Date: Wed, 11 Dec 2019 10:48:00 +0100 From: Szabolcs Nagy <nsz@...t70.net> To: Stefan Kanthak <stefan.kanthak@...go.de> Cc: musl@...ts.openwall.com Subject: Re: An addition to the math subtree * Stefan Kanthak <stefan.kanthak@...go.de> [2019-12-10 17:58:40 +0100]: > Optimised implementations of copysign() for i386 note that in most user code gcc would inline copysign calls instead of calling into libc. when it is a call into libc then it wont be fast no matter what because of the call overhead (spilling registers). so libc copysign is not performance critical (except currently musl code itself calls it but that can be fixed) i386 asm is also not very interesting (it introduces maintenance burden and not many users care about it) > > JFTR: I'm NOT subscribed to your mailing list, so CC: me in replies! > > --- -/dev/null > +++ +/src/math/i386/copysign.S > @@ -0,0 +1,26 @@ > +.global copysignf > +.type copysignf,@function > +copysignf: > + shlb $1,4+3(%esp) > + shlb $1,8+3(%esp) > + rcrb $1,4+3(%esp) > + flds 4(%esp) > + ret > + > +.global copysignl > +.type copysignl,@function > +copysignl: > + shlb $1,4+9(%esp) > + shlb $1,16+9(%esp) > + rcrb $1,4+9(%esp) > + fldt 4(%esp) > + ret > + > +.global copysign > +.type copysign,@function > +copysign: > + shlb $1,4+7(%esp) > + shlb $1,12+7(%esp) > + rcrb $1,4+7(%esp) > + fldl 4(%esp) > + ret
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