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
* libc/include/math.h: (llround, llroundf): Declare.
* libm/common/s_llround.c: New file, implementing llround().
* libm/common/sf_llround.c: New file, implementing llroundf().
* libm/common/sf_lround.c: Remove spurious cast in _DOUBLE_IS_32BITS
version of function.
* libm/common/sf_lrint.c: Ditto.
* libm/common/sf_logb.c: Corrected return for subnormal argument
by replacing existing function with a version created from sf_ilogb.c.
* libm/common/s_logb.c: Ditto, except starting point s_ilogb.c. Also
added documentation for logb() and logbf().
* libm/common/s_signbit.c: Add signbit() documentation.
* libm/common/s_log2.c: Update return values to match what w_log2.c has,
since log2 uses log(); add note about being derived instead of direct.
* libm/common/sf_fma.c: Add casts to attempt to get correct results,
as well as comments pointing out problems with the implementation.
* libm/common/s_fma.c: Add fma() and fmaf() documentation.
* libm/common/sf_remquo.c: Incorrect quotient returns for large values
corrected by discarding existing function and replacing with Sun
verion, with some enhancements.
* libm/common/s_remquo.c: Ditto. Add remquo() and remquof()
documentation.
* libm/common/s_fmax.c: Add fmax() and fmaxf() documentation.
* libm/common/s_fmin.c: Add fmin() and fminf() documentation.
* libm/common/s_fdim.c: Return NAN for NAN arg, add fdim() and fdimf()
documentation.
* libm/common/sf_fdim.c: Return NAN for NAN arg, HUGE_VALF for inf arg.
* libm/common/s_trunc.c: Add trunc() and truncf() documentation.
* libm/common/s_rint.c: Add rint() and rintf() documentation.
* libm/common/s_round.c: Add round() and roundf() documentation.
* libm/common/s_scalbn.c: Add scalbln() and scalblnf() documentation.
* libm/common/s_infinity.c: Add infinity() and infinityf()
documentation.
* libm/common/s_lround.c: Add lround(), lroundf(), llround(), and
llroundf() documentation.
* libm/common/s_lrint.c: Add lrint(), lrintf(), llrint(), and llrintf()
documentation.
* libm/common/isgreater.c: New file for documenting math.h function-like
macros isgreater(), isgreaterequal(), isless(), islessequal(),
islessgreater(), and isunordered().
* libm/common/s_isnan.c: Add documentation for function-like macros
fpclassify(), isfinite(), isinf(), isnan(), and isnormal().
* libm/common/s_nearbyint.c: Add nearbyint() and nearbyintf()
documentation.
* libm/common/Makefile.am: Add s_llround.c (src); sf_llround.c (fsrc);
s_fdim.def, s_fma.def, s_fmax.def, s_fmin.def,
s_logb.def, s_lrint.def, s_lround.def, s_nearbyint.def, s_remquo.def,
s_rint.def, s_round.def, s_signbit.def, s_trunc.def, and
isgreater.def (chobj);
re-name all existing chew files (chobj) to match source file base
names (put in underscores), delete all special targets for chew files
(leaving all to be generated by rule).
* libm/common/Makefile.in: regenerate.
* libm/math/w_exp2.c: Add "base 2" to documentation description (and
delete TRAD_SYNOPSIS).
* libm/math/w_gamma.c: Add tgamma() and tgammaf() documentation, along
with some history behind the function names.
* libm/math/math.tex: Add includes for newly-added documentation (see
.def additions to common/Makefile.am and math/Makefile.am in this
ChangeLog list), adjusted existing .def file names to match source file
base names (added underscores); add mention of HUGE_VALF; rename
"Version of library" section to "Error Handling" and add some text
about floating-point exception; added section "Standards Compliance And
Portability".
* libm/math/Makefile.am: Add w_exp2.def (chobj);
re-name all existing chew files (chobj) to match source file base
names, delete all special targets for chew files (leaving all to be
generated by rule).
* libm/math/Makefile.in: regenerated
* doc/makedoc.c: Change silent ignoring of commands < 5 characters
to a failure when reading macro file for commands < 4 characters;
add -v (verbose) option for printing some debugging information;
get rid of spurious translation of "@*" to "*" (no source files used @*,
so no existing doc pages were affected); clean up some compiler
warnings.
* doc/doc.str: add BUGS and SEEALSO sections (to match texi2pod.pl
which has them); Remove ITEM command (redundant with makedoc built-in
"o", not used in any present source file so nothing is lost, anyway).
* HOWTO: New file to hold information for maintainers regarding how
to do things. Initial sections on documentation and ELIX levels.
* Makefile.am (MATHOBJS_IN_LIBC): Add s_isinfd, sf_isinff,
s_isnand, and sf_isnanf object files.
* Makefile.in: Regenerated.
* libc/include/ieeefp.h: Undef isnan and isinf to avoid
conflict if <math.h> has previously been included.
* libc/include/math.h
* libm/common/Makefile.am: Add new s_isinfd, s_isnand, sf_isinff,
and sf_isnanf files. Also support s_isnan, sf_isnan, s_isinf, and
sf_isinf files which have been moved from math/mathfp directories.
* libm/common/Makefile.in: Regenerated.
* libm/common/s_isinfd.c: New file.
* libm/common/s_isnand.c: Ditto.
* libm/common/sf_isinff.c: Ditto.
* libm/common/sf_isnanf.c: Ditto.
* libm/common/s_isinf.c: Moved from libm/math directory.
* libm/common/s_isnan.c: Ditto.
* libm/common/sf_isinf.c: Ditto.
* libm/common/sf_isnan.c: Ditto.
* libm/math/Makefile.am: Remove isinf and isnan family functions
which have been moved into common directory.
* libm/mathfp/Makefile.am: Ditto.
* libm/math/Makefile.in: Regenerated.
* libm/mathfp/Makefile.in: Ditto.
* libm/math/s_isinf.c: Removed.
* libm/math/s_isnan.c: Ditto.
* libm/math/sf_isinf.c: Ditto.
* libm/math/sf_isnan.c: Ditto.
* libm/mathfp/s_isinf.c: Ditto.
* libm/mathfp/s_isnan.c: Ditto.
* libm/mathfp/sf_isinf.c: Ditto.
* libm/mathfp/sf_isnan.c: Ditto.
* libc/include/math.h (HUGE_VALF, HUGE_VALL): New.
* libm/common/Makefile.am: Add s_infconst.c support.
* libm/common/Makefile.in: Regenerated.
* libm/common/s_infconst.c: New file with float and
long double infinity support added.
* libm/math/Makefile.am: Remove s_infconst.c support.
* libm/math/Makefile.in: Regenerated.
* libm/math/s_infconst.c: Moved to common directory.
* libm/mathfp/Makefile.am: Remove s_infconst.c support.
* libm/mathfp/Makefile.in: Regenerated.
* libm/mathfp/s_infconst.c: Moved to common directory.
Szabolcs Nagy
Jeff Johnston
Nick Clifton
Corinna Vinschen
Thomas Fitzsimmons
Christopher Faylor