Fix j1, jn missing underflows (bug 16559).

Similar to various other bugs in this area, j1 and jn implementations
can fail to raise the underflow exception when the internal
computation is exact although the actual function is inexact.  This
patch forces the exception in a similar way to other such fixes.  (The
ldbl-128 / ldbl-128ibm j1l implementation is different and doesn't
need a change for this until spurious underflows in it are fixed.)

Tested for x86_64, x86, mips64 and powerpc.

	[BZ #16559]
	* sysdeps/ieee754/dbl-64/e_j1.c: Include <float.h>.
	(__ieee754_j1): Force underflow exception for small results.
	* sysdeps/ieee754/dbl-64/e_jn.c (__ieee754_jn): Likewise.
	* sysdeps/ieee754/flt-32/e_j1f.c: Include <float.h>.
	(__ieee754_j1f): Force underflow exception for small results.
	* sysdeps/ieee754/flt-32/e_jnf.c (__ieee754_jnf): Likewise.
	* sysdeps/ieee754/ldbl-128/e_jnl.c (__ieee754_jnl): Likewise.
	* sysdeps/ieee754/ldbl-128ibm/e_jnl.c (__ieee754_jnl): Likewise.
	* sysdeps/ieee754/ldbl-96/e_j1l.c: Include <float.h>.
	(__ieee754_j1l): Force underflow exception for small results.
	* sysdeps/ieee754/ldbl-96/e_jnl.c (__ieee754_jnl): Likewise.
	* math/auto-libm-test-in: Add more tests of j1 and jn.
	* math/auto-libm-test-out: Regenerated.

1 files changed, 11 insertions, 2 deletions

diff --git a/sysdeps/ieee754/dbl-64/e_j1.c b/sysdeps/ieee754/dbl-64/e_j1.c
index 653f33abe1..26ffdfe282 100644
--- a/sysdeps/ieee754/dbl-64/e_j1.c
+++ b/sysdeps/ieee754/dbl-64/e_j1.c
@@ -59,6 +59,7 @@
  */
 
 #include <errno.h>
+#include <float.h>
 #include <math.h>
 #include <math_private.h>
 
@@ -124,8 +125,16 @@ __ieee754_j1 (double x)
     }
   if (__glibc_unlikely (ix < 0x3e400000))                  /* |x|<2**-27 */
     {
-      if (huge + x > one)
-	return 0.5 * x;                 /* inexact if x!=0 necessary */
+      if (huge + x > one)                 /* inexact if x!=0 necessary */
+	{
+	  double ret = 0.5 * x;
+	  if (fabs (ret) < DBL_MIN)
+	    {
+	      double force_underflow = ret * ret;
+	      math_force_eval (force_underflow);
+	    }
+	  return ret;
+	}
     }
   z = x * x;
   r1 = z * R[0]; z2 = z * z;