[FunctionAttrs] Handle potential access of captured argument

We have to account for accesses to argument memory via captures.
I don't think there's any way to make this produce incorrect
results right now (because as soon as "other" is set, we lose the
ability to infer argmemonly), but this avoids incorrect results
once we have more precise representation.

Author: nikic

llvm/lib/Transforms/IPO/FunctionAttrs.cpp

@@ -171,6 +171,12 @@ checkFunctionMemoryAccess(Function &F, bool ThisBody, AAResults &AAR,
 
       MRB |= CallMRB.getWithoutLoc(FunctionModRefBehavior::ArgMem);
 
+      // If the call accesses captured memory (currently part of "other") and
+      // an argument is captured (currently not tracked), then it may also
+      // access argument memory.
+      ModRefInfo OtherMR = CallMRB.getModRef(FunctionModRefBehavior::Other);
+      MRB |= FunctionModRefBehavior::argMemOnly(OtherMR);
+
       // Check whether all pointer arguments point to local memory, and
       // ignore calls that only access local memory.
       ModRefInfo ArgMR = CallMRB.getModRef(FunctionModRefBehavior::ArgMem);