From 2d5c28da0d14883cd0cd6fcf38d7e28040b634c0 Mon Sep 17 00:00:00 2001 From: Bob Wilson Date: Tue, 4 Sep 2012 03:30:13 +0000 Subject: [PATCH] Be conservative about allocations that may alias the accessed pointer. If an allocation has a must-alias relation to the access pointer, we treat it as a Def. Otherwise, without this check, the code here was just skipping over the allocation call and ignoring it. I noticed this by inspection and don't have a specific testcase that it breaks, but it seems like we need to treat a may-alias allocation as a Clobber. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163127 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Analysis/MemoryDependenceAnalysis.cpp | 3 +++ 1 file changed, 3 insertions(+) diff --git a/lib/Analysis/MemoryDependenceAnalysis.cpp b/lib/Analysis/MemoryDependenceAnalysis.cpp index 804217a83d1..5736c3569dc 100644 --- a/lib/Analysis/MemoryDependenceAnalysis.cpp +++ b/lib/Analysis/MemoryDependenceAnalysis.cpp @@ -485,6 +485,9 @@ getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad, if (AccessPtr == Inst || AA->isMustAlias(Inst, AccessPtr)) return MemDepResult::getDef(Inst); + // Be conservative if the accessed pointer may alias the allocation. + if (AA->alias(Inst, AccessPtr) != AliasAnalysis::NoAlias) + return MemDepResult::getClobber(Inst); // If the allocation is not aliased and does not read memory (like // strdup), it is safe to ignore. if (isa(Inst) ||