[PATCH] _mktm_r: optimize speed

[Freddie Chopin <freddie_chopin at op dot pl>]

I attach patch (with ChangeLog entry) for _mktm_r() which replaces 
iterative calculations of day with a few divisions and multiplications.

This change results in the function working two times faster on ARM 
Cortex-M3 microcontroller - one million calls of "old" function using 
random numbers take ~70s, while the same calculations with "new" code 
take ~33s (clock of chip is 16MHz). Obviously the improvement depends on 
the input value - sometimes the patched code can be slower than the old 
one - for input values "close" to year 1970. On the other hand, the 
"further" from 1970, the bigger is the performance gain.

Both versions give the same results - tested with a few million random 
numbers - both versions were called for the same input value and result 
was compared with memcmp().

Regards,
FCh

Attachment: ChangeLog.txt
Description: Text document

Attachment: 0001-_mktm_r-optimize-speed.patch
Description: Text document