From c122c625ce018e33f25ba35150bed10183ae2b40 Mon Sep 17 00:00:00 2001 From: Dan Gohman Date: Sat, 4 Jun 2011 00:46:31 +0000 Subject: Reapply r131781 (revert r131809), now that some BasicAA shortcomings it exposed are fixed. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132611 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Analysis/BasicAliasAnalysis.cpp | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) (limited to 'lib/Analysis/BasicAliasAnalysis.cpp') diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp index 24297d4a0f..3d10a5fd4d 100644 --- a/lib/Analysis/BasicAliasAnalysis.cpp +++ b/lib/Analysis/BasicAliasAnalysis.cpp @@ -944,7 +944,17 @@ BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, uint64_t V1Size, return NoAlias; } - return MayAlias; + // Statically, we can see that the base objects are the same, but the + // pointers have dynamic offsets which we can't resolve. And none of our + // little tricks above worked. + // + // TODO: Returning PartialAlias instead of MayAlias is a mild hack; the + // practical effect of this is protecting TBAA in the case of dynamic + // indices into arrays of unions. An alternative way to solve this would + // be to have clang emit extra metadata for unions and/or union accesses. + // A union-specific solution wouldn't handle the problem for malloc'd + // memory however. + return PartialAlias; } static AliasAnalysis::AliasResult -- cgit v1.2.3-18-g5258