------- Additional Comments From dberlin at gcc dot gnu dot org 2005-05-22 22:24 ------- Subject: Re: missed optimization due with const function and pulling out of loops
> on the other hand, we should not let the definition make the concept > useless. Being able to make The definition actually matches what other compilers call "isolated" (no access to global variables) combined with the property called "side-effect free" (calling multiple times with same parameters is same as calling once). We could of course, split these concepts if we wanted to. > > int something(int i) > { > static int a[100]; > > if (a[i] == 0) > a[i] = somewhat_slow_computation; > return a[i]; > } > > const is fairly useful. > > Anyway, moving possibly non-executed const function may cause also > other problems. Consider > > int my_fancy_divide(int x, int z) attribute(const) > { > return x / z; > } > > while (...) > { > if (z != 0) > x = my_fancy_divide (x,z) > } Uh, this may be const, but you can't move these out anyway because the value of the parameters has changed, so i'm not sure what you are going for. > Thus you would also have to require the const function to be total. > Making const still more and more useless. > > const has a very specific definition already. Moving get_type2 out of the loop is consistent with that definition. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21712