From ad993521accbdec06983d9d4c5921cb642e64167 Mon Sep 17 00:00:00 2001 From: Florian Hahn Date: Sat, 15 Jul 2017 13:13:19 +0000 Subject: [PATCH] [LoopInterchange] Add some optimization remarks. Reviewers: anemet, karthikthecool, blitz.opensource Reviewed By: anemet Subscribers: mzolotukhin, llvm-commits Differential Revision: https://reviews.llvm.org/D35122 llvm-svn: 308094 --- .../lib/Transforms/Scalar/LoopInterchange.cpp | 119 +++++++++- .../loop-interchange-optimization-remarks.ll | 220 ++++++++++++++++++ 2 files changed, 330 insertions(+), 9 deletions(-) create mode 100644 llvm/test/Transforms/LoopInterchange/loop-interchange-optimization-remarks.ll diff --git a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp index 606136dc31a4..2e0d8e0374c0 100644 --- a/llvm/lib/Transforms/Scalar/LoopInterchange.cpp +++ b/llvm/lib/Transforms/Scalar/LoopInterchange.cpp @@ -22,6 +22,7 @@ #include "llvm/Analysis/LoopInfo.h" #include "llvm/Analysis/LoopIterator.h" #include "llvm/Analysis/LoopPass.h" +#include "llvm/Analysis/OptimizationDiagnosticInfo.h" #include "llvm/Analysis/ScalarEvolution.h" #include "llvm/Analysis/ScalarEvolutionExpander.h" #include "llvm/Analysis/ScalarEvolutionExpressions.h" @@ -323,9 +324,10 @@ static PHINode *getInductionVariable(Loop *L, ScalarEvolution *SE) { class LoopInterchangeLegality { public: LoopInterchangeLegality(Loop *Outer, Loop *Inner, ScalarEvolution *SE, - LoopInfo *LI, DominatorTree *DT, bool PreserveLCSSA) + LoopInfo *LI, DominatorTree *DT, bool PreserveLCSSA, + OptimizationRemarkEmitter *ORE) : OuterLoop(Outer), InnerLoop(Inner), SE(SE), LI(LI), DT(DT), - PreserveLCSSA(PreserveLCSSA), InnerLoopHasReduction(false) {} + PreserveLCSSA(PreserveLCSSA), ORE(ORE), InnerLoopHasReduction(false) {} /// Check if the loops can be interchanged. bool canInterchangeLoops(unsigned InnerLoopId, unsigned OuterLoopId, @@ -353,6 +355,8 @@ private: LoopInfo *LI; DominatorTree *DT; bool PreserveLCSSA; + /// Interface to emit optimization remarks. + OptimizationRemarkEmitter *ORE; bool InnerLoopHasReduction; }; @@ -361,8 +365,9 @@ private: /// loop. class LoopInterchangeProfitability { public: - LoopInterchangeProfitability(Loop *Outer, Loop *Inner, ScalarEvolution *SE) - : OuterLoop(Outer), InnerLoop(Inner), SE(SE) {} + LoopInterchangeProfitability(Loop *Outer, Loop *Inner, ScalarEvolution *SE, + OptimizationRemarkEmitter *ORE) + : OuterLoop(Outer), InnerLoop(Inner), SE(SE), ORE(ORE) {} /// Check if the loop interchange is profitable. bool isProfitable(unsigned InnerLoopId, unsigned OuterLoopId, @@ -376,6 +381,8 @@ private: /// Scev analysis. ScalarEvolution *SE; + /// Interface to emit optimization remarks. + OptimizationRemarkEmitter *ORE; }; /// LoopInterchangeTransform interchanges the loop. @@ -422,6 +429,9 @@ struct LoopInterchange : public FunctionPass { DependenceInfo *DI; DominatorTree *DT; bool PreserveLCSSA; + /// Interface to emit optimization remarks. + OptimizationRemarkEmitter *ORE; + LoopInterchange() : FunctionPass(ID), SE(nullptr), LI(nullptr), DI(nullptr), DT(nullptr) { initializeLoopInterchangePass(*PassRegistry::getPassRegistry()); @@ -435,6 +445,7 @@ struct LoopInterchange : public FunctionPass { AU.addRequired(); AU.addRequiredID(LoopSimplifyID); AU.addRequiredID(LCSSAID); + AU.addRequired(); } bool runOnFunction(Function &F) override { @@ -446,6 +457,7 @@ struct LoopInterchange : public FunctionPass { DI = &getAnalysis().getDI(); auto *DTWP = getAnalysisIfAvailable(); DT = DTWP ? &DTWP->getDomTree() : nullptr; + ORE = &getAnalysis().getORE(); PreserveLCSSA = mustPreserveAnalysisID(LCSSAID); // Build up a worklist of loop pairs to analyze. @@ -575,18 +587,23 @@ struct LoopInterchange : public FunctionPass { Loop *OuterLoop = LoopList[OuterLoopId]; LoopInterchangeLegality LIL(OuterLoop, InnerLoop, SE, LI, DT, - PreserveLCSSA); + PreserveLCSSA, ORE); if (!LIL.canInterchangeLoops(InnerLoopId, OuterLoopId, DependencyMatrix)) { DEBUG(dbgs() << "Not interchanging Loops. Cannot prove legality\n"); return false; } DEBUG(dbgs() << "Loops are legal to interchange\n"); - LoopInterchangeProfitability LIP(OuterLoop, InnerLoop, SE); + LoopInterchangeProfitability LIP(OuterLoop, InnerLoop, SE, ORE); if (!LIP.isProfitable(InnerLoopId, OuterLoopId, DependencyMatrix)) { DEBUG(dbgs() << "Interchanging loops not profitable\n"); return false; } + ORE->emit(OptimizationRemark(DEBUG_TYPE, "Interchanged", + InnerLoop->getStartLoc(), + InnerLoop->getHeader()) + << "Loop interchanged with enclosing loop."); + LoopInterchangeTransform LIT(OuterLoop, InnerLoop, SE, LI, DT, LoopNestExit, LIL.hasInnerLoopReduction()); LIT.transform(); @@ -760,6 +777,12 @@ bool LoopInterchangeLegality::currentLimitations() { if (!findInductionAndReductions(InnerLoop, Inductions, Reductions)) { DEBUG(dbgs() << "Only inner loops with induction or reduction PHI nodes " << "are supported currently.\n"); + ORE->emit(OptimizationRemarkMissed(DEBUG_TYPE, + "UnsupportedPHIInner", + InnerLoop->getStartLoc(), + InnerLoop->getHeader()) + << "Only inner loops with induction or reduction PHI nodes can be" + " interchange currently."); return true; } @@ -767,6 +790,12 @@ bool LoopInterchangeLegality::currentLimitations() { if (Inductions.size() != 1) { DEBUG(dbgs() << "We currently only support loops with 1 induction variable." << "Failed to interchange due to current limitation\n"); + ORE->emit(OptimizationRemarkMissed(DEBUG_TYPE, + "MultiInductionInner", + InnerLoop->getStartLoc(), + InnerLoop->getHeader()) + << "Only inner loops with 1 induction variable can be " + "interchanged currently."); return true; } if (Reductions.size() > 0) @@ -777,6 +806,12 @@ bool LoopInterchangeLegality::currentLimitations() { if (!findInductionAndReductions(OuterLoop, Inductions, Reductions)) { DEBUG(dbgs() << "Only outer loops with induction or reduction PHI nodes " << "are supported currently.\n"); + ORE->emit(OptimizationRemarkMissed(DEBUG_TYPE, + "UnsupportedPHIOuter", + OuterLoop->getStartLoc(), + OuterLoop->getHeader()) + << "Only outer loops with induction or reduction PHI nodes can be" + " interchanged currently."); return true; } @@ -785,18 +820,35 @@ bool LoopInterchangeLegality::currentLimitations() { if (!Reductions.empty()) { DEBUG(dbgs() << "Outer loops with reductions are not supported " << "currently.\n"); + ORE->emit(OptimizationRemarkMissed(DEBUG_TYPE, + "ReductionsOuter", + OuterLoop->getStartLoc(), + OuterLoop->getHeader()) + << "Outer loops with reductions cannot be interchangeed " + "currently."); return true; } // TODO: Currently we handle only loops with 1 induction variable. if (Inductions.size() != 1) { DEBUG(dbgs() << "Loops with more than 1 induction variables are not " << "supported currently.\n"); + ORE->emit(OptimizationRemarkMissed(DEBUG_TYPE, + "MultiIndutionOuter", + OuterLoop->getStartLoc(), + OuterLoop->getHeader()) + << "Only outer loops with 1 induction variable can be " + "interchanged currently."); return true; } // TODO: Triangular loops are not handled for now. if (!isLoopStructureUnderstood(InnerInductionVar)) { DEBUG(dbgs() << "Loop structure not understood by pass\n"); + ORE->emit(OptimizationRemarkMissed(DEBUG_TYPE, + "UnsupportedStructureInner", + InnerLoop->getStartLoc(), + InnerLoop->getHeader()) + << "Inner loop structure not understood currently."); return true; } @@ -805,12 +857,24 @@ bool LoopInterchangeLegality::currentLimitations() { getLoopLatchExitBlock(OuterLoopLatch, OuterLoopHeader); if (!LoopExitBlock || !containsSafePHI(LoopExitBlock, true)) { DEBUG(dbgs() << "Can only handle LCSSA PHIs in outer loops currently.\n"); + ORE->emit(OptimizationRemarkMissed(DEBUG_TYPE, + "NoLCSSAPHIOuter", + OuterLoop->getStartLoc(), + OuterLoop->getHeader()) + << "Only outer loops with LCSSA PHIs can be interchange " + "currently."); return true; } LoopExitBlock = getLoopLatchExitBlock(InnerLoopLatch, InnerLoopHeader); if (!LoopExitBlock || !containsSafePHI(LoopExitBlock, false)) { DEBUG(dbgs() << "Can only handle LCSSA PHIs in inner loops currently.\n"); + ORE->emit(OptimizationRemarkMissed(DEBUG_TYPE, + "NoLCSSAPHIOuterInner", + InnerLoop->getStartLoc(), + InnerLoop->getHeader()) + << "Only inner loops with LCSSA PHIs can be interchange " + "currently."); return true; } @@ -835,6 +899,11 @@ bool LoopInterchangeLegality::currentLimitations() { if (!InnerIndexVarInc) { DEBUG(dbgs() << "Did not find an instruction to increment the induction " << "variable.\n"); + ORE->emit(OptimizationRemarkMissed(DEBUG_TYPE, + "NoIncrementInInner", + InnerLoop->getStartLoc(), + InnerLoop->getHeader()) + << "The inner loop does not increment the induction variable."); return true; } @@ -852,6 +921,12 @@ bool LoopInterchangeLegality::currentLimitations() { if (!I.isIdenticalTo(InnerIndexVarInc)) { DEBUG(dbgs() << "Found unsupported instructions between induction " << "variable increment and branch.\n"); + ORE->emit(OptimizationRemarkMissed(DEBUG_TYPE, + "UnsupportedInsBetweenInduction", + InnerLoop->getStartLoc(), + InnerLoop->getHeader()) + << "Found unsupported instruction between induction variable " + "increment and branch."); return true; } @@ -862,6 +937,11 @@ bool LoopInterchangeLegality::currentLimitations() { // current limitation. if (!FoundInduction) { DEBUG(dbgs() << "Did not find the induction variable.\n"); + ORE->emit(OptimizationRemarkMissed(DEBUG_TYPE, + "NoIndutionVariable", + InnerLoop->getStartLoc(), + InnerLoop->getHeader()) + << "Did not find the induction variable."); return true; } return false; @@ -875,6 +955,11 @@ bool LoopInterchangeLegality::canInterchangeLoops(unsigned InnerLoopId, DEBUG(dbgs() << "Failed interchange InnerLoopId = " << InnerLoopId << " and OuterLoopId = " << OuterLoopId << " due to dependence\n"); + ORE->emit(OptimizationRemarkMissed(DEBUG_TYPE, + "Dependence", + InnerLoop->getStartLoc(), + InnerLoop->getHeader()) + << "Cannot interchange loops due to dependences."); return false; } @@ -910,6 +995,12 @@ bool LoopInterchangeLegality::canInterchangeLoops(unsigned InnerLoopId, // Check if the loops are tightly nested. if (!tightlyNested(OuterLoop, InnerLoop)) { DEBUG(dbgs() << "Loops not tightly nested\n"); + ORE->emit(OptimizationRemarkMissed(DEBUG_TYPE, + "NotTightlyNested", + InnerLoop->getStartLoc(), + InnerLoop->getHeader()) + << "Cannot interchange loops because they are not tightly " + "nested."); return false; } @@ -1005,9 +1096,18 @@ bool LoopInterchangeProfitability::isProfitable(unsigned InnerLoopId, // It is not profitable as per current cache profitability model. But check if // we can move this loop outside to improve parallelism. - bool ImprovesPar = - isProfitableForVectorization(InnerLoopId, OuterLoopId, DepMatrix); - return ImprovesPar; + if (isProfitableForVectorization(InnerLoopId, OuterLoopId, DepMatrix)) + return true; + + ORE->emit(OptimizationRemarkMissed(DEBUG_TYPE, + "InterchangeNotProfitable", + InnerLoop->getStartLoc(), + InnerLoop->getHeader()) + << "Interchanging loops is too costly (cost=" + << ore::NV("Cost", Cost) << ", threshold=" + << ore::NV("Threshold", LoopInterchangeCostThreshold) << + ") and it does not improve parallelism."); + return false; } void LoopInterchangeTransform::removeChildLoop(Loop *OuterLoop, @@ -1291,6 +1391,7 @@ INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass) INITIALIZE_PASS_DEPENDENCY(LoopSimplify) INITIALIZE_PASS_DEPENDENCY(LCSSAWrapperPass) INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass) +INITIALIZE_PASS_DEPENDENCY(OptimizationRemarkEmitterWrapperPass) INITIALIZE_PASS_END(LoopInterchange, "loop-interchange", "Interchanges loops for cache reuse", false, false) diff --git a/llvm/test/Transforms/LoopInterchange/loop-interchange-optimization-remarks.ll b/llvm/test/Transforms/LoopInterchange/loop-interchange-optimization-remarks.ll new file mode 100644 index 000000000000..e14598cfdd60 --- /dev/null +++ b/llvm/test/Transforms/LoopInterchange/loop-interchange-optimization-remarks.ll @@ -0,0 +1,220 @@ +; Test optimization remarks generated by the LoopInterchange pass. +; +; RUN: opt < %s -basicaa -loop-interchange -pass-remarks-output=%t -pass-remarks-missed='loop-interchange' \ +; RUN: -pass-remarks='loop-interchange' -S +; RUN: cat %t | FileCheck %s + +@A = common global [100 x [100 x i32]] zeroinitializer +@B = common global [100 x [100 x i32]] zeroinitializer +@C = common global [100 x i32] zeroinitializer + +;;---------------------------------------Test case 01--------------------------------- +;; Loops interchange is not profitable. +;; for(int i=1;i