From a0b3909d432e9f2c79aee8ec3133f9b9ec71dc1a Mon Sep 17 00:00:00 2001 From: Devang Patel Date: Tue, 26 Aug 2008 17:57:54 +0000 Subject: [PATCH] If IV is used in a int-to-float cast inside the loop then try to eliminate the cast operation. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55374 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Scalar/LoopStrengthReduce.cpp | 120 +++++++++++++++++- .../LoopStrengthReduce/2008-08-14-ShadowIV.ll | 1 - 2 files changed, 118 insertions(+), 3 deletions(-) diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp index 04faa0aa508..c5a9c1f0a1c 100644 --- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp +++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp @@ -45,6 +45,7 @@ STATISTIC(NumReduced , "Number of GEPs strength reduced"); STATISTIC(NumInserted, "Number of PHIs inserted"); STATISTIC(NumVariable, "Number of PHIs with variable strides"); STATISTIC(NumEliminated , "Number of strides eliminated"); +STATISTIC(NumShadow , "Number of Shadow IVs optimized"); namespace { @@ -164,6 +165,7 @@ namespace { AU.addRequired(); AU.addRequired(); AU.addRequired(); + AU.addPreserved(); } /// getCastedVersionOf - Return the specified value casted to uintptr_t. @@ -177,8 +179,13 @@ private: IVStrideUse* &CondUse, const SCEVHandle* &CondStride); void OptimizeIndvars(Loop *L); + + /// OptimizeShadowIV - If IV is used in a int-to-float cast + /// inside the loop then try to eliminate the cast opeation. + void OptimizeShadowIV(Loop *L); + bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse, - const SCEVHandle *&CondStride); + const SCEVHandle *&CondStride); bool RequiresTypeConversion(const Type *Ty, const Type *NewTy); unsigned CheckForIVReuse(bool, bool, const SCEVHandle&, IVExpr&, const Type*, @@ -1689,12 +1696,122 @@ ICmpInst *LoopStrengthReduce::ChangeCompareStride(Loop *L, ICmpInst *Cond, return Cond; } +/// OptimizeShadowIV - If IV is used in a int-to-float cast +/// inside the loop then try to eliminate the cast opeation. +void LoopStrengthReduce::OptimizeShadowIV(Loop *L) { + + SCEVHandle IterationCount = SE->getIterationCount(L); + if (isa(IterationCount)) + return; + + for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e; + ++Stride) { + std::map::iterator SI = + IVUsesByStride.find(StrideOrder[Stride]); + assert(SI != IVUsesByStride.end() && "Stride doesn't exist!"); + if (!isa(SI->first)) + continue; + + for (std::vector::iterator UI = SI->second.Users.begin(), + E = SI->second.Users.end(); UI != E; /* empty */) { + std::vector::iterator CandidateUI = UI; + UI++; + Instruction *ShadowUse = CandidateUI->User; + const Type *DestTy = NULL; + + /* If shadow use is a int->float cast then insert a second IV + to elminate this cast. + + for (unsigned i = 0; i < n; ++i) + foo((double)i); + + is trnasformed into + + double d = 0.0; + for (unsigned i = 0; i < n; ++i, ++d) + foo(d); + */ + UIToFPInst *UCast = dyn_cast(CandidateUI->User); + if (UCast) + DestTy = UCast->getDestTy(); + else { + SIToFPInst *SCast = dyn_cast(CandidateUI->User); + if (!SCast) continue; + DestTy = SCast->getDestTy(); + } + + PHINode *PH = dyn_cast(ShadowUse->getOperand(0)); + if (!PH) continue; + if (PH->getNumIncomingValues() != 2) continue; + + const Type *SrcTy = PH->getType(); + int Mantissa = DestTy->getFPMantissaWidth(); + if (Mantissa == -1) continue; + if ((int)TD->getTypeSizeInBits(SrcTy) > Mantissa) + continue; + + unsigned Entry, Latch; + if (PH->getIncomingBlock(0) == L->getLoopPreheader()) { + Entry = 0; + Latch = 1; + } else { + Entry = 1; + Latch = 0; + } + + ConstantInt *Init = dyn_cast(PH->getIncomingValue(Entry)); + if (!Init) continue; + ConstantFP *NewInit = ConstantFP::get(DestTy, Init->getZExtValue()); + + BinaryOperator *Incr = + dyn_cast(PH->getIncomingValue(Latch)); + if (!Incr) continue; + if (Incr->getOpcode() != Instruction::Add + && Incr->getOpcode() != Instruction::Sub) + continue; + + /* Initialize new IV, double d = 0.0 in above example. */ + ConstantInt *C = NULL; + if (Incr->getOperand(0) == PH) + C = dyn_cast(Incr->getOperand(1)); + else if (Incr->getOperand(1) == PH) + C = dyn_cast(Incr->getOperand(0)); + else + continue; + + if (!C) continue; + + /* Add new PHINode. */ + PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH); + + /* create new icnrement. '++d' in above example. */ + ConstantFP *CFP = ConstantFP::get(DestTy, C->getZExtValue()); + BinaryOperator *NewIncr = + BinaryOperator::Create(Incr->getOpcode(), + NewPH, CFP, "IV.S.next.", Incr); + + NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry)); + NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch)); + + /* Remove cast operation */ + SE->deleteValueFromRecords(ShadowUse); + ShadowUse->replaceAllUsesWith(NewPH); + ShadowUse->eraseFromParent(); + SI->second.Users.erase(CandidateUI); + NumShadow++; + break; + } + } +} + // OptimizeIndvars - Now that IVUsesByStride is set up with all of the indvar // uses in the loop, look to see if we can eliminate some, in favor of using // common indvars for the different uses. void LoopStrengthReduce::OptimizeIndvars(Loop *L) { // TODO: implement optzns here. + OptimizeShadowIV(L); + // Finally, get the terminating condition for the loop if possible. If we // can, we want to change it to use a post-incremented version of its // induction variable, to allow coalescing the live ranges for the IV into @@ -1852,6 +1969,5 @@ bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager &LPM) { } DeleteTriviallyDeadInstructions(DeadInsts); } - return Changed; } diff --git a/test/Transforms/LoopStrengthReduce/2008-08-14-ShadowIV.ll b/test/Transforms/LoopStrengthReduce/2008-08-14-ShadowIV.ll index 3169f3d9b44..2377589b0eb 100644 --- a/test/Transforms/LoopStrengthReduce/2008-08-14-ShadowIV.ll +++ b/test/Transforms/LoopStrengthReduce/2008-08-14-ShadowIV.ll @@ -1,5 +1,4 @@ ; RUN: llvm-as < %s | opt -loop-reduce | llvm-dis | grep "phi double" | count 1 -; XFAIL: * define void @foobar(i32 %n) nounwind { entry: -- 2.34.1