[LAD] gcc and pointer aliasing... missing optimizations in some cases

[Gabriel M. Beddingfield]

On Tue, 22 Dec 2009, torbenh wrote:

> class Ramp
> {
>    private:
> 	float _phase;
> 	float _omega;
>    public:
> 	Ramp();
> 	float process()
> 	{
> 	    _phase += _omega;
> 	    return  _phase;
> 	}
> };

Is the problem that _phase and _omega get reloaded from 
memory every time they're used?

Would it not work to declare process() as:

     float process() __restrict
     { ... }

Thus telling the compiler that `this` is not an alias when 
process() is called.

Or perhaps:

> int process( jack_nframes_t nframes, void *arg )
> {
>    int i;
>
>    float * __restrict__ buf = (float *) jack_port_get_buffer( out_port, nframes );

      Ramp * __restrict__ o = &osc_block;

>
>    for( i=0; i<nframes; i++ ) {
> 	buf[i] = osc_block.process();

Change to:
         buf[i] = o->process();

-gabriel