michael@0: // Copyright (c) 2004 by Arthur Langereis (arthur_ext at domain xfinitegames, tld com
michael@0: 
michael@0: // 1 op = 6 ANDs, 3 SHRs, 3 SHLs, 4 assigns, 2 ADDs
michael@0: // O(1)
michael@0: function fast3bitlookup(b) {
michael@0: var c, bi3b = 0xE994; // 0b1110 1001 1001 0100; // 3 2 2 1  2 1 1 0
michael@0: c  = 3 & (bi3b >> ((b << 1) & 14));
michael@0: c += 3 & (bi3b >> ((b >> 2) & 14));
michael@0: c += 3 & (bi3b >> ((b >> 5) & 6));
michael@0: return c;
michael@0: 
michael@0: /*
michael@0: lir4,0xE994; 9 instructions, no memory access, minimal register dependence, 6 shifts, 2 adds, 1 inline assign
michael@0: rlwinmr5,r3,1,28,30
michael@0: rlwinmr6,r3,30,28,30
michael@0: rlwinmr7,r3,27,29,30
michael@0: rlwnmr8,r4,r5,30,31
michael@0: rlwnmr9,r4,r6,30,31
michael@0: rlwnmr10,r4,r7,30,31
michael@0: addr3,r8,r9
michael@0: addr3,r3,r10
michael@0: */
michael@0: }
michael@0: 
michael@0: var ret = 0;
michael@0: function TimeFunc(func) {
michael@0:   var x, y, t;
michael@0:   for(var x=0; x<500; x++)
michael@0:   for(var y=0; y<256; y++) {
michael@0:     ret += func(y);
michael@0:   }
michael@0: }
michael@0: 
michael@0: TimeFunc(fast3bitlookup);
michael@0: assertEq(ret, 512000)