From: Anna Thomas Date: Tue, 21 Feb 2017 14:40:28 +0000 (+0000) Subject: [InstCombine] Do not exercise nested max/min pattern on abs X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=20c0e163afb537231da605a06d1d112cde44fe42;p=llvm [InstCombine] Do not exercise nested max/min pattern on abs Summary: This is a fix for assertion failure in `getInverseMinMaxSelectPattern` when ABS is passed in as a select pattern. We should not be invoking the simplification rule for ABS(MIN(~ x,y))) or ABS(MAX(~x,y)) combinations. Added a test case which would cause an assertion failure without the patch. Reviewers: sanjoy, majnemer Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D30051 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@295719 91177308-0d34-0410-b5e6-96231b3b80d8 --- diff --git a/lib/Transforms/InstCombine/InstCombineSelect.cpp b/lib/Transforms/InstCombine/InstCombineSelect.cpp index b5718c3a9e0..dcfacc2e7d9 100644 --- a/lib/Transforms/InstCombine/InstCombineSelect.cpp +++ b/lib/Transforms/InstCombine/InstCombineSelect.cpp @@ -785,7 +785,9 @@ Instruction *InstCombiner::foldSPFofSPF(Instruction *Inner, // This transform is performance neutral if we can elide at least one xor from // the set of three operands, since we'll be tacking on an xor at the very // end. - if (IsFreeOrProfitableToInvert(A, NotA, ElidesXor) && + if (SelectPatternResult::isMinOrMax(SPF1) && + SelectPatternResult::isMinOrMax(SPF2) && + IsFreeOrProfitableToInvert(A, NotA, ElidesXor) && IsFreeOrProfitableToInvert(B, NotB, ElidesXor) && IsFreeOrProfitableToInvert(C, NotC, ElidesXor) && ElidesXor) { if (!NotA) diff --git a/test/Transforms/InstCombine/max-of-nots.ll b/test/Transforms/InstCombine/max-of-nots.ll index 96fac522897..519f1c6a90b 100644 --- a/test/Transforms/InstCombine/max-of-nots.ll +++ b/test/Transforms/InstCombine/max-of-nots.ll @@ -90,6 +90,28 @@ define i32 @max_of_nots(i32 %x, i32 %y) { ret i32 %smax96 } + ; negative test case (i.e. can not simplify) : ABS(MIN(NOT x,y)) +define i32 @abs_of_min_of_not(i32 %x, i32 %y) { +; CHECK-LABEL: @abs_of_min_of_not( +; CHECK-NEXT: xor +; CHECK-NEXT: add +; CHECK-NEXT: icmp sge +; CHECK-NEXT: select +; CHECK-NEXT: icmp sgt +; CHECK-NEXT: sub +; CHECK-NEXT: select +; CHECK-NEXT: ret + + %xord = xor i32 %x, -1 + %yadd = add i32 %y, 2 + %cond.i = icmp sge i32 %yadd, %xord + %min = select i1 %cond.i, i32 %xord, i32 %yadd + %cmp2 = icmp sgt i32 %min, -1 + %sub = sub i32 0, %min + %abs = select i1 %cmp2, i32 %min, i32 %sub + ret i32 %abs +} + define <2 x i32> @max_of_nots_vec(<2 x i32> %x, <2 x i32> %y) { ; CHECK-LABEL: @max_of_nots_vec( ; CHECK-NEXT: [[TMP1:%.*]] = icmp sgt <2 x i32> %y, zeroinitializer