/*

 * 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, %o1

1:

	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

#endif

LOC(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 result

END(.mul)