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/*
* Copyright (c) 2020 Arm Limited.
*
* SPDX-License-Identifier: MIT
*
* 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.
*/
#ifndef ARM_COMPUTE_BFLOAT16_H
#define ARM_COMPUTE_BFLOAT16_H
#include <cstdint>
namespace arm_compute
{
namespace
{
/** Convert float to bfloat16
*
* @param[in] v Floating-point value to convert to bfloat
*
* @return Converted value
*/
inline uint16_t float_to_bf16(const float v)
{
const uint32_t *fromptr = reinterpret_cast<const uint32_t *>(&v);
#if defined(__ARM_FEATURE_BF16_VECTOR_ARITHMETIC) || defined(ARM_COMPUTE_FORCE_BF16)
uint16_t res;
__asm __volatile(
"ldr s0, [%[fromptr]]\n"
".inst 0x1e634000\n" // BFCVT h0, s0
"str h0, [%[toptr]]\n"
:
: [fromptr] "r"(fromptr), [toptr] "r"(&res)
: "v0", "memory");
#else /* defined(__ARM_FEATURE_BF16_VECTOR_ARITHMETIC) || defined(ARM_COMPUTE_FORCE_BF16) */
uint16_t res = (*fromptr >> 16);
const uint16_t error = (*fromptr & 0x0000ffff);
uint16_t bf_l = res & 0x0001;
if((error > 0x8000) || ((error == 0x8000) && (bf_l != 0)))
{
res += 1;
}
#endif /* defined(__ARM_FEATURE_BF16_VECTOR_ARITHMETIC) || defined(ARM_COMPUTE_FORCE_BF16) */
return res;
}
/** Convert bfloat16 to float
*
* @param[in] v Bfloat16 value to convert to float
*
* @return Converted value
*/
inline float bf16_to_float(const uint16_t &v)
{
const uint32_t lv = (v << 16);
const float *fp = reinterpret_cast<const float *>(&lv);
return *fp;
}
}
/** Brain floating point representation class */
class bfloat16 final
{
public:
/** Default Constructor */
bfloat16()
: value(0)
{
}
/** Constructor
*
* @param[in] v Floating-point value
*/
explicit bfloat16(float v)
: value(float_to_bf16(v))
{
}
/** Assignment operator
*
* @param[in] v Floating point value to assign
*
* @return The updated object
*/
bfloat16 &operator=(float v)
{
value = float_to_bf16(v);
return *this;
}
/** Floating point conversion operator
*
* @return Floating point representation of the value
*/
operator float() const
{
return bf16_to_float(value);
}
/** Lowest representative value
*
* @return Returns the lowest finite value representable by bfloat16
*/
static bfloat16 lowest()
{
bfloat16 val;
val.value = 0xFF7F;
return val;
}
/** Largest representative value
*
* @return Returns the largest finite value representable by bfloat16
*/
static bfloat16 max()
{
bfloat16 val;
val.value = 0x7F7F;
return val;
}
private:
uint16_t value;
};
} // namespace arm_compute
#endif /* ARM_COMPUTE_BFLOAT16_H */
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