/* * Signed multiply, from Appendix E of the Sparc Version 8 * Architecture Manual. *//* * Returns %o0 * %o1 in %o1%o0 (i.e., %o1 holds the upper 32 bits of * the 64-bit product). * * This code optimizes short (less than 13-bit) multiplies. */#include <sysdep.h>ENTRY(.mul)	mov	%o0, %y		! multiplier -> Y	andncc	%o0, 0xfff, %g0	! test bits 12..31	be	LOC(mul_shortway)	! if zero, can do it the short way	andcc	%g0, %g0, %o4	! zero the partial product and clear N and V	/*	 * Long multiply.  32 steps, followed by a final shift step.	 */	mulscc	%o4, %o1, %o4	! 1	mulscc	%o4, %o1, %o4	! 2	mulscc	%o4, %o1, %o4	! 3	mulscc	%o4, %o1, %o4	! 4	mulscc	%o4, %o1, %o4	! 5	mulscc	%o4, %o1, %o4	! 6	mulscc	%o4, %o1, %o4	! 7	mulscc	%o4, %o1, %o4	! 8	mulscc	%o4, %o1, %o4	! 9	mulscc	%o4, %o1, %o4	! 10	mulscc	%o4, %o1, %o4	! 11	mulscc	%o4, %o1, %o4	! 12	mulscc	%o4, %o1, %o4	! 13	mulscc	%o4, %o1, %o4	! 14	mulscc	%o4, %o1, %o4	! 15	mulscc	%o4, %o1, %o4	! 16	mulscc	%o4, %o1, %o4	! 17	mulscc	%o4, %o1, %o4	! 18	mulscc	%o4, %o1, %o4	! 19	mulscc	%o4, %o1, %o4	! 20	mulscc	%o4, %o1, %o4	! 21	mulscc	%o4, %o1, %o4	! 22	mulscc	%o4, %o1, %o4	! 23	mulscc	%o4, %o1, %o4	! 24	mulscc	%o4, %o1, %o4	! 25	mulscc	%o4, %o1, %o4	! 26	mulscc	%o4, %o1, %o4	! 27	mulscc	%o4, %o1, %o4	! 28	mulscc	%o4, %o1, %o4	! 29	mulscc	%o4, %o1, %o4	! 30	mulscc	%o4, %o1, %o4	! 31	mulscc	%o4, %o1, %o4	! 32	mulscc	%o4, %g0, %o4	! final shift	! If %o0 was negative, the result is	!	(%o0 * %o1) + (%o1 << 32))	! We fix that here.#if 0	tst	%o0	bge	1f	rd	%y, %o0	! %o0 was indeed negative; fix upper 32 bits of result by subtracting 	! %o1 (i.e., return %o4 - %o1 in %o1).	retl	sub	%o4, %o1, %o11:	retl	mov	%o4, %o1#else	/* Faster code adapted from tege@sics.se's code for umul.S.  */	sra	%o0, 31, %o2	! make mask from sign bit	and	%o1, %o2, %o2	! %o2 = 0 or %o1, depending on sign of %o0	rd	%y, %o0		! get lower half of product	retl	sub	%o4, %o2, %o1	! subtract compensation 				!  and put upper half in place#endifLOC(mul_shortway):	/*	 * Short multiply.  12 steps, followed by a final shift step.	 * The resulting bits are off by 12 and (32-12) = 20 bit positions,	 * but there is no problem with %o0 being negative (unlike above).	 */	mulscc	%o4, %o1, %o4	! 1	mulscc	%o4, %o1, %o4	! 2	mulscc	%o4, %o1, %o4	! 3	mulscc	%o4, %o1, %o4	! 4	mulscc	%o4, %o1, %o4	! 5	mulscc	%o4, %o1, %o4	! 6	mulscc	%o4, %o1, %o4	! 7	mulscc	%o4, %o1, %o4	! 8	mulscc	%o4, %o1, %o4	! 9	mulscc	%o4, %o1, %o4	! 10	mulscc	%o4, %o1, %o4	! 11	mulscc	%o4, %o1, %o4	! 12	mulscc	%o4, %g0, %o4	! final shift	/*	 *  %o4 has 20 of the bits that should be in the low part of the	 * result; %y has the bottom 12 (as %y's top 12).  That is:	 *	 *	  %o4		    %y	 * +----------------+----------------+	 * | -12- |   -20-  | -12- |   -20-  |	 * +------(---------+------)---------+	 *  --hi-- ----low-part----	 *	 * The upper 12 bits of %o4 should be sign-extended to form the	 * high part of the product (i.e., highpart = %o4 >> 20).	 */	rd	%y, %o5	sll	%o4, 12, %o0	! shift middle bits left 12	srl	%o5, 20, %o5	! shift low bits right 20, zero fill at left	or	%o5, %o0, %o0	! construct low part of result	retl	sra	%o4, 20, %o1	! ... and extract high part of resultEND(.mul)