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// Copyright (c) 2004 by Arthur Langereis (arthur_ext at domain xfinitegames, tld com↩
↩
// 1 op = 6 ANDs, 3 SHRs, 3 SHLs, 4 assigns, 2 ADDs↩
// O(1)↩
function fast3bitlookup(b) {↩
var c, bi3b = 0xE994; // 0b1110 1001 1001 0100; // 3 2 2 1 2 1 1 0↩
c = 3 & (bi3b >> ((b << 1) & 14));↩
c += 3 & (bi3b >> ((b >> 2) & 14));↩
c += 3 & (bi3b >> ((b >> 5) & 6));↩
return c;↩
↩
/*↩
lir4,0xE994; 9 instructions, no memory access, minimal register dependence, 6 shifts, 2 adds, 1 inline assign↩
rlwinmr5,r3,1,28,30↩
rlwinmr6,r3,30,28,30↩
rlwinmr7,r3,27,29,30↩
rlwnmr8,r4,r5,30,31↩
rlwnmr9,r4,r6,30,31↩
rlwnmr10,r4,r7,30,31↩
addr3,r8,r9↩
addr3,r3,r10↩
*/↩
}↩
↩
↩
function TimeFunc(func) {↩
var x, y, t;↩
for(var x=0; x<500; x++)↩
for(var y=0; y<256; y++) func(y);↩
}↩
↩
TimeFunc(fast3bitlookup);↩