gallium/util: pregenerate half float tables
This solution avoids the issue of how to run the initializers and also allows those pages (and the parts of them in processor caches) to be shared between multiple processes. The drawback is slightly higher library size.
This commit is contained in:
Luca Barbieri
parent
2ae66e9b97
commit
c476305cde
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@ -169,7 +169,8 @@ GALLIVM_CPP_SOURCES = \
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GENERATED_SOURCES = \
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indices/u_indices_gen.c \
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indices/u_unfilled_gen.c \
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util/u_format_table.c
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util/u_format_table.c \
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util/u_half.c
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ifeq ($(MESA_LLVM),1)
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@ -198,3 +199,5 @@ util/u_format_table.c: util/u_format_table.py util/u_format_pack.py util/u_forma
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util/u_format_access.c: util/u_format_access.py util/u_format_parse.py util/u_format.csv
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python util/u_format_access.py util/u_format.csv > $@
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util/u_half.c: util/u_half.py
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python util/u_half.py > $@
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@ -29,6 +29,14 @@ env.CodeGenerate(
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source = ['util/u_format.csv'],
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command = 'python $SCRIPT $SOURCE > $TARGET'
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)
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env.CodeGenerate(
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target = 'util/u_half.c',
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script = 'util/u_half.py',
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source = [],
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command = 'python $SCRIPT > $TARGET'
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)
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env.Depends('util/u_format_table.c', [
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'util/u_format_parse.py',
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'util/u_format_pack.py',
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@ -124,5 +124,4 @@ void
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util_format_do_init(void)
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{
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util_format_s3tc_init();
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util_half_init();
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}
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@ -1,165 +0,0 @@
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/*
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* Copyright 2010 Luca Barbieri
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice (including the
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* next paragraph) shall be included in all copies or substantial
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* portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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* IN NO EVENT SHALL THE COPYRIGHT OWNER(S) AND/OR ITS SUPPLIERS BE
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* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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**************************************************************************/
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/* The code is a reimplementation of the algorithm in
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* www.fox-toolkit.org/ftp/fasthalffloatconversion.pdf
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* "Fast Half Float Conversions" by Jeroen van der Zijp, Nov 2008
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*
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* The table contents have been slightly changed so that the exponent
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* bias is now in the exponent table instead of the mantissa table (mostly
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* for cosmetic reasons, and because it theoretically allows a variant
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* that flushes denormal to zero but uses a mantissa table with 24-bit
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* entries).
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*
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* The tables are also constructed slightly differently.
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*/
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/* Note that using a 64K * 4 table is a terrible idea since it will not fit
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* in the L1 cache and will massively pollute the L2 cache as well
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*
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* These should instead fit in the L1 cache.
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*
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* TODO: we could use a denormal bias table instead of the mantissa/offset
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* tables: this would reduce the L1 cache usage from 8704 to 2304 bytes
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* but would involve more computation
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*
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* Note however that if denormals are never encountered, the L1 cache usage
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* is only about 4608 bytes anyway.
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*/
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#include "util/u_half.h"
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#include "util/u_init.h"
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uint32_t util_half_to_float_mantissa_table[2048];
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uint32_t util_half_to_float_exponent_table[64];
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uint32_t util_half_to_float_offset_table[64];
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uint16_t util_float_to_half_base_table[512];
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uint8_t util_float_to_half_shift_table[512];
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boolean util_half_inited;
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void
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util_half_do_init(void)
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{
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int i;
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/* zero */
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util_half_to_float_mantissa_table[0] = 0;
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/* denormals */
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for(i = 1; i < 1024; ++i)
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{
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unsigned int m = i << 13;
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unsigned int e = 0;
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/* Normalize number */
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while(!(m & 0x00800000))
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{
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e -= 0x00800000;
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m <<= 1;
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}
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m &= ~0x00800000;
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e += 0x38800000;
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util_half_to_float_mantissa_table[i] = m | e;
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}
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/* normals */
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for(i = 1024; i < 2048; ++i)
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util_half_to_float_mantissa_table[i] = ((i - 1024) << 13);
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/* positive zero or denormals */
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util_half_to_float_exponent_table[0] = 0;
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/* positive numbers */
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for(i = 1; i <= 30; ++i)
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util_half_to_float_exponent_table[i] = 0x38000000 + (i << 23);
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/* positive infinity/NaN */
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util_half_to_float_exponent_table[31] = 0x7f800000;
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/* negative zero or denormals */
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util_half_to_float_exponent_table[32] = 0x80000000;
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/* negative numbers */
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for(i = 33; i <= 62; ++i)
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util_half_to_float_exponent_table[i] = 0xb8000000 + ((i - 32) << 23);
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/* negative infinity/NaN */
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util_half_to_float_exponent_table[63] = 0xff800000;
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/* positive zero or denormals */
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util_half_to_float_offset_table[0] = 0;
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/* positive normals */
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for(i = 1; i < 32; ++i)
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util_half_to_float_offset_table[i] = 1024;
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/* negative zero or denormals */
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util_half_to_float_offset_table[32] = 0;
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/* negative normals */
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for(i = 33; i < 64; ++i)
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util_half_to_float_offset_table[i] = 1024;
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/* very small numbers mapping to zero */
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for(i = -127; i < -24; ++i)
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{
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util_float_to_half_base_table[127 + i] = 0;
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util_float_to_half_shift_table[127 + i] = 24;
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}
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/* small numbers mapping to denormals */
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for(i = -24; i < -14; ++i)
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{
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util_float_to_half_base_table[127 + i] = 0x0400 >> (-14 - i);
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util_float_to_half_shift_table[127 + i] = -i - 1;
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}
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/* normal numbers */
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for(i = -14; i < 16; ++i)
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{
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util_float_to_half_base_table[127 + i] = (i + 15) << 10;
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util_float_to_half_shift_table[127 + i] = 13;
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}
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/* large numbers mapping to infinity */
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for(i = 16; i < 128; ++i)
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{
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util_float_to_half_base_table[127 + i] = 0x7c00;
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util_float_to_half_shift_table[127 + i] = 24;
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}
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/* infinity and NaNs */
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util_float_to_half_base_table[255] = 0x7c00;
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util_float_to_half_shift_table[255] = 13;
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/* negative numbers */
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for(i = 0; i < 256; ++i)
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{
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util_float_to_half_base_table[256 + i] = util_float_to_half_base_table[i] | 0x8000;
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util_float_to_half_shift_table[256 + i] = util_float_to_half_shift_table[i];
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}
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}
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@ -3,7 +3,6 @@
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#include "pipe/p_compiler.h"
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#include "util/u_math.h"
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#include "util/u_inline_init.h"
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#ifdef __cplusplus
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extern "C" {
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@ -56,8 +55,6 @@ util_float_to_half(float f)
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return util_floatui_to_half(i.ui);
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}
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UTIL_INLINE_INIT(util_half);
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#ifdef __cplusplus
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}
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#endif
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@ -0,0 +1,179 @@
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# Copyright 2010 Luca Barbieri
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#
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# Permission is hereby granted, free of charge, to any person obtaining
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# a copy of this software and associated documentation files (the
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# "Software"), to deal in the Software without restriction, including
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# without limitation the rights to use, copy, modify, merge, publish,
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# distribute, sublicense, and/or sell copies of the Software, and to
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# permit persons to whom the Software is furnished to do so, subject to
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# the following conditions:
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#
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# The above copyright notice and this permission notice (including the
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# next paragraph) shall be included in all copies or substantial
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# portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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# IN NO EVENT SHALL THE COPYRIGHT OWNER(S) AND/OR ITS SUPPLIERS BE
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# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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#
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# *************************************************************************
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# The code is a reimplementation of the algorithm in
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# www.fox-toolkit.org/ftp/fasthalffloatconversion.pdf
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# "Fast Half Float Conversions" by Jeroen van der Zijp, Nov 2008
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#
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# The table contents have been slightly changed so that the exponent
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# bias is now in the exponent table instead of the mantissa table (mostly
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# for cosmetic reasons, and because it theoretically allows a variant
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# that flushes denormal to zero but uses a mantissa table with 24-bit
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# entries).
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#
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# The tables are also constructed slightly differently.
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#
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# Note that using a 64K * 4 table is a terrible idea since it will not fit
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# in the L1 cache and will massively pollute the L2 cache as well
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#
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# These should instead fit in the L1 cache.
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#
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# TODO: we could use a denormal bias table instead of the mantissa/offset
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# tables: this would reduce the L1 cache usage from 8704 to 2304 bytes
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# but would involve more computation
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#
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# Note however that if denormals are never encountered, the L1 cache usage
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# is only about 4608 bytes anyway.
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table_index = None
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table_length = None
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def begin(t, n, l):
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global table_length
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global table_index
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table_index = 0
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table_length = l
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print
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print t + " " + n + "[" + str(l) + "] = {"
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def value(v):
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global table_index
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table_index += 1
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print "\t" + hex(v) + ","
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def end():
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global table_length
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global table_index
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print "};"
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assert table_index == table_length
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print "/* This file is autogenerated by u_half.py. Do not edit directly. */"
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print "#include \"util/u_half.h\""
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begin("uint32_t", "util_half_to_float_mantissa_table", 2048)
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# zero
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value(0)
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# denormals
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for i in xrange(1, 1024):
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m = i << 13
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e = 0
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# normalize number
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while (m & 0x00800000) == 0:
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e -= 0x00800000;
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m <<= 1;
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m &= ~0x00800000;
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e += 0x38800000;
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value(m | e)
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# normals
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for i in xrange(1024, 2048):
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value((i - 1024) << 13)
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end()
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begin("uint32_t", "util_half_to_float_exponent_table", 64)
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# positive zero or denormals
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value(0)
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# positive numbers
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for i in xrange(1, 31):
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value(0x38000000 + (i << 23))
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# positive infinity/NaN
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value(0x7f800000)
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# negative zero or denormals
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value(0x80000000)
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# negative numbers
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for i in range(33, 63):
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value(0xb8000000 + ((i - 32) << 23))
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# negative infinity/NaN
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value(0xff800000)
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end()
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begin("uint32_t", "util_half_to_float_offset_table", 64)
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# positive zero or denormals
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value(0)
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# positive normals
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for i in range(1, 32):
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value(1024)
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# negative zero or denormals
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value(0)
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# negative normals
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for i in xrange(33, 64):
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value(1024)
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end()
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begin("uint16_t", "util_float_to_half_base_table", 512)
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for sign in (0, 0x8000):
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# very small numbers mapping to zero
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for i in xrange(-127, -24):
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value(sign | 0)
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# small numbers mapping to denormals
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for i in xrange(-24, -14):
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value(sign | (0x400 >> (-14 -i)))
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# normal numbers
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for i in xrange(-14, 16):
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value(sign | ((i + 15) << 10))
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# large numbers mapping to infinity
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for i in xrange(16, 128):
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value(sign | 0x7c00)
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# infinity and NaNs
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value(sign | 0x7c00)
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end()
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begin("uint8_t", "util_float_to_half_shift_table", 512)
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for sign in (0, 0x8000):
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# very small numbers mapping to zero
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for i in xrange(-127, -24):
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value(24)
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# small numbers mapping to denormals
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for i in xrange(-24, -14):
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value(-1 - i)
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# normal numbers
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for i in xrange(-14, 16):
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value(13)
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# large numbers mapping to infinity
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for i in xrange(16, 128):
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value(24)
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# infinity and NaNs
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value(13)
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end()
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