[PATCH] D69778: Make -fmodules-codegen and -fmodules-debuginfo work also with precompiled headers

Wed Mar 18 14:40:58 PDT 2020

dblaikie added a comment.

In D69778#1929817 <https://reviews.llvm.org/D69778#1929817>, @llunak wrote:

> In D69778#1929737 <https://reviews.llvm.org/D69778#1929737>, @dblaikie wrote:
>
> > I'm not sure how that could be possible - there's no data transferred between the compilation of the TU's object files and the PCH's object file, right?
>
>
> Yes, there is, in a way - the PCH itself. I didn't say everything from the PCH was shared, in fact it's exactly the point that it's not everything from the PCH, unlike -fmodules-codegen.
>
> > Looks to me like the original patch claims the PCH object file contains all the dllexported inline functions from the header. Which, yes, is different from -fmodules-codegen, but doesn't sound like it's based on usage & I'm not sure how it could be based on usage.
>
> It's based on what's to be emitted. See ASTContext::DeclMustBeEmitted(), I think the comment there says it all.

Ah, I understand what you're getting at now - thanks for walking me through it!

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D69778/new/

https://reviews.llvm.org/D69778