[all-commits] [llvm/llvm-project] 762253: [DAE] Don't DAE if we musttail call a "live" (non-...

[Mircea Trofin via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 762253b048e9f760624dea3537535c3657435902
      https://github.com/llvm/llvm-project/commit/762253b048e9f760624dea3537535c3657435902
  Author: Mircea Trofin <mtrofin at google.com>
  Date:   2023-03-16 (Thu, 16 Mar 2023)

  Changed paths:
    M llvm/include/llvm/Transforms/IPO/DeadArgumentElimination.h
    M llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp
    A llvm/test/Transforms/DeadArgElim/musttail-indirect.ll

  Log Message:
  -----------
  [DAE] Don't DAE if we musttail call a "live" (non-DAE-able) function

There are 2 such base cases: indirect calls and calls to functions external
to the module; and then any musttail calls to live functions (because of
the first 2 reasons or otherwise).

The IR validator reports, in these cases, that it "cannot guarantee tail
call due to mismatched parameter counts".

The fix is two-fold: first, we mark as "live" (i.e. non-DAE-able)
functions that make an indirect musttail call.

Then, we propagate live-ness to musttail callers of live functions.

Declared functions are already marked "live".

Differential Revision: https://reviews.llvm.org/D145209