[PATCH] Fix carry bug in 128-bit unsigned integer adding
galak at kernel.crashing.org
Wed Jan 16 01:37:55 EST 2008
On Jan 8, 2008, at 9:05 PM, Liu Yu wrote:
>> take a look at how include/math-emu/op-4.h implements
>> __FP_FRAC_ADD_4 & __FP_FRAC_SUB_4. Will that fix the bug, if
>> so we should make the code match how its done there.
>> - k
> The macro define __FP_FRAC_ADD_4 is below. It can fix the carry bug.
> But still exist a problem that r[0-2] and x[0-2] cannot be referred to
> the same variable.
> If r0 and x0 are the same variable, the comparison ( r0 < x0 ) will
> always fail.
> I don't know whether we need to fix this problem.
Not sure. Probably worth asking this on the glibc list and see if
they have theories. (For the short term I'd say lets use the version
from include/math-emu/op-4.h as a fix. If r0 & x0 can be the same
variable the bug exists in a lot more places (glibc soft-fp and
generic kernel mathemu)
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