Re: The Kommunity vs. Dick Johnson
yodaiken@chelm.cs.nmt.edu
Tue, 17 Nov 1998 12:31:18 -0700 (MST)
>
> Date: Mon, 16 Nov 1998 08:17:25 -0500 (EST)
> From: Isaac Connor <iconnor@penultima.ml.org>
>
> I am aware of many instances where gcc was able to produce better code
> than some asm-advocates I know. It also seems to me, that you have to
> look at register use, and how that affects code before and after the asm
> function.
>
> This of course proves nothing. The real acid test is whether or not GCC
> can produce better code than the what the *best* asm-advocates can
> produce. For example, I've yet to see a version of gcc which can do a
> good job of compiling the MD5 crypto checksum. The problem is that you
> have to be really clever to keep all of the MD5 accumulators in
> registers, and every gcc I've played with fails to do this, and ends up
> placing at least one or more of the MD5 state variables on the stack.
> Hence, in general gcc doesn't seem to handle algorithms which puts
> pressure on the i386's absurdly small register file.
Does that have a measurable cost on a PII? The likelhood that the register
will be in a shadow register, a write buffer, or in cache seems close to
100% if it is used soon again. I'm curious about whether the hardware is
making register allocation less critical.
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