Re: Mips optimized versions of strlen, strncpy, strcmp

[Joel Sherrill <joel dot sherrill at OARcorp dot com>]

"Aaron J. Grier" wrote:
> 
> On Tue, Nov 13, 2001 at 03:44:06PM -0500, Michael Meissner wrote:
> 
> > In general, I feel that the str* (& to some extent the mem*) functions
> > in newlib could be better tuned for different machines (I suspect you
> > may wind up with 3-4 versions, depending on whether a machine has pre
> > or post incrementation, how deep the pipeline is to/from memory,
> > etc.).
> 
> I was looking at these a few weeks ago as well...  the loop unrolling
> done in some of the string operations is silly to do on m68k cpu32
> variants, since they have a loop mode.  I imagine other architectures
> are similar.

I tend to agree with Michael, if there were probably a handful of standard C
implementations from which the architectures could choose, most would end
up with a better performing version.  One implementation could favor code 
space, another could unroll loops, another could do memory operations in
larger non-octet chunks, etc.  The trick is to make sure the various
implementations can be shared and that an architecture pick the one
that suits it the best.  

For example, I am pretty sure that the m68k and other CISC would do well with
an
implementation that arranged to move 32-bit quantities as much as possible.
The i386 would do OK with this but its string instructions are probably still
better.

> maybe some of these could be moved to libgloss for the architecture-
> specific implementations?

I think libgloss is for board specific code.  This type of code
is normally in libc/machine.

> --
>   Aaron J. Grier  |   Frye Electronics, Tigard, OR   |  aaron@frye.com
>      "In a few thousand years people will be scratching their heads
>        wondering how on earth the first computer was invented and
>           bootstrapped without a prior computer to do it with."
>                     --  Chris Malcolm, on comp.arch

-- 
Joel Sherrill, Ph.D.             Director of Research & Development
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