75 lines
1.8 KiB
ArmAsm
75 lines
1.8 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0 */
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#include <linux/linkage.h>
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/*
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* modulo operation for 32 bit integers.
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* Input : op1 in Reg r5
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* op2 in Reg r6
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* Output: op1 mod op2 in Reg r3
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*/
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.text
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.globl __modsi3
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.type __modsi3, @function
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.ent __modsi3
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__modsi3:
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.frame r1, 0, r15
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addik r1, r1, -16
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swi r28, r1, 0
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swi r29, r1, 4
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swi r30, r1, 8
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swi r31, r1, 12
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beqi r6, div_by_zero /* div_by_zero division error */
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beqi r5, result_is_zero /* result is zero */
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bgeid r5, r5_pos
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/* get the sign of the result [ depends only on the first arg] */
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add r28, r5, r0
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rsubi r5, r5, 0 /* make r5 positive */
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r5_pos:
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bgei r6, r6_pos
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rsubi r6, r6, 0 /* make r6 positive */
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r6_pos:
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addik r3, r0, 0 /* clear mod */
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addik r30, r0, 0 /* clear div */
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addik r29, r0, 32 /* initialize the loop count */
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/* first part try to find the first '1' in the r5 */
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div1:
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add r5, r5, r5 /* left shift logical r5 */
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bgeid r5, div1
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addik r29, r29, -1
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div2:
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/* left shift logical r5 get the '1' into the carry */
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add r5, r5, r5
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addc r3, r3, r3 /* move that bit into the mod register */
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rsub r31, r6, r3 /* try to subtract (r30 a r6) */
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blti r31, mod_too_small
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/* move the r31 to mod since the result was positive */
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or r3, r0, r31
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addik r30, r30, 1
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mod_too_small:
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addik r29, r29, -1
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beqi r29, loop_end
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add r30, r30, r30 /* shift in the '1' into div */
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bri div2 /* div2 */
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loop_end:
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bgei r28, return_here
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brid return_here
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rsubi r3, r3, 0 /* negate the result */
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div_by_zero:
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result_is_zero:
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or r3, r0, r0 /* set result to 0 [both mod as well as div are 0] */
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return_here:
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/* restore values of csrs and that of r3 and the divisor and the dividend */
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lwi r28, r1, 0
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lwi r29, r1, 4
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lwi r30, r1, 8
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lwi r31, r1, 12
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rtsd r15, 8
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addik r1, r1, 16
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.size __modsi3, . - __modsi3
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.end __modsi3
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