forked from AuroraMiddleware/gtk
151 lines
3.6 KiB
C
151 lines
3.6 KiB
C
/* fp16.c
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*
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* Copyright 2021 Red Hat, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this program. If not, see <http://www.gnu.org/licenses/>.
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*
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* SPDX-License-Identifier: LGPL-2.1-or-later
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*/
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#include <config.h>
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#include "fp16private.h"
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#ifdef HAVE_F16C
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#include <immintrin.h>
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#endif
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static inline guint
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as_uint (const float x)
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{
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return *(guint*)&x;
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}
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static inline float
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as_float (const guint x)
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{
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return *(float*)&x;
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}
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// IEEE-754 16-bit floating-point format (without infinity): 1-5-10
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static inline float
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half_to_float (const guint16 x)
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{
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const guint e = (x&0x7C00)>>10; // exponent
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const guint m = (x&0x03FF)<<13; // mantissa
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const guint v = as_uint((float)m)>>23;
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return as_float((x&0x8000)<<16 | (e!=0)*((e+112)<<23|m) | ((e==0)&(m!=0))*((v-37)<<23|((m<<(150-v))&0x007FE000)));
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}
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static inline guint16
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float_to_half (const float x)
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{
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const guint b = as_uint(x)+0x00001000; // round-to-nearest-even
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const guint e = (b&0x7F800000)>>23; // exponent
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const guint m = b&0x007FFFFF; // mantissa
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return (b&0x80000000)>>16 | (e>112)*((((e-112)<<10)&0x7C00)|m>>13) | ((e<113)&(e>101))*((((0x007FF000+m)>>(125-e))+1)>>1) | (e>143)*0x7FFF; // sign : normalized : denormalized : saturate
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}
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static void
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float_to_half4_c (const float f[4],
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guint16 h[4])
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{
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h[0] = float_to_half (f[0]);
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h[1] = float_to_half (f[1]);
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h[2] = float_to_half (f[2]);
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h[3] = float_to_half (f[3]);
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}
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static void
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half_to_float4_c (const guint16 h[4],
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float f[4])
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{
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f[0] = half_to_float (h[0]);
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f[1] = half_to_float (h[1]);
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f[2] = half_to_float (h[2]);
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f[3] = half_to_float (h[3]);
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}
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#ifdef HAVE_F16C
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static void
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float_to_half4_f16c (const float f[4],
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guint16 h[4])
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{
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__m128 s = _mm_loadu_ps (f);
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__m128i i = _mm_cvtps_ph (s, 0);
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_mm_storel_epi64 ((__m128i*)h, i);
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}
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static void
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half_to_float4_f16c (const guint16 h[4],
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float f[4])
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{
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__m128i i = _mm_loadl_epi64 ((__m128i_u const *)h);
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__m128 s = _mm_cvtph_ps (i);
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_mm_store_ps (f, s);
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}
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void float_to_half4 (const float f[4], guint16 h[4]) __attribute__((ifunc ("resolve_float_to_half4")));
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void half_to_float4 (const guint16 h[4], float f[4]) __attribute__((ifunc ("resolve_half_to_float4")));
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static void *
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resolve_float_to_half4 (void)
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{
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__builtin_cpu_init ();
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if (__builtin_cpu_supports ("f16c"))
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return float_to_half4_f16c;
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else
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return float_to_half4_c;
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}
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static void *
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resolve_half_to_float4 (void)
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{
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__builtin_cpu_init ();
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if (__builtin_cpu_supports ("f16c"))
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return half_to_float4_f16c;
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else
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return half_to_float4_c;
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}
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#else
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#ifdef __APPLE__
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// turns out aliases don't work on Darwin
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void
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float_to_half4 (const float f[4],
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guint16 h[4])
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{
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float_to_half4_c (f, h);
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}
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void
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half_to_float4 (const guint16 h[4],
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float f[4])
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{
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half_to_float4_c (h, f);
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}
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#else
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void float_to_half4 (const float f[4], guint16 h[4]) __attribute__((alias ("float_to_half4_c")));
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void half_to_float4 (const guint16 h[4], float f[4]) __attribute__((alias ("half_to_float4_c")));
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#endif
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#endif /* GTK_HAS_F16C */
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