Date: Tue, 9 Mar 1999 23:09:03 +0100
To: pgcc AT delorie DOT com
Subject: Re: loop unrolling
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In-Reply-To: <36DA64A8.5EEBA3B0@rug.ac.be>; from Marc Palmans on Mon, Mar 01, 1999 at 10:58:00AM +0100
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From: Marc Lehmann <pcg AT goof DOT com>
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On Mon, Mar 01, 1999 at 10:58:00AM +0100, Marc Palmans wrote:
> Marc Lehmann wrote:
> > > From: =?iso-8859-1?Q?Johnny_Teve=DFen?= <j DOT tevessen AT gmx DOT de>
> > > of the loop, the FPU is nearly totally left alone (well, I don't think
> > > the load-"d"-from-stack still occupies it here). And is the pentiumpro
> > > (i686) really capable of collecting 6 fp multiplications in its queue?
> > 
> > Yes ;)
> 
> Is this because of the out of order execution ? In one of the manuals it
> states that the execution unit cannot accept another fmul after the
> cycle it has accepted the first or am I missing something.
> Where in the source can I find this (okay, I'm new at this :), in the
> machine description I can only find a reference to the execution units. 

This is true, however, the p-ii (I'm not so sure about the ppro) can
collect upto 6 instructions in its decoder-queue. However, there are other
instructions and other sources of stalls, so that goal is likely not to
get reached with normal code.

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