From: | Noah Misch <noah(at)leadboat(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Bernd Helmle <mailings(at)oopsware(dot)de> |
Subject: | Re: [HACKERS] Deadlock in XLogInsert at AIX |
Date: | 2019-08-31 22:30:26 |
Message-ID: | 20190831223026.GA3257395@rfd.leadboat.com |
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Lists: | pgsql-hackers |
On Sat, Aug 31, 2019 at 02:27:55PM -0400, Tom Lane wrote:
> Noah Misch <noah(at)leadboat(dot)com> writes:
> > Done. fetch-add-variable-test-v1.patch just adds tests for non-constant
> > addends and 16-bit edge cases. Today's implementation handles those,
> > PostgreSQL doesn't use them, and I might easily have broken them.
> > fetch-add-xlc-asm-v1.patch moves xlc builds from the __fetch_and_add()
> > intrinsic to inline asm. fetch-add-gcc-xlc-unify-v1.patch moves fetch_add to
> > inline asm for all other ppc compilers. gcc-7.2.0 generates equivalent code
> > before and after. I plan to keep the third patch HEAD-only, back-patching the
> > other two. I tested with xlc v12 and v13.
>
> Hm, no objection to the first two patches, but I don't understand
> why the third patch goes to so much effort just to use "addi" rather
> than (one assumes) "li" then "add"? It doesn't seem likely that
> that's buying much.
Changing an addi to li+add may not show up on benchmarks, but I can't claim
it's immaterial. I shouldn't unify the code if that makes the compiled code
materially worse than what the gcc intrinsics produce today, hence the
nontrivial (~50 line) bits to match the intrinsics' capabilities.
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