[PATCH] D40894: [XRay][compiler-rt+llvm] Update XRay trampoline CFI and register stashing semantics

[Eric Christopher via Phabricator via llvm-commits]

echristo added a comment.

A bit late, but I have some concerns here.

I think the problem is that you were clobbering a bunch of registers that weren't "available" for you to clobber, but if you set this up as a normal calling convention they'll be saved - which I don't think you want to do. How about just saving all of the registers explicitly in your trampoline? If not, then you might just want to make it a normal call and save/restore over it? Given the goals of the work I'd probably lean toward the former. I think if you clobber all of the registers in call lowering you're just making the surrounding code worse?

Thoughts?

-eric


https://reviews.llvm.org/D40894