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

From: YunQiang Su <wzssyqa(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-bugs(at)lists(dot)postgresql(dot)org
Subject: Re: BUG #15844: MIPS: remove .set mips2 in s_lock.h to fix r6 build
Date: 2019-06-16 03:52:54
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Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> 于2019年6月16日周日 上午11:32写道:
> YunQiang Su <wzssyqa(at)gmail(dot)com> writes:
> > Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)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.

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
> #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
> " .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

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