Messages in this thread | | | Date | Tue, 1 Jul 2003 22:09:14 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [PATCH] Kill div64.h dupes, parenthesize do_div() macro params |
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On Tue, 1 Jul 2003, Andrew Morton wrote: > > By requiring an explicit do_div we are made aware of all those 64-bit > divides and are made to think about them.
do_div() is NOT a 64-bit divide.
It's a 64/32->64+32 div/mod operation, which is a totally different thing than a full 64/64 divide, and is usually much faster to compute on most 32-bit architectures.
> Why 64-bit divides in particular were victimised in this manner is a matter > for speculation ;)
Because gcc historically _cannot_ generate an efficient 64/32->64 divide. It ends up doing a full 64/64 divide thing.
Linus
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