lib/i386/math/arch_round.c

   1 #include <errno.h>
   2 #include <fenv.h>
   3 #include <math.h>
   4
   5 #include "fpu_cw.h"
   6 #include "fpu_round.h"
   7
   8 static double rndint(double x, u16_t cw_bits, u16_t cw_mask)
   9 {
  10         u16_t cw;
  11
  12         /* set FPUCW to the right value */
  13         cw = fpu_cw_get();
  14         fpu_cw_set((cw & cw_mask) | cw_bits);
  15
  16         /* perform the round */
  17         fpu_rndint(&x);
  18
  19         /* restore FPUCW */
  20         fpu_cw_set(cw);
  21         return x;
  22 }
  23
  24 double nearbyint(double x)
  25 {
  26         /* round, disabling floating point precision error */
  27         return rndint(x, FPUCW_EXCEPTION_MASK_PM, ~0);
  28 }
  29
  30 double remainder(double x, double y)
  31 {
  32         int xclass, yclass;
  33
  34         /* check arguments */
  35         xclass = fpclassify(x);
  36         yclass = fpclassify(y);
  37         if (xclass == FP_NAN || yclass == FP_NAN)
  38                 return NAN;
  39
  40         if (xclass == FP_INFINITE || yclass == FP_ZERO)
  41         {
  42                 errno = EDOM;
  43                 return NAN;
  44         }
  45
  46         /* call the assembly implementation */
  47         fpu_remainder(&x, y);
  48         return x;
  49 }
  50
  51 double trunc(double x)
  52 {
  53         /* round in truncate mode, disabling floating point precision error */
  54         return rndint(x,
  55                 FPUCW_EXCEPTION_MASK_PM | FPUCW_ROUNDING_CONTROL_TRUNC,
  56                 ~FPUCW_ROUNDING_CONTROL);
  57 }