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glibc/sysdeps/ieee754/ldbl-128
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Joseph Myers 739babd775 Fix fma spurious underflows (bug 18824). 
Various fma implementations have logic that, when computing fma (x, y,
z) where z is large (so care needs taking to avoid internal overflow)
but x * y is small, scale x * y up instead of down to avoid internal
underflows resulting from scaling down.  (In these cases, x * y is
small enough that only its sign actually matters rather than the exact
value.)

The threshold for scaling up instead of down was correct for "if the
unscaled values were multiplied, the low part of the multiplication
could underflow", and the scaling was sufficient to ensure that the
low part of the multiplication did not underflow (given that cases of
very small x * y - less than half the least subnormal - were
previously dealt with).  However, the choice in the functions wasn't
between scaling up or no scaling, but between scaling up and scaling
down (scaling down actually being needed when x * y isn't so small
compared to z and so the exact value does matter).  Thus a larger
threshold is needed to ensure that scaling down doesn't produce values
the multiplication of whose low parts underflows.  This patch
increases the thresholds accordingly.

Tested for x86_64, x86 and mips64 (with the MIPS version of s_fmal.c
removed so that the ldbl-128 version gets tested instead of the
soft-fp one).

	[BZ #18824]
	* sysdeps/ieee754/dbl-64/s_fma.c (__fma): Increase threshold for
	scaling x * y up instead of down.
	* sysdeps/ieee754/ldbl-128/s_fmal.c (__fmal): Likewise.
	* sysdeps/ieee754/ldbl-96/s_fmal.c (__fmal): Likewise.
	* math/auto-libm-test-in: Add more tests of fma.
	* math/auto-libm-test-out: Regenerated.
2015-08-14 17:15:06 +00:00
..
e_acoshl.c Use <> for math.h and math_private.h everywhere. 2012-03-09 16:09:10 -08:00
e_acosl.c Fix ldbl-128/ldbl-128ibm acosl inaccuracy (bug 18038, bug 18039). 2015-02-26 21:06:34 +00:00
e_asinl.c Fix ldbl-128 / ldbl-128ibm asinl for -Wuninitialized. 2015-05-22 17:36:52 +00:00
e_atan2l.c Use <> for math.h and math_private.h everywhere. 2012-03-09 16:09:10 -08:00
e_atanhl.c Fix atanhl missing underflows (bug 16352). 2015-05-15 22:07:57 +00:00
e_coshl.c Fix cosh spurious underflows from expm1 (bug 16354), inaccurate results near 0 (bug 17061). 2014-06-23 20:20:10 +00:00
e_exp10l.c This patch renames all uses of __isinf*, __isnan*, __finite* and __signbit* to use standard C99 macros. This has no effect on generated code. 2015-06-03 15:41:36 +01:00
e_expl.c Fix ldbl-128 expl missing underflows (bug 18586). 2015-06-24 15:12:03 +00:00
e_fmodl.c Use <> for math.h and math_private.h everywhere. 2012-03-09 16:09:10 -08:00
e_gammal_r.c Improve tgamma accuracy (bug 18613). 2015-06-29 23:29:35 +00:00
e_hypotl.c Fix hypot handling of subnormals (bug 16316, bug 16330). 2013-12-17 13:42:13 +00:00
e_ilogbl.c Finish ilogb changes 2012-04-18 14:31:43 +02:00
e_j0l.c This patch renames all uses of __isinf*, __isnan*, __finite* and __signbit* to use standard C99 macros. This has no effect on generated code. 2015-06-03 15:41:36 +01:00
e_j1l.c Fix ldbl-128 j1l spurious underflows (bug 18612). 2015-06-29 17:51:32 +00:00
e_jnl.c Fix j1, jn missing underflows (bug 16559). 2015-06-29 16:52:16 +00:00
e_lgammal_r.c This patch renames all uses of __isinf*, __isnan*, __finite* and __signbit* to use standard C99 macros. This has no effect on generated code. 2015-06-03 15:41:36 +01:00
e_log2l.c Fix log2 (1) in round-downward mode (bug 17042). 2014-06-10 12:07:15 +00:00
e_log10l.c Fix log10 (1) in round-downward mode (bug 16977). 2014-05-23 12:07:50 +00:00
e_logl.c Fix log (1) in round-downward mode (bug 16731). 2014-03-21 18:13:58 +00:00
e_powl.c Fix ldbl-128 powl sign of result in overflow / underflow cases (bug 17097). 2014-06-29 11:49:08 +00:00
e_rem_pio2l.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
e_remainderl.c Use <> for math.h and math_private.h everywhere. 2012-03-09 16:09:10 -08:00
e_sinhl.c Fix sinh missing underflows (bug 16519). 2015-08-06 23:01:09 +00:00
gamma_productl.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
ieee754.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
k_cosl.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
k_sincosl.c Fix sin, sincos missing underflows (bug 16526, bug 16538). 2015-06-23 22:24:20 +00:00
k_sinl.c Fix sin, sincos missing underflows (bug 16526, bug 16538). 2015-06-23 22:24:20 +00:00
k_tanl.c Fix tan missing underflows (bug 16517). 2015-08-07 23:10:35 +00:00
ldbl2mpn.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
Makefile * sysdeps/ieee754/ldbl-128/Makefile: New file. 2007-03-14 17:36:18 +00:00
math_ldbl.h Update. 1999-07-15 18:26:25 +00:00
mpn2ldbl.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
printf_fphex.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
s_asinhl.c Fix asinh missing underflows (bug 16350). 2015-06-18 23:27:41 +00:00
s_atanl.c Fix atan / atan2 missing underflows (bug 15319). 2015-02-18 21:10:49 +00:00
s_cbrtl.c This patch renames all uses of __isinf*, __isnan*, __finite* and __signbit* to use standard C99 macros. This has no effect on generated code. 2015-06-03 15:41:36 +01:00
s_ceill.c Use <> for math.h and math_private.h everywhere. 2012-03-09 16:09:10 -08:00
s_copysignl.c Use <> for math.h and math_private.h everywhere. 2012-03-09 16:09:10 -08:00
s_cosl.c Use <> for math.h and math_private.h everywhere. 2012-03-09 16:09:10 -08:00
s_erfl.c Fix ldbl-128 / ldbl-128ibm erfcl for -Wuninitialized 2015-05-22 17:48:45 +00:00
s_expm1l.c Fix ldbl-128 expm1l (-min_subnorm) result sign (bug 18619). 2015-07-01 22:27:49 +00:00
s_fabsl.c Use <> for math.h and math_private.h everywhere. 2012-03-09 16:09:10 -08:00
s_finitel.c Use <> for math.h and math_private.h everywhere. 2012-03-09 16:09:10 -08:00
s_floorl.c Use <> for math.h and math_private.h everywhere. 2012-03-09 16:09:10 -08:00
s_fma.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
s_fmal.c Fix fma spurious underflows (bug 18824). 2015-08-14 17:15:06 +00:00
s_fpclassifyl.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
s_frexpl.c Use <> for math.h and math_private.h everywhere. 2012-03-09 16:09:10 -08:00
s_isinf_nsl.c Use <> for math.h and math_private.h everywhere. 2012-03-09 16:09:10 -08:00
s_isinfl.c Use <> for math.h and math_private.h everywhere. 2012-03-09 16:09:10 -08:00
s_isnanl.c Use <> for math.h and math_private.h everywhere. 2012-03-09 16:09:10 -08:00
s_issignalingl.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
s_llrintl.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
s_llroundl.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
s_log1pl.c Fix log1p missing underflows (bug 16339). 2015-05-14 23:38:07 +00:00
s_logbl.c Optimize handling of denormals in logb/logbf/logbl 2012-05-26 13:53:22 +02:00
s_lrintl.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
s_lroundl.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
s_modfl.c Use <> for math.h and math_private.h everywhere. 2012-03-09 16:09:10 -08:00
s_nearbyintl.c Fix nearbyint scheduling of arithmetic past fesetenv (bug 15490). 2013-05-19 18:40:25 +00:00
s_nextafterl.c Fix nextafter overflow in non-default rounding modes (bug 16677). 2014-03-11 22:24:00 +00:00
s_nexttoward.c Fix leading whitespaces. 2013-06-06 20:36:07 +02:00
s_nexttowardf.c Remove trailing whitespace. 2013-06-05 20:44:03 +00:00
s_remquol.c Fix sign of remquo zero remainder in round-downward mode (bug 17987). 2015-02-17 00:41:50 +00:00
s_rintl.c Fix set-but-not-used warnings in ldbl-128 nearbyintl, rintl. 2012-11-20 14:26:07 +00:00
s_roundl.c Fix ldbl-128 roundl for exponents in [31, 47] (bug 18346). 2015-04-28 17:27:02 +00:00
s_scalblnl.c [BZ #6803] Set errno for scalbln, scalbn 2014-06-20 07:48:20 +05:30
s_scalbnl.c Remove trailing whitespace. 2013-06-05 20:44:03 +00:00
s_signbitl.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
s_sincosl.c Fix sincos errno setting (bug 15467). 2015-02-11 23:17:25 +00:00
s_sinl.c Use <> for math.h and math_private.h everywhere. 2012-03-09 16:09:10 -08:00
s_tanhl.c Fix tanh missing underflows (bug 16520). 2015-08-13 16:40:39 +00:00
s_tanl.c Remove trailing whitespace. 2013-06-05 20:44:03 +00:00
s_truncl.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
strtold_l.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
t_expl.h Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
t_sincosl.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00
w_expl.c This patch renames all uses of __isinf*, __isnan*, __finite* and __signbit* to use standard C99 macros. This has no effect on generated code. 2015-06-03 15:41:36 +01:00
x2y2m1l.c Update copyright dates with scripts/update-copyrights. 2015-01-02 16:29:47 +00:00