+ AliasAnalysis::ModRefResult Mask = ModRef;
+
+ // If CS1 only reads memory, the only dependence on CS2 can be
+ // from CS1 reading memory written by CS2.
+ if (onlyReadsMemory(CS1B))
+ 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 (onlyAccessesArgPointees(CS2B)) {
+ AliasAnalysis::ModRefResult R = NoModRef;
+ if (doesAccessArgPointees(CS2B))
+ 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 (onlyAccessesArgPointees(CS1B)) {
+ AliasAnalysis::ModRefResult R = NoModRef;
+ if (doesAccessArgPointees(CS1B))
+ 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;
+ }
+
+ // If this is the end of the chain, don't forward.
+ if (!AA) return Mask;
+
+ // Otherwise, fall back to the next AA in the chain. But we can merge
+ // in any mask we've managed to compute.
+ return ModRefResult(AA->getModRefInfo(CS1, CS2) & Mask);