[clang] [llvm] [Clang][inlineasm] Add special support for "rm" output constraints (PR #92040)

[Bill Wendling via cfe-commits]

bwendling wrote:

> Didn't get far, but a few initial comments. The PR description needs an update

Yes. I'll be taking care of that soon.

> > @nikic I'm still considering merging this with CallBrPrepare, though CallBr now handles more than just ASM instructions. :-) But keeping this separated will help with the code review for this change. In other words, I can merge the two afterwards as an NFC, but before the compiler release. :-)
> 
> Not sure I get how that helps with review. I think if you just put your InlineAsmPrepare code into CallBrPrepare things would be a bit simpler because we don't need the pass boilerplate and pipeline test changes anymore? (Doing a CallBrPrepare -> InlineAsmPrepare as an NFC first would be good though.)

It helps the review, because this is a big-ish change and more-or-less self-contained within the `InlineAsmPrepare` patch. But like I said, I'm happy to merge it with `CallBrPrepare` either before submission or as a follow-up commit.

https://github.com/llvm/llvm-project/pull/92040