amd64/115581: [patch] -mfancy-math-387 has no effect
brde at optusnet.com.au
Wed Aug 22 03:00:08 PDT 2007
The following reply was made to PR amd64/115581; it has been noted by GNATS.
From: Bruce Evans <brde at optusnet.com.au>
To: Simun Mikecin <numisemis at yahoo.com>
Cc: Bruce Evans <brde at optusnet.com.au>, bug-followup at FreeBSD.org
Subject: Re: amd64/115581: [patch] -mfancy-math-387 has no effect
Date: Wed, 22 Aug 2007 19:50:17 +1000 (EST)
On Tue, 21 Aug 2007, Simun Mikecin wrote:
> --- Bruce Evans <brde at optusnet.com.au> wrote:
>>> This PR is about -mfancy-math-387 usage when compiling 32-bit compatibility
>>> libraries that are gone be used on FreeBSD/amd64.
>>> As far as I can see FreeBSD's libm on i386 uses those fancy instructions (for
>>> example /usr/src.current/lib/msun/i387/s_sin.S), so the same libm will be
>>> used for running 32-bit apps on FreeBSD/amd64.
>> Well, that's in asm so it is not affected by compiler flags. Compiler
>> flags can cause the library to be not used at all in some cases where
>> the library is better.
> I'm just wondering will it have a positive impact on performance if FreeBSD/i386 libm is changed
> not to use that asm code with fancy instructions (just like FreeBSD/amd64 does).
Maybe someday. The easy cases have already been looked at and resulted in
removing the asm implementations of functions like sinf() and asin().
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