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Date: Thu, 17 May 2007 22:03:26 +0200
From: Gautier <gautier@fakeaddress.nil>
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Subject: Re: GNAT Optimization of Constant Expressions
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Date: 2007-05-17T22:03:26+02:00
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Randy:

[a brilliant dissertation about optimization]
> After all, your original code is written to make a bunch of very expensive
> calls ("Sin(0.5)", for instance) many times. Expecting the compiler to
> remove those calls is asking a lot;

I agree for any function call, but in the special case of functions from 
Generic_Elementary_Functions, it is _not_ asking a lot! A decent compiler 
should perform optimizations around these functions as well as around 
arithmetic operators.

> it is much better to avoid making extra
> calls with appropriate constant declarations. (I'd have that advice for any
> language; why force the optimizer to work hard and possibly fail??)

Obviously, there are compilers where the optimizer is working hard for the 
programmer, and other ones where the programmer has to work hard to make the 
optimizer work!

______________________________________________________________
Gautier         -- http://www.mysunrise.ch/users/gdm/index.htm
Ada programming -- http://www.mysunrise.ch/users/gdm/gsoft.htm

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