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Diffstat (limited to 'arch/sparc/lib/mul.S')
| -rw-r--r-- | arch/sparc/lib/mul.S | 135 | 
1 files changed, 135 insertions, 0 deletions
diff --git a/arch/sparc/lib/mul.S b/arch/sparc/lib/mul.S new file mode 100644 index 00000000000..83dffbc2f62 --- /dev/null +++ b/arch/sparc/lib/mul.S @@ -0,0 +1,135 @@ +/* $Id: mul.S,v 1.4 1996/09/30 02:22:32 davem Exp $ + * mul.S:       This routine was taken from glibc-1.09 and is covered + *              by the GNU Library General Public License Version 2. + */ + +/* + * 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. + */ + +	.globl .mul +.mul: +	mov	%o0, %y		! multiplier -> Y +	andncc	%o0, 0xfff, %g0	! test bits 12..31 +	be	Lmul_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 + +Lmul_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 + +	.globl	.mul_patch +.mul_patch: +	smul	%o0, %o1, %o0 +	retl +	 rd	%y, %o1 +	nop  |