From:	DougEleveld <deleveld AT dds DOT nl>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: How safe is the -march=pentium flag?
Date:	Sat, 15 Aug 1998 02:29:12 +0200
Organization:	Rijksuniversiteit Groningen
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To:	djgpp AT delorie DOT com
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Eli Zaretskii wrote:

> On Mon, 10 Aug 1998 D DOT J DOT Eleveld AT anest DOT azg DOT nl wrote:
>
> > > How huge is ``huge''?  Can you give some numbers?
> >
> > Ok, I was playing with optimizing the inner loops of the AllegPeg
> Mpeg player
> > library for Allegro.  I do my profiling stuff with some
> pentium-specific code
> > that counts clock cycles.  With -march=pentium I get 27.7M clock
> cycles per
> > frame with my Pentiun 133 with painfully slow (banked) video card.
> Exactly
> > the same flags and code (just changed the compiler options in Rhide,
> and
> > rebuilt) gets me 32.6M clock cycles per frame.
>
> The difference between 27.7 and 32.6 is merely 17%.  I would hardly
> call that a ``huge speed increase''.  Numbers around 10%-20% are what
> you would usually get by playing with different optimization
> switches.  See section 14.2 of the DJGPP FAQ for more details.

   Well, OK, it's not huge, but it is larger than PGCC gave me.  -06
made some of my code slower.  I'm also pretty sure that -march=pentium
makes things slower on my 350 Mhz pentium II.  Anyway, thanks for the
help, I appreciate it.

Doug Eleveld

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