Bug 16516 reports spurious underflows from erf (for all floating-point
types), when the result is close to underflowing but does not actually
underflow.
erf (x) is about (2/sqrt(pi))*x for x close to 0, so there are
subnormal arguments for which it does not underflow. The various
implementations do (x + efx*x) (for efx = 2/sqrt(pi) - 1), for greater
accuracy than if just using a single multiplication by an
approximation to 2/sqrt(pi) (effectively, this way there are a few
more bits in the approximation to 2/sqrt(pi)). This can introduce
underflows when efx*x underflows even though the final result does
not, so a scaled calculation with 8*efx is done in these cases - but 8
is not a big enough scale factor to avoid all such underflows. 16 is
(any underflows with a scale factor of 16 would only occur when the
final result underflows), so this patch changes the code to use that
factor. Rather than recomputing all the values of the efx8 variable,
it is removed, leaving it to the compiler's constant folding to
compute 16*efx. As such scaling can also lose underflows when the
final scaling down happens to be exact, appropriate checks are added
to ensure underflow exceptions occur when required in such cases.
Tested x86_64 and x86; no ulps updates needed. Also spot-checked for
powerpc32 and mips64 to verify the changes to the ldbl-128ibm and
ldbl-128 implementations.
[BZ #16516]
* sysdeps/ieee754/dbl-64/s_erf.c (efx8): Remove variable.
(__erf): Scale by 16 instead of 8 in potentially underflowing
case. Ensure exception if result actually underflows.
* sysdeps/ieee754/flt-32/s_erff.c (efx8): Remove variable.
(__erff): Scale by 16 instead of 8 in potentially underflowing
case. Ensure exception if result actually underflows.
* sysdeps/ieee754/ldbl-128/s_erfl.c: Include <float.h>.
(efx8): Remove variable.
(__erfl): Scale by 16 instead of 8 in potentially underflowing
case. Ensure exception if result actually underflows.
* sysdeps/ieee754/ldbl-128ibm/s_erfl.c: Include <float.h>.
(efx8): Remove variable.
(__erfl): Scale by 16 instead of 8 in potentially underflowing
case. Ensure exception if result actually underflows.
* sysdeps/ieee754/ldbl-96/s_erfl.c: Include <float.h>.
(efx8): Remove variable.
(__erfl): Scale by 16 instead of 8 in potentially underflowing
case. Ensure exception if result actually underflows.
* math/auto-libm-test-in: Add more tests of erf.
* math/auto-libm-test-out: Regenerated.
http://sourceware.org/ml/libc-alpha/2013-08/msg00084.html
Another batch of ieee854 macros and union replacement. These four
files also have bugs fixed with this patch. The fact that the two
doubles in an IBM long double may have different signs means that
negation and absolute value operations can't just twiddle one sign bit
as you can with ieee864 style extended double. fmodl, remainderl,
erfl and erfcl all had errors of this type. erfl also returned +1 for
large magnitude negative input where it should return -1. The hypotl
error is innocuous since the value adjusted twice is only used as a
flag. The e_hypotl.c tests for large "a" and small "b" are mutually
exclusive because we've already exited when x/y > 2**120. That allows
some further small simplifications.
[BZ #15734], [BZ #15735]
* sysdeps/ieee754/ldbl-128ibm/e_fmodl.c (__ieee754_fmodl): Rewrite
all uses of ieee875 long double macros and unions. Simplify test
for 0.0L. Correct |x|<|y| and |x|=|y| test. Use
ldbl_extract_mantissa value for ix,iy exponents. Properly
normalize after ldbl_extract_mantissa, and don't add hidden bit
already handled. Don't treat low word of ieee854 mantissa like
low word of IBM long double and mask off bit when testing for
zero.
* sysdeps/ieee754/ldbl-128ibm/e_hypotl.c (__ieee754_hypotl): Rewrite
all uses of ieee875 long double macros and unions. Simplify tests
for 0.0L and inf. Correct double adjustment of k. Delete dead code
adjusting ha,hb. Simplify code setting kld. Delete two600 and
two1022, instead use their values. Recognise that tests for large
"a" and small "b" are mutually exclusive. Rename vars. Comment.
* sysdeps/ieee754/ldbl-128ibm/e_remainderl.c (__ieee754_remainderl):
Rewrite all uses of ieee875 long double macros and unions. Simplify
test for 0.0L and nan. Correct negation.
* sysdeps/ieee754/ldbl-128ibm/s_erfl.c (__erfl): Rewrite all uses of
ieee875 long double macros and unions. Correct output for large
magnitude x. Correct absolute value calculation.
(__erfcl): Likewise.
* math/libm-test.inc: Add tests for errors discovered in IBM long
double versions of fmodl, remainderl, erfl and erfcl.
Jakub Jelinek <jakub@redhat.com>
Roland McGrath <roland@redhat.com>
Steven Munroe <sjmunroe@us.ibm.com>
Alan Modra <amodra@bigpond.net.au>
* sysdeps/powerpc/powerpc64/fpu/s_truncf.S: Comment fix.
* sysdeps/powerpc/powerpc32/fpu/s_truncf.S: Likewise.
* sysdeps/powerpc/powerpc64/fpu/s_llroundf.S: Likewise.
* sysdeps/powerpc/fpu/libm-test-ulps: Update.
* math/libm-test.inc (check_float_internal): Allow ulp <= 0.5.
(erfc_test): Don't run erfcl (27.0L) test if erfcl (27.0L) is
denormal.
[TEST_LDOUBLE] (ceil_test, floor_test, llrint_test, llround_test,
rint_test, round_test, trunc_test): Add new tests.
* sysdeps/powerpc/powerpc32/fpu/s_copysignl.S: New file.
* sysdeps/powerpc/powerpc32/fpu/s_fabs.S: New file.
* sysdeps/powerpc/powerpc32/fpu/s_fabsl.S: New file.
* sysdeps/powerpc/powerpc32/fpu/s_fdim.c: New file.
* sysdeps/powerpc/powerpc32/fpu/s_fmax.S: New file.
* sysdeps/powerpc/powerpc32/fpu/s_fmin.S: New file.
* sysdeps/powerpc/powerpc32/fpu/s_isnan.c: New file.
* sysdeps/powerpc/powerpc64/fpu/s_ceill.S: New file.
* sysdeps/powerpc/powerpc64/fpu/s_copysignl.S: New file.
* sysdeps/powerpc/powerpc64/fpu/s_fabs.S: New file.
* sysdeps/powerpc/powerpc64/fpu/s_fabsl.S: New file.
* sysdeps/powerpc/powerpc64/fpu/s_fdim.c: New file.
* sysdeps/powerpc/powerpc64/fpu/s_floorl.S: New file.
* sysdeps/powerpc/powerpc64/fpu/s_fmax.S: New file.
* sysdeps/powerpc/powerpc64/fpu/s_fmin.S: New file.
* sysdeps/powerpc/powerpc64/fpu/s_isnan.c: New file.
* sysdeps/powerpc/powerpc64/fpu/s_llrintl.S: New file.
* sysdeps/powerpc/powerpc64/fpu/s_llroundl.S: New file.
* sysdeps/powerpc/powerpc64/fpu/s_lrintl.S: New file.
* sysdeps/powerpc/powerpc64/fpu/s_lroundl.S: New file.
* sysdeps/powerpc/powerpc64/fpu/s_nearbyintl.S: New file.
* sysdeps/powerpc/powerpc64/fpu/s_rintl.S: New file.
* sysdeps/powerpc/powerpc64/fpu/s_roundl.S: New file.
* sysdeps/powerpc/powerpc64/fpu/s_truncl.S: New file.
* sysdeps/unix/sysv/linux/powerpc/Implies: New file.
* sysdeps/unix/sysv/linux/powerpc/powerpc64/fpu/Implies: New file.
* sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/Implies: New file.
* sysdeps/unix/sysv/linux/powerpc/configure.in: New file.
* sysdeps/unix/sysv/linux/powerpc/configure: New file.
* sysdeps/unix/sysv/linux/powerpc/bits/wordsize.h
(__LONG_DOUBLE_MATH_OPTIONAL): Define.
(__NO_LONG_DOUBLE_MATH): Define.
* sysdeps/unix/sysv/linux/powerpc/nldbl-abi.h: New file.
* sysdeps/powerpc/fpu/s_isnan.c: Include math_ldbl_opt.h.
* sysdeps/powerpc/powerpc64/fpu/s_ceil.S: Include math_ldbl_opt.h.
[LONG_DOUBLE_COMPAT] (ceill): Add compatibility symbols.
* sysdeps/powerpc/powerpc64/fpu/s_copysign.S: Include math_ldbl_opt.h.
[LONG_DOUBLE_COMPAT] (copysignl): Add compatibility symbols.
* sysdeps/powerpc/powerpc64/fpu/s_floor.S: Include math_ldbl_opt.h.
[LONG_DOUBLE_COMPAT] (floorl): Add compatibility symbols.
* sysdeps/powerpc/powerpc64/fpu/s_llrint.S: Include math_ldbl_opt.h.
[LONG_DOUBLE_COMPAT] (llrintl, lrintl): Add compatibility symbols.
* sysdeps/powerpc/powerpc64/fpu/s_llround.S: Include math_ldbl_opt.h.
[LONG_DOUBLE_COMPAT] (llroundl, lroundl): Add compatibility symbols.
* sysdeps/powerpc/powerpc64/fpu/s_rint.S: Include math_ldbl_opt.h.
[LONG_DOUBLE_COMPAT] (rintl): Add compatibility symbols.
* sysdeps/powerpc/powerpc64/fpu/s_round.S: Include math_ldbl_opt.h.
[LONG_DOUBLE_COMPAT] (roundl): Add compatibility symbols.
* sysdeps/powerpc/powerpc64/fpu/s_trunc.S: Include math_ldbl_opt.h.
[LONG_DOUBLE_COMPAT] (truncl): Add compatibility symbols.
* sysdeps/powerpc/powerpc32/fpu/s_ceil.S: Include math_ldbl_opt.h.
[LONG_DOUBLE_COMPAT] (ceill): Add compatibility symbols.
* sysdeps/powerpc/powerpc32/fpu/s_copysign.S: Include math_ldbl_opt.h.
[LONG_DOUBLE_COMPAT] (copysignl): Add compatibility symbols.
* sysdeps/powerpc/powerpc32/fpu/s_floor.S: Include math_ldbl_opt.h.
[LONG_DOUBLE_COMPAT] (floorl): Add compatibility symbols.
* sysdeps/powerpc/powerpc32/fpu/s_lrint.S: Include math_ldbl_opt.h.
[LONG_DOUBLE_COMPAT] (lrintl): Add compatibility symbols.
* sysdeps/powerpc/powerpc32/fpu/s_llrint.c: Include math_ldbl_opt.h.
[LONG_DOUBLE_COMPAT] (llrintl): Add compatibility symbols.
* sysdeps/powerpc/powerpc32/fpu/s_lround.S: Include math_ldbl_opt.h.
[LONG_DOUBLE_COMPAT] (lroundl): Add compatibility symbols.
* sysdeps/powerpc/powerpc32/fpu/s_rint.S: Include math_ldbl_opt.h.
[LONG_DOUBLE_COMPAT] (rintl): Add compatibility symbols.
* sysdeps/powerpc/powerpc32/fpu/s_round.S: Include math_ldbl_opt.h.
[LONG_DOUBLE_COMPAT] (roundl): Add compatibility symbols.
* sysdeps/powerpc/powerpc32/fpu/s_trunc.S: Include math_ldbl_opt.h.
[LONG_DOUBLE_COMPAT] (truncl): Add compatibility symbols.
* misc/qefgcvt_r.c [LDBL_MIN_10_EXP == -291] (FLOAT_MIN_10_NORM): New.
* sysdeps/powerpc/fpu/bits/mathdef.h (__NO_LONG_DOUBLE_MATH): Remove.
* sysdeps/powerpc/Implies: Add ieee754/ldbl-128ibm.
* sysdeps/powerpc/powerpc32/Implies: Remove powerpc/soft-fp.
* sysdeps/ieee754/ldbl-128ibm/Makefile: New file.
* sysdeps/ieee754/ldbl-128ibm/e_acoshl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_acosl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_asinl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_atan2l.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_atanhl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_coshl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_expl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_fmodl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_gammal_r.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_hypotl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_j0l.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_j1l.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_jnl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_lgammal_r.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_log10l.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_log2l.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_logl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_powl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_rem_pio2l.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_remainderl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_sinhl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/e_sqrtl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/ieee754.h: New file.
* sysdeps/ieee754/ldbl-128ibm/k_cosl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/k_sincosl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/k_sinl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/k_tanl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/ldbl2mpn.c: New file.
* sysdeps/ieee754/ldbl-128ibm/math_ldbl.h: New file.
* sysdeps/ieee754/ldbl-128ibm/mpn2ldbl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/printf_fphex.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_asinhl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_atanl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_cbrtl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_cosl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_erfl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_expm1l.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_fabsl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_finitel.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_fpclassifyl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_frexpl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_ilogbl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_isinfl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_isnanl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_log1pl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_logbl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_modfl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_nextafterl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_nexttoward.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_nexttowardf.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_remquol.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_rintl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_scalblnl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_scalbnl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_signbitl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_sincosl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_sinl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_tanhl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_tanl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_truncl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/strtold_l.c: New file.
* sysdeps/ieee754/ldbl-128ibm/t_sincosl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/w_expl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_copysignl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_floorl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_llrintl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_llroundl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_roundl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_ceill.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_nearbyintl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_lrintl.c: New file.
* sysdeps/ieee754/ldbl-128ibm/s_lroundl.c: New file.
* sysdeps/ieee754/ldbl-128/e_powl.c: Fix old comment.
