From 2becaaf3a15a8815f93e65f768038427051ee004 Mon Sep 17 00:00:00 2001 From: Arnold Schwaighofer Date: Sun, 19 Jan 2014 03:18:31 +0000 Subject: [PATCH] LoopVectorizer: A reduction that has multiple uses of the reduction value is not a reduction. Really. Under certain circumstances (the use list of an instruction has to be set up right - hence the extra pass in the test case) we would not recognize when a value in a potential reduction cycle was used multiple times by the reduction cycle. Fixes PR18526. radar://15851149 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199570 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Vectorize/LoopVectorize.cpp | 13 +++++- .../LoopVectorize/multi-use-reduction-bug.ll | 42 +++++++++++++++++++ 2 files changed, 53 insertions(+), 2 deletions(-) create mode 100644 test/Transforms/LoopVectorize/multi-use-reduction-bug.ll diff --git a/lib/Transforms/Vectorize/LoopVectorize.cpp b/lib/Transforms/Vectorize/LoopVectorize.cpp index c05288bd070..695ee03ea76 100644 --- a/lib/Transforms/Vectorize/LoopVectorize.cpp +++ b/lib/Transforms/Vectorize/LoopVectorize.cpp @@ -4535,13 +4535,22 @@ bool LoopVectorizationLegality::AddReductionVar(PHINode *Phi, continue; } - // Process instructions only once (termination). + // Process instructions only once (termination). Each reduction cycle + // value must only be used once, except by phi nodes and min/max + // reductions which are represented as a cmp followed by a select. + ReductionInstDesc IgnoredVal(false, 0); if (VisitedInsts.insert(Usr)) { if (isa(Usr)) PHIs.push_back(Usr); else NonPHIs.push_back(Usr); - } + } else if (!isa(Usr) && + ((!isa(Usr) && + !isa(Usr) && + !isa(Usr)) || + !isMinMaxSelectCmpPattern(Usr, IgnoredVal).IsReduction)) + return false; + // Remember that we completed the cycle. if (Usr == Phi) FoundStartPHI = true; diff --git a/test/Transforms/LoopVectorize/multi-use-reduction-bug.ll b/test/Transforms/LoopVectorize/multi-use-reduction-bug.ll new file mode 100644 index 00000000000..88a29c50df5 --- /dev/null +++ b/test/Transforms/LoopVectorize/multi-use-reduction-bug.ll @@ -0,0 +1,42 @@ +; RUN: opt -indvars -loop-vectorize -force-vector-width=2 -force-vector-unroll=1 -S < %s | FileCheck %s + +target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128" +target triple = "x86_64-apple-macosx10.9.0" + +; We must not vectorize this loop. %add55 is not reduction. Its value is used +; multiple times. + +; PR18526 + +; CHECK: multiple_use_of_value +; CHECK-NOT: <2 x i32> + +define void @multiple_use_of_value() { +entry: + %n = alloca i32, align 4 + %k7 = alloca i32, align 4 + %nf = alloca i32, align 4 + %0 = load i32* %k7, align 4 + %.neg1 = sub i32 0, %0 + %n.promoted = load i32* %n, align 4 + %nf.promoted = load i32* %nf, align 4 + br label %for.body + +for.body: + %inc107 = phi i32 [ undef, %entry ], [ %inc10, %for.body ] + %inc6 = phi i32 [ %nf.promoted, %entry ], [ undef, %for.body ] + %add55 = phi i32 [ %n.promoted, %entry ], [ %add5, %for.body ] + %.neg2 = sub i32 0, %inc6 + %add.neg = add i32 0, %add55 + %add4.neg = add i32 %add.neg, %.neg1 + %sub = add i32 %add4.neg, %.neg2 + %add5 = add i32 %sub, %add55 + %inc10 = add i32 %inc107, 1 + %cmp = icmp ult i32 %inc10, 61 + br i1 %cmp, label %for.body, label %for.end + +for.end: + %add5.lcssa = phi i32 [ %add5, %for.body ] + store i32 %add5.lcssa, i32* %n, align 4 + ret void +}