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author | Devang Patel <dpatel@apple.com> | 2008-08-14 20:58:31 +0000 |
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committer | Devang Patel <dpatel@apple.com> | 2008-08-14 20:58:31 +0000 |
commit | 79ceb4463efc699c8aa1647d4ecbc15bed19e1c9 (patch) | |
tree | c32e28beb1c4b5af12d1c466f6be2ee3ecef3613 /lib/Transforms | |
parent | 9d7f0b76aac3bf0524e9285101e34c15e1e2c599 (diff) | |
download | llvm-79ceb4463efc699c8aa1647d4ecbc15bed19e1c9.tar.gz llvm-79ceb4463efc699c8aa1647d4ecbc15bed19e1c9.tar.bz2 llvm-79ceb4463efc699c8aa1647d4ecbc15bed19e1c9.tar.xz |
If IV is used in a int-to-float cast inside the loop then try to eliminate the cast opeation.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@54786 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms')
-rw-r--r-- | lib/Transforms/Scalar/LoopStrengthReduce.cpp | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp index 04faa0aa50..37a93e114a 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 Shdow IVs optimized"); namespace { @@ -177,6 +178,10 @@ 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); bool RequiresTypeConversion(const Type *Ty, const Type *NewTy); @@ -1689,12 +1694,108 @@ 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) { + + for (unsigned Stride = 0, e = StrideOrder.size(); Stride != e; + ++Stride) { + std::map<SCEVHandle, IVUsersOfOneStride>::iterator SI = + IVUsesByStride.find(StrideOrder[Stride]); + assert(SI != IVUsesByStride.end() && "Stride doesn't exist!"); + + for (std::vector<IVStrideUse>::iterator UI = SI->second.Users.begin(), + E = SI->second.Users.end(); UI != E; /* empty */) { + std::vector<IVStrideUse>::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<UIToFPInst>(CandidateUI->User); + if (UCast) + DestTy = UCast->getDestTy(); + else { + SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->User); + if (!SCast) continue; + DestTy = SCast->getDestTy(); + } + + PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0)); + if (!PH) continue; + if (PH->getNumIncomingValues() != 2) continue; + + unsigned Entry, Latch; + if (PH->getIncomingBlock(0) == L->getLoopPreheader()) { + Entry = 0; + Latch = 1; + } else { + Entry = 1; + Latch = 0; + } + + ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry)); + if (!Init) continue; + ConstantFP *NewInit = ConstantFP::get(DestTy, Init->getZExtValue()); + + BinaryOperator *Incr = + dyn_cast<BinaryOperator>(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<ConstantInt>(Incr->getOperand(1)); + else if (Incr->getOperand(1) == PH) + C = dyn_cast<ConstantInt>(Incr->getOperand(0)); + else + continue; + + if (!C) continue; + + /* create new icnrement. '++d' in above example. */ + ConstantFP *CFP = ConstantFP::get(DestTy, C->getZExtValue()); + BinaryOperator *NewIncr = + BinaryOperator::Create(Incr->getOpcode(), + NewInit, CFP, "IV.S.next.", Incr); + + /* Add new PHINode. */ + PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH); + NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry)); + NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch)); + + /* Remove cast operation */ + 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 |