logb now works correctly on large integers
* admin/merge-gnulib (GNULIB_MODULES): Add count-leading-zeros. * etc/NEWS: Document the change. * lib/count-leading-zeros.c, lib/count-leading-zeros.h: * m4/count-leading-zeros.m4: New files, copied from Gnulib. * lib/gnulib.mk, m4/gnulib-comp.m4: Regenerate. * src/floatfns.c: Include count-leading-zeros.h. (Flogb): Do not convert fixnum to float before taking the log, as the rounding error can cause the answer to be off by 1. * src/lisp.h (EMACS_UINT_WIDTH): New constant. * test/src/floatfns-tests.el (logb-extreme-fixnum): New test.
This commit is contained in:
Paul Eggert
parent
f1fe3fcfc5
commit
74f87fd111
10 changed files with 185 additions and 19 deletions
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@ -27,7 +27,8 @@ GNULIB_URL=git://git.savannah.gnu.org/gnulib.git
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GNULIB_MODULES='
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alloca-opt binary-io byteswap c-ctype c-strcase
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careadlinkat close-stream count-one-bits count-trailing-zeros
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careadlinkat close-stream
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count-leading-zeros count-one-bits count-trailing-zeros
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crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512
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dtoastr dtotimespec dup2 environ execinfo faccessat
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fcntl fcntl-h fdatasync fdopendir
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6
etc/NEWS
6
etc/NEWS
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@ -903,9 +903,9 @@ compares their numerical values. According to this predicate,
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"foo2.png" is smaller than "foo12.png".
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---
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** Numeric comparisons no longer return incorrect answers due to
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internal rounding errors. For example, (< most-positive-fixnum (+ 1.0
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most-positive-fixnum)) now correctly returns t on 64-bit hosts.
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** Numeric comparisons and 'logb' no longer return incorrect answers
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due to internal rounding errors. For example, (< most-positive-fixnum
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(+ 1.0 most-positive-fixnum)) now correctly returns t on 64-bit hosts.
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+++
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** The new function 'char-from-name' converts a Unicode name string
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3
lib/count-leading-zeros.c
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3
lib/count-leading-zeros.c
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@ -0,0 +1,3 @@
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#include <config.h>
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#define COUNT_LEADING_ZEROS_INLINE _GL_EXTERN_INLINE
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#include "count-leading-zeros.h"
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114
lib/count-leading-zeros.h
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114
lib/count-leading-zeros.h
Normal file
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@ -0,0 +1,114 @@
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/* count-leading-zeros.h -- counts the number of leading 0 bits in a word.
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Copyright (C) 2012-2017 Free Software Foundation, Inc.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program 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
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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/* Written by Eric Blake. */
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#ifndef COUNT_LEADING_ZEROS_H
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#define COUNT_LEADING_ZEROS_H 1
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#include <limits.h>
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#include <stdlib.h>
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#ifndef _GL_INLINE_HEADER_BEGIN
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#error "Please include config.h first."
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#endif
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_GL_INLINE_HEADER_BEGIN
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#ifndef COUNT_LEADING_ZEROS_INLINE
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# define COUNT_LEADING_ZEROS_INLINE _GL_INLINE
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#endif
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/* Assuming the GCC builtin is BUILTIN and the MSC builtin is MSC_BUILTIN,
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expand to code that computes the number of leading zeros of the local
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variable 'x' of type TYPE (an unsigned integer type) and return it
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from the current function. */
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#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
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# define COUNT_LEADING_ZEROS(BUILTIN, MSC_BUILTIN, TYPE) \
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return x ? BUILTIN (x) : CHAR_BIT * sizeof x;
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#elif _MSC_VER
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# pragma intrinsic _BitScanReverse
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# pragma intrinsic _BitScanReverse64
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# define COUNT_LEADING_ZEROS(BUILTIN, MSC_BUILTIN, TYPE) \
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do \
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{ \
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unsigned long result; \
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return MSC_BUILTIN (&result, x) ? result : CHAR_BIT * sizeof x; \
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} \
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while (0)
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#else
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# define COUNT_LEADING_ZEROS(BUILTIN, MSC_BUILTIN, TYPE) \
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do \
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{ \
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int count; \
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unsigned int leading_32; \
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if (! x) \
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return CHAR_BIT * sizeof x; \
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for (count = 0; \
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(leading_32 = ((x >> (sizeof (TYPE) * CHAR_BIT - 32)) \
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& 0xffffffffU), \
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count < CHAR_BIT * sizeof x - 32 && !leading_32); \
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count += 32) \
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x = x << 31 << 1; \
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return count + count_leading_zeros_32 (leading_32); \
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} \
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while (0)
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/* Compute and return the number of leading zeros in X,
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where 0 < X < 2**32. */
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COUNT_LEADING_ZEROS_INLINE int
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count_leading_zeros_32 (unsigned int x)
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{
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/* http://graphics.stanford.edu/~seander/bithacks.html */
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static const char de_Bruijn_lookup[32] = {
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31, 22, 30, 21, 18, 10, 29, 2, 20, 17, 15, 13, 9, 6, 28, 1,
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23, 19, 11, 3, 16, 14, 7, 24, 12, 4, 8, 25, 5, 26, 27, 0
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};
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x |= x >> 1;
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x |= x >> 2;
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x |= x >> 4;
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x |= x >> 8;
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x |= x >> 16;
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return de_Bruijn_lookup[((x * 0x07c4acddU) & 0xffffffffU) >> 27];
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}
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#endif
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/* Compute and return the number of leading zeros in X. */
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COUNT_LEADING_ZEROS_INLINE int
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count_leading_zeros (unsigned int x)
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{
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COUNT_LEADING_ZEROS (__builtin_clz, _BitScanReverse, unsigned int);
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}
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/* Compute and return the number of leading zeros in X. */
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COUNT_LEADING_ZEROS_INLINE int
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count_leading_zeros_l (unsigned long int x)
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{
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COUNT_LEADING_ZEROS (__builtin_clzl, _BitScanReverse, unsigned long int);
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}
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#if HAVE_UNSIGNED_LONG_LONG_INT
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/* Compute and return the number of leading zeros in X. */
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COUNT_LEADING_ZEROS_INLINE int
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count_leading_zeros_ll (unsigned long long int x)
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{
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COUNT_LEADING_ZEROS (__builtin_clzll, _BitScanReverse64,
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unsigned long long int);
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}
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#endif
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_GL_INLINE_HEADER_END
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#endif /* COUNT_LEADING_ZEROS_H */
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@ -21,7 +21,7 @@
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# the same distribution terms as the rest of that program.
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#
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# Generated by gnulib-tool.
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# Reproduce by: gnulib-tool --import --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=close --avoid=dup --avoid=fchdir --avoid=fstat --avoid=malloc-posix --avoid=msvc-inval --avoid=msvc-nothrow --avoid=open --avoid=openat-die --avoid=opendir --avoid=raise --avoid=save-cwd --avoid=select --avoid=setenv --avoid=sigprocmask --avoid=stdarg --avoid=stdbool --avoid=threadlib --avoid=unsetenv --makefile-name=gnulib.mk --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt binary-io byteswap c-ctype c-strcase careadlinkat close-stream count-one-bits count-trailing-zeros crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 dtoastr dtotimespec dup2 environ execinfo faccessat fcntl fcntl-h fdatasync fdopendir filemode filevercmp flexmember fstatat fsync getloadavg getopt-gnu gettime gettimeofday gitlog-to-changelog ignore-value intprops largefile lstat manywarnings memrchr mkostemp mktime pipe2 pselect pthread_sigmask putenv qcopy-acl readlink readlinkat sig2str socklen stat-time std-gnu11 stdalign stddef stdio stpcpy strftime strtoimax strtoumax symlink sys_stat sys_time time time_r time_rz timegm timer-time timespec-add timespec-sub unsetenv update-copyright utimens vla warnings
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# Reproduce by: gnulib-tool --import --lib=libgnu --source-base=lib --m4-base=m4 --doc-base=doc --tests-base=tests --aux-dir=build-aux --avoid=close --avoid=dup --avoid=fchdir --avoid=fstat --avoid=malloc-posix --avoid=msvc-inval --avoid=msvc-nothrow --avoid=open --avoid=openat-die --avoid=opendir --avoid=raise --avoid=save-cwd --avoid=select --avoid=setenv --avoid=sigprocmask --avoid=stdarg --avoid=stdbool --avoid=threadlib --avoid=unsetenv --makefile-name=gnulib.mk --conditional-dependencies --no-libtool --macro-prefix=gl --no-vc-files alloca-opt binary-io byteswap c-ctype c-strcase careadlinkat close-stream count-leading-zeros count-one-bits count-trailing-zeros crypto/md5 crypto/sha1 crypto/sha256 crypto/sha512 dtoastr dtotimespec dup2 environ execinfo faccessat fcntl fcntl-h fdatasync fdopendir filemode filevercmp flexmember fstatat fsync getloadavg getopt-gnu gettime gettimeofday gitlog-to-changelog ignore-value intprops largefile lstat manywarnings memrchr mkostemp mktime pipe2 pselect pthread_sigmask putenv qcopy-acl readlink readlinkat sig2str socklen stat-time std-gnu11 stdalign stddef stdio stpcpy strftime strtoimax strtoumax symlink sys_stat sys_time time time_r time_rz timegm timer-time timespec-add timespec-sub unsetenv update-copyright utimens vla warnings
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MOSTLYCLEANFILES += core *.stackdump
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@ -151,6 +151,14 @@ EXTRA_DIST += close-stream.h
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## end gnulib module close-stream
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## begin gnulib module count-leading-zeros
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libgnu_a_SOURCES += count-leading-zeros.c
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EXTRA_DIST += count-leading-zeros.h
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## end gnulib module count-leading-zeros
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## begin gnulib module count-one-bits
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libgnu_a_SOURCES += count-one-bits.c
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12
m4/count-leading-zeros.m4
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12
m4/count-leading-zeros.m4
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@ -0,0 +1,12 @@
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# count-leading-zeros.m4 serial 2
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dnl Copyright (C) 2012-2017 Free Software Foundation, Inc.
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dnl This file is free software; the Free Software Foundation
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dnl gives unlimited permission to copy and/or distribute it,
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dnl with or without modifications, as long as this notice is preserved.
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AC_DEFUN([gl_COUNT_LEADING_ZEROS],
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[
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dnl We don't need (and can't compile) count_leading_zeros_ll
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dnl unless the type 'unsigned long long int' exists.
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AC_REQUIRE([AC_TYPE_UNSIGNED_LONG_LONG_INT])
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])
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@ -54,6 +54,7 @@ AC_DEFUN([gl_EARLY],
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# Code from module careadlinkat:
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# Code from module clock-time:
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# Code from module close-stream:
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# Code from module count-leading-zeros:
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# Code from module count-one-bits:
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# Code from module count-trailing-zeros:
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# Code from module crypto/md5:
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@ -190,6 +191,7 @@ AC_DEFUN([gl_INIT],
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gl_CLOCK_TIME
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gl_CLOSE_STREAM
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gl_MODULE_INDICATOR([close-stream])
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gl_COUNT_LEADING_ZEROS
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gl_COUNT_ONE_BITS
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gl_COUNT_TRAILING_ZEROS
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gl_MD5
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@ -871,6 +873,8 @@ AC_DEFUN([gl_FILE_LIST], [
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lib/careadlinkat.h
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lib/close-stream.c
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lib/close-stream.h
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lib/count-leading-zeros.c
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lib/count-leading-zeros.h
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lib/count-one-bits.c
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lib/count-one-bits.h
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lib/count-trailing-zeros.c
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@ -1000,6 +1004,7 @@ AC_DEFUN([gl_FILE_LIST], [
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m4/c-strtod.m4
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m4/clock_time.m4
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m4/close-stream.m4
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m4/count-leading-zeros.m4
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m4/count-one-bits.m4
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m4/count-trailing-zeros.m4
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m4/dirent_h.m4
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@ -45,6 +45,8 @@ along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. */
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#include <math.h>
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#include <count-leading-zeros.h>
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/* 'isfinite' and 'isnan' cause build failures on Solaris 10 with the
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bundled GCC in c99 mode. Work around the bugs with simple
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implementations that are good enough. */
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@ -290,28 +292,46 @@ DEFUN ("float", Ffloat, Sfloat, 1, 1, 0,
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return arg;
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}
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static int
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ecount_leading_zeros (EMACS_UINT x)
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{
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return (EMACS_UINT_WIDTH == UINT_WIDTH ? count_leading_zeros (x)
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: EMACS_UINT_WIDTH == ULONG_WIDTH ? count_leading_zeros_l (x)
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: count_leading_zeros_ll (x));
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}
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DEFUN ("logb", Flogb, Slogb, 1, 1, 0,
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doc: /* Returns largest integer <= the base 2 log of the magnitude of ARG.
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This is the same as the exponent of a float. */)
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(Lisp_Object arg)
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{
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Lisp_Object val;
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EMACS_INT value;
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double f = extract_float (arg);
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CHECK_NUMBER_OR_FLOAT (arg);
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if (f == 0.0)
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value = MOST_NEGATIVE_FIXNUM;
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else if (isfinite (f))
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if (FLOATP (arg))
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{
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int ivalue;
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frexp (f, &ivalue);
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value = ivalue - 1;
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double f = XFLOAT_DATA (arg);
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if (f == 0)
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value = MOST_NEGATIVE_FIXNUM;
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else if (isfinite (f))
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{
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int ivalue;
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frexp (f, &ivalue);
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value = ivalue - 1;
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}
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else
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value = MOST_POSITIVE_FIXNUM;
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}
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else
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value = MOST_POSITIVE_FIXNUM;
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{
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EMACS_INT i = eabs (XINT (arg));
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value = (i == 0
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? MOST_NEGATIVE_FIXNUM
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: EMACS_UINT_WIDTH - 1 - ecount_leading_zeros (i));
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}
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XSETINT (val, value);
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return val;
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return make_number (value);
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}
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@ -80,19 +80,19 @@ DEFINE_GDB_SYMBOL_END (GCTYPEBITS)
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# elif INTPTR_MAX <= INT_MAX && !defined WIDE_EMACS_INT
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typedef int EMACS_INT;
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typedef unsigned int EMACS_UINT;
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enum { EMACS_INT_WIDTH = INT_WIDTH };
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enum { EMACS_INT_WIDTH = INT_WIDTH, EMACS_UINT_WIDTH = UINT_WIDTH };
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# define EMACS_INT_MAX INT_MAX
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# define pI ""
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# elif INTPTR_MAX <= LONG_MAX && !defined WIDE_EMACS_INT
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typedef long int EMACS_INT;
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typedef unsigned long EMACS_UINT;
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enum { EMACS_INT_WIDTH = LONG_WIDTH };
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enum { EMACS_INT_WIDTH = LONG_WIDTH, EMACS_UINT_WIDTH = ULONG_WIDTH };
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# define EMACS_INT_MAX LONG_MAX
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# define pI "l"
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# elif INTPTR_MAX <= LLONG_MAX
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typedef long long int EMACS_INT;
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typedef unsigned long long int EMACS_UINT;
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enum { EMACS_INT_WIDTH = LLONG_WIDTH };
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enum { EMACS_INT_WIDTH = LLONG_WIDTH, EMACS_UINT_WIDTH = ULLONG_WIDTH };
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# define EMACS_INT_MAX LLONG_MAX
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# ifdef __MINGW32__
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# define pI "I64"
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@ -25,4 +25,7 @@
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(should-error (round most-negative-fixnum -1.0))
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(should-error (truncate most-negative-fixnum -1.0)))
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(ert-deftest logb-extreme-fixnum ()
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(should (= (logb most-negative-fixnum) (1+ (logb most-positive-fixnum)))))
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(provide 'floatfns-tests)
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Loading…
Add table
Reference in a new issue