IABSD.fr/src/lib/libcompiler_rt/floatundisf.c

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• Author : patrick
  Date : 2018-09-18 20:21:40
  Hash : 3d56ebce
  Message : Update to compiler-rt 6.0.0. tested by naddy@ ok kettenis@

• lib/libcompiler_rt/floatundisf.c

• /*===-- floatundisf.c - Implement __floatundisf ---------------------------===
   *
   *                     The LLVM Compiler Infrastructure
   *
   * This file is dual licensed under the MIT and the University of Illinois Open
   * Source Licenses. See LICENSE.TXT for details.
   *
   * ===----------------------------------------------------------------------===
   *
   * This file implements __floatundisf for the compiler_rt library.
   *
   *===----------------------------------------------------------------------===
   */
  
  /* Returns: convert a to a float, rounding toward even. */
  
  /* Assumption: float is a IEEE 32 bit floating point type 
   *            du_int is a 64 bit integral type
   */
  
  /* seee eeee emmm mmmm mmmm mmmm mmmm mmmm */
  
  #include "int_lib.h"
  
  COMPILER_RT_ABI float
  __floatundisf(du_int a)
  {
      if (a == 0)
          return 0.0F;
      const unsigned N = sizeof(du_int) * CHAR_BIT;
      int sd = N - __builtin_clzll(a);  /* number of significant digits */
      int e = sd - 1;             /* 8 exponent */
      if (sd > FLT_MANT_DIG)
      {
          /*  start:  0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx
           *  finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR
           *                                                12345678901234567890123456
           *  1 = msb 1 bit
           *  P = bit FLT_MANT_DIG-1 bits to the right of 1
           *  Q = bit FLT_MANT_DIG bits to the right of 1
           *  R = "or" of all bits to the right of Q
           */
          switch (sd)
          {
          case FLT_MANT_DIG + 1:
              a <<= 1;
              break;
          case FLT_MANT_DIG + 2:
              break;
          default:
              a = (a >> (sd - (FLT_MANT_DIG+2))) |
                  ((a & ((du_int)(-1) >> ((N + FLT_MANT_DIG+2) - sd))) != 0);
          };
          /* finish: */
          a |= (a & 4) != 0;  /* Or P into R */
          ++a;  /* round - this step may add a significant bit */
          a >>= 2;  /* dump Q and R */
          /* a is now rounded to FLT_MANT_DIG or FLT_MANT_DIG+1 bits */
          if (a & ((du_int)1 << FLT_MANT_DIG))
          {
              a >>= 1;
              ++e;
          }
          /* a is now rounded to FLT_MANT_DIG bits */
      }
      else
      {
          a <<= (FLT_MANT_DIG - sd);
          /* a is now rounded to FLT_MANT_DIG bits */
      }
      float_bits fb;
      fb.u = ((e + 127) << 23)       |  /* exponent */
             ((su_int)a & 0x007FFFFF);  /* mantissa */
      return fb.f;
  }
  
  #if defined(__ARM_EABI__)
  #if defined(COMPILER_RT_ARMHF_TARGET)
  AEABI_RTABI float __aeabi_ul2f(du_int a) {
    return __floatundisf(a);
  }
  #else
  AEABI_RTABI float __aeabi_ul2f(du_int a) COMPILER_RT_ALIAS(__floatundisf);
  #endif
  #endif