modsi3.S 1.8 KB

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  1. /* SPDX-License-Identifier: GPL-2.0 */
  2. #include <linux/linkage.h>
  3. /*
  4. * modulo operation for 32 bit integers.
  5. * Input : op1 in Reg r5
  6. * op2 in Reg r6
  7. * Output: op1 mod op2 in Reg r3
  8. */
  9. .text
  10. .globl __modsi3
  11. .type __modsi3, @function
  12. .ent __modsi3
  13. __modsi3:
  14. .frame r1, 0, r15
  15. addik r1, r1, -16
  16. swi r28, r1, 0
  17. swi r29, r1, 4
  18. swi r30, r1, 8
  19. swi r31, r1, 12
  20. beqi r6, div_by_zero /* div_by_zero division error */
  21. beqi r5, result_is_zero /* result is zero */
  22. bgeid r5, r5_pos
  23. /* get the sign of the result [ depends only on the first arg] */
  24. add r28, r5, r0
  25. rsubi r5, r5, 0 /* make r5 positive */
  26. r5_pos:
  27. bgei r6, r6_pos
  28. rsubi r6, r6, 0 /* make r6 positive */
  29. r6_pos:
  30. addik r3, r0, 0 /* clear mod */
  31. addik r30, r0, 0 /* clear div */
  32. addik r29, r0, 32 /* initialize the loop count */
  33. /* first part try to find the first '1' in the r5 */
  34. div1:
  35. add r5, r5, r5 /* left shift logical r5 */
  36. bgeid r5, div1
  37. addik r29, r29, -1
  38. div2:
  39. /* left shift logical r5 get the '1' into the carry */
  40. add r5, r5, r5
  41. addc r3, r3, r3 /* move that bit into the mod register */
  42. rsub r31, r6, r3 /* try to subtract (r30 a r6) */
  43. blti r31, mod_too_small
  44. /* move the r31 to mod since the result was positive */
  45. or r3, r0, r31
  46. addik r30, r30, 1
  47. mod_too_small:
  48. addik r29, r29, -1
  49. beqi r29, loop_end
  50. add r30, r30, r30 /* shift in the '1' into div */
  51. bri div2 /* div2 */
  52. loop_end:
  53. bgei r28, return_here
  54. brid return_here
  55. rsubi r3, r3, 0 /* negate the result */
  56. div_by_zero:
  57. result_is_zero:
  58. or r3, r0, r0 /* set result to 0 [both mod as well as div are 0] */
  59. return_here:
  60. /* restore values of csrs and that of r3 and the divisor and the dividend */
  61. lwi r28, r1, 0
  62. lwi r29, r1, 4
  63. lwi r30, r1, 8
  64. lwi r31, r1, 12
  65. rtsd r15, 8
  66. addik r1, r1, 16
  67. .size __modsi3, . - __modsi3
  68. .end __modsi3