[PATCH] x86: Add x86_is_elf to optimize out the ELF check

[H.J. Lu]

On Thu, Sep 26, 2024 at 6:35 PM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 26.09.2024 12:22, H.J. Lu wrote:
> > On Tue, Sep 24, 2024 at 5:57 PM Jan Beulich <jbeulich@suse.com> wrote:
> >>
> >> On 24.09.2024 11:10, H.J. Lu wrote:
> >>>  On Tue, Sep 24, 2024 at 4:19 PM Jan Beulich <jbeulich@suse.com> wrote:
> >>>>
> >>>> On 24.09.2024 00:56, H.J. Lu wrote:
> >>>>> Add x86_is_elf and replace IS_ELF with x86_is_elf () so that compiler
> >>>>> can optimize out the ELF check when OBJ_ELF is defined and OBJ_MAYBE_ELF
> >>>>> isn't defined.
> >>>>>
> >>>>> * config/tc-i386.c (x86_is_elf): New function.
> >>>>> (check_cpu_arch_compatible): Replace IS_ELF with x86_is_elf ().
> >>>>> (i386_arch): Likewise.
> >>>>> (i386_mach): Likewise.
> >>>>> (tc_i386_fix_adjustable): Likewise.
> >>>>> (i386_assemble): Likewise.
> >>>>> (need_plt32_p): Likewise.
> >>>>> (x86_cleanup): Likewise.
> >>>>> (output_insn): Likewise.
> >>>>> (lex_got): Likewise.
> >>>>> (s_insn): Likewise.
> >>>>> (md_estimate_size_before_relax): Likewise.
> >>>>> (md_apply_fix): Likewise.
> >>>>> (md_parse_option): Likewise.
> >>>>> (i386_target_format): Likewise.
> >>>>> (i386_validate_fix): Likewise.
> >>>>> (tc_gen_reloc): Likewise.
> >>>>>
> >>>>
> >>>> Sadly there's no actual patch, so I can only guess what it does. I think
> >>>> we don't need this anymore, with the plan to do away with OBJ_MAYBE_ELF
> >>>
> >>> OBJ_MAYBE_ELF is used by the configure option like,
> >>>
> >>> --enable-targets=x86_64-mingw64
> >>>
> >>> I don't think we should remove it unless there is a very good reason.
> >>
> >> You give precisely an example of why we should remove it: That target
> >> wants PE/COFF support, but what it gets as emulation is plain COFF.
> >> That's wrong. I was actually half way through addressing this aspect,
> >> when it occurred to me that the issue is far worse. While even COFF
> >> has more than 2 sub-flavors (go32 for example), ELF has yet more
> >> (GNU, Solaris, FreeBSD, Lynx, NetBSD, VxWorks, and maybe more). If we
> >> wanted to get things right, all TE_* checks anywhere (including ones
> >> which are presently missing anyway) would need to become runtime
> >> checks, and we'd need an emulation for each flavor. That's simply
> >> going to be unwieldy. Hence Nick and I agreed that we'd drop
> >> emulation support for i386 instead. (Note also that there's been no
> >> testing of those emulations in the x86 gas testsuite, which may be
> >> part of why no issues were ever noticed with the wrong COFF emulation
> >> being chosen when enabling a PE/COFF target as secondary one.)
> >
> > When will OBJ_MAYBE_ELF be removed?  If it won't happen soon,
> > I'd like to check my patch.
>
> As said, I'm intending to get to this (as in: re-working the patches
> fixing the shortcomings to become simple removal); if all goes well it
> may be as soon as tomorrow. Please can you be a little patient? There's
> no reason to rush here afaics, and there's also no reason to introduce
> extra code churn.
>
> Jan

Tomorrow or next week work for me.

Thanks.

-- 
H.J.