| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> |
| Cc: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Andres Freund <andres(at)anarazel(dot)de>, Yuqi Gu <Yuqi(dot)Gu(at)arm(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Optimize Arm64 crc32c implementation in Postgresql |
| Date: | 2018-05-02 14:30:39 |
| Message-ID: | 17188.1525271439@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> writes:
> Ahh, OpenSSL's armcap.c shows how to do this. You need to
> siglongjmp() out of there. Here's a patch that does it that way.
> Isn't this better?
Do you really need the pg_crc32c_armv8_choose_dummy global variable?
That seems pretty ugly. If you're concerned about the compiler
optimizing away the call to the crc function, you could write it like
result = (pg_comp_crc32c_armv8(0, 0, 0) == expected-value);
which'd provide a bit of extra checking that the code's not broken,
too.
regards, tom lane
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