Pawn attacks by Strelka

[Gerd Isenberg]

In Strelka's eval.c following line appears twice:

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  mob_w = (((mob_w & 0xFFFF7F7F7F7F7F7F) << 2) | (mob_w & 0x00FEFEFEFEFEFEFE)) << 7;

I first thought about a typo - 2 instead of 9. It took me some seconds to get the parenthesis right. The constants look like disassembled from "optimized" 32-bit code

I prefer it with one dependency less:

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  mob_w = ((mob_w & 0x7F7F7F7F7F7F7F7F) << 9) | ((mob_w & 0xFEFEFEFEFEFEFEFE) << 7);

or to eventually share the 64-bit constant notA:

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  const U64 notA = C64(0xFEFEFEFEFEFEFEFE);
  mob_w = ((mob_w << 9) & notA) | ((mob_w & notA) << 7);

But likely compilers have their own opinions about pre- and post-shift masks.