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Re: float4/float8/int64 passed by value with tsearchfixup

From: Gregory Stark <stark(at)enterprisedb(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Alvaro Herrera" <alvherre(at)commandprompt(dot)com>, "Zoltan Boszormenyi" <zb(at)cybertec(dot)at>, <pgsql-patches(at)postgresql(dot)org>, "Hans-Juergen Schoenig" <hs(at)cybertec(dot)at>, "Magnus Hagander" <magnus(at)hagander(dot)net>
Subject: Re: float4/float8/int64 passed by value with tsearchfixup
Date: 2008-04-20 09:23:33
Message-ID: 87wsms98x6.fsf@oxford.xeocode.com (view raw or flat)
Thread:
Lists: pgsql-patches
"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

> Gregory Stark <stark(at)enterprisedb(dot)com> writes:
>>> Tom Lane wrote:
>>>> Specifically, I think what you missed is that on some platforms C
>>>> functions pass or return float values differently from similar-sized
>>>> integer or pointer values (typically, the float values get passed in
>>>> floating-point registers).
>
>> But I'm skeptical that it would hit such a wide swathe of the build farm. In
>> particular AFAIK the standard ABI for i386 does no such thing.
>
> I did some digging, and it seems you're mistaken.  The standard gcc ABI
> for both i386 and x86_64 returns floats in float registers (387
> registers in the first case, and SSE registers in the second case).
> This appears to have been the case for a very long time.  I quote from
> the manual for gcc 2.95:

Ah, return values. I accidentally glossed over that point and was looking for
how parameters were passed.

-- 
  Gregory Stark
  EnterpriseDB          http://www.enterprisedb.com
  Ask me about EnterpriseDB's 24x7 Postgres support!

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