[all-commits] [llvm/llvm-project] 8653db: [lld-macho][test] Make reloc-subtractor.s robust

[Fangrui Song via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 8653db9503774c0f70a5ae3858ceaf180815fe3b
      https://github.com/llvm/llvm-project/commit/8653db9503774c0f70a5ae3858ceaf180815fe3b
  Author: Fangrui Song <i at maskray.me>
  Date:   2023-06-20 (Tue, 20 Jun 2023)

  Changed paths:
    M lld/test/MachO/reloc-subtractor.s

  Log Message:
  -----------
  [lld-macho][test] Make reloc-subtractor.s robust

The test requires that LLVM integreated assembler generates
SUBTRACTOR/UNSIGNED relocations for `.long _minuend_1 - _subtrahend_1`.
This currently works by luck because:

* `_minuend_1` and `_subtrahend_1` are in different fragments (separated by a MCFillFragment)
* and the result is known to be negative at parsing time.

D153096 will change the assembler to fold `.long _minuend_1 - _subtrahend_1` to
a constant, giving ld -order_file no chance to change the result.

To fix the test, move the referenced labels after the label differences to block
constant folding.

Note: you may think the model is somewhat broken and it is. The
.subsections_via_symbols mechanism does not block such constant folding. In
reality SUBTRACTOR/UNSIGNED is for references to another section, which does not
have the problem.

Reviewed By: #lld-macho, smeenai

Differential Revision: https://reviews.llvm.org/D153382