forked from OSchip/llvm-project
[SimplifyIndvar] Replace the sdiv used by IV if we can prove both of its operands are non-negative
Since there is no sdiv in SCEV, an 'udiv' is a better canonical form than an 'sdiv' as the user of induction variable Differential Revision: https://reviews.llvm.org/D31488 llvm-svn: 299118
This commit is contained in:
Hongbin Zheng
parent
623efd8a75
commit
bfd7c38de7
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@ -35,6 +35,9 @@ using namespace llvm;
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STATISTIC(NumElimIdentity, "Number of IV identities eliminated");
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STATISTIC(NumElimOperand, "Number of IV operands folded into a use");
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STATISTIC(NumElimRem , "Number of IV remainder operations eliminated");
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STATISTIC(
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NumSimplifiedSDiv,
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"Number of IV signed division operations converted to unsigned division");
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STATISTIC(NumElimCmp , "Number of IV comparisons eliminated");
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namespace {
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@ -75,6 +78,7 @@ namespace {
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void eliminateIVComparison(ICmpInst *ICmp, Value *IVOperand);
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void eliminateIVRemainder(BinaryOperator *Rem, Value *IVOperand,
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bool IsSigned);
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bool eliminateSDiv(BinaryOperator *SDiv);
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bool strengthenOverflowingOperation(BinaryOperator *OBO, Value *IVOperand);
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};
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}
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@ -265,6 +269,33 @@ void SimplifyIndvar::eliminateIVComparison(ICmpInst *ICmp, Value *IVOperand) {
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Changed = true;
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}
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bool SimplifyIndvar::eliminateSDiv(BinaryOperator *SDiv) {
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// Get the SCEVs for the ICmp operands.
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auto *N = SE->getSCEV(SDiv->getOperand(0));
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auto *D = SE->getSCEV(SDiv->getOperand(1));
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// Simplify unnecessary loops away.
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const Loop *L = LI->getLoopFor(SDiv->getParent());
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N = SE->getSCEVAtScope(N, L);
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D = SE->getSCEVAtScope(D, L);
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// Replace sdiv by udiv if both of the operands are non-negative
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if (SE->isKnownNonNegative(N) && SE->isKnownNonNegative(D)) {
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auto *UDiv = BinaryOperator::Create(
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BinaryOperator::UDiv, SDiv->getOperand(0), SDiv->getOperand(1),
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SDiv->getName() + ".udiv", SDiv);
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UDiv->setIsExact(SDiv->isExact());
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SDiv->replaceAllUsesWith(UDiv);
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DEBUG(dbgs() << "INDVARS: Simplified sdiv: " << *SDiv << '\n');
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++NumSimplifiedSDiv;
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Changed = true;
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DeadInsts.push_back(SDiv);
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return true;
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}
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return false;
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}
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/// SimplifyIVUsers helper for eliminating useless
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/// remainder operations operating on an induction variable.
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void SimplifyIndvar::eliminateIVRemainder(BinaryOperator *Rem,
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@ -426,12 +457,15 @@ bool SimplifyIndvar::eliminateIVUser(Instruction *UseInst,
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eliminateIVComparison(ICmp, IVOperand);
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return true;
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}
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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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if (BinaryOperator *Bin = dyn_cast<BinaryOperator>(UseInst)) {
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bool IsSRem = Bin->getOpcode() == Instruction::SRem;
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if (IsSRem || Bin->getOpcode() == Instruction::URem) {
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eliminateIVRemainder(Bin, IVOperand, IsSRem);
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return true;
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}
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if (Bin->getOpcode() == Instruction::SDiv)
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return eliminateSDiv(Bin);
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}
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if (auto *CI = dyn_cast<CallInst>(UseInst))
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@ -0,0 +1,130 @@
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; RUN: opt < %s -indvars -S | FileCheck %s
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define void @test0(i32* %a) {
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; CHECK-LABEL: @test0(
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entry:
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br label %for.body
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for.body: ; preds = %entry, %for.body
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%i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
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%div = sdiv i32 %i.01, 2
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; CHECK-NOT: sdiv
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; CHECK: udiv
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%idxprom = sext i32 %div to i64
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%arrayidx = getelementptr inbounds i32, i32* %a, i64 %idxprom
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store i32 %i.01, i32* %arrayidx, align 4
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%inc = add nsw i32 %i.01, 1
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%cmp = icmp slt i32 %inc, 64
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br i1 %cmp, label %for.body, label %for.end
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for.end: ; preds = %for.body
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ret void
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}
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define void @test1(i32* %a) {
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; CHECK-LABEL: @test1(
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entry:
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br label %for.body
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for.body: ; preds = %entry, %for.body
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%i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
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%div = sdiv exact i32 %i.01, 2
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; CHECK-NOT: sdiv
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; CHECK: udiv exact
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%idxprom = sext i32 %div to i64
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%arrayidx = getelementptr inbounds i32, i32* %a, i64 %idxprom
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store i32 %i.01, i32* %arrayidx, align 4
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%inc = add nsw i32 %i.01, 1
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%cmp = icmp slt i32 %inc, 64
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br i1 %cmp, label %for.body, label %for.end
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for.end: ; preds = %for.body
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ret void
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}
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define void @test2(i32* %a, i32 %d) {
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; CHECK-LABEL: @test2(
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entry:
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br label %for.body
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for.body: ; preds = %entry, %for.body
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%i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
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%mul = mul nsw i32 %i.01, 64
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%div = sdiv i32 %mul, %d
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; CHECK-NOT: udiv
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%idxprom = sext i32 %div to i64
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%arrayidx = getelementptr inbounds i32, i32* %a, i64 %idxprom
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store i32 %i.01, i32* %arrayidx, align 4
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%inc = add nsw i32 %i.01, 1
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%cmp = icmp slt i32 %inc, 64
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br i1 %cmp, label %for.body, label %for.end
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for.end: ; preds = %for.body
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ret void
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}
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define void @test3(i32* %a) {
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; CHECK-LABEL: @test3(
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entry:
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br label %for.body
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for.body: ; preds = %entry, %for.body
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%i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
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%div = sdiv i32 2048, %i.01
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; CHECK: udiv
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; CHECK-NOT: sdiv
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%idxprom = sext i32 %div to i64
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%arrayidx = getelementptr inbounds i32, i32* %a, i64 %idxprom
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store i32 %i.01, i32* %arrayidx, align 4
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%inc = add nsw i32 %i.01, 1
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%cmp = icmp slt i32 %inc, 64
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br i1 %cmp, label %for.body, label %for.end
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for.end: ; preds = %for.body
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ret void
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}
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define void @test4(i32* %a) {
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; CHECK-LABEL: @test4(
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entry:
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br label %for.body
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for.body: ; preds = %entry, %for.body
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%i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
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%mul = mul nsw i32 %i.01, 64
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%div = sdiv i32 %mul, 8
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; CHECK: udiv
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; CHECK-NOT: sdiv
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%idxprom = sext i32 %div to i64
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%arrayidx = getelementptr inbounds i32, i32* %a, i64 %idxprom
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store i32 %i.01, i32* %arrayidx, align 4
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%inc = add nsw i32 %i.01, 1
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%cmp = icmp slt i32 %inc, 64
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br i1 %cmp, label %for.body, label %for.end
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for.end: ; preds = %for.body
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ret void
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}
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define void @test5(i32* %a) {
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; CHECK-LABEL: @test5(
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entry:
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br label %for.body
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for.body: ; preds = %entry, %for.body
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%i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
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%mul = mul nsw i32 %i.01, 64
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%div = sdiv i32 %mul, 6
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; CHECK: udiv
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; CHECK-NOT: sdiv
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%idxprom = sext i32 %div to i64
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%arrayidx = getelementptr inbounds i32, i32* %a, i64 %idxprom
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store i32 %i.01, i32* %arrayidx, align 4
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%inc = add nsw i32 %i.01, 1
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%cmp = icmp slt i32 %inc, 64
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br i1 %cmp, label %for.body, label %for.end
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for.end: ; preds = %for.body
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ret void
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}
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