div64.S 1.7 KB

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  1. /* SPDX-License-Identifier: GPL-2.0-or-later */
  2. /*
  3. * Divide a 64-bit unsigned number by a 32-bit unsigned number.
  4. * This routine assumes that the top 32 bits of the dividend are
  5. * non-zero to start with.
  6. * On entry, r3 points to the dividend, which get overwritten with
  7. * the 64-bit quotient, and r4 contains the divisor.
  8. * On exit, r3 contains the remainder.
  9. *
  10. * Copyright (C) 2002 Paul Mackerras, IBM Corp.
  11. */
  12. #include <asm/ppc_asm.h>
  13. #include <asm/processor.h>
  14. _GLOBAL(__div64_32)
  15. lwz r5,0(r3) # get the dividend into r5/r6
  16. lwz r6,4(r3)
  17. cmplw r5,r4
  18. li r7,0
  19. li r8,0
  20. blt 1f
  21. divwu r7,r5,r4 # if dividend.hi >= divisor,
  22. mullw r0,r7,r4 # quotient.hi = dividend.hi / divisor
  23. subf. r5,r0,r5 # dividend.hi %= divisor
  24. beq 3f
  25. 1: mr r11,r5 # here dividend.hi != 0
  26. andis. r0,r5,0xc000
  27. bne 2f
  28. cntlzw r0,r5 # we are shifting the dividend right
  29. li r10,-1 # to make it < 2^32, and shifting
  30. srw r10,r10,r0 # the divisor right the same amount,
  31. addc r9,r4,r10 # rounding up (so the estimate cannot
  32. andc r11,r6,r10 # ever be too large, only too small)
  33. andc r9,r9,r10
  34. addze r9,r9
  35. or r11,r5,r11
  36. rotlw r9,r9,r0
  37. rotlw r11,r11,r0
  38. divwu r11,r11,r9 # then we divide the shifted quantities
  39. 2: mullw r10,r11,r4 # to get an estimate of the quotient,
  40. mulhwu r9,r11,r4 # multiply the estimate by the divisor,
  41. subfc r6,r10,r6 # take the product from the divisor,
  42. add r8,r8,r11 # and add the estimate to the accumulated
  43. subfe. r5,r9,r5 # quotient
  44. bne 1b
  45. 3: cmplw r6,r4
  46. blt 4f
  47. divwu r0,r6,r4 # perform the remaining 32-bit division
  48. mullw r10,r0,r4 # and get the remainder
  49. add r8,r8,r0
  50. subf r6,r10,r6
  51. 4: stw r7,0(r3) # return the quotient in *r3
  52. stw r8,4(r3)
  53. mr r3,r6 # return the remainder in r3
  54. blr