50  *	v = 2^n v1  *  v0
54  *	uv = 2^2n u1 v1  +  2^n u1 v0  +  2^n v1 u0  +  u0 v0
55  *	   = 2^2n u1 v1  +     2^n (u1 v0 + v1 u0)   +  u0 v0
58  * and add 2^n u0 v0 to the last term and subtract it from the middle.
62  *	         (2^n)    (u1 v0 - u1 v1 + u0 v1 - u0 v0)  +
63  *	       (2^n + 1)  (u0 v0)
68  *		 (2^n)    (u1 - u0) (v0 - v1)  +	[(u1-u0)... = mid]
69  *	       (2^n + 1)  (u0 v0)			[u0v0 = low]
71  * The terms (u1 v1), (u1 - u0) (v0 - v1), and (u0 v0) can all be done
73  * of (u1 - u0) or (v0 - v1) may be negative.)
109 #define	v0	v.ul[L]  in __muldi3()  macro
113 	 * u1, u0, v1, and v0 will be directly accessible through the  in __muldi3()
129 		 * are small.  Here the product is just u0*v0.  in __muldi3()
131 		prod.q = __lmulq(u0, v0);  in __muldi3()
139 		low.q = __lmulq(u0, v0);  in __muldi3()
145 		if (v0 >= v1)  in __muldi3()
146 			vdiff = v0 - v1;  in __muldi3()
148 			vdiff = v1 - v0, negmid ^= 1;  in __muldi3()
164 #undef v0  in __muldi3()
187 	u_int u1, u0, v1, v0, udiff, vdiff, high, mid, low;  in __lmulq()  local
195 	v0 = LHALF(v);  in __lmulq()
197 	low = u0 * v0;  in __lmulq()
207 	if (v0 >= v1)  in __lmulq()
208 		vdiff = v0 - v1;  in __lmulq()
210 		vdiff = v1 - v0, neg ^= 1;  in __lmulq()