modsi3.S
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#include <linux/linkage.h>
/*
* modulo operation for 32 bit integers.
* Input : op1 in Reg r5
* op2 in Reg r6
* Output: op1 mod op2 in Reg r3
*/
.text
.globl __modsi3
.type __modsi3, @function
.ent __modsi3
__modsi3:
.frame r1, 0, r15
addik r1, r1, -16
swi r28, r1, 0
swi r29, r1, 4
swi r30, r1, 8
swi r31, r1, 12
beqi r6, div_by_zero /* div_by_zero division error */
beqi r5, result_is_zero /* result is zero */
bgeid r5, r5_pos
/* get the sign of the result [ depends only on the first arg] */
add r28, r5, r0
rsubi r5, r5, 0 /* make r5 positive */
r5_pos:
bgei r6, r6_pos
rsubi r6, r6, 0 /* make r6 positive */
r6_pos:
addik r3, r0, 0 /* clear mod */
addik r30, r0, 0 /* clear div */
addik r29, r0, 32 /* initialize the loop count */
/* first part try to find the first '1' in the r5 */
div1:
add r5, r5, r5 /* left shift logical r5 */
bgeid r5, div1
addik r29, r29, -1
div2:
/* left shift logical r5 get the '1' into the carry */
add r5, r5, r5
addc r3, r3, r3 /* move that bit into the mod register */
rsub r31, r6, r3 /* try to subtract (r30 a r6) */
blti r31, mod_too_small
/* move the r31 to mod since the result was positive */
or r3, r0, r31
addik r30, r30, 1
mod_too_small:
addik r29, r29, -1
beqi r29, loop_end
add r30, r30, r30 /* shift in the '1' into div */
bri div2 /* div2 */
loop_end:
bgei r28, return_here
brid return_here
rsubi r3, r3, 0 /* negate the result */
div_by_zero:
result_is_zero:
or r3, r0, r0 /* set result to 0 [both mod as well as div are 0] */
return_here:
/* restore values of csrs and that of r3 and the divisor and the dividend */
lwi r28, r1, 0
lwi r29, r1, 4
lwi r30, r1, 8
lwi r31, r1, 12
rtsd r15, 8
addik r1, r1, 16
.size __modsi3, . - __modsi3
.end __modsi3