dp_tint.c 2.5 KB

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  1. /* IEEE754 floating point arithmetic
  2. * double precision: common utilities
  3. */
  4. /*
  5. * MIPS floating point support
  6. * Copyright (C) 1994-2000 Algorithmics Ltd.
  7. *
  8. * This program is free software; you can distribute it and/or modify it
  9. * under the terms of the GNU General Public License (Version 2) as
  10. * published by the Free Software Foundation.
  11. *
  12. * This program is distributed in the hope it will be useful, but WITHOUT
  13. * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14. * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
  15. * for more details.
  16. *
  17. * You should have received a copy of the GNU General Public License along
  18. * with this program; if not, write to the Free Software Foundation, Inc.,
  19. * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20. */
  21. #include "ieee754dp.h"
  22. int ieee754dp_tint(union ieee754dp x)
  23. {
  24. u64 residue;
  25. int round;
  26. int sticky;
  27. int odd;
  28. COMPXDP;
  29. ieee754_clearcx();
  30. EXPLODEXDP;
  31. FLUSHXDP;
  32. switch (xc) {
  33. case IEEE754_CLASS_SNAN:
  34. case IEEE754_CLASS_QNAN:
  35. case IEEE754_CLASS_INF:
  36. ieee754_setcx(IEEE754_INVALID_OPERATION);
  37. return ieee754si_indef();
  38. case IEEE754_CLASS_ZERO:
  39. return 0;
  40. case IEEE754_CLASS_DNORM:
  41. case IEEE754_CLASS_NORM:
  42. break;
  43. }
  44. if (xe > 31) {
  45. /* Set invalid. We will only use overflow for floating
  46. point overflow */
  47. ieee754_setcx(IEEE754_INVALID_OPERATION);
  48. return ieee754si_indef();
  49. }
  50. /* oh gawd */
  51. if (xe > DP_FBITS) {
  52. xm <<= xe - DP_FBITS;
  53. } else if (xe < DP_FBITS) {
  54. if (xe < -1) {
  55. residue = xm;
  56. round = 0;
  57. sticky = residue != 0;
  58. xm = 0;
  59. } else {
  60. residue = xm << (64 - DP_FBITS + xe);
  61. round = (residue >> 63) != 0;
  62. sticky = (residue << 1) != 0;
  63. xm >>= DP_FBITS - xe;
  64. }
  65. /* Note: At this point upper 32 bits of xm are guaranteed
  66. to be zero */
  67. odd = (xm & 0x1) != 0x0;
  68. switch (ieee754_csr.rm) {
  69. case FPU_CSR_RN:
  70. if (round && (sticky || odd))
  71. xm++;
  72. break;
  73. case FPU_CSR_RZ:
  74. break;
  75. case FPU_CSR_RU: /* toward +Infinity */
  76. if ((round || sticky) && !xs)
  77. xm++;
  78. break;
  79. case FPU_CSR_RD: /* toward -Infinity */
  80. if ((round || sticky) && xs)
  81. xm++;
  82. break;
  83. }
  84. /* look for valid corner case 0x80000000 */
  85. if ((xm >> 31) != 0 && (xs == 0 || xm != 0x80000000)) {
  86. /* This can happen after rounding */
  87. ieee754_setcx(IEEE754_INVALID_OPERATION);
  88. return ieee754si_indef();
  89. }
  90. if (round || sticky)
  91. ieee754_setcx(IEEE754_INEXACT);
  92. }
  93. if (xs)
  94. return -xm;
  95. else
  96. return xm;
  97. }