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Date: Sat, 1 Jun 1996 01:08:37 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199605311508.BAA09743@godzilla.zeta.org.au>
To: freebsd-hackers@FreeBSD.org, mrm@MARMOT.Mole.ORG
Subject: Re: TARGET_NO_FANCY_MATH_387
Sender: owner-hackers@FreeBSD.org
X-Loop: FreeBSD.org
Precedence: bulk

>Might it be a good thing now to change the default in gcc to enable
>FP sin, cos and sqrt.

It would only give the inline sqrt.  The inline sin and cos are disabled
in the FSF version of gcc-2.6.3 for other reasons.  At least the i386
versions of them were broken.  You can use -mfancy-math-387 to get the
inline sqrt and -ffast-math to get the inline sin and cos together with
other fast and broken "math", or you can use inline assembler to get
inline math functions exactly where you want, or you can use the i387
version of libm to get non-inline hardware math functions in more cases.

>'387's have come down a fair amount in price
>for those of us with trusty '386/16's. Those still dependent upon
>FP simulation could use -mno-fancy-math-387...

The price of an i386 sqrt() emulation (in milliPentiums :-) has gone
up.  Those dependent on FP emulation would probably have difficulty
bootstrapping to use it.  At least the following utilities use sqrt(),
so they might fail when their inline sqrt() doesn't work: as, awk, bc,
cc1, cc1plus, dc, gdb, groff (parts), perl.

>and document
>-mfancy-math-387, -mno-fancy-math-387 in the man page for cc? ;-)

They have been documented for 5 months in -current, and the changes were
merged into -stable a couple of days ago.

Bruce