Implement AccessesArguments checking in the two-callsite form
of BasicAA::getModRefInfo. This allows BasicAA to say that two
memset calls to non-aliasing memory locations don't interfere.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110393 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp
index 11cba99..33c04c1 100644
--- a/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/lib/Analysis/BasicAliasAnalysis.cpp
@@ -429,13 +429,43 @@
if (CS1B == OnlyReadsMemory && CS2B == OnlyReadsMemory)
return NoModRef;
+ AliasAnalysis::ModRefResult Mask = ModRef;
+
// If CS1 only reads memory, the only dependence on CS2 can be
// from CS1 reading memory written by CS2.
if (CS1B == OnlyReadsMemory)
- return Ref;
+ Mask = ModRefResult(Mask & Ref);
+ // If CS2 only access memory through arguments, accumulate the mod/ref
+ // information from CS1's references to the memory referenced by
+ // CS2's arguments.
+ if (CS2B == AccessesArguments) {
+ AliasAnalysis::ModRefResult R = NoModRef;
+ for (ImmutableCallSite::arg_iterator
+ I = CS2.arg_begin(), E = CS2.arg_end(); I != E; ++I) {
+ R = ModRefResult((R | getModRefInfo(CS1, *I, UnknownSize)) & Mask);
+ if (R == Mask)
+ break;
+ }
+ return R;
+ }
+
+ // If CS1 only accesses memory through arguments, check if CS2 references
+ // any of the memory referenced by CS1's arguments. If not, return NoModRef.
+ if (CS1B == AccessesArguments) {
+ AliasAnalysis::ModRefResult R = NoModRef;
+ for (ImmutableCallSite::arg_iterator
+ I = CS1.arg_begin(), E = CS1.arg_end(); I != E; ++I)
+ if (getModRefInfo(CS2, *I, UnknownSize) != NoModRef) {
+ R = Mask;
+ break;
+ }
+ if (R == NoModRef)
+ return R;
+ }
+
// Otherwise, fall back to NoAA (mod+ref).
- return NoAA::getModRefInfo(CS1, CS2);
+ return ModRefResult(NoAA::getModRefInfo(CS1, CS2) & Mask);
}
/// GetIndexDifference - Dest and Src are the variable indices from two