1// Copyright (c) 2004 by Arthur Langereis (arthur_ext at domain xfinitegames, tld com 2 3// 1 op = 6 ANDs, 3 SHRs, 3 SHLs, 4 assigns, 2 ADDs 4// O(1) 5function fast3bitlookup(b) { 6var c, bi3b = 0xE994; // 0b1110 1001 1001 0100; // 3 2 2 1 2 1 1 0 7c = 3 & (bi3b >> ((b << 1) & 14)); 8c += 3 & (bi3b >> ((b >> 2) & 14)); 9c += 3 & (bi3b >> ((b >> 5) & 6)); 10return c; 11 12/* 13lir4,0xE994; 9 instructions, no memory access, minimal register dependence, 6 shifts, 2 adds, 1 inline assign 14rlwinmr5,r3,1,28,30 15rlwinmr6,r3,30,28,30 16rlwinmr7,r3,27,29,30 17rlwnmr8,r4,r5,30,31 18rlwnmr9,r4,r6,30,31 19rlwnmr10,r4,r7,30,31 20addr3,r8,r9 21addr3,r3,r10 22*/ 23} 24 25 26function TimeFunc(func) { 27var x, y, t; 28for(var x=0; x<500; x++) 29for(var y=0; y<256; y++) func(y); 30} 31 32TimeFunc(fast3bitlookup); 33