From cc742dd9e4e9b625733fd0de83476da461f9efe0 Mon Sep 17 00:00:00 2001 From: Arnold Schwaighofer Date: Sun, 19 Jan 2014 03:18:31 +0000 Subject: 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 llvm-svn: 199570 --- llvm/lib/Transforms/Vectorize/LoopVectorize.cpp | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) (limited to 'llvm/lib/Transforms/Vectorize/LoopVectorize.cpp') diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp index c05288bd070..695ee03ea76 100644 --- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp +++ b/llvm/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; -- cgit v1.2.3