fast 64-bit dividend minu remainder calculation

[pshemu]

hi,

is there a way to fast calculate x-x%y (greatest multiplication of y
before x), where x and y are 64-bit integers on a 32-bit machine??
Maybe MMX registers would be useful?? I am writing this with gcc and
gas. Any help would be appreciated and thanks in advance.

Best regards,

Przemek

[P.J. Plauger]

<ps****@gmail.comwrote in message
news:11*********************@n59g2000hsh.googlegro ups.com...

is there a way to fast calculate x-x%y (greatest multiplication of y
before x), where x and y are 64-bit integers on a 32-bit machine??
Maybe MMX registers would be useful?? I am writing this with gcc and
gas. Any help would be appreciated and thanks in advance.

If you have long long support, I think (x / y) * y gives you what you want.

P.J. Plauger
Dinkumware, Ltd.
http://www.dinkumware.com

[CBFalconer]

ps****@gmail.com wrote:

>
is there a way to fast calculate x-x%y (greatest multiplication of y
before x), where x and y are 64-bit integers on a 32-bit machine??
Maybe MMX registers would be useful?? I am writing this with gcc and
gas. Any help would be appreciated and thanks in advance.

Easy, if you have a C99 compiler and the long long type. Otherwise
look at your compiler documentation.

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