On 9/22/15 22:45, Richard Henderson wrote: > On 09/21/2015 10:54 PM, Chen Gang wrote: >> On 2015年09月19日 10:34, Richard Henderson wrote: >>> >>> There's a trick for this that's more efficient for 4 or more elements >>> per vector (i.e. good for v2 and v1, but not v4): >>> >>> a + b = (a & 0x7f7f7f7f) + (b & 0x7f7f7f7f)) ^ ((a ^ b) & 0x80808080) >>> >>> a - b = (a | 0x80808080) - (b & 0x7f7f7f7f)) ^ ((a ^ ~b) & 0x80808080) >>> >> >> For me, we need use "(a ^ b) & 0x80..." instead of "(a ^ ~b) & 0x80...". > > No. What you did wrong was not use (a | 0x80808080). >
Oh, sorry. I shall send patch v3 for it. :-) Thanks. -- Chen Gang (陈刚) Open, share, and attitude like air, water, and life which God blessed
