+AliasAnalysis::getModRefInfo(ImmutableCallSite CS1, ImmutableCallSite CS2) {
+ assert(AA && "AA didn't call InitializeAliasAnalysis in its run method!");
+
+ // If CS1 or CS2 are readnone, they don't interact.
+ ModRefBehavior CS1B = getModRefBehavior(CS1);
+ if (CS1B == DoesNotAccessMemory) return NoModRef;
+
+ ModRefBehavior CS2B = getModRefBehavior(CS2);
+ if (CS2B == DoesNotAccessMemory) return NoModRef;
+
+ // If they both only read from memory, there is no dependence.
+ if (onlyReadsMemory(CS1B) && onlyReadsMemory(CS2B))
+ 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 (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) {
+ const Value *Arg = *I;
+ if (!Arg->getType()->isPointerTy())
+ continue;
+ ModRefResult ArgMask;
+ Location CS2Loc =
+ getArgLocation(CS2, (unsigned) std::distance(CS2.arg_begin(), I),
+ ArgMask);
+ // ArgMask indicates what CS2 might do to CS2Loc, and the dependence of
+ // CS1 on that location is the inverse.
+ if (ArgMask == Mod)
+ ArgMask = ModRef;
+ else if (ArgMask == Ref)
+ ArgMask = Mod;
+
+ R = ModRefResult((R | (getModRefInfo(CS1, CS2Loc) & ArgMask)) & 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) {
+ const Value *Arg = *I;
+ if (!Arg->getType()->isPointerTy())
+ continue;
+ ModRefResult ArgMask;
+ Location CS1Loc =
+ getArgLocation(CS1, (unsigned) std::distance(CS1.arg_begin(), I),
+ ArgMask);
+ // ArgMask indicates what CS1 might do to CS1Loc; if CS1 might Mod
+ // CS1Loc, then we care about either a Mod or a Ref by CS2. If CS1
+ // might Ref, then we care only about a Mod by CS2.
+ ModRefResult ArgR = getModRefInfo(CS2, CS1Loc);
+ if (((ArgMask & Mod) != NoModRef && (ArgR & ModRef) != NoModRef) ||
+ ((ArgMask & Ref) != NoModRef && (ArgR & Mod) != NoModRef))
+ R = ModRefResult((R | ArgMask) & Mask);
+
+ if (R == Mask)
+ break;
+ }
+ }
+ 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);
+}
+
+AliasAnalysis::ModRefBehavior
+AliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {