div64.c 2.1 KB

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  1. // SPDX-License-Identifier: BSD-3-Clause
  2. /*
  3. * This file is copied from the coreboot repository as part of
  4. * the libpayload project:
  5. *
  6. * Copyright 2014 Google Inc.
  7. */
  8. #include <common.h>
  9. union overlay64 {
  10. u64 longw;
  11. struct {
  12. u32 lower;
  13. u32 higher;
  14. } words;
  15. };
  16. u64 __ashldi3(u64 num, unsigned int shift)
  17. {
  18. union overlay64 output;
  19. output.longw = num;
  20. if (shift >= 32) {
  21. output.words.higher = output.words.lower << (shift - 32);
  22. output.words.lower = 0;
  23. } else {
  24. if (!shift)
  25. return num;
  26. output.words.higher = (output.words.higher << shift) |
  27. (output.words.lower >> (32 - shift));
  28. output.words.lower = output.words.lower << shift;
  29. }
  30. return output.longw;
  31. }
  32. u64 __lshrdi3(u64 num, unsigned int shift)
  33. {
  34. union overlay64 output;
  35. output.longw = num;
  36. if (shift >= 32) {
  37. output.words.lower = output.words.higher >> (shift - 32);
  38. output.words.higher = 0;
  39. } else {
  40. if (!shift)
  41. return num;
  42. output.words.lower = output.words.lower >> shift |
  43. (output.words.higher << (32 - shift));
  44. output.words.higher = output.words.higher >> shift;
  45. }
  46. return output.longw;
  47. }
  48. #define MAX_32BIT_UINT ((((u64)1) << 32) - 1)
  49. static u64 _64bit_divide(u64 dividend, u64 divider, u64 *rem_p)
  50. {
  51. u64 result = 0;
  52. /*
  53. * If divider is zero - let the rest of the system care about the
  54. * exception.
  55. */
  56. if (!divider)
  57. return 1 / (u32)divider;
  58. /* As an optimization, let's not use 64 bit division unless we must. */
  59. if (dividend <= MAX_32BIT_UINT) {
  60. if (divider > MAX_32BIT_UINT) {
  61. result = 0;
  62. if (rem_p)
  63. *rem_p = divider;
  64. } else {
  65. result = (u32)dividend / (u32)divider;
  66. if (rem_p)
  67. *rem_p = (u32)dividend % (u32)divider;
  68. }
  69. return result;
  70. }
  71. while (divider <= dividend) {
  72. u64 locald = divider;
  73. u64 limit = __lshrdi3(dividend, 1);
  74. int shifts = 0;
  75. while (locald <= limit) {
  76. shifts++;
  77. locald = locald + locald;
  78. }
  79. result |= __ashldi3(1, shifts);
  80. dividend -= locald;
  81. }
  82. if (rem_p)
  83. *rem_p = dividend;
  84. return result;
  85. }
  86. u64 __udivdi3(u64 num, u64 den)
  87. {
  88. return _64bit_divide(num, den, NULL);
  89. }
  90. u64 __umoddi3(u64 num, u64 den)
  91. {
  92. u64 v = 0;
  93. _64bit_divide(num, den, &v);
  94. return v;
  95. }