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  1. /*
  2.  * Copyright © 2014 Intel Corporation
  3.  *
  4.  * Permission is hereby granted, free of charge, to any person obtaining a
  5.  * copy of this software and associated documentation files (the "Software"),
  6.  * to deal in the Software without restriction, including without limitation
  7.  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  8.  * and/or sell copies of the Software, and to permit persons to whom the
  9.  * Software is furnished to do so, subject to the following conditions:
  10.  *
  11.  * The above copyright notice and this permission notice (including the next
  12.  * paragraph) shall be included in all copies or substantial portions of the
  13.  * Software.
  14.  *
  15.  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16.  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17.  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18.  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19.  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20.  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21.  * IN THE SOFTWARE.
  22.  */
  23. #include "brw_reg.h"
  24.  
  25. union fu {
  26.    float f;
  27.    unsigned u;
  28.    struct {
  29.       unsigned mantissa:23;
  30.       unsigned exponent:8;
  31.       unsigned sign:1;
  32.    } s;
  33. };
  34.  
  35. int
  36. brw_float_to_vf(float f)
  37. {
  38.    union fu fu = { .f = f };
  39.  
  40.    /* ±0.0f is special cased. */
  41.    if (f == 0.0f)
  42.       return fu.s.sign << 7;
  43.  
  44.    unsigned mantissa = fu.s.mantissa >> (23 - 4);
  45.    unsigned exponent = fu.s.exponent - (127 - 3);
  46.    unsigned vf = (fu.s.sign << 7) | (exponent << 4) | mantissa;
  47.  
  48.    /* 0.125 would have had the same representation as 0.0, so reject it. */
  49.    if ((vf & 0x7f) == 0)
  50.       return -1;
  51.  
  52.    /* Make sure the mantissa fits in 4-bits and the exponent in 3-bits. */
  53.    if (fu.u & 0x7ffff || exponent > 7)
  54.       return -1;
  55.  
  56.    return vf;
  57. }
  58.  
  59. float
  60. brw_vf_to_float(unsigned char vf)
  61. {
  62.    union fu fu;
  63.  
  64.    /* ±0.0f is special cased. */
  65.    if (vf == 0x00 || vf == 0x80) {
  66.       fu.u = vf << 24;
  67.       return fu.f;
  68.    }
  69.  
  70.    fu.s.sign = vf >> 7;
  71.    fu.s.exponent = ((vf & 0x70) >> 4) + (127 - 3);
  72.    fu.s.mantissa = (vf & 0xf) << (23 - 4);
  73.  
  74.    return fu.f;
  75. }
  76.