8  * a supported configuration.
10  * With just a barrel shifter, we can implement an efficient constant
11  * multiply using shifts and adds.  GCC can find a 9-step solution, but
12  * this 6-step solution was found by Yevgen Voronenko's implementation
15  * That software is really not designed for a single multiplier this large,
17  * 6-shift, 6-add sequences for computing x * 0x61C88647.  They are all
19  *	a = (x <<  9) + c;
20  *	b = (x << 23) + a;
21  *	return (a<<11) + (b<<6) + (c<<3) - b;
24  * Without even a shifter, it's hopless; any hash function will suck.
32 static inline u32 __attribute_const__ __hash_32(u32 a)  in __hash_32()  argument
38 	b =  a << 23;  in __hash_32()
39 	c = (a << 19) + a;  in __hash_32()
40 	a = (a <<  9) + c;  in __hash_32()
41 	b += a;  in __hash_32()
43 	/* Phase 2: Compute (a << 11) + (b << 6) + (c << 3) - b */  in __hash_32()
44 	a <<= 5;  in __hash_32()
45 	a += b;		/* (a << 5) + b */  in __hash_32()
46 	a <<= 3;  in __hash_32()
47 	a += c;		/* (a << 8) + (b << 3) + c */  in __hash_32()
48 	a <<= 3;  in __hash_32()
49 	return a - b;	/* (a << 11) + (b << 6) + (c << 3) - b */  in __hash_32()
54 	 * Without a barrel shifter, left shifts are implemented as  in __hash_32()
57 	 * optimal, but at 37 steps, it's decent for a 31-bit multiplier.  in __hash_32()
64 	b = a << 4;	/* 4    */  in __hash_32()
66 	b += a;		/* 1  6 */  in __hash_32()
69 	c -= a;		/* 1 11 */  in __hash_32()
73 	d += a;		/* 1 28 */  in __hash_32()
76 	d <<= 6;	/* 6 36 */  in __hash_32()