This patch fixes bug 16337, ldbl-128 lgammal spurious overflows for
small negative arguments (the arguments in question are already in the
testsuite). The implementation uses the reflection formula to compute
lgamma of negative x from lgamma of -x, effectively resulting in a
calculation -log(x^2) + log(-x); cancellation isn't problematic in
this case (bugs for problematic cancellation in lgamma are 2542, 2543,
2558), but the x^2 calculation can underflow (in which case there is
spurious logic to return an overflowing value - lgamma can only ever
correctly overflow for large positive arguments, though tgamma can
overflow for small arguments of either sign as well as large positive
arguments). The fix is simply to calculate the result directly with
logl when the argument is a small enough negative number.
Tested mips64.
* sysdeps/ieee754/ldbl-128/e_lgammal_r.c (__ieee754_lgammal_r):
Calculate results for small negative arguments directly rather
than using reflection formula with special underflow handling.
This patch fixes bug 16338, ldbl-128 logl not handling subnormals
(with consequent inaccuracy for lgammal as well). The fix is simply
to use __frexpl when determining the exponent, as done already in
log2l and log10l. Given the lack of testing of small arguments to any
of the log* functions, appropriate tests are added for all of them.
Tested x86_64 and x86 and ulps updated accordingly, and spot tests
also run for mips64 to confirm the ldbl-128 fix.
Note that while this fixes lgammal inaccuracy for small positive
arguments, I suspect that there will still be problems with spurious
underflows in that case.
* sysdeps/ieee754/ldbl-128/e_logl.c (__ieee754_logl): Use __frexpl
to determine exponent and adjust argument to have exponent of -1.
* math/auto-libm-test-in: Add more tests of log, log10, log1p and
log2.
* math/auto-libm-test-out: Regenerated.
* sysdeps/x86_64/fpu/libm-test-ulps: Update.
http://sourceware.org/ml/libc-alpha/2013-08/msg00081.html
This is the first of a series of patches to ban ieee854_long_double
and the ieee854_long_double macros when using IBM long double. union
ieee854_long_double just isn't correct for IBM long double, especially
when little-endian, and pretending it is OK has allowed a number of
bugs to remain undetected in sysdeps/ieee754/ldbl-128ibm/.
This changes the few places in generic code that use it.
* stdio-common/printf_size.c (__printf_size): Don't use
union ieee854_long_double in fpnum union.
* stdio-common/printf_fphex.c (__printf_fphex): Likewise. Use
signbit macro to retrieve sign from long double.
* stdio-common/printf_fp.c (___printf_fp): Use signbit macro to
retrieve sign from long double.
* sysdeps/ieee754/ldbl-128ibm/printf_fphex.c: Adjust for fpnum change.
* sysdeps/ieee754/ldbl-128/printf_fphex.c: Likewise.
* sysdeps/ieee754/ldbl-96/printf_fphex.c: Likewise.
* sysdeps/x86_64/fpu/printf_fphex.c: Likewise.
* math/test-misc.c (main): Don't use union ieee854_long_double.
ports/
* sysdeps/ia64/fpu/printf_fphex.c: Adjust for fpnum change.
With help from Joseph Myers.
* sysdeps/ieee754/ldbl-128/s_atanl.c (__atanl): Handle tiny and
very large arguments properly.
* math/libm-test.inc (atan_test): New tests.
(atan2_test): New tests.
* sysdeps/sparc/fpu/libm-test-ulps: Update.
* sysdeps/x86_64/fpu/libm-test-ulps: Update.
With help from Joseph Myers.
* sysdeps/ieee754/flt-32/e_j0f.c (__ieee754_y0f): Adjust tinyness
cutoff to 2**-13.
* sysdeps/ieee754/flt-32/e_j1f.c (__ieee754_y1f): Adjust tinyness
cutoff to 2**-25.
* sysdeps/ieee754/ldbl-128/e_j0l.c (U0): New constant.
( __ieee754_y0l): Avoid arithmetic underflow when 'x' is very
small.
* sysdeps/ieee754/ldbl-128/e_j1l.c (__ieee754_y1l): Likewise.
* math/libm-test.inc (y0_test): New tests.
(y1_test): New tests.
* sysdeps/i386/fpu/libm-test-ulps: Update.
* sysdeps/x86_64/fpu/libm-test-ulps: Update.
* sysdeps/sparc/fpu/libm-test-ulps: Update.
POSIX 2008 states that if the input for 'logb[f|l]' is a subnormal number
it should be treated as if it were normalized. This means the
implementation should calculate the log2 of the mantissa and add it to the
subnormal exponent (-126 for float and -1022 for double and IBM long
double). This patch takes care of that.
[BZ# 6794]
* sysdeps/ieee754/ldbl-96/s_ilogbl.c: Moved to ...
* sysdeps/ieee754/ldbl-96/e_ilogbl.c: ... here.
Rename __ilogbl to __ieee754_ilogbl and remove weak_alias.
* sysdeps/ieee754/ldbl-128/s_ilogbl.c: Moved to ...
* sysdeps/ieee754/ldbl-128/e_ilogbl.c: ... here.
Rename __ilogbl to __ieee754_ilogbl and remove weak_alias.
* sysdeps/ieee754/ldbl-64-128/s_ilogbl.c: Moved to ...
* sysdeps/ieee754/ldbl-64-128/e_ilogbl.c: ... here.
* sysdeps/sparc/sparc64/soft-fp/s_ilogbl.c: Moved to ...
* sysdeps/sparc/sparc64/soft-fp/e_ilogbl.c: ... here.
Rename __ilogbl to __ieee754_ilogbl and remove weak_alias.
* sysdeps/ieee754/ldbl-128/s_nearbyintl.c (__nearbyintl): Do not
manipulate bits before adding and subtracting TWO112[sx].
* sysdeps/ieee754/ldbl-128/s_rintl.c (__rintl): Likewise.
