// Copyright (c) 2004 by Arthur Langereis (arthur_ext at domain xfinitegames, tld com var result = 0; // 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; var sum = 0; for(var x=0; x<50000; x++) for(var y=0; y<256; y++) sum += func(y); return sum; } sum = TimeFunc(fast3bitlookup); var expected = 51200000; if (sum != expected) throw "ERROR: bad result: expected " + expected + " but got " + sum;