/* SPDX-License-Identifier: GPL-2.0 */
#include <linux/linkage.h>

/*
* Divide operation for 32 bit integers.
*       Input : Dividend in Reg r5
*               Divisor in Reg r6
*       Output: Result in Reg r3
*/
        .text
        .globl  __divsi3
        .type __divsi3, @function
        .ent __divsi3
__divsi3:
        .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
        xor     r28, r5, r6 /* get the sign of the result */
        rsubi   r5, r5, 0 /* make r5 positive */
r5_pos:
        bgei    r6, r6_pos
        rsubi   r6, r6, 0 /* make r6 positive */
r6_pos:
        addik   r30, r0, 0 /* clear mod */
        addik   r3, r0, 0 /* clear div */
        addik   r29, r0, 32 /* initialize the loop count */

        /* first part try to find the first '1' in the r5 */
div0:
        blti    r5, div2 /* this traps r5 == 0x80000000 */
div1:
        add     r5, r5, r5 /* left shift logical r5 */
        bgtid   r5, div1
        addik   r29, r29, -1
div2:
        /* left shift logical r5 get the '1' into the carry */
        add     r5, r5, r5
        addc    r30, r30, r30 /* move that bit into the mod register */
        rsub    r31, r6, r30 /* try to subtract (r30 a r6) */
        blti    r31, mod_too_small
        /* move the r31 to mod since the result was positive */
        or      r30, r0, r31
        addik   r3, r3, 1
mod_too_small:
        addik   r29, r29, -1
        beqi    r29, loop_end
        add     r3, r3, r3 /* 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 */
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 __divsi3, . - __divsi3
.end __divsi3