C compilers may fold const values at compile time, so expressions
which try to elicit underflow/overflow by performing simple
arithemetic on suitable values will not generate the required
exceptions.
Work around this by replacing code which does these arithmetic
operations with calls to the existing __math_xflow functions that are
designed to do this correctly.
Signed-off-by: Keith Packard <keithp@keithp.com>
----
v2:
libm/math: Pass sign to __math_xflow instead of muliplying result
The IEEE spec for pow only has special case for x**0 and 1**y when x/y
are quiet NaN. For signaling NaN, the general case applies and these functions
should signal the invalid exception and return a quiet NaN.
Signed-off-by: Keith Packard <keithp@keithp.com>
Based on code from https://github.com/ARM-software/optimized-routines/
This patch adds a highly optimized generic implementation of expf,
exp2f, logf, log2f and powf. The new functions are not only
faster (6x for powf!), but are also smaller and more accurate.
In order to achieve this, the algorithm uses double precision
arithmetic for accuracy, avoids divisions and uses small table
lookups to minimize the polynomials. Special cases are handled
inline to avoid the unnecessary overhead of wrapper functions and
set errno to POSIX requirements.
The new functions are added under newlib/libm/common, but the old
implementations are kept (in newlib/libm/math) for non-IEEE or
pre-C99 systems. Targets can enable the new math code by defining
__OBSOLETE_MATH_DEFAULT to 0 in newlib/libc/include/machine/ieeefp.h,
users can override the default by defining __OBSOLETE_MATH.
Currently the new code is enabled for AArch64 and AArch32 with VFP.
Targets with a single precision FPU may still prefer the old
implementation.
libm.a size changes:
arm: -1692
arm/thumb/v7-a/nofp: -878
arm/thumb/v7-a+fp/hard: -864
arm/thumb/v7-a+fp/softfp: -908
aarch64: -1476
compiler warnings found this way.
* libc/stdio/freopen.c (_freopen_r): Fix bug setting _flags.
* libc/include/stdio.h (_rename): Define when building newlib.
* libc/include/sys/signal.h (_kill): Ditto.
* libc/include/sys/stat.h (_mkdir): Ditto.
* libc/include/sys/time.h (_gettimeofday): Ditto.
* libc/include/sys/times.h (_times): Ditto.
* libc/include/sys/wait.h (_wait): Ditto.
* libc/locale/lmessages.c (empty): Don't define for Cygwin.
* libc/locale/lmonetary.c (cnv): Ditto.
* libc/locale/nl_langinfo.c (nl_langinfo): Ditto for variable s.
* libc/posix/collate.c: Throughout cast to avoid compiler warning.
* libc/posix/engine.c (matcher): Initialize dp to avoid compiler
warning.
* libc/posix/glob.c: Disable on Cygwin. Explain why.
* libc/posix/regcomp.c: Fix "uninitialized" compiler warnings.
(dissect): Deliberately silence gcc compiler warning. Add comment to
explain why.
* libc/posix/wordexp.c (wordexp): Remove num_bytes variable since result
is never used.
* libc/posix/popen.c (popen): Ditto for variable last.
* libc/reent/mkdirr.c: Include sys/stat.h.
* libc/reent/renamer.c: Include stdio.h.
* libc/search/hash.c: Throughout use underscored variants of the stat
function family.
(init_hash): Add missing definition for the __USE_INTERNAL_STAT64 case.
* libc/search/hash_bigkey.c (__big_insert): Add parenthesis to avoid
compiler warning.
* libc/search/hash_page.c (overflow_page): Initalize freep to NULL to
avoid compiler warning.
* libc/stdio/asiprintf.c (_asiprintf_r): Cast unsigned char * to char *
to avoid compiler warning.
(asiprintf): Ditto.
* libc/stdio/asprintf.c (_asprintf_r): Ditto.
(asprintf): Ditto.
* libc/stdio/vasiprintf.c (_vasiprintf_r): Ditto.
* libc/stdio/vasprintf.c (_vasprintf_r): Ditto.
* libc/stdio/mktemp.c (_gettemp): Cast to unsigned char in call to
isdigit to avoid compiler warning.
* libc/stdio/vfprintf.c (_VFPRINTF_R): Initialize variables used for
grouping to avoid compiler warning. Only define and set nseps and
nrepeats if they are really used.
* libc/stdio/vfwprintf.c (_VFWPRINTF_R): Ditto. Only define state if
it is really used.
* libc/stdio/vfscanf.c (u_char): Revert to be defined as unsigned char.
(__SVFSCANF_R): Cast fmt in call to __mbtowc.
* libc/stdlib/mbtowc_r.c (JIS_state_table): Disable when building
Cygwin.
(JIS_action_table): Ditto.
* libc/stdlib/wctomb_r.c (__utf8_wctomb): Add parenthesis to avoid
compiler warning.
* libc/string/strcasestr.c: Deliberately silence gcc compiler warning.
Add comment to explain why.
* libc/time/strptime.c (strptime): Cast to unsigned char in calls to
isspace to avoid compiler warning.
* libm/math/e_atan2.c (__ieee754_atan2): Add parenthesis to avoid
compiler warning.
* libm/math/e_exp.c (__ieee754_exp): Initialize k to 0 to avoid
compiler warning. Drop setting it to 0 later.
* libm/math/ef_exp.c (__ieee754_expf): Ditto.
* libm/math/e_pow.c (__ieee754_pow): Add braces to avoid compiler
warning.
* libm/math/ef_pow.c (__ieee754_powf): Ditto.
* libm/math/er_lgamma.c (__ieee754_lgamma_r): Initialize nadj to 0 to
avoid compiler warning.
* libm/math/erf_lgamma.c (__ieee754_lgammaf_r): Ditto.
* libm/math/e_rem_pio2.c (__ieee754_rem_pio2): Ditto for variable z.
* libm/common/sf_round.c (roundf): Remove signbit variable since result
is never used.
* libm/math/e_pow.c: Fix to be consistent with glibc with regards
to treatment of NaN and +-inf arguments.
* libm/math/ef_pow.c: Ditto.
* libm/math/w_pow.c: Ditto.
* libm/math/wf_pow.c: Ditto.
* libm/math/w_acos.c: Fix domain errors to return NaN.
* libm/math/w_asin.c: Ditto.
* libm/math/wf_acos.c: Ditto.
* libm/math/wf_asin.c: Ditto.
* libm/math/w_log.c: Fix to return NaN for negative number inputs.
* libm/math/wf_log.c: Ditto.
* libm/math/wf_log10.c: Ditto.
* libm/math/w_log10.c: Ditto.
* libm/math/e_pow.c (__ieee754_pow): Fix case whereby
x is close to -1.0 and y is very large to use ax (absolute value)
instead of x.
* libm/math/ef_pow.c (__ieee754_powf): Ditto.
Keith Packard
Keith Packard via Newlib
Fabian Schriever
Szabolcs Nagy
Corinna Vinschen
Jeff Johnston
Richard Sandiford
Christopher Faylor