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Re: -funsafe-loop-optimizations

On 2005-01-01, at 17:53, Zdenek Dvorak wrote:

I think Richard means issuing warning in case where -funsafe-loop-optimizations causes us to ignore some conditions for optimizations we were not able to prove. Which definitely is a good idea.

Micro tweaking on this level isn't supposed to be done on the scope of whole
files/compilation units. Perhaps a pragma directive allowing to get better assembler output
from a particular carefully selected part of the code after profiling could be of some use:

#include <stdio.h>

#pragma begin tighten code
int some_read_init_paramaters(...)
// We don't give a sh*t about the speed, since it's string parsing
// and we do it only once here. Better generate compact code to save flash
// on this microcontroller here.
#pragma end tighten code

/* Uff, I didn't have to go to assembler coding on this DSP, since I discovered that the
* following pragma did result in sufficiently performing code output by
* a margin of 5%... The video doesn't stutter anymore...
#pragma begin assume infinite arithmetic domains
int fft(unsigned int *real, unsigned int *imaginary, unsigned int *signal)
/* butterfly... butterfly... */
#pragma end assume infinite arithmeric domains

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