Since we're discussing bit-exactness, I have a related question. One nice group of instructions in ARMv6 are capable of doing things like
a += (b * c) + (d * e) in a single cycle, where b, c, d and e are 16-bit quantities. This is potentially useful for certain types of compositing - except that the way rounding is currently done, ((t + (t >> 8)) >> 8) is assumed to be applied after every multiply. If I do one of those fancy dual-multiply instructions and then round the result, it will be technically more accurate because the intermediate result was effectively held in 16-bit precision, yet it won't match the exact bit pattern tested for by some of the "make check" tests. If the plan is to allow greater deviations, how can this be reconciled with the tests that require bitwise exact results? Ben _______________________________________________ Pixman mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/pixman
