enhance basicaa to return "Mod" for a memcpy call when the
queried location doesn't overlap the source, and add a testcase.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@120370 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index 3e63424..74bee94 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -687,10 +687,15 @@
Len = LenCI->getZExtValue();
Value *Dest = II->getArgOperand(0);
Value *Src = II->getArgOperand(1);
+ // If it can't overlap the source dest, then it doesn't modref the loc.
if (isNoAlias(Location(Dest, Len), Loc)) {
if (isNoAlias(Location(Src, Len), Loc))
return NoModRef;
+ // If it can't overlap the dest, then worst case it reads the loc.
Min = Ref;
+ } else if (isNoAlias(Location(Src, Len), Loc)) {
+ // If it can't overlap the source, then worst case it mutates the loc.
+ Min = Mod;
}
break;
}