GH-131278: Support building using "computed gotos" for clang-cl on Windows

[chris-eibl]

For details please see #131278.

• Issue: Support building using "computed gotos" for clang-cl on Windows #131278

[picnixz]

Some readability comments. Do you want to actually add a What's New as well? (I don't know how wide is the audience)

[Fidget-Spinner]

I don't remember if we had a Whats New for the original clang-cl issue. We should definitely mention in the whats new that clang cl building on Windows is now possible, and say PGO too.

[Fidget-Spinner]

Woops sorry pressed the wrong button!

[picnixz]

@chris-eibl How do you plan to address:

We should definitely mention in the whats new that clang cl building on Windows is now possible, and say PGO too.

Are there more PRs for those kind of optimizations on Windows? if so, we can delay everything until they are done. Otherwise, let's mention that in the What's New entry

[chris-eibl]

I don't remember if we had a Whats New for the original clang-cl issue. We should definitely mention in the whats new that clang cl building on Windows is now possible, and say PGO too.

Building with clang-cl has been possible for a very long time: #101352.

The only fixes I am aware of are just these two (and just main and current 3.14 alphas are/have been affected):

• _GENERATE_DEBUG_SECTION_WINDOWS https://github.com/python/cpython/pull/130040/files#r1981801677 already fixed by you
• blake2module.c needs to be compiled with libhacl SIMD flags #130213: close to being fixed

So maybe just mention PGO in the Whats New?
Maybe this here and -flto=thin, too?

@zooba treats clang-cl as quite optional in #129907 (comment)
but I think a Whats New entry would not hurt.

Shall I give it a go here and mention those three things?

[chris-eibl]

@Fidget-Spinner : your tail call for Windows #130040 (comment) came without What's new, too. Shall I add an entry, too?

Are there more PRs for those kind of optimizations on Windows?

I'd like to work on the many warnings clang-cl emits, but IMHO that won't go into What's new. Regarding optimizations, I think that's it atm, we can amend later, anyway.

[Fidget-Spinner]

@Fidget-Spinner : your tail call for Windows #130040 (comment) came without What's new, too. Shall I add an entry, too?

We don't need it, as there's already a whats new for tail call in general.

[chris-eibl]

IMHO "computed gotos and/or tail calls" would be better here, but up to @Fidget-Spinner 's liking :)