Re: Optimizing calls to GSL functions

[Tommy Nordgren <tommy dot nordgren at comhem dot se>]

On 9 jun 2007, at 10.19, Brian Gough wrote:

> At Sat, 9 Jun 2007 04:25:55 +0200,
> Tommy Nordgren wrote:
> > Are there any way, when using the GNU Compiler Collection, to make
> > the compiler optimize expressions where the same function call
> > occurs more than once.  (Same function, same parameters) GCC does
> > this for standard C functions such as cos and sin, when passed -O3
> > or -Os -fgcse I'm interested in this, because most special functions
> > computed by GSL are probably more expensive to compute than the
> > basic transcendental functions, and in general you can get many
> > common subexpressions when generating C code from symbol math
> > programs.
>
> __attribute__ ((pure), see "Function attributes" in the GCC manual for
> details.
>
> --
> Brian Gough
	Thanks, Brian. I got another suggestion too, : __attribute__((const)) .
I've checked that it works in C++ headers too.
	I suggest you mention the use of __attribute__ in the next edition of
"An Introduction to GCC"
------------------------------------------------------
"Home is not where you are born, but where your heart finds peace" -
Tommy Nordgren, "The dying old crone"
tommy.nordgren@comhem.se