Marcus Comstedt <marcus@mc.pp.se> writes:
> So, where does this buy you performance? The only CPU I can think of
> where the bit test would be faster is 6502, where the mere act of
> LDA:ing somthing would set the N flag in the status register to the
> eight bit of the loaded value. On a RISC cpu, I expect the bit test
> to be same speed or slower compared to an arithmetic comparison.
>
> (You _could_ make it one cycle faster on the Hitachi SH-4 by removing
> the cast to unsigned char *, since unsignedness is not required for
> the bit test to work, and reading unsigned chars is one cycle slower
> than reading signed chars on that CPU.)
My mother raised me to always treat a bit test as faster than an
arithmetic operation.
Are you saying my mother is *wrong*???
:-)
> C99 guarantees that char is _at least_ eight-bits. It can be 4711
> bits without breaking the standard though. In practice, not much of a
> problem though. Some PDPs have 9 bit chars, I think. But I don't
> expect to find chars any other size than 8 anywhere where svn will
> run.
I think Brane's solution (to use the apr_isascii and isctrl tests) is
best.
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Received on Thu Jul 18 16:19:17 2002