[PATCH] D123283: [MC] Improve st_size propagation rule

[Fangrui Song via Phabricator via llvm-commits]

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`.symver foo, foo at ver` creates the MCSymbolELF `foo at ver` whose almost all
attributes (including st_size) should inherit from `foo` (GNU as behavior).

a041ef1bd8905f0d58e301c6830b183002ff1847 added st_size propagation which works
for many cases but fails for the following one:

  .set __GLIBC_2_12_sys_errlist, _sys_errlist_internal
  .type   __GLIBC_2_12_sys_errlist, at object
  .size   __GLIBC_2_12_sys_errlist, 1080
  .symver __GLIBC_2_12_sys_errlist, sys_errlist at GLIBC_2.12
  ...
  _sys_errlist_internal:
  .size   _sys_errlist_internal, 1072

`sys_errlist at GLIBC_2.12`'s st_size is 1072 (incorrect), which does not match
`__GLIBC_2_12_sys_errlist`'s st_size: 1080.

The problem is that `Base` is (the final) `_sys_errlist_internal` while we want
to respect (the intermediate) `__GLIBC_2_12_sys_errlist`'s st_size. Just detect
the `MCSymbolRefExpr` case. We'd still fail for more chained assignments,
but they are obscure enough to matter.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D123283

Files:
  llvm/lib/MC/ELFObjectWriter.cpp
  llvm/test/MC/ELF/offset.s

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