[WPD] Emit vcall_visibility metadata for MicrosoftCXXABI

Authored by tejohnson on Jan 25 2020, 7:26 AM.


[WPD] Emit vcall_visibility metadata for MicrosoftCXXABI

The MicrosoftCXXABI uses a separate mechanism for emitting vtable
type metadata, and thus didn't pick up the change from D71907
to emit the vcall_visibility metadata under -fwhole-program-vtables.

I believe this is the cause of a Windows bot failure when I committed
follow on change D71913 that required a revert. The failure occurred
in a CFI test that was expecting to not abort because it expected a
devirtualization to occur, and without the necessary vcall_visibility
metadata we would not get devirtualization.

Note in the equivalent code in CodeGenModule::EmitVTableTypeMetadata
(used by the ItaniumCXXABI), we also emit the vcall_visibility metadata
when Virtual Function Elimination is enabled. Since I am not as familiar
with the details of that optimization, I have marked that as a TODO and
am only inserting under -fwhole-program-vtables.

Reviewers: evgeny777

Subscribers: Prazek, ostannard, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D73418