From 7c7aba6e5fef47a01a136be655b0a92cfd7090f6 Mon Sep 17 00:00:00 2001 From: Dimitry Andric Date: Fri, 16 Jun 2017 21:03:24 +0000 Subject: Vendor import of llvm trunk r305575: https://llvm.org/svn/llvm-project/llvm/trunk@305575 --- lib/Analysis/BasicAliasAnalysis.cpp | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) (limited to 'lib/Analysis/BasicAliasAnalysis.cpp') diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp index f743cb234c455..dbb1b01b94ac2 100644 --- a/lib/Analysis/BasicAliasAnalysis.cpp +++ b/lib/Analysis/BasicAliasAnalysis.cpp @@ -1011,10 +1011,24 @@ static AliasResult aliasSameBasePointerGEPs(const GEPOperator *GEP1, // equal each other so we can exit early. if (C1 && C2) return NoAlias; - if (isKnownNonEqual(GEP1->getOperand(GEP1->getNumOperands() - 1), - GEP2->getOperand(GEP2->getNumOperands() - 1), - DL)) - return NoAlias; + { + Value *GEP1LastIdx = GEP1->getOperand(GEP1->getNumOperands() - 1); + Value *GEP2LastIdx = GEP2->getOperand(GEP2->getNumOperands() - 1); + if (isa(GEP1LastIdx) || isa(GEP2LastIdx)) { + // If one of the indices is a PHI node, be safe and only use + // computeKnownBits so we don't make any assumptions about the + // relationships between the two indices. This is important if we're + // asking about values from different loop iterations. See PR32314. + // TODO: We may be able to change the check so we only do this when + // we definitely looked through a PHINode. + KnownBits Known1 = computeKnownBits(GEP1LastIdx, DL); + KnownBits Known2 = computeKnownBits(GEP2LastIdx, DL); + if (Known1.Zero.intersects(Known2.One) || + Known1.One.intersects(Known2.Zero)) + return NoAlias; + } else if (isKnownNonEqual(GEP1LastIdx, GEP2LastIdx, DL)) + return NoAlias; + } return MayAlias; } else if (!LastIndexedStruct || !C1 || !C2) { return MayAlias; -- cgit v1.2.3