src/intel/compiler/brw_packed_float.c

   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 = (unsigned)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 }