Make ff_inverse stay with libavutil, and optional copy it to libavcodec.

The ff_inverse table is used by FASTDIV macro, defined in libavutil, but up
to now the table was defined only in libavcodec.

After this change, the main copy of ff_inverse is part of libavutil (just
like FASTDIV), but if CONFIG_SMALL is unset, then a different copy is made
available to libavcodec, to avoid the performance penalty of using an
external look up table.

Dynamic linking works, because the libraries are linked with -Bsymbolic, so
the local copy of the symbol has priority over the external; static linking
works because the table is on a standalone object file in both libraries,
so the linker is able to discard one of the two.

Tested on Linux/x86-64 and Mac OS X/x86-64.

Originally committed as revision 24383 to svn://svn.ffmpeg.org/ffmpeg/trunk

2 files changed, 61 insertions, 0 deletions

diff --git a/libavutil/Makefile b/libavutil/Makefile
index 9238808ce9..0c25ce16bb 100644
--- a/libavutil/Makefile
+++ b/libavutil/Makefile
@@ -39,6 +39,7 @@ OBJS = adler32.o                                                        \
        eval.o                                                           \
        fifo.o                                                           \
        intfloat_readwrite.o                                             \
+       inverse.o                                                        \
        lfg.o                                                            \
        lls.o                                                            \
        log.o                                                            \
diff --git a/libavutil/inverse.c b/libavutil/inverse.c
new file mode 100644
index 0000000000..74df1c2473
--- /dev/null
+++ b/libavutil/inverse.c
@@ -0,0 +1,60 @@
+/*
+ * Inverse table
+ * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "libavutil/intmath.h"
+
+/* a*inverse[b]>>32 == a/b for all 0<=a<=16909558 && 2<=b<=256
+ * for a>16909558, is an overestimate by less than 1 part in 1<<24 */
+const uint32_t ff_inverse[257]={
+         0, 4294967295U,2147483648U,1431655766, 1073741824,  858993460,  715827883,  613566757,
+ 536870912,  477218589,  429496730,  390451573,  357913942,  330382100,  306783379,  286331154,
+ 268435456,  252645136,  238609295,  226050911,  214748365,  204522253,  195225787,  186737709,
+ 178956971,  171798692,  165191050,  159072863,  153391690,  148102321,  143165577,  138547333,
+ 134217728,  130150525,  126322568,  122713352,  119304648,  116080198,  113025456,  110127367,
+ 107374183,  104755300,  102261127,   99882961,   97612894,   95443718,   93368855,   91382283,
+  89478486,   87652394,   85899346,   84215046,   82595525,   81037119,   79536432,   78090315,
+  76695845,   75350304,   74051161,   72796056,   71582789,   70409300,   69273667,   68174085,
+  67108864,   66076420,   65075263,   64103990,   63161284,   62245903,   61356676,   60492498,
+  59652324,   58835169,   58040099,   57266231,   56512728,   55778797,   55063684,   54366675,
+  53687092,   53024288,   52377650,   51746594,   51130564,   50529028,   49941481,   49367441,
+  48806447,   48258060,   47721859,   47197443,   46684428,   46182445,   45691142,   45210183,
+  44739243,   44278014,   43826197,   43383509,   42949673,   42524429,   42107523,   41698712,
+  41297763,   40904451,   40518560,   40139882,   39768216,   39403370,   39045158,   38693400,
+  38347923,   38008561,   37675152,   37347542,   37025581,   36709123,   36398028,   36092163,
+  35791395,   35495598,   35204650,   34918434,   34636834,   34359739,   34087043,   33818641,
+  33554432,   33294321,   33038210,   32786010,   32537632,   32292988,   32051995,   31814573,
+  31580642,   31350127,   31122952,   30899046,   30678338,   30460761,   30246249,   30034737,
+  29826162,   29620465,   29417585,   29217465,   29020050,   28825284,   28633116,   28443493,
+  28256364,   28071682,   27889399,   27709467,   27531842,   27356480,   27183338,   27012373,
+  26843546,   26676816,   26512144,   26349493,   26188825,   26030105,   25873297,   25718368,
+  25565282,   25414008,   25264514,   25116768,   24970741,   24826401,   24683721,   24542671,
+  24403224,   24265352,   24129030,   23994231,   23860930,   23729102,   23598722,   23469767,
+  23342214,   23216040,   23091223,   22967740,   22845571,   22724695,   22605092,   22486740,
+  22369622,   22253717,   22139007,   22025474,   21913099,   21801865,   21691755,   21582751,
+  21474837,   21367997,   21262215,   21157475,   21053762,   20951060,   20849356,   20748635,
+  20648882,   20550083,   20452226,   20355296,   20259280,   20164166,   20069941,   19976593,
+  19884108,   19792477,   19701685,   19611723,   19522579,   19434242,   19346700,   19259944,
+  19173962,   19088744,   19004281,   18920561,   18837576,   18755316,   18673771,   18592933,
+  18512791,   18433337,   18354562,   18276457,   18199014,   18122225,   18046082,   17970575,
+  17895698,   17821442,   17747799,   17674763,   17602325,   17530479,   17459217,   17388532,
+  17318417,   17248865,   17179870,   17111424,   17043522,   16976156,   16909321,   16843010,
+  16777216
+};