On Tue, Mar 16, 2010 at 4:11 PM, Dominique Dhumieres <domi...@lps.ens.fr> wrote: > In the block "Handle constant exponents." in gcc/builtins.c, the condition > !optimize_size has been replaced with optimize_insn_for_speed_p () between > gcc 4.3 and 4.4, but I have not been able to find when and why. > Does anybody remembers the when and why? > > This change make the optimization sensitive to PR40106 and unless it has > compeling reasons it should be reverted in this piece of code. > > My second question is why using optimize_size? I think it would be better > to define an upper bound instead of POWI_MAX_MULTS that depends on the kind > of optimisation. I cannot see any situation in which sqrt(a) would not be > better that pow(a,0.5) for speed, size, and accuracy.
pow (a, 0.5) is always expanded to sqrt(a). It is when we require additional multiplications, pow (a, n) -> sqrt (a) * a**(n/2), that optimize_insn_for_speed_p () is checked. Richard. > TIA > > Dominique > >
