A little warning in GMP.h

Brian Gladman brg at gladman.plus.com
Mon Sep 27 16:51:55 CEST 2004

Torbjorn Granlund wrote:

> Brian Gladman <brg at gladman.plus.com> writes:
>   Designing GMP to work well with poor compilers at the expense of good ones
>   is fine if you really think that this makes sense. But in my view this is a
>   design philosophy that is from a bygone age.
> You would know more about those datk age than me, but it baffles
> me that people ever behaved that irrationally.  :-)
>   And, of course, you can always trust someone on this list to turn a serious
>   point into a cheap jibe at the Microsoft compiler.
> Oh, I misunerstood you.  I thought you were showing a horror
> example of the poor optimizer of the Microsoft compiler, when you,
> in fact, where making a serious point.

Ok, now that we have got that misunderstanding out of the way, I think 
it is worth asking Brian Hurt's question but 'in reverse'.

That is, are there still compilers around that: (a) are important for 
GMP, and (b) cannot produce branchless code from:

	return (__gmp_n != 0) ? __gmp_l : 0;

on those architectures where this matters?

All the x86 compilers that I use regularly have no problem producing 
branchless code in this situation.  I don't use GCC but can I assume 
that it is now good enough on the X86 to do the same?

If modern C compilers don't need such tricks it would surely be better
to abandon them since they only serve to make the code more obscure 
without producing benefits.

    Brian Gladman

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