Re: [PATCH] Fix carry bug in 128-bit unsigned integer adding

On Jan 8, 2008, at 9:05 PM, Liu Yu wrote:

quoted

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)

- k