From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@lists.postgresql.org, Tom Lane <tgl@sss.pgh.pa.us>
Cc: Andrew Gierth <andrew@tao11.riddles.org.uk>
Cc: David Rowley <david.rowley@2ndquadrant.com>
Cc: Thomas Munro <thomas.munro@enterprisedb.com>
Subject: Re: Using POPCNT and other advanced bit manipulation instructions
Date: Wed, 13 Feb 2019 17:12:11 -0300
Message-ID: <20190213201211.GA5800@alvherre.pgsql> (raw)
In-Reply-To: <2F6CDF3B-08B9-4A15-ABDF-55D7F82AB76E@anarazel.de>
On 2019-Feb-13, Andres Freund wrote:
> Hi,
>
> On February 13, 2019 8:40:14 PM GMT+01:00, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> >Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> >> I've pushed this now. Let's see what the buildfarm has to say about
> >it.
> >
> >It's likely to be hard to tell, given the amount of pink from the Ryu
> >patch. If Andrew is not planning to clean that up PDQ, I'd suggest
> >reverting that patch pending having some repairs for it.
>
> I'd assume that breaking bit counting would cause distinct enough
> damage (compile time or crashes).
I was a bit surprised to find out that the assembly generated by
compiling the code in test for __builtin_foo() does not actually include
the calls being tested ... (they're only used to generate the value for
a static variable, and that gets optimized away); but then the comment
for the test does say that we're only testing that the compiler
understands the construct, so I suppose that's fine. Also, we already
do that for bswap.
This "compiler explorer" tool is nice:
https://gcc.godbolt.org/#g:!((g:!((g:!((h:codeEditor,i:(j:1,source:'int+main(int+argc+,+char**+a...
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-hackers@postgresql.org
Cc: alvherre@2ndquadrant.com, andres@anarazel.de, tgl@sss.pgh.pa.us, andrew@tao11.riddles.org.uk, david.rowley@2ndquadrant.com, thomas.munro@enterprisedb.com
Subject: Re: Using POPCNT and other advanced bit manipulation instructions
In-Reply-To: <20190213201211.GA5800@alvherre.pgsql>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox