1// Copyright (c) 2004 by Arthur Langereis (arthur_ext at domain xfinitegames, tld com
2
3var result = 0;
4
5// 1 op = 6 ANDs, 3 SHRs, 3 SHLs, 4 assigns, 2 ADDs
6// O(1)
7function fast3bitlookup(b) {
8var c, bi3b = 0xE994; // 0b1110 1001 1001 0100; // 3 2 2 1  2 1 1 0
9c  = 3 & (bi3b >> ((b << 1) & 14));
10c += 3 & (bi3b >> ((b >> 2) & 14));
11c += 3 & (bi3b >> ((b >> 5) & 6));
12return c;
13
14/*
15lir4,0xE994; 9 instructions, no memory access, minimal register dependence, 6 shifts, 2 adds, 1 inline assign
16rlwinmr5,r3,1,28,30
17rlwinmr6,r3,30,28,30
18rlwinmr7,r3,27,29,30
19rlwnmr8,r4,r5,30,31
20rlwnmr9,r4,r6,30,31
21rlwnmr10,r4,r7,30,31
22addr3,r8,r9
23addr3,r3,r10
24*/
25}
26
27
28function TimeFunc(func) {
29var x, y, t;
30var sum = 0;
31for(var x=0; x<500; x++)
32for(var y=0; y<256; y++) sum += func(y);
33return sum;
34}
35
36sum = TimeFunc(fast3bitlookup);
37