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/*
* Copyright (c) Facebook, Inc. and its affiliates.
* All rights reserved.
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree.
*/
#pragma once
#include <cstdint>
#include <cstdlib>
#include <cstring>
namespace fbgemm {
typedef struct __attribute__((aligned(2))) __f16 {
uint16_t x;
} float16;
static inline float16 cpu_float2half_rn(float f) {
float16 ret;
static_assert(
sizeof(unsigned int) == sizeof(float),
"Programming error sizeof(unsigned int) != sizeof(float)");
unsigned* xp = reinterpret_cast<unsigned int*>(&f);
unsigned x = *xp;
unsigned u = (x & 0x7fffffff), remainder, shift, lsb, lsb_s1, lsb_m1;
unsigned sign, exponent, mantissa;
// Get rid of +NaN/-NaN case first.
if (u > 0x7f800000) {
ret.x = 0x7fffU;
return ret;
}
sign = ((x >> 16) & 0x8000);
// Get rid of +Inf/-Inf, +0/-0.
if (u > 0x477fefff) {
ret.x = sign | 0x7c00U;
return ret;
}
if (u < 0x33000001) {
ret.x = (sign | 0x0000);
return ret;
}
exponent = ((u >> 23) & 0xff);
mantissa = (u & 0x7fffff);
if (exponent > 0x70) {
shift = 13;
exponent -= 0x70;
} else {
shift = 0x7e - exponent;
exponent = 0;
mantissa |= 0x800000;
}
lsb = (1 << shift);
lsb_s1 = (lsb >> 1);
lsb_m1 = (lsb - 1);
// Round to nearest even.
remainder = (mantissa & lsb_m1);
mantissa >>= shift;
if (remainder > lsb_s1 || (remainder == lsb_s1 && (mantissa & 0x1))) {
++mantissa;
if (!(mantissa & 0x3ff)) {
++exponent;
mantissa = 0;
}
}
ret.x = (sign | (exponent << 10) | mantissa);
return ret;
}
static inline float cpu_half2float(float16 h) {
unsigned sign = ((h.x >> 15) & 1);
unsigned exponent = ((h.x >> 10) & 0x1f);
unsigned mantissa = ((h.x & 0x3ff) << 13);
if (exponent == 0x1f) { /* NaN or Inf */
mantissa = (mantissa ? (sign = 0, 0x7fffff) : 0);
exponent = 0xff;
} else if (!exponent) { /* Denorm or Zero */
if (mantissa) {
unsigned int msb;
exponent = 0x71;
do {
msb = (mantissa & 0x400000);
mantissa <<= 1; /* normalize */
--exponent;
} while (!msb);
mantissa &= 0x7fffff; /* 1.mantissa is implicit */
}
} else {
exponent += 0x70;
}
unsigned i = ((sign << 31) | (exponent << 23) | mantissa);
float ret;
memcpy(&ret, &i, sizeof(i));
return ret;
}
static inline uint8_t tconv(float x, int8_t /*rtype*/) {
return int8_t(x);
}
static inline uint8_t tconv(float x, uint8_t /*rtype*/) {
return uint8_t(x);
}
static inline float16 tconv(float x, float16 /*rtype*/) {
return cpu_float2half_rn(x);
}
template <typename T>
T tconv(T x, T /*rtype*/) {
return x;
}
} // namespace fbgemm
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