static inline u32 __attribute_const__ __hash_32()

in include/asm/hash.h [32:79]

• 32 lines of code
• 1 McCabe index (conditional complexity)

static inline u32 __attribute_const__ __hash_32(u32 a)
{
#if CONFIG_XILINX_MICROBLAZE0_USE_BARREL
	unsigned int b, c;

	/* Phase 1: Compute three intermediate values */
	b =  a << 23;
	c = (a << 19) + a;
	a = (a <<  9) + c;
	b += a;

	/* Phase 2: Compute (a << 11) + (b << 6) + (c << 3) - b */
	a <<= 5;
	a += b;		/* (a << 5) + b */
	a <<= 3;
	a += c;		/* (a << 8) + (b << 3) + c */
	a <<= 3;
	return a - b;	/* (a << 11) + (b << 6) + (c << 3) - b */
#else
	/*
	 * "This is really going to hurt."
	 *
	 * Without a barrel shifter, left shifts are implemented as
	 * repeated additions, and the best we can do is an optimal
	 * addition-subtraction chain.  This one is not known to be
	 * optimal, but at 37 steps, it's decent for a 31-bit multiplier.
	 *
	 * Question: given its size (37*4 = 148 bytes per instance),
	 * and slowness, is this worth having inline?
	 */
	unsigned int b, c, d;

	b = a << 4;	/* 4    */
	c = b << 1;	/* 1  5 */
	b += a;		/* 1  6 */
	c += b;		/* 1  7 */
	c <<= 3;	/* 3 10 */
	c -= a;		/* 1 11 */
	d = c << 7;	/* 7 18 */
	d += b;		/* 1 19 */
	d <<= 8;	/* 8 27 */
	d += a;		/* 1 28 */
	d <<= 1;	/* 1 29 */
	d += b;		/* 1 30 */
	d <<= 6;	/* 6 36 */
	return d + c;	/* 1 37 total instructions*/
#endif
}