tree d2603d37ee41c818be25f1eae696212d223da9c4
parent b17bd95fb96f43795d95b8747b7a93d55a0621b2
author Jez Ng <jezng@fb.com> 1615487293 -0500
committer Copybara-Service <copybara-worker@google.com> 1616052931 -0700

[lld-macho][nfc] Refactor subtractor reloc handling

SUBTRACTOR relocations are always paired with UNSIGNED
relocations to indicate a pair of symbols whose address difference we
want. Functionally they are like a single relocation: only one pointer
gets written / relocated. Previously, we would handle these pairs by
skipping over the SUBTRACTOR relocation and writing the pointer when
handling the UNSIGNED reloc. This diff reverses things, so we write
while handling SUBTRACTORs and skip over the UNSIGNED relocs instead.

Being able to distinguish between SUBTRACTOR and UNSIGNED relocs in the
write phase (i.e. inside `relocateOne`) is useful for the upcoming range
check diff: we want to check that SUBTRACTOR relocs write signed values,
but UNSIGNED relocs (naturally) write unsigned values.

Reviewed By: #lld-macho, thakis

Differential Revision: https://reviews.llvm.org/D98386

GitOrigin-RevId: a723db92d87d098d564ac8ace8b1d24bb02a9fdb