[rescue] OT: FeeCee rescue

Mike Meredith mike at blackhairy.demon.co.uk
Tue Sep 30 16:53:33 CDT 2003

On Tue, 30 Sep 2003 16:23:32 -0500, Joshua D. Boyd wrote:
> W.r.t. register shortage.
> I'm told that MIPSpro mainly only uses 4 out of the 32 registers a
> MIPS chip has, except for special cases (which would be tight loops
> that don't make function calls mainly).  

I don't know enough MIPS assembler to be able to tell for sure, but 'dis
/usr/bin/ls' on an IRIX system seems to show more than 4 registers being
used. Mind you limiting the number of registers you use allows you to
call functions (which use a different set of registers) without worrying
about your registers being scribbled on. And MIPSpro is quite probably
capable of doing that kind of optimisation.

> What I'm seeing looking
> through tons of Hitachi SH-3 assembly code (obviously a non-scientific
> survey) suggests that GCC for this chip doesn't use very many
> registers either. 

GCC is notorious for not generating good code on RISC processors.

> I'm beginning to wonder if lots of general purpose
> registers is quite what its cracked up to be.

Registers are very fast memory ... the more very fast memory you have,
the better. Aren't register windows used for fast context switching on

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