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/*
* Copyright (c) 2014 Advanced Micro Devices, Inc.
*
* Copyright (c) 2017 Michal Babej / Tampere University of Technology
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
_CL_OVERLOADABLE vtype exp2(vtype x)
{
// Reduce x
const vtype ln2HI = (vtype)0x1.62e300p-1f;
const vtype ln2LO = (vtype)0x1.2fefa2p-17f;
vtype t = rint(x);
itype p = convert_itype(t);
vtype tt = x - t;
vtype hi = tt * ln2HI;
vtype lo = tt * ln2LO;
// Evaluate poly
t = hi + lo;
tt = t*t;
vtype v = mad(tt,
-mad(tt,
mad(tt,
mad(tt,
mad(tt, (vtype)0x1.637698p-25f,
(vtype)-0x1.bbd41cp-20f),
(vtype)0x1.1566aap-14f),
(vtype)-0x1.6c16c2p-9f),
(vtype)0x1.555556p-3f),
t);
vtype y = (vtype)1.0f - (((-lo) - MATH_DIVIDE(t * v,
(vtype)2.0f - v)) - hi);
// Scale by 2^p
vtype r = as_vtype(as_itype(y) + (p << 23));
const vtype ulim = (vtype)128.0f;
const vtype llim = (vtype)-126.0f;
r = x < llim ? (vtype)0.0f : r;
r = x < ulim ? r : as_vtype((utype)EXPBITS_SP32);
return isnan(x) ? x : r;
}
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