Author: Zappa
Date: 20:24:52 12/05/05
I am getting really, really tired of coding all my evaluation twice (once for white and once for black). However, one of the things that is keeping me from switching to a for(i < 2) loop is that I can't do a shift! For example, if I have some pattern based on (pawns << 8) for white, than that is (pawns >> 8) for black, and you can't do a negative shift in IA32. My ideas: Eugene will happily point out that on the Itanium doing two shifts and selecting the correct value is 1 (2?) bundles. Otherwise on AMD64 I could do a) two shifts & cmov. I think 5 instructions (as compared to 1, and I have a LOT of shifts). b) << followed by >>. 1 extra instruction but I have twice as many loads for constants. c) rotate (X | 64-x) (but then I have the possibility of things ending up rotating around). d) your name here . . . :) I am not that concerned about latency because there would usually be alot of stuff around that could be rescheduled, but if I have to do 5 instructions for every shift my code size will triple. anthony
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