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indvars: Added SimplifyIVUsers.
Interleave IV simplifications. Currently involves EliminateComparison and EliminateRemainder. Next I'll add EliminateExtend. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131210 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick
parent
6dcd413fbb
commit
aeee4616dd
@ -109,8 +109,11 @@ namespace {
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private:
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bool isValidRewrite(Value *FromVal, Value *ToVal);
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void EliminateIVComparisons();
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void EliminateIVRemainders();
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void SimplifyIVUsers();
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void EliminateIVComparison(ICmpInst *ICmp, Value *IVOperand);
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void EliminateIVRemainder(BinaryOperator *Rem,
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Value *IVOperand,
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bool isSigned);
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void RewriteNonIntegerIVs(Loop *L);
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const Type *WidenIVs(Loop *L, SCEVExpander &Rewriter);
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@ -451,96 +454,111 @@ void IndVarSimplify::RewriteNonIntegerIVs(Loop *L) {
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SE->forgetLoop(L);
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}
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void IndVarSimplify::EliminateIVComparisons() {
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// Look for ICmp users.
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/// SimplifyIVUsers - Iteratively perform simplification on IVUsers within this
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/// loop. IVUsers is treated as a worklist. Each successive simplification may
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/// push more users which may themselves be candidates for simplification.
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void IndVarSimplify::SimplifyIVUsers() {
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for (IVUsers::iterator I = IU->begin(), E = IU->end(); I != E; ++I) {
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IVStrideUse &UI = *I;
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ICmpInst *ICmp = dyn_cast<ICmpInst>(UI.getUser());
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if (!ICmp) continue;
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Instruction *UseInst = I->getUser();
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Value *IVOperand = I->getOperandValToReplace();
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bool Swapped = UI.getOperandValToReplace() == ICmp->getOperand(1);
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ICmpInst::Predicate Pred = ICmp->getPredicate();
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if (Swapped) Pred = ICmpInst::getSwappedPredicate(Pred);
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// Get the SCEVs for the ICmp operands.
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const SCEV *S = IU->getReplacementExpr(UI);
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const SCEV *X = SE->getSCEV(ICmp->getOperand(!Swapped));
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// Simplify unnecessary loops away.
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const Loop *ICmpLoop = LI->getLoopFor(ICmp->getParent());
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S = SE->getSCEVAtScope(S, ICmpLoop);
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X = SE->getSCEVAtScope(X, ICmpLoop);
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// If the condition is always true or always false, replace it with
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// a constant value.
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if (SE->isKnownPredicate(Pred, S, X))
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ICmp->replaceAllUsesWith(ConstantInt::getTrue(ICmp->getContext()));
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else if (SE->isKnownPredicate(ICmpInst::getInversePredicate(Pred), S, X))
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ICmp->replaceAllUsesWith(ConstantInt::getFalse(ICmp->getContext()));
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else
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if (ICmpInst *ICmp = dyn_cast<ICmpInst>(UseInst)) {
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EliminateIVComparison(ICmp, IVOperand);
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continue;
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}
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DEBUG(dbgs() << "INDVARS: Eliminated comparison: " << *ICmp << '\n');
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DeadInsts.push_back(ICmp);
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if (BinaryOperator *Rem = dyn_cast<BinaryOperator>(UseInst)) {
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bool isSigned = Rem->getOpcode() == Instruction::SRem;
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if (isSigned || Rem->getOpcode() == Instruction::URem) {
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EliminateIVRemainder(Rem, IVOperand, isSigned);
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continue;
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}
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}
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}
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}
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void IndVarSimplify::EliminateIVRemainders() {
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// Look for SRem and URem users.
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for (IVUsers::iterator I = IU->begin(), E = IU->end(); I != E; ++I) {
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IVStrideUse &UI = *I;
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BinaryOperator *Rem = dyn_cast<BinaryOperator>(UI.getUser());
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if (!Rem) continue;
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bool isSigned = Rem->getOpcode() == Instruction::SRem;
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if (!isSigned && Rem->getOpcode() != Instruction::URem)
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continue;
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// We're only interested in the case where we know something about
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// the numerator.
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if (UI.getOperandValToReplace() != Rem->getOperand(0))
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continue;
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// Get the SCEVs for the ICmp operands.
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const SCEV *S = SE->getSCEV(Rem->getOperand(0));
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const SCEV *X = SE->getSCEV(Rem->getOperand(1));
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// Simplify unnecessary loops away.
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const Loop *ICmpLoop = LI->getLoopFor(Rem->getParent());
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S = SE->getSCEVAtScope(S, ICmpLoop);
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X = SE->getSCEVAtScope(X, ICmpLoop);
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// i % n --> i if i is in [0,n).
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if ((!isSigned || SE->isKnownNonNegative(S)) &&
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SE->isKnownPredicate(isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
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S, X))
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Rem->replaceAllUsesWith(Rem->getOperand(0));
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else {
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// (i+1) % n --> (i+1)==n?0:(i+1) if i is in [0,n).
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const SCEV *LessOne =
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SE->getMinusSCEV(S, SE->getConstant(S->getType(), 1));
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if ((!isSigned || SE->isKnownNonNegative(LessOne)) &&
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SE->isKnownPredicate(isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
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LessOne, X)) {
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ICmpInst *ICmp = new ICmpInst(Rem, ICmpInst::ICMP_EQ,
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Rem->getOperand(0), Rem->getOperand(1),
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"tmp");
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SelectInst *Sel =
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SelectInst::Create(ICmp,
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ConstantInt::get(Rem->getType(), 0),
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Rem->getOperand(0), "tmp", Rem);
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Rem->replaceAllUsesWith(Sel);
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} else
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continue;
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}
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// Inform IVUsers about the new users.
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if (Instruction *I = dyn_cast<Instruction>(Rem->getOperand(0)))
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IU->AddUsersIfInteresting(I);
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DEBUG(dbgs() << "INDVARS: Simplified rem: " << *Rem << '\n');
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DeadInsts.push_back(Rem);
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void IndVarSimplify::EliminateIVComparison(ICmpInst *ICmp, Value *IVOperand) {
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unsigned IVOperIdx = 0;
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ICmpInst::Predicate Pred = ICmp->getPredicate();
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if (IVOperand != ICmp->getOperand(0)) {
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// Swapped
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assert(IVOperand == ICmp->getOperand(1) && "Can't find IVOperand");
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IVOperIdx = 1;
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Pred = ICmpInst::getSwappedPredicate(Pred);
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}
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// Get the SCEVs for the ICmp operands.
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const SCEV *S = SE->getSCEV(ICmp->getOperand(IVOperIdx));
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const SCEV *X = SE->getSCEV(ICmp->getOperand(1 - IVOperIdx));
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// Simplify unnecessary loops away.
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const Loop *ICmpLoop = LI->getLoopFor(ICmp->getParent());
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S = SE->getSCEVAtScope(S, ICmpLoop);
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X = SE->getSCEVAtScope(X, ICmpLoop);
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// If the condition is always true or always false, replace it with
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// a constant value.
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if (SE->isKnownPredicate(Pred, S, X))
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ICmp->replaceAllUsesWith(ConstantInt::getTrue(ICmp->getContext()));
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else if (SE->isKnownPredicate(ICmpInst::getInversePredicate(Pred), S, X))
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ICmp->replaceAllUsesWith(ConstantInt::getFalse(ICmp->getContext()));
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else
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return;
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DEBUG(dbgs() << "INDVARS: Eliminated comparison: " << *ICmp << '\n');
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DeadInsts.push_back(ICmp);
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}
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void IndVarSimplify::EliminateIVRemainder(BinaryOperator *Rem,
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Value *IVOperand,
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bool isSigned) {
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// We're only interested in the case where we know something about
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// the numerator.
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if (IVOperand != Rem->getOperand(0))
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return;
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// Get the SCEVs for the ICmp operands.
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const SCEV *S = SE->getSCEV(Rem->getOperand(0));
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const SCEV *X = SE->getSCEV(Rem->getOperand(1));
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// Simplify unnecessary loops away.
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const Loop *ICmpLoop = LI->getLoopFor(Rem->getParent());
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S = SE->getSCEVAtScope(S, ICmpLoop);
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X = SE->getSCEVAtScope(X, ICmpLoop);
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// i % n --> i if i is in [0,n).
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if ((!isSigned || SE->isKnownNonNegative(S)) &&
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SE->isKnownPredicate(isSigned ? ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
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S, X))
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Rem->replaceAllUsesWith(Rem->getOperand(0));
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else {
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// (i+1) % n --> (i+1)==n?0:(i+1) if i is in [0,n).
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const SCEV *LessOne =
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SE->getMinusSCEV(S, SE->getConstant(S->getType(), 1));
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if (isSigned && !SE->isKnownNonNegative(LessOne))
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return;
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if (!SE->isKnownPredicate(isSigned ?
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ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
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LessOne, X))
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return;
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ICmpInst *ICmp = new ICmpInst(Rem, ICmpInst::ICMP_EQ,
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Rem->getOperand(0), Rem->getOperand(1),
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"tmp");
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SelectInst *Sel =
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SelectInst::Create(ICmp,
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ConstantInt::get(Rem->getType(), 0),
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Rem->getOperand(0), "tmp", Rem);
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Rem->replaceAllUsesWith(Sel);
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}
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// Inform IVUsers about the new users.
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if (Instruction *I = dyn_cast<Instruction>(Rem->getOperand(0)))
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IU->AddUsersIfInteresting(I);
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DEBUG(dbgs() << "INDVARS: Simplified rem: " << *Rem << '\n');
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DeadInsts.push_back(Rem);
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}
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bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
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@ -589,11 +607,7 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
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if (!isa<SCEVCouldNotCompute>(BackedgeTakenCount))
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RewriteLoopExitValues(L, Rewriter);
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// Simplify ICmp IV users.
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EliminateIVComparisons();
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// Simplify SRem and URem IV users.
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EliminateIVRemainders();
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SimplifyIVUsers();
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// Compute the type of the largest recurrence expression, and decide whether
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// a canonical induction variable should be inserted.
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