Fix ldbl-128 logl for subnormals (bug 16338).

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.

1 files changed, 2 insertions, 3 deletions

diff --git a/sysdeps/ieee754/ldbl-128/e_logl.c b/sysdeps/ieee754/ldbl-128/e_logl.c
index 395a76302a..3d1034dd61 100644
--- a/sysdeps/ieee754/ldbl-128/e_logl.c
+++ b/sysdeps/ieee754/ldbl-128/e_logl.c
@@ -212,9 +212,8 @@ __ieee754_logl(long double x)
     }
 
   /* Extract exponent and reduce domain to 0.703125 <= u < 1.40625  */
-  e = (int) (m >> 16) - (int) 0x3ffe;
-  m &= 0xffff;
-  u.parts32.w0 = m | 0x3ffe0000;
+  u.value = __frexpl (x, &e);
+  m = u.parts32.w0 & 0xffff;
   m |= 0x10000;
   /* Find lookup table index k from high order bits of the significand. */
   if (m < 0x16800)