate() == ICmpInst::ICMP_EQ) - // If it is possible to eliminate loop then do so. - Changed = processOneIterationLoop(LPM); - else - Changed = splitLoop(); + // First see if it is possible to eliminate loop itself or not. + for (SmallVector<SplitInfo, 4>::iterator SI = SplitData.begin(), + E = SplitData.end(); SI != E; ++SI) { + SplitInfo &SD = *SI; + if (SD.SplitCondition->getPredicate() == ICmpInst::ICMP_EQ) { + Changed = processOneIterationLoop(SD,LPM); + if (Changed) { + ++NumIndexSplit; + // If is loop is eliminated then nothing else to do here. + return Changed; + } + } + } + + for (SmallVector<SplitInfo, 4>::iterator SI = SplitData.begin(), + E = SplitData.end(); SI != E; ++SI) { + SplitInfo &SD = *SI; + + // ICM_EQs are already handled above. + if (SD.SplitCondition->getPredicate() == ICmpInst::ICMP_EQ) + continue; + + // FIXME : Collect Spliting cost for all SD. Only operate on profitable SDs. + Changed = splitLoop(SD); + } if (Changed) ++NumIndexSplit; - + return Changed; } /// Find condition inside a loop that is suitable candidate for index split. void LoopIndexSplit::findSplitCondition() { - BasicBlock *Header = L->getHeader(); + SplitInfo SD; + BasicBlock *Header = L->getHeader(); for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) { PHINode *PN = cast<PHINode>(I); @@ -140,29 +170,29 @@ void LoopIndexSplit::findSplitCondition() { for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E; ++UI) { if (ICmpInst *CI = dyn_cast<ICmpInst>(*UI)) { - SplitCondition = CI; + SD.SplitCondition = CI; break; } } // Valid SplitCondition's one operand is phi node and the other operand // is loop invariant. - if (SplitCondition) { - if (SplitCondition->getOperand(0) != PN) - SplitValue = SplitCondition->getOperand(0); + if (SD.SplitCondition) { + if (SD.SplitCondition->getOperand(0) != PN) + SD.SplitValue = SD.SplitCondition->getOperand(0); else - SplitValue = SplitCondition->getOperand(1); - SCEVHandle ValueSCEV = SE->getSCEV(SplitValue); + SD.SplitValue = SD.SplitCondition->getOperand(1); + SCEVHandle ValueSCEV = SE->getSCEV(SD.SplitValue); // If SplitValue is not invariant then SplitCondition is not appropriate. if (!ValueSCEV->isLoopInvariant(L)) - SplitCondition = NULL; + SD.SplitCondition = NULL; } // We are looking for only one split condition. - if (SplitCondition) { - IndVar = PN; - break; + if (SD.SplitCondition) { + SD.IndVar = PN; + SplitData.push_back(SD); } } } @@ -182,7 +212,7 @@ void LoopIndexSplit::findSplitCondition() { /// i = somevalue; /// loop_body /// } -bool LoopIndexSplit::processOneIterationLoop(LPPassManager &LPM) { +bool LoopIndexSplit::processOneIterationLoop(SplitInfo &SD, LPPassManager &LPM) { BasicBlock *Header = L->getHeader(); @@ -191,7 +221,7 @@ bool LoopIndexSplit::processOneIterationLoop(LPPassManager &LPM) { // If SplitCondition is not in loop header then this loop is not suitable // for this transformation. - if (SplitCondition->getParent() != Header) + if (SD.SplitCondition->getParent() != Header) return false; // If one of the Header block's successor is not an exit block then this @@ -209,12 +239,12 @@ bool LoopIndexSplit::processOneIterationLoop(LPPassManager &LPM) { // If loop header includes loop variant instruction operands then // this loop may not be eliminated. - if (!safeHeader(Header)) + if (!safeHeader(SD, Header)) return false; // If Exit block includes loop variant instructions then this // loop may not be eliminated. - if (!safeExitBlock(ExitBlock)) + if (!safeExitBlock(SD, ExitBlock)) return false; // Update CFG. @@ -235,7 +265,7 @@ bool LoopIndexSplit::processOneIterationLoop(LPPassManager &LPM) { BasicBlock *Preheader = L->getLoopPreheader(); Instruction *Terminator = Header->getTerminator(); - Value *StartValue = IndVar->getIncomingValueForBlock(Preheader); + Value *StartValue = SD.IndVar->getIncomingValueForBlock(Preheader); // Replace split condition in header. // Transform @@ -244,16 +274,19 @@ bool LoopIndexSplit::processOneIterationLoop(LPPassManager &LPM) { // c1 = icmp uge i32 SplitValue, StartValue // c2 = icmp ult i32 vSplitValue, ExitValue // and i32 c1, c2 - bool SignedPredicate = ExitCondition->isSignedPredicate(); + bool SignedPredicate = SD.ExitCondition->isSignedPredicate(); Instruction *C1 = new ICmpInst(SignedPredicate ? ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE, - SplitValue, StartValue, "lisplit", Terminator); + SD.SplitValue, StartValue, "lisplit", + Terminator); Instruction *C2 = new ICmpInst(SignedPredicate ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT, - SplitValue, ExitValue, "lisplit", Terminator); - Instruction *NSplitCond = BinaryOperator::createAnd(C1, C2, "lisplit", Terminator); - SplitCondition->replaceAllUsesWith(NSplitCond); - SplitCondition->eraseFromParent(); + SD.SplitValue, SD.ExitValue, "lisplit", + Terminator); + Instruction *NSplitCond = BinaryOperator::createAnd(C1, C2, "lisplit", + Terminator); + SD.SplitCondition->replaceAllUsesWith(NSplitCond); + SD.SplitCondition->eraseFromParent(); // Now, clear latch block. Remove instructions that are responsible // to increment induction variable. @@ -275,7 +308,7 @@ bool LoopIndexSplit::processOneIterationLoop(LPPassManager &LPM) { // If loop header includes loop variant instruction operands then // this loop can not be eliminated. This is used by processOneIterationLoop(). -bool LoopIndexSplit::safeHeader(BasicBlock *Header) { +bool LoopIndexSplit::safeHeader(SplitInfo &SD, BasicBlock *Header) { Instruction *Terminator = Header->getTerminator(); for(BasicBlock::iterator BI = Header->begin(), BE = Header->end(); @@ -287,7 +320,7 @@ bool LoopIndexSplit::safeHeader(BasicBlock *Header) { continue; // SplitCondition itself is OK. - if (I == SplitCondition) + if (I == SD.SplitCondition) continue; // Terminator is also harmless. @@ -303,7 +336,7 @@ bool LoopIndexSplit::safeHeader(BasicBlock *Header) { // If Exit block includes loop variant instructions then this // loop may not be eliminated. This is used by processOneIterationLoop(). -bool LoopIndexSplit::safeExitBlock(BasicBlock *ExitBlock) { +bool LoopIndexSplit::safeExitBlock(SplitInfo &SD, BasicBlock *ExitBlock) { Instruction *IndVarIncrement = NULL; @@ -334,7 +367,7 @@ bool LoopIndexSplit::safeExitBlock(BasicBlock *ExitBlock) { IndVarIncrement = I; } - if (IndVarIncrement && PN == IndVar && CI->isOne()) + if (IndVarIncrement && PN == SD.IndVar && CI->isOne()) continue; } @@ -345,7 +378,7 @@ bool LoopIndexSplit::safeExitBlock(BasicBlock *ExitBlock) { ++BI; Instruction *N = BI; if (N == ExitBlock->getTerminator()) { - ExitCondition = EC; + SD.ExitCondition = EC; continue; } } @@ -357,19 +390,19 @@ bool LoopIndexSplit::safeExitBlock(BasicBlock *ExitBlock) { // Check if Exit condition is comparing induction variable against // loop invariant value. If one operand is induction variable and // the other operand is loop invaraint then Exit condition is safe. - if (ExitCondition) { - Value *Op0 = ExitCondition->getOperand(0); - Value *Op1 = ExitCondition->getOperand(1); + if (SD.ExitCondition) { + Value *Op0 = SD.ExitCondition->getOperand(0); + Value *Op1 = SD.ExitCondition->getOperand(1); Instruction *Insn0 = dyn_cast<Instruction>(Op0); Instruction *Insn1 = dyn_cast<Instruction>(Op1); if (Insn0 && Insn0 == IndVarIncrement) - ExitValue = Op1; + SD.ExitValue = Op1; else if (Insn1 && Insn1 == IndVarIncrement) - ExitValue = Op0; + SD.ExitValue = Op0; - SCEVHandle ValueSCEV = SE->getSCEV(ExitValue); + SCEVHandle ValueSCEV = SE->getSCEV(SD.ExitValue); if (!ValueSCEV->isLoopInvariant(L)) return false; } @@ -378,7 +411,7 @@ bool LoopIndexSplit::safeExitBlock(BasicBlock *ExitBlock) { return true; } -bool LoopIndexSplit::splitLoop() { +bool LoopIndexSplit::splitLoop(SplitInfo &SD) { // FIXME :) return false; } |