Article View: comp.arch
Article #3397Re: Integer Multiply/Divide on Sparc
From: John Mashey
Date: Tue, 16 Jan 1990 16:52
Date: Tue, 16 Jan 1990 16:52
18 lines
1512 bytes
1512 bytes
In article <2819@auspex.auspex.com> guy@auspex.auspex.com (Guy Harris) writes:
....
>the compiler writers were too lazy to change the compiler, I think it
>was done because it was *still* faster to do the shifts and adds. I
>can't speak for MIPS, but I wouldn't be surprised to hear that even
>though they had a multiply instruction since Day 1 they still did shifts
>and adds for multiplies by constants.
Yes, of course: shifts, adds, and subtracts, up to the point where
it takes about as long as a multiply. (I think there's a bias to use
multiply if its equal or close, since the code sequence is shorter,
andthere may be code scheduling opportunities in the shadow of the
multiply, although not many.)
--
-john mashey DISCLAIMER: <generic disclaimer, I speak for me only, etc>
UUCP: {ames,decwrl,prls,pyramid}!mips!mash OR mash@mips.com
DDD: 408-991-0253 or 408-720-1700, x253
USPS: MIPS Computer Systems, 930 E. Arques, Sunnyvale, CA 94086
Technical Details
Message-ID:
<34530@mips.mips.COM>Path:
arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!apple!oliveb!pyramid!prls!mips!winchester!mashReferences:
<8840005@hpfcso.HP.COM> <1249@otc.otca.oz> <KHB.90Jan11212327@chiba.kbierman@sun.com> <1255@otc.otca.oz> <2819@auspex.auspex.com>Show Full Headers
Complete Article Headers
Path: arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!apple!oliveb!pyramid!prls!mips!winchester!mash From: mash@mips.COM (John Mashey) Newsgroups: comp.arch Subject: Re: Integer Multiply/Divide on Sparc Message-ID: <34530@mips.mips.COM> Date: 16 Jan 90 16:52:34 GMT References: <8840005@hpfcso.HP.COM> <1249@otc.otca.oz> <KHB.90Jan11212327@chiba.kbierman@sun.com> <1255@otc.otca.oz> <2819@auspex.auspex.com> Sender: news@mips.COM Reply-To: mash@mips.COM (John Mashey) Organization: MIPS Computer Systems, Inc. Lines: 18