Re: optimisation question

[Robert Dewar <dewar at adacore dot com>]

Dale Johannesen wrote:

> > The statement about reordering is for compilers. It is completely
> > irrelevant for a C programmer, and you should not contort your
> > code in any way for this or any other similar low level reason.
>
>
> That's good general advice, but out here in the Real World there are 
> times when
> performance is more important than how pretty the code looks.  Certainly 
> if you're
> looking at lines that are taking less than 1% of the execution time, 
> Robert's
> advice is good.

Even in more difficult cases, people who mess with code at the C source
level in an attempt to do improve ILP often make things worse by trying
to second guess the compiler. ILP is really the domain of the compiler
or of a (fairly heroic) human assembly language writer.