Andrew Morton wrote:
Christian Leber <[email protected]> wrote:
[...]
+ for (pb = 0; prop0 >= (9 * 5); pb++, prop0 -= (9 * 5));
+ for (lp = 0; prop0 >= 9; lp++, prop0 -= 9);
Put the ";" on a line of its own.
I'd have thought the above could be done arithmetically?
I just tried a small test program to see the speed/code size difference
to this code, which is the arithmetic equivalent:
pb = prop0 / (9 * 5);
prop0 %= (9 * 5);
lp = prop0 / 9;
prop0 %= 9;
This code runs a lot faster than the original. This is not very
important since it runs only once AFAICT.
As for the code size, it is smaller if compiled with -Os, but larger
when compiled with -O2 or -O3.
When compiled with -Os, gcc uses the idiv instruction and it even uses
its reminder so that it only does 2 idiv instructions to do the 4
operations above.
With -O2 or -O3, it does a hard to follow division "by hand" using
several instructions, rendering the code about 2.5x larger (but
amazingly a lot faster).
The tests were done with gcc 3.3.2.
--
Paulo Marques - www.grupopie.com
An expert is a person who has made all the mistakes that can be
made in a very narrow field.
Niels Bohr (1885 - 1962)
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]