140 lines
3.8 KiB
C++
140 lines
3.8 KiB
C++
/*
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* Copyright (c) 2020 Arm Limited.
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*
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* SPDX-License-Identifier: MIT
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to
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* deal in the Software without restriction, including without limitation the
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* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
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* sell copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#ifndef ARM_COMPUTE_BFLOAT16_H
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#define ARM_COMPUTE_BFLOAT16_H
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#include <cstdint>
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namespace arm_compute
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{
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namespace
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{
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/** Convert float to bfloat16
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*
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* @param[in] v Floating-point value to convert to bfloat
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*
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* @return Converted value
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*/
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inline uint16_t float_to_bf16(const float v)
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{
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const uint32_t *fromptr = reinterpret_cast<const uint32_t *>(&v);
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#if defined(__ARM_FEATURE_BF16_VECTOR_ARITHMETIC) || defined(ARM_COMPUTE_FORCE_BF16)
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uint16_t res;
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__asm __volatile(
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"ldr s0, [%[fromptr]]\n"
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".inst 0x1e634000\n" // BFCVT h0, s0
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"str h0, [%[toptr]]\n"
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:
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: [fromptr] "r"(fromptr), [toptr] "r"(&res)
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: "v0", "memory");
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#else /* defined(__ARM_FEATURE_BF16_VECTOR_ARITHMETIC) || defined(ARM_COMPUTE_FORCE_BF16) */
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uint16_t res = (*fromptr >> 16);
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const uint16_t error = (*fromptr & 0x0000ffff);
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uint16_t bf_l = res & 0x0001;
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if((error > 0x8000) || ((error == 0x8000) && (bf_l != 0)))
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{
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res += 1;
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}
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#endif /* defined(__ARM_FEATURE_BF16_VECTOR_ARITHMETIC) || defined(ARM_COMPUTE_FORCE_BF16) */
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return res;
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}
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/** Convert bfloat16 to float
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*
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* @param[in] v Bfloat16 value to convert to float
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*
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* @return Converted value
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*/
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inline float bf16_to_float(const uint16_t &v)
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{
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const uint32_t lv = (v << 16);
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const float *fp = reinterpret_cast<const float *>(&lv);
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return *fp;
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}
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}
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/** Brain floating point representation class */
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class bfloat16 final
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{
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public:
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/** Default Constructor */
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bfloat16()
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: value(0)
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{
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}
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/** Constructor
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*
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* @param[in] v Floating-point value
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*/
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explicit bfloat16(float v)
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: value(float_to_bf16(v))
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{
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}
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/** Assignment operator
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*
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* @param[in] v Floating point value to assign
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*
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* @return The updated object
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*/
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bfloat16 &operator=(float v)
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{
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value = float_to_bf16(v);
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return *this;
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}
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/** Floating point conversion operator
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*
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* @return Floating point representation of the value
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*/
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operator float() const
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{
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return bf16_to_float(value);
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}
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/** Lowest representative value
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*
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* @return Returns the lowest finite value representable by bfloat16
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*/
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static bfloat16 lowest()
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{
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bfloat16 val;
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val.value = 0xFF7F;
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return val;
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}
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/** Largest representative value
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*
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* @return Returns the largest finite value representable by bfloat16
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*/
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static bfloat16 max()
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{
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bfloat16 val;
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val.value = 0x7F7F;
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return val;
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}
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private:
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uint16_t value;
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};
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} // namespace arm_compute
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#endif /* ARM_COMPUTE_BFLOAT16_H */ |