[all-commits] [llvm/llvm-project] 5913d7: [Globals] Treat nobuiltin fns as maybe-derefined.

[Florian Hahn via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 5913d7705618a7ccacf8207086c2bb0fc0d032a8
      https://github.com/llvm/llvm-project/commit/5913d7705618a7ccacf8207086c2bb0fc0d032a8
  Author: Florian Hahn <flo at fhahn.com>
  Date:   2022-08-23 (Tue, 23 Aug 2022)

  Changed paths:
    M llvm/include/llvm/IR/GlobalValue.h
    M llvm/lib/IR/Globals.cpp
    M llvm/test/Transforms/DeadArgElim/pr49022-builtin-nobuiltin.ll

  Log Message:
  -----------
  [Globals] Treat nobuiltin fns as maybe-derefined.

Callsites could be marked as `builtin` while calling `nobuiltin`
functions. This can lead to problems, if local optimizations apply
transformations based on the semantics of the builtin, but then IPO
treats the function as `nobuiltin` and applies a transform that breaks
builtin semantics (assumed earlier).

To avoid this, mark such functions as maybey-derefined, to avoid IPO
transforms on them that may break assumptions of earlier calls.

Fixes #57075
Fixes #48366

Reviewed By: ychen

Differential Revision: https://reviews.llvm.org/D97735