From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 115aec,d275ffeffdf83655 X-Google-Attributes: gid115aec,public X-Google-Thread: 103376,d275ffeffdf83655 X-Google-Attributes: gid103376,public From: robert_dewar@my-dejanews.com Subject: Re: Instruction Set Semantics Date: 1999/01/28 Message-ID: <78pqi8$6gt$1@nnrp1.dejanews.com>#1/1 X-Deja-AN: 437775860 References: <369C1F31.AE5AF7EF@concentric.net> <369DDDC3.FDE09999@sea.ericsson.se> <369e309a.32671759@news.demon.co.uk> <77ledn$eu7$1@remarQ.com> <77pnqc$cgi$1@newnews.global.net.uk> <8p64spq5lo5.fsf@Eng.Sun.COM> <782r25$k18$1@nnrp1.dejanews.com> <36AEDCEE.23964EF7@enea.se> <78o59b$31a$1@plug.news.pipex.net> X-Http-Proxy: 1.0 x7.dejanews.com:80 (Squid/1.1.22) for client 205.232.38.14 Organization: Deja News - The Leader in Internet Discussion X-Article-Creation-Date: Thu Jan 28 14:00:46 1999 GMT Newsgroups: comp.lang.ada,comp.realtime X-Http-User-Agent: Mozilla/4.04 [en] (OS/2; I) Date: 1999-01-28T00:00:00+00:00 List-Id: In article <78o59b$31a$1@plug.news.pipex.net>, "Nick Roberts" wrote: > And as for the little differences in semantics (what the > instruction does, but not how fast it does it) between > different versions of superscalar processors: the 'little > differences' go on and on ;-) Indeed! As an example, we just had to work in emergency mode to fix an important bug for SGI. It turns out that an instruction to convert integer to float on the R10000 is not fully implemented, and traps to the operating system if the absolute magnitude of the integer exceeds 2**53. The operating system correctly interprets the intent in the trap routine. BUT, it takes for ever to do it. Since in the real world, people ARE concerned about how long things take (and not just the semantics in some pure sense :-) this caused serious performance problems, and we had to change the compiler to avoid generating these traps. Robert Dewar -----------== Posted via Deja News, The Discussion Network ==---------- http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own