From 11fa8e39fd25153c7d6420948f4b7562bf4e8240 Mon Sep 17 00:00:00 2001 From: Max Kazantsev Date: Fri, 27 Oct 2017 04:17:44 +0000 Subject: [PATCH] Revert rL316568 because of sudden performance drop on ARM git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@316739 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Analysis/ScalarEvolutionExpander.cpp | 10 ++++++-- test/Transforms/IndVarSimplify/udiv.ll | 40 ++------------------------------ 2 files changed, 10 insertions(+), 40 deletions(-) diff --git a/lib/Analysis/ScalarEvolutionExpander.cpp b/lib/Analysis/ScalarEvolutionExpander.cpp index 964a79803fa..47bdac00ae1 100644 --- a/lib/Analysis/ScalarEvolutionExpander.cpp +++ b/lib/Analysis/ScalarEvolutionExpander.cpp @@ -2250,6 +2250,10 @@ namespace { // only needed when the expression includes some subexpression that is not IV // derived. // +// Currently, we only allow division by a nonzero constant here. If this is +// inadequate, we could easily allow division by SCEVUnknown by using +// ValueTracking to check isKnownNonZero(). +// // We cannot generally expand recurrences unless the step dominates the loop // header. The expander handles the special case of affine recurrences by // scaling the recurrence outside the loop, but this technique isn't generally @@ -2264,11 +2268,13 @@ struct SCEVFindUnsafe { bool follow(const SCEV *S) { if (const SCEVUDivExpr *D = dyn_cast(S)) { - if (!SE.isKnownNonZero(D->getRHS())) { + const SCEVConstant *SC = dyn_cast(D->getRHS()); + if (!SC || SC->getValue()->isZero()) { IsUnsafe = true; return false; } - } else if (const SCEVAddRecExpr *AR = dyn_cast(S)) { + } + if (const SCEVAddRecExpr *AR = dyn_cast(S)) { const SCEV *Step = AR->getStepRecurrence(SE); if (!AR->isAffine() && !SE.dominates(Step, AR->getLoop()->getHeader())) { IsUnsafe = true; diff --git a/test/Transforms/IndVarSimplify/udiv.ll b/test/Transforms/IndVarSimplify/udiv.ll index 0f9a54e8c4f..b3f2c2a6a66 100644 --- a/test/Transforms/IndVarSimplify/udiv.ll +++ b/test/Transforms/IndVarSimplify/udiv.ll @@ -130,11 +130,11 @@ declare i32 @printf(i8* nocapture, ...) nounwind ; IndVars doesn't emit a udiv in for.body.preheader since SCEVExpander::expand will ; find out there's already a udiv in the original code. -; CHECK-LABEL: @foo_01( +; CHECK-LABEL: @foo( ; CHECK: for.body.preheader: ; CHECK-NOT: udiv -define void @foo_01(double* %p, i64 %n) nounwind { +define void @foo(double* %p, i64 %n) nounwind { entry: %div0 = udiv i64 %n, 7 ; [#uses=1] %div1 = add i64 %div0, 1 @@ -160,39 +160,3 @@ for.end.loopexit: ; preds = %for.body for.end: ; preds = %for.end.loopexit, %entry ret void } - -; Same as foo_01, but we divide by non-constant value. - -; CHECK-LABEL: @foo_02( -; CHECK: for.body.preheader: -; CHECK-NOT: udiv - -define void @foo_02(double* %p, i64 %n, i64* %lp) nounwind { -entry: - %denom = load i64, i64* %lp, align 4, !range !0 - %div0 = udiv i64 %n, %denom ; [#uses=1] - %div1 = add i64 %div0, 1 - %cmp2 = icmp ult i64 0, %div1 ; [#uses=1] - br i1 %cmp2, label %for.body.preheader, label %for.end - -for.body.preheader: ; preds = %entry - br label %for.body - -for.body: ; preds = %for.body.preheader, %for.body - %i.03 = phi i64 [ %inc, %for.body ], [ 0, %for.body.preheader ] ; [#uses=2] - %arrayidx = getelementptr inbounds double, double* %p, i64 %i.03 ; [#uses=1] - store double 0.000000e+00, double* %arrayidx - %inc = add i64 %i.03, 1 ; [#uses=2] - %divx = udiv i64 %n, %denom ; [#uses=1] - %div = add i64 %divx, 1 - %cmp = icmp ult i64 %inc, %div ; [#uses=1] - br i1 %cmp, label %for.body, label %for.end.loopexit - -for.end.loopexit: ; preds = %for.body - br label %for.end - -for.end: ; preds = %for.end.loopexit, %entry - ret void -} - -!0 = !{i64 1, i64 10} -- 2.11.0