[all-commits] [llvm/llvm-project] 757a0e: [SystemZ] Treat FAKE_USE instructions as instructi...

[Stephen Tozer via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 757a0e6d3b6130a984960ee413a3c8a6f99c7cb5
      https://github.com/llvm/llvm-project/commit/757a0e6d3b6130a984960ee413a3c8a6f99c7cb5
  Author: Stephen Tozer <stephen.tozer at sony.com>
  Date:   2025-06-18 (Wed, 18 Jun 2025)

  Changed paths:
    M llvm/lib/Target/SystemZ/SystemZLongBranch.cpp
    A llvm/test/CodeGen/SystemZ/fake-use-size.ll

  Log Message:
  -----------
  [SystemZ] Treat FAKE_USE instructions as instructions without a size (#144390)

This patch fixes an error in which `FAKE_USE` instructions would trigger
an assertion in SystemZLongBranch due to them having a size of 0 without
being excepted in the assertion that each instruction, other than a set
of known 0-size instruction types, should have a non-0 size.

`FAKE_USE` instructions are no-op instructions that are emitted into
LLVM by the `-fextend-variable-liveness` clang flag to help preserve the
liveness of source variables in optimized code, and therefore they
should be understood as being valid size 0 instructions.



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