[PATCH] D43842: CodeGenObjCXX: handle inalloca appropriately for msgSend variant

[John McCall via Phabricator via cfe-commits]

rjmccall added a comment.

That's a fair point.  I agree that separate allocas would make this a lot cleaner, in both IR and frontend implementation.  We could also set an inalloca bit (+ field index? or maybe keep the arg index -> field index mapping on the CGFunctionInfo) on each arg info *in addition* to the standard ABI info; then most of the cases could just do a final store after their normal transformations.  Are there really no cases where you have to e.g. sign-extend before doing inalloca, or do you just special-case all that in actual argument emission?

Yeah, the block-soup basis of LLVM IR is really annoying for a lot of things that otherwise ought to be simple tasks.  I spent some time trying to think about how I could support (scoped) dynamic allocas in coroutines for Swift and eventually just gave up and introduced a bunch of intrinsics based around a token.  Trying to optimize static allocas based on lifetime intrinsics isn't going to be a picnic, either.


Repository:
  rC Clang

https://reviews.llvm.org/D43842