Messages in this thread | | | Date | Wed, 10 Dec 2008 11:25:12 -0600 | From | Scott Wood <> | Subject | Re: [PATCH] fork_init: fix division by zero |
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On Wed, Dec 10, 2008 at 01:29:12PM +0300, Yuri Tikhonov wrote: > On Wednesday, December 10, 2008 you wrote: > > x * y / z is parsed as (x * y) / z, not x * (y / z). > > Here we believe in preprocessor: since all PAGE_SIZE, 8, and > THREAD_SIZE are the constants we expect it will calculate this. > > E.g. here is the result from this line as produced by cross-gcc > 4.2.2: > > lis r9,0 > rlwinm r29,r29,2,16,29 > stw r29,0(r9) > > As you see - only rotate-left, i.e. multiplication to the constant.
Yes, and also note that it is masking the result by 0xfffc, to preserve the effect of any overflow in (x * y).
-Scott
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