[PATCH] D68043: [AArch64][GlobalISel] Support lowering variadic musttail calls

[Jessica Paquette via Phabricator via llvm-commits]

paquette created this revision.
paquette added a reviewer: aemerson.
Herald added subscribers: Petar.Avramovic, volkan, hiraditya, kristof.beyls, rovka.
Herald added a project: LLVM.

This adds support for lowering variadic musttail calls. To do this, we have to...

- Detect a musttail call in a variadic function before attempting to lower the call's formal arguments. This is done in the IRTranslator.
- Compute forwarded registers in `lowerFormalArguments`, and add copies for those registers.
- Restore the forwarded registers in `lowerTailCall`.

Because there doesn't seem to be any nice way to wrap these up into the outgoing argument handler, the restore code in `lowerTailCall` is done separately.

Also, irritatingly, you have to make sure that the registers don't overlap with any passed parameters. Otherwise, the scheduler doesn't know what to do with the extra copies and asserts.

Add call-translator-variadic-musttail.ll to test this. This is pretty much the same as the X86 musttail-varargs.ll test. We didn't have as nice of a test to base this off of, but the idea is the same.


https://reviews.llvm.org/D68043

Files:
  llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
  llvm/lib/Target/AArch64/AArch64CallLowering.cpp
  llvm/test/CodeGen/AArch64/GlobalISel/call-translator-variadic-musttail.ll

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