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From: Toon Moene <toon@moene.indiv.nluug.nl>
To: law@cygnus.com
Cc: egcs@cygnus.com
Subject: Re: my EGCS status (really Fortran patches)
Date: Wed, 22 Oct 1997 22:55:00 -0000	[thread overview]
Message-ID: <9710230552.AA21715@moene.indiv.nluug.nl> (raw)
In-Reply-To: <4712.877581304@hurl.cygnus.com>

Jeff,

L$0009
        fldds,ma 8(0,%r26),%fr24
        fldds,ma 8(0,%r24),%fr23
        fldds 0(0,%r25),%fr22
        fmpy,dbl %fr24,%fr23,%fr23
        fldds,ma 8(0,%r23),%fr25
        fsub,dbl %fr22,%fr23,%fr22
        fmpy,dbl %fr22,%fr25,%fr22
        fstds,ma %fr22,8(0,%r25)
        fldds,ma 8(0,%r22),%fr23
        fldds 0(0,%r20),%fr22
        fmpy,dbl %fr24,%fr23,%fr24
        fsub,dbl %fr22,%fr24,%fr22
        fmpy,dbl %fr22,%fr25,%fr22
        addib,>= -1,%r28,L$0009
        fstds,ma %fr22,8(0,%r20)


>  Now, I don't actually know if one version executes any
>  faster than the other -- this is just something I noticed
>  when looking for why tomcatv ran 10% slower with the USE
>  patch.

[ I once saw HP-PA assembler before, about a year ago, because  
someone complained to the g77-bug list that he couldn't get Fortran  
code with assigned goto's to assemble - turned out the HP assembler  
can't cope with forward labels in instructions other than jumps.  So  
take this with a grain of salt ]

I gather, from looking at this code that instructions ending in .ma  
do (implicit) post-increment addressing ?  That would explain a  
lot: The instructions normally associated with updating address  
registers can be interspersed between the floating point ops, which  
is a win on a CPU that has separate integer and floating point  
units.  You lose this advantage when these integer instructions  
aren't explicit.  On the m68k post-increment addressing is a real  
win, because you're actually saving instructions.  Seems that HP  
wanted the best of both worlds ... and lost (wonder how they solve  
this themselves ...)

I don't see a simple way out of this.

HTH,
Toon.

  reply	other threads:[~1997-10-22 22:55 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <9710211752.AA19479@moene.indiv.nluug.nl>
1997-10-22 21:33 ` Jeffrey A Law
1997-10-22 22:55   ` Toon Moene [this message]
1997-10-22 23:26     ` Jeffrey A Law
1997-10-23  0:47     ` Jeffrey A Law
1997-10-23 10:45       ` Toon Moene
1997-10-23 11:04         ` Jeffrey A Law
1997-10-23 12:18           ` Joe Buck
1997-10-24 22:37     ` -frerun-loop Jeffrey A Law
1997-10-22 22:33 ` my EGCS status (really Fortran patches) Jeffrey A Law
1997-10-26  9:18 ` Jeffrey A Law
1997-10-27 16:30   ` Jim Wilson
1997-10-27 15:54     ` Jeffrey A Law
1997-10-27 17:21       ` Jim Wilson
1997-10-28 12:35         ` Jeffrey A Law
1997-10-28 12:35           ` Toon Moene

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