[PATCH 1/2] LoongArch: bfd: Remove elf_seg_map condition in loongarch_elf_relax_section

[Xi Ruoyao]

On Thu, 2023-10-05 at 18:09 +0800, Xi Ruoyao via Binutils wrote:
> Hi Jinyang,
> 
> Any progress on this?  During my attempt trying to balance relaxation
> and scheduling better in GCC I found the elf_seg_map condition is
> preventing relaxation on *every* shared library (when we are linking a
> shared library the elf_seg_map of .text is NULL).
> 
> On a modern system most code paths are in shared libraries, so it's
> really bad not to perform the relaxation on them.  Esp. now we are
> disabling explicit relocs for relaxation, so if we don't relax shared
> libraries we are likely regressing the overall performance of the
> system.

Phew.  It's not only a performance issue.  It's actually a *correctness*
issue because the condition also causes R_LARCH_ALIGN skipped, so some
programs depending on code alignment (for e.g. duff-device-like code
using pcaddi for eg) will be broken.

Generally skipping the entire relaxation pass for any section containing
R_LARCH_ALIGN is wrong (as we've discussed in
https://github.com/llvm/llvm-project/pull/67424).  Even if we don't
really relax a thing we still *must* process R_LARCH_ALIGN.

> Sorry for disturbing you during the national holiday, feel free to defer
> the reply until the holiday ends!

-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University