* "Andrey A. Chernov" <[EMAIL PROTECTED]> [ 2007-10-27 ]
[ cvs commit: src/include _ctype.h ]
> ache 2007-10-27 22:32:28 UTC
>
> FreeBSD src repository
>
> Modified files:
> include _ctype.h
> Log:
> Micro-optimization of prev. commit, change
> (_c < 0 || _c >= 128) to (_c & ~0x7F)
Isn't that a non-optimization in code and a minor pessimization of readability?
Maybe I'm getting rusty, but those seem to result in nearly identical code on
i386 with a relatively modern GCC. Did you look at the compiler output for this
optimization? Is there a specific expensive instruction you're trying to avoid?
For such thoroughyl bit-aligned range checks, you shouldn't even get a branch
for the former case. Is there a platform other than i386 I should look at where
the previous expression is more clearly pessimized? Or a different compiler
than GCC?
juli.
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