From: Tom Lane <tgl@sss.pgh.pa.us>
To: wzssyqa@gmail.com
cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #15844: MIPS: remove .set mips2 in s_lock.h to fix r6 build
In-reply-to: <15844-8f62fe7e163939b3@postgresql.org>
References: <15844-8f62fe7e163939b3@postgresql.org>
Comments: In-reply-to PG Bug reporting form <noreply@postgresql.org>
	message dated "Tue, 11 Jun 2019 04:39:35 -0000"
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Content-ID: <7748.1560434835.1@sss.pgh.pa.us>
Date: Thu, 13 Jun 2019 10:07:15 -0400
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PG Bug reporting form <noreply@postgresql.org> writes:
> MIPS r6 changes the encoding of LL/SC instruction,
> while the .set mips2 will force assembler to generate
> old encoding.
> This patch can fix this problem.

So I have a bunch of questions about this patch.

1. What problem is this actually solving?  We have what I think are
reasonably modern MIPS machines in the buildfarm (frogfish,
topminnow) and they aren't complaining.

2. What toolchains define __mips_isa_rev at all?  Seems like we could
be trading one portability issue for another one.

3. If we actually need something here, don't we need a run-time probe
rather than a compile-time check?  Distro packagers, for example,
can't assume that their packages will be run on exactly the hardware
they build on.

			regards, tom lane