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Diffstat (limited to 'src/gallium/auxiliary/util/u_half.py')
| -rw-r--r-- | src/gallium/auxiliary/util/u_half.py | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/src/gallium/auxiliary/util/u_half.py b/src/gallium/auxiliary/util/u_half.py new file mode 100644 index 00000000000..8007482e971 --- /dev/null +++ b/src/gallium/auxiliary/util/u_half.py @@ -0,0 +1,179 @@ +# Copyright 2010 Luca Barbieri +# +# 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 (including the +# next paragraph) 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 COPYRIGHT OWNER(S) AND/OR ITS SUPPLIERS 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. +# +# ************************************************************************* + +# The code is a reimplementation of the algorithm in +# www.fox-toolkit.org/ftp/fasthalffloatconversion.pdf +# "Fast Half Float Conversions" by Jeroen van der Zijp, Nov 2008 +# +# The table contents have been slightly changed so that the exponent +# bias is now in the exponent table instead of the mantissa table (mostly +# for cosmetic reasons, and because it theoretically allows a variant +# that flushes denormal to zero but uses a mantissa table with 24-bit +# entries). +# +# The tables are also constructed slightly differently. +# + +# Note that using a 64K * 4 table is a terrible idea since it will not fit +# in the L1 cache and will massively pollute the L2 cache as well +# +# These should instead fit in the L1 cache. +# +# TODO: we could use a denormal bias table instead of the mantissa/offset +# tables: this would reduce the L1 cache usage from 8704 to 2304 bytes +# but would involve more computation +# +# Note however that if denormals are never encountered, the L1 cache usage +# is only about 4608 bytes anyway. + +table_index = None +table_length = None + +def begin(t, n, l): + global table_length + global table_index + table_index = 0 + table_length = l + print + print "const " + t + " " + n + "[" + str(l) + "] = {" + +def value(v): + global table_index + table_index += 1 + print "\t" + hex(v) + "," + +def end(): + global table_length + global table_index + print "};" + assert table_index == table_length + +print "/* This file is autogenerated by u_half.py. Do not edit directly. */" +print "#include \"util/u_half.h\"" + +begin("uint32_t", "util_half_to_float_mantissa_table", 2048) +# zero +value(0) + +# denormals +for i in xrange(1, 1024): + m = i << 13 + e = 0 + + # normalize number + while (m & 0x00800000) == 0: + e -= 0x00800000; + m <<= 1; + + m &= ~0x00800000; + e += 0x38800000; + value(m | e) + +# normals +for i in xrange(1024, 2048): + value((i - 1024) << 13) +end() + +begin("uint32_t", "util_half_to_float_exponent_table", 64) +# positive zero or denormals +value(0) + +# positive numbers +for i in xrange(1, 31): + value(0x38000000 + (i << 23)) + +# positive infinity/NaN +value(0x7f800000) + +# negative zero or denormals +value(0x80000000) + +# negative numbers +for i in range(33, 63): + value(0xb8000000 + ((i - 32) << 23)) + +# negative infinity/NaN +value(0xff800000) +end() + +begin("uint32_t", "util_half_to_float_offset_table", 64) +# positive zero or denormals +value(0) + +# positive normals +for i in range(1, 32): + value(1024) + +# negative zero or denormals +value(0) + +# negative normals +for i in xrange(33, 64): + value(1024) +end() + +begin("uint16_t", "util_float_to_half_base_table", 512) +for sign in (0, 0x8000): + # very small numbers mapping to zero + for i in xrange(-127, -24): + value(sign | 0) + + # small numbers mapping to denormals + for i in xrange(-24, -14): + value(sign | (0x400 >> (-14 -i))) + + # normal numbers + for i in xrange(-14, 16): + value(sign | ((i + 15) << 10)) + + # large numbers mapping to infinity + for i in xrange(16, 128): + value(sign | 0x7c00) + + # infinity and NaNs + value(sign | 0x7c00) +end() + +begin("uint8_t", "util_float_to_half_shift_table", 512) +for sign in (0, 0x8000): + # very small numbers mapping to zero + for i in xrange(-127, -24): + value(24) + + # small numbers mapping to denormals + for i in xrange(-24, -14): + value(-1 - i) + + # normal numbers + for i in xrange(-14, 16): + value(13) + + # large numbers mapping to infinity + for i in xrange(16, 128): + value(24) + + # infinity and NaNs + value(13) +end() + |