The dbl-64 implementation of atan2 does computations that expect to
run in round-to-nearest mode, and in other modes the errors can
accumulate to more than the maximum accepted 9ulp. This patch makes
it use FE_TONEAREST internally, similar to other functions with such
issues. Tests that previously produced large errors are added for
atan2 and the closely related carg, clog and clog10 functions.
Tested for x86_64 and x86 and ulps updated accordingly.
[BZ #18210]
[BZ #18211]
* sysdeps/ieee754/dbl-64/e_atan2.c: Include <fenv.h>.
(__ieee754_atan2): Set FE_TONEAREST mode for internal
computations.
* math/auto-libm-test-in: Add more tests of atan2, carg, clog and
clog10.
* math/auto-libm-test-out: Regenerated.
* sysdeps/i386/fpu/libm-test-ulps: Update.
* sysdeps/x86_64/fpu/libm-test-ulps: Likewise.
This patch fixes bug 15319, missing underflows from atan / atan2 when
the result of atan is very close to its small argument (or that of
atan2 is very close to the ratio of its arguments, which may be an
exact division).
The usual approach of doing an underflowing computation if the
computed result is subnormal is followed. For 32-bit x86, there are
extra complications: the inline __ieee754_atan2 in bits/mathinline.h
needs to be disabled for float and double because other libm functions
using it generally rely on getting proper underflow exceptions from
it, while the out-of-line functions have to remove excess range and
precision from the underflowing result so as to return an exact 0 in
the case where errno should be set for underflow to 0. (The failures
I saw without that are similar to those Carlos reported for other
functions, where I haven't seen a response to
<https://sourceware.org/ml/libc-alpha/2015-01/msg00485.html>
confirming if my diagnosis is correct. Arguably all libm functions
with float and double returns should remove excess range and
precision, but that's a separate matter.)
The x86_64 long double case reported in a comment in bug 15319 is not
a bug (it's an argument of LDBL_MIN, and x86_64 is an after-rounding
architecture so the correct IEEE result is not to raise underflow in
the given rounding mode, in addition to treating the result as an
exact LDBL_MIN being within the newly clarified documentation of
accuracy goals). I'm presuming that the fpatan instruction can be
trusted to raise appropriate exceptions when the (long double) result
underflows (after rounding) and so no changes are needed for x86 /
x86_64 long double functions here; empirically this is the case for
the cases covered in the testsuite, on my system.
Tested for x86_64, x86, powerpc and mips64. Only 32-bit x86 needs
ulps updates (for the changes to inlines meaning some functions no
longer get excess precision from their __ieee754_atan2* calls).
[BZ #15319]
* sysdeps/i386/fpu/e_atan2.S (dbl_min): New object.
(MO): New macro.
(__ieee754_atan2): For results with small absolute value, force
underflow exception and remove excess range and precision from
return value.
* sysdeps/i386/fpu/e_atan2f.S (flt_min): New object.
(MO): New macro.
(__ieee754_atan2f): For results with small absolute value, force
underflow exception and remove excess range and precision from
return value.
* sysdeps/i386/fpu/s_atan.S (dbl_min): New object.
(MO): New macro.
(__atan): For results with small absolute value, force underflow
exception and remove excess range and precision from return value.
* sysdeps/i386/fpu/s_atanf.S (flt_min): New object.
(MO): New macro.
(__atanf): For results with small absolute value, force underflow
exception and remove excess range and precision from return value.
* sysdeps/ieee754/dbl-64/e_atan2.c: Include <float.h> and
<math.h>.
(__ieee754_atan2): Force underflow exception for results with
small absolute value.
* sysdeps/ieee754/dbl-64/s_atan.c: Include <float.h> and
<math_private.h>.
(atan): Force underflow exception for results with small absolute
value.
* sysdeps/ieee754/flt-32/s_atanf.c: Include <float.h>.
(__atanf): Force underflow exception for results with small
absolute value.
* sysdeps/ieee754/ldbl-128/s_atanl.c: Include <float.h> and
<math.h>.
(__atanl): Force underflow exception for results with small
absolute value.
* sysdeps/ieee754/ldbl-128ibm/s_atanl.c: Include <float.h>.
(__atanl): Force underflow exception for results with small
absolute value.
* sysdeps/x86/fpu/bits/mathinline.h
[!__SSE2_MATH__ && !__x86_64__ && __LIBC_INTERNAL_MATH_INLINES]
(__ieee754_atan2): Only define inline for long double.
* sysdeps/x86_64/fpu/multiarch/e_atan2.c
[HAVE_FMA4_SUPPORT || HAVE_AVX_SUPPORT]: Include <math.h>.
* math/auto-libm-test-in: Do not mark underflow exceptions as
possibly missing for bug 15319. Add more tests of atan2.
* math/auto-libm-test-out: Regenerated.
* math/libm-test.inc (casin_test_data): Do not mark underflow
exceptions as possibly missing for bug 15319.
(casinh_test_data): Likewise.
* sysdeps/i386/fpu/libm-test-ulps: Update.
Add systemtap probes to various slow paths in libm so that application
developers may use systemtap to find out if their applications are
hitting these slow paths. We have added probes for pow, exp, log,
tan, atan and atan2.
2001-03-12 Ulrich Drepper <drepper@redhat.com>
* sysdeps/ieee754/dbl-64/e_remainder.c: Fix handling of boundary
conditions.
* sysdeps/ieee754/dbl-64/e_pow.c: Fix handling of boundary
conditions.
* sysdeps/ieee754/dbl-64/s_sin.c (__sin): Handle Inf and NaN
correctly.
(__cos): Likewise.
* sysdeps/ieee754/dbl-64/e_asin.c (__ieee754_asin): Handle NaN
correctly.
(__ieee754_acos): Likewise.
redefinition.
* sysdeps/ieee754/dbl-64/endian.h: Define also one of BIG_ENDI and
LITTLE_ENDI.
* sysdeps/ieee754/dbl-64/MathLib.h (Init_Lib): Use void as
parameter list.
2001-03-11 Ulrich Drepper <drepper@redhat.com>
Last-bit accurate math library implementation by IBM Haifa.
Contributed by Abraham Ziv <ziv@il.ibm.com>, Moshe Olshansky
<olshansk@il.ibm.com>, Ealan Henis <ealan@il.ibm.com>, and
Anna Reitman <reitman@il.ibm.com>.
* math/Makefile (dbl-only-routines): New variable.
(libm-routines): Add $(dbl-only-routines).
* sysdeps/ieee754/dbl-64/e_acos.c: Empty, definition is in e_asin.c.
* sysdeps/ieee754/dbl-64/e_asin.c: Replaced with accurate asin
implementation.
* sysdeps/ieee754/dbl-64/e_atan2.c: Replaced with accurate atan2
implementation.
* sysdeps/ieee754/dbl-64/e_exp.c: Replaced with accurate exp
implementation.
* sysdeps/ieee754/dbl-64/e_lgamma_r.c: Don't use __kernel_sin and
__kernel_cos.
* sysdeps/ieee754/dbl-64/e_log.c: Replaced with accurate log
implementation.
* sysdeps/ieee754/dbl-64/e_remainder.c: Replaced with accurate
remainder implementation.
* sysdeps/ieee754/dbl-64/e_pow.c: Replaced with accurate pow
implementation.
* sysdeps/ieee754/dbl-64/e_sqrt.c: Replaced with accurate sqrt
implementation.
* sysdeps/ieee754/dbl-64/k_cos.c: Empty, definition is in s_sin.c.
* sysdeps/ieee754/dbl-64/k_sin.c: Empty, definition is in s_sin.c.
* sysdeps/ieee754/dbl-64/s_atan.c: Replaced with accurate atan
implementation.
* sysdeps/ieee754/dbl-64/s_cos.c: Empty, definition is in s_sin.c.
* sysdeps/ieee754/dbl-64/s_sin.c: Replaced with accurate sin/cos
implementation.
* sysdeps/ieee754/dbl-64/s_sincos.c: Rewritten to not use __kernel_sin
and __kernel_cos.
* sysdeps/ieee754/dbl-64/s_tan.c: Replaced with accurate tan
implementation.
* sysdeps/ieee754/dbl-64/Dist: Add new non-code files.
* sysdeps/ieee754/dbl-64/MathLib.h: New file.
* sysdeps/ieee754/dbl-64/asincos.tbl: New file.
* sysdeps/ieee754/dbl-64/atnat.h: New file.
* sysdeps/ieee754/dbl-64/atnat2.h: New file.
* sysdeps/ieee754/dbl-64/branred.c: New file.
* sysdeps/ieee754/dbl-64/branred.h: New file.
* sysdeps/ieee754/dbl-64/dla.h: New file.
* sysdeps/ieee754/dbl-64/doasin.c: New file.
* sysdeps/ieee754/dbl-64/doasin.h: New file.
* sysdeps/ieee754/dbl-64/dosincos.c: New file.
* sysdeps/ieee754/dbl-64/dosincos.h: New file.
* sysdeps/ieee754/dbl-64/endian.h: New file.
* sysdeps/ieee754/dbl-64/halfulp.c: New file.
* sysdeps/ieee754/dbl-64/mpa.c: New file.
* sysdeps/ieee754/dbl-64/mpa.h: New file.
* sysdeps/ieee754/dbl-64/mpa2.h: New file.
* sysdeps/ieee754/dbl-64/mpatan.c: New file.
* sysdeps/ieee754/dbl-64/mpatan.h: New file.
* sysdeps/ieee754/dbl-64/mpatan2.c: New file.
* sysdeps/ieee754/dbl-64/mpexp.c: New file.
* sysdeps/ieee754/dbl-64/mpexp.h: New file.
* sysdeps/ieee754/dbl-64/mplog.c: New file.
* sysdeps/ieee754/dbl-64/mplog.h: New file.
* sysdeps/ieee754/dbl-64/mpsqrt.c: New file.
* sysdeps/ieee754/dbl-64/mpsqrt.h: New file.
* sysdeps/ieee754/dbl-64/mptan.c: New file.
* sysdeps/ieee754/dbl-64/mydefs.h: New file.
* sysdeps/ieee754/dbl-64/powtwo.tbl: New file.
* sysdeps/ieee754/dbl-64/root.tbl: New file.
* sysdeps/ieee754/dbl-64/sincos.tbl: New file.
* sysdeps/ieee754/dbl-64/sincos32.c: New file.
* sysdeps/ieee754/dbl-64/sincos32.h: New file.
* sysdeps/ieee754/dbl-64/slowexp.c: New file.
* sysdeps/ieee754/dbl-64/slowpow.c: New file.
* sysdeps/ieee754/dbl-64/uasncs.h: New file.
* sysdeps/ieee754/dbl-64/uatan.tbl: New file.
* sysdeps/ieee754/dbl-64/uexp.h: New file.
* sysdeps/ieee754/dbl-64/uexp.tbl: New file.
* sysdeps/ieee754/dbl-64/ulog.h: New file.
* sysdeps/ieee754/dbl-64/ulog.tbl: New file.
* sysdeps/ieee754/dbl-64/upow.h: New file.
* sysdeps/ieee754/dbl-64/upow.tbl: New file.
* sysdeps/ieee754/dbl-64/urem.h: New file.
* sysdeps/ieee754/dbl-64/uroot.h: New file.
* sysdeps/ieee754/dbl-64/usncs.h: New file.
* sysdeps/ieee754/dbl-64/utan.h: New file.
* sysdeps/ieee754/dbl-64/utan.tbl: New file.
* sysdeps/i386/fpu/branred.c: New file.
* sysdeps/i386/fpu/doasin.c: New file.
* sysdeps/i386/fpu/dosincos.c: New file.
* sysdeps/i386/fpu/halfulp.c: New file.
* sysdeps/i386/fpu/mpa.c: New file.
* sysdeps/i386/fpu/mpatan.c: New file.
* sysdeps/i386/fpu/mpatan2.c: New file.
* sysdeps/i386/fpu/mpexp.c: New file.
* sysdeps/i386/fpu/mplog.c: New file.
* sysdeps/i386/fpu/mpsqrt.c: New file.
* sysdeps/i386/fpu/mptan.c: New file.
* sysdeps/i386/fpu/sincos32.c: New file.
* sysdeps/i386/fpu/slowexp.c: New file.
* sysdeps/i386/fpu/slowpow.c: New file.
* sysdeps/ia64/fpu/branred.c: New file.
* sysdeps/ia64/fpu/doasin.c: New file.
* sysdeps/ia64/fpu/dosincos.c: New file.
* sysdeps/ia64/fpu/halfulp.c: New file.
* sysdeps/ia64/fpu/mpa.c: New file.
* sysdeps/ia64/fpu/mpatan.c: New file.
* sysdeps/ia64/fpu/mpatan2.c: New file.
* sysdeps/ia64/fpu/mpexp.c: New file.
* sysdeps/ia64/fpu/mplog.c: New file.
* sysdeps/ia64/fpu/mpsqrt.c: New file.
* sysdeps/ia64/fpu/mptan.c: New file.
* sysdeps/ia64/fpu/sincos32.c: New file.
* sysdeps/ia64/fpu/slowexp.c: New file.
* sysdeps/ia64/fpu/slowpow.c: New file.
* sysdeps/m68k/fpu/branred.c: New file.
* sysdeps/m68k/fpu/doasin.c: New file.
* sysdeps/m68k/fpu/dosincos.c: New file.
* sysdeps/m68k/fpu/halfulp.c: New file.
* sysdeps/m68k/fpu/mpa.c: New file.
* sysdeps/m68k/fpu/mpatan.c: New file.
* sysdeps/m68k/fpu/mpatan2.c: New file.
* sysdeps/m68k/fpu/mpexp.c: New file.
* sysdeps/m68k/fpu/mplog.c: New file.
* sysdeps/m68k/fpu/mpsqrt.c: New file.
* sysdeps/m68k/fpu/mptan.c: New file.
* sysdeps/m68k/fpu/sincos32.c: New file.
* sysdeps/m68k/fpu/slowexp.c: New file.
* sysdeps/m68k/fpu/slowpow.c: New file.
* iconvdata/gconv-modules: Add a number of alias, mostly for IBM
codepages.
