On Sat, 2010-11-06 at 02:16 +0900, Tetsuo Handa wrote:
> Tetsuo Handa wrote:
> > Eric Paris wrote:
> > > Interesting, is this a result of the compiler previously being able to
> > > optimize the division since it could tell it was a power of 2 and now
> > > that we have a private variable it can't? The patch can easily be
> > > reverted without breaking anyone else....
> >
> I meant to say that it seems that GCC 3.x can optimize
>
> #define roundup(x, y) ((((x) + ((y) - 1)) / (y)) * (y))
>
> for roundup((long long), (const)) case but cannot optimize
>
> #define roundup(x, y) ( \
> { \
> typeof(y) __y = y; \
> (((x) + (__y - 1)) / __y) * __y; \
> } \
> )
>
> for roundup((long long), (const)) case.
I guess this is my fault (I'm not completely convinced) since my testing
was done with gcc 4. I just retested to make sure that
gcc-4.5.1-4.fc14.x86_64 is able to optimize both (and it does). Is the
fact that it requires compiler optimizations for the code to build a
good thing?
-Eric
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