Re: BUG #15844: MIPS: remove .set mips2 in s_lock.h to fix r6 build

Tom Lane <tgl@sss.pgh.pa.us> 于2019年6月16日周日 上午11:32写道：
>
> YunQiang Su <wzssyqa@gmail.com> writes:
> > Tom Lane <tgl@sss.pgh.pa.us> 于2019年6月14日周五 上午3:53写道：
> >> After further digging around, I'm liking the alternative of just
> >> removing the ".set mips2" lines.  MIPS-I has been obsolete since 1989,
> >> and the MIPS-II instruction set has a lot of other substantial advantages
> >> over MIPS-I besides having LL/SC, so it's pretty hard to believe that
> >> anyone is still using toolchains that default to assuming MIPS-I
> >> instruction set.
>
> > You are right. I have no idea anyone is using MIPS I.
>
> After further looking, it seems that isn't going to fly.  I found from
> the Debian release notes that they dropped MIPS-I support as of Stretch,
> which means removing ".set mips2" would break both of our live MIPS
> buildfarm machines (which run wheezy and jessie).  I also found by

The default of wheezy and jessie is MIPS II.
https://metadata.ftp-master.debian.org/changelogs//main/g/gcc-4.8/gcc-4.8_4.8.4-1_changelog

Debian use MIPS II as default since gcc 4.5, (may be Squeeze)

> experimentation that NetBSD as of 7.0.2 doesn't default to assuming

I have no idea about NetBSD. Can you run gcc -v on it?

> MIPS2 either.  (I didn't try anything newer, but a scan through the
> port-mips mailing list found no suggestion that they've changed the
> default since then.)  So even though the hardware in use nowadays might
> be fine with this, the toolchains are still behind the times.
>
> So we'll have to go with the #if solution, I think.  But I dislike
> hardwiring "#if __mips_isa_rev >= 6" into s_lock.h.  I'd suggest
> modeling this hack on our rather-ancient hacks for similar problems
> with PPC: put something like this into pg_config_manual.h
>
> #if __mips_isa_rev >= 6
> #define FORCE_MIPS2_ARCHITECTURE
> #endif
>

If you'd like to do like this:
#if __mips_isa_rev > 0
is enough.

> (with a suitable comment) and then make s_lock.h do
>
> #ifdef FORCE_MIPS2_ARCHITECTURE
>                 "       .set mips2          \n"
> #endif
>
> That'll make it a lot easier for people to tweak the condition
> if they need to.
>
>                         regards, tom lane



--
YunQiang Su