138 lines
3.5 KiB
ArmAsm
138 lines
3.5 KiB
ArmAsm
/*
|
|
* 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
|
|
.globl _Mul
|
|
.mul:
|
|
_Mul: /* needed for export */
|
|
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
|