Roland Dreier wrote:
Julien> Not very important but ((get_random_int() % 4096) << 4)
Julien> could be optimized into get_random_int() & 0xFFF0.
HPA> .. and gcc knows that.
HPA> 8: 25 ff 0f 00 00 and $0xfff,%eax
HPA> d: 83 c4 0c add $0xc,%esp
HPA> 10: c1 e0 04 shl $0x4,%eax
Actually gcc isn't quite that smart (since it obviously can't
understand the semantics of get_random int()). The original point was
that the "shl $0x4" can be avoided by directly &'ing with 0xfff0, not
that "% 4096" can be strength reduced to "& 0xfff".
Oh, right. D'oh! :)
-hpa
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