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Teach IndVarSimplify how to eliminate remainder operators where the
numerator is an induction variable. For example, with code like this:
for (i=0;i<n;++i)
x[i%n] = 0;
IndVarSimplify will now recognize that i is always less than n inside
the loop, and eliminate the remainder.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101113 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
parent
afc9a0c6b0
commit
a590b79ee2
@ -98,6 +98,7 @@ namespace {
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private:
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void EliminateIVComparisons();
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void EliminateIVRemainders();
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void RewriteNonIntegerIVs(Loop *L);
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ICmpInst *LinearFunctionTestReplace(Loop *L, const SCEV *BackedgeTakenCount,
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@ -398,6 +399,73 @@ void IndVarSimplify::EliminateIVComparisons() {
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RecursivelyDeleteTriviallyDeadInstructions(Inst);
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}
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void IndVarSimplify::EliminateIVRemainders() {
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SmallVector<WeakVH, 16> DeadInsts;
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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->getIntegerSCEV(1, S->getType()));
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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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}
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// Now that we're done iterating through lists, clean up any instructions
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// which are now dead.
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while (!DeadInsts.empty())
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if (Instruction *Inst =
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dyn_cast_or_null<Instruction>(DeadInsts.pop_back_val()))
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RecursivelyDeleteTriviallyDeadInstructions(Inst);
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}
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bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
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IU = &getAnalysis<IVUsers>();
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LI = &getAnalysis<LoopInfo>();
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@ -427,6 +495,9 @@ bool IndVarSimplify::runOnLoop(Loop *L, LPPassManager &LPM) {
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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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// 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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const Type *LargestType = 0;
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121
test/Transforms/IndVarSimplify/eliminate-rem.ll
Normal file
121
test/Transforms/IndVarSimplify/eliminate-rem.ll
Normal file
@ -0,0 +1,121 @@
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; RUN: opt -indvars -S < %s | FileCheck %s
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target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
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; Indvars should be able to eliminate this srem.
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; CHECK: @simple
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; CHECK-NOT: rem
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; CHECK: ret
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define void @simple(i64 %arg, double* %arg3) nounwind {
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bb:
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%t = icmp slt i64 0, %arg ; <i1> [#uses=1]
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br i1 %t, label %bb4, label %bb12
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bb4: ; preds = %bb
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br label %bb5
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bb5: ; preds = %bb4, %bb5
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%t6 = phi i64 [ %t9, %bb5 ], [ 0, %bb4 ] ; <i64> [#uses=2]
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%t7 = srem i64 %t6, %arg ; <i64> [#uses=1]
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%t8 = getelementptr inbounds double* %arg3, i64 %t7 ; <double*> [#uses=1]
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store double 0.000000e+00, double* %t8
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%t9 = add nsw i64 %t6, 1 ; <i64> [#uses=2]
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%t10 = icmp slt i64 %t9, %arg ; <i1> [#uses=1]
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br i1 %t10, label %bb5, label %bb11
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bb11: ; preds = %bb5
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br label %bb12
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bb12: ; preds = %bb11, %bb
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ret void
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}
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; Indvars should be able to eliminate the (i+1)%n.
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; CHECK: @f
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; CHECK-NOT: rem
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; CHECK: rem
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; CHECK-NOT: rem
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; CHECK: ret
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define i32 @f(i64* %arg, i64 %arg1, i64 %arg2, i64 %arg3) nounwind {
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bb:
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%t = icmp sgt i64 %arg1, 0 ; <i1> [#uses=1]
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br i1 %t, label %bb4, label %bb54
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bb4: ; preds = %bb
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br label %bb5
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bb5: ; preds = %bb49, %bb4
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%t6 = phi i64 [ %t51, %bb49 ], [ 0, %bb4 ] ; <i64> [#uses=4]
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%t7 = phi i32 [ %t50, %bb49 ], [ 0, %bb4 ] ; <i32> [#uses=2]
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%t8 = add nsw i64 %t6, %arg1 ; <i64> [#uses=1]
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%t9 = add nsw i64 %t8, -2 ; <i64> [#uses=1]
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%t10 = srem i64 %t9, %arg1 ; <i64> [#uses=1]
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%t11 = add nsw i64 %t10, 1 ; <i64> [#uses=1]
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%t12 = add nsw i64 %t6, 1 ; <i64> [#uses=1]
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%t13 = srem i64 %t12, %arg1 ; <i64> [#uses=1]
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%t14 = icmp sgt i64 %arg1, 0 ; <i1> [#uses=1]
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br i1 %t14, label %bb15, label %bb49
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bb15: ; preds = %bb5
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br label %bb16
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bb16: ; preds = %bb44, %bb15
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%t17 = phi i64 [ %t46, %bb44 ], [ 0, %bb15 ] ; <i64> [#uses=1]
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%t18 = phi i32 [ %t45, %bb44 ], [ %t7, %bb15 ] ; <i32> [#uses=2]
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%t19 = icmp sgt i64 %arg1, 0 ; <i1> [#uses=1]
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br i1 %t19, label %bb20, label %bb44
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bb20: ; preds = %bb16
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br label %bb21
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bb21: ; preds = %bb21, %bb20
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%t22 = phi i64 [ %t41, %bb21 ], [ 0, %bb20 ] ; <i64> [#uses=4]
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%t23 = phi i32 [ %t40, %bb21 ], [ %t18, %bb20 ] ; <i32> [#uses=1]
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%t24 = mul i64 %t6, %arg1 ; <i64> [#uses=1]
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%t25 = mul i64 %t13, %arg1 ; <i64> [#uses=1]
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%t26 = add nsw i64 %t24, %t22 ; <i64> [#uses=1]
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%t27 = mul i64 %t11, %arg1 ; <i64> [#uses=1]
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%t28 = add nsw i64 %t25, %t22 ; <i64> [#uses=1]
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%t29 = getelementptr inbounds i64* %arg, i64 %t26 ; <i64*> [#uses=1]
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%t30 = add nsw i64 %t27, %t22 ; <i64> [#uses=1]
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%t31 = getelementptr inbounds i64* %arg, i64 %t28 ; <i64*> [#uses=1]
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%t32 = zext i32 %t23 to i64 ; <i64> [#uses=1]
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%t33 = load i64* %t29 ; <i64> [#uses=1]
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%t34 = getelementptr inbounds i64* %arg, i64 %t30 ; <i64*> [#uses=1]
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%t35 = load i64* %t31 ; <i64> [#uses=1]
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%t36 = add nsw i64 %t32, %t33 ; <i64> [#uses=1]
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%t37 = add nsw i64 %t36, %t35 ; <i64> [#uses=1]
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%t38 = load i64* %t34 ; <i64> [#uses=1]
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%t39 = add nsw i64 %t37, %t38 ; <i64> [#uses=1]
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%t40 = trunc i64 %t39 to i32 ; <i32> [#uses=2]
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%t41 = add nsw i64 %t22, 1 ; <i64> [#uses=2]
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%t42 = icmp slt i64 %t41, %arg1 ; <i1> [#uses=1]
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br i1 %t42, label %bb21, label %bb43
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bb43: ; preds = %bb21
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br label %bb44
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bb44: ; preds = %bb43, %bb16
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%t45 = phi i32 [ %t18, %bb16 ], [ %t40, %bb43 ] ; <i32> [#uses=2]
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%t46 = add nsw i64 %t17, 1 ; <i64> [#uses=2]
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%t47 = icmp slt i64 %t46, %arg1 ; <i1> [#uses=1]
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br i1 %t47, label %bb16, label %bb48
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bb48: ; preds = %bb44
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br label %bb49
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bb49: ; preds = %bb48, %bb5
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%t50 = phi i32 [ %t7, %bb5 ], [ %t45, %bb48 ] ; <i32> [#uses=2]
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%t51 = add nsw i64 %t6, 1 ; <i64> [#uses=2]
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%t52 = icmp slt i64 %t51, %arg1 ; <i1> [#uses=1]
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br i1 %t52, label %bb5, label %bb53
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bb53: ; preds = %bb49
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br label %bb54
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bb54: ; preds = %bb53, %bb
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%t55 = phi i32 [ 0, %bb ], [ %t50, %bb53 ] ; <i32> [#uses=1]
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ret i32 %t55
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}
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