Date: Tue, 9 Dec 2014 07:48:26 +0000 (UTC) From: Dimitry Andric <dim@FreeBSD.org> To: src-committers@freebsd.org, svn-src-projects@freebsd.org Subject: svn commit: r275634 - projects/clang350-import/contrib/llvm/lib/Transforms/Vectorize Message-ID: <201412090748.sB97mQub087197@svn.freebsd.org>
next in thread | raw e-mail | index | archive | help
Author: dim Date: Tue Dec 9 07:48:25 2014 New Revision: 275634 URL: https://svnweb.freebsd.org/changeset/base/275634 Log: Pull in r223171 from upstream llvm trunk (by Michael Zolotukhin): PR21302. Vectorize only bottom-tested loops. rdar://problem/18886083 This fixes a bug in the llvm vectorizer, which could sometimes cause vectorized loops to perform an additional iteration, leading to possible buffer overruns. Symptoms of this, which are usually segfaults, were first noticed when building gcc ports, here: https://lists.freebsd.org/pipermail/freebsd-ports/2014-September/095466.html https://lists.freebsd.org/pipermail/freebsd-toolchain/2014-September/001211.html Note: because this is applied on top of llvm/clang 3.5.0, this fix is slightly different from the one just checked into head in r275633. Modified: projects/clang350-import/contrib/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp Modified: projects/clang350-import/contrib/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp ============================================================================== --- projects/clang350-import/contrib/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp Tue Dec 9 07:34:28 2014 (r275633) +++ projects/clang350-import/contrib/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp Tue Dec 9 07:48:25 2014 (r275634) @@ -3466,6 +3466,15 @@ bool LoopVectorizationLegality::canVecto return false; } + // We only handle bottom-tested loops, i.e. loop in which the condition is + // checked at the end of each iteration. With that we can assume that all + // instructions in the loop are executed the same number of times. + if (TheLoop->getExitingBlock() != TheLoop->getLoopLatch()) { + emitAnalysis( + Report() << "loop control flow is not understood by vectorizer"); + return false; + } + // We need to have a loop header. DEBUG(dbgs() << "LV: Found a loop: " << TheLoop->getHeader()->getName() << '\n');
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?201412090748.sB97mQub087197>