From 041f74e762c8092e38224da7d6abbc2acfa960b1 Mon Sep 17 00:00:00 2001 From: Dan Gohman Date: Fri, 10 Dec 2010 20:47:03 +0000 Subject: Implement PartialAlias checking in BasicAA. llvm-svn: 121520 --- llvm/lib/Analysis/BasicAliasAnalysis.cpp | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'llvm/lib/Analysis/BasicAliasAnalysis.cpp') diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp index 3ab18fd3c0d..17a502e1f78 100644 --- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp +++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp @@ -857,6 +857,17 @@ BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, uint64_t V1Size, if (GEP1BaseOffset == 0 && GEP1VariableIndices.empty()) return MustAlias; + // If there is a difference betwen the pointers, but the difference is + // less than the size of the associated memory object, then we know + // that the objects are partially overlapping. + if (GEP1BaseOffset != 0 && GEP1VariableIndices.empty()) { + if (GEP1BaseOffset >= 0 ? + (V2Size != UnknownSize && (uint64_t)GEP1BaseOffset < V2Size) : + (V1Size != UnknownSize && -(uint64_t)GEP1BaseOffset < V1Size && + GEP1BaseOffset != INT64_MIN)) + return PartialAlias; + } + // If we have a known constant offset, see if this offset is larger than the // access size being queried. If so, and if no variable indices can remove // pieces of this constant, then we know we have a no-alias. For example, -- cgit v1.2.3