[Inline] Don't add noalias metadata to inaccessiblememonly calls

It will not do anything useful for them, as we already know that
they don't modref with any accessible memory.

In particular, this prevents noalias metadata from being placed
on noalias.scope.decl intrinsics. This reduces the amount of
metadata needed, and makes it more likely that unnecessary decls
can be eliminated.

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/InlineFunction.cpp b/llvm/lib/Transforms/Utils/InlineFunction.cpp
index 60fc5b2..201e4e1 100644
--- a/llvm/lib/Transforms/Utils/InlineFunction.cpp
+++ b/llvm/lib/Transforms/Utils/InlineFunction.cpp
@@ -1041,6 +1041,11 @@ static void AddAliasScopeMetadata(CallBase &CB, ValueToValueMapTy &VMap,
         IsFuncCall = true;
         if (CalleeAAR) {
           FunctionModRefBehavior MRB = CalleeAAR->getModRefBehavior(Call);
+
+          // We'll retain this knowledge without additional metadata.
+          if (AAResults::onlyAccessesInaccessibleMem(MRB))
+            continue;
+
           if (AAResults::onlyAccessesArgPointees(MRB))
             IsArgMemOnlyCall = true;
         }