Fix ldbl-128 expl missing underflows (bug 18586).

Similar to various other bugs in this area, the ldbl-128 expl
implementation does not raise the underflow exception for all
subnormal results, if the scaling down is exact although the actual
result is inexact.  This patch fixes this by forcing the exception in
this case (the tests that failed before and pass after the test are
already in the testsuite).

Tested for mips64.

	[BZ #18586]
	* sysdeps/ieee754/ldbl-128/e_expl.c (__ieee754_expl): Force
	underflow exception for small results.

diff --git a/ChangeLog b/ChangeLog
index b5e19b1..b103dcd 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2015-06-24  Joseph Myers  <joseph@codesourcery.com>
+
+       [BZ #18586]
+       * sysdeps/ieee754/ldbl-128/e_expl.c (__ieee754_expl): Force
+       underflow exception for small results.
+
 2015-06-24  Andrew Senkevich  <andrew.senkevich@intel.com>
 
        * sysdeps/x86_64/fpu/Makefile (libmvec-support): Fixed files list.

diff --git a/NEWS b/NEWS
index aacd894..e8c84b8 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -24,7 +24,7 @@ Version 2.22
   18444, 18468, 18469, 18470, 18479, 18483, 18495, 18496, 18497, 18498,
   18507, 18512, 18513, 18519, 18520, 18522, 18527, 18528, 18529, 18530,
   18532, 18533, 18534, 18536, 18539, 18540, 18542, 18544, 18545, 18546,
-  18547, 18553, 18558, 18569, 18583.
+  18547, 18553, 18558, 18569, 18583, 18586.
 
 * Cache information can be queried via sysconf() function on s390 e.g. with
   _SC_LEVEL1_ICACHE_SIZE as argument.

diff --git a/sysdeps/ieee754/ldbl-128/e_expl.c b/sysdeps/ieee754/ldbl-128/e_expl.c
index b4b7896..1cd095c 100644 (file)
--- a/sysdeps/ieee754/ldbl-128/e_expl.c
+++ b/sysdeps/ieee754/ldbl-128/e_expl.c
@@ -230,7 +230,15 @@ __ieee754_expl (long double x)
       if (!unsafe)
        return result;
       else
-       return result * scale_u.d;
+       {
+         result *= scale_u.d;
+         if (result < LDBL_MIN)
+           {
+             long double force_underflow = result * result;
+             math_force_eval (force_underflow);
+           }
+         return result;
+       }
     }
   /* Exceptional cases:  */
   else if (isless (x, himark))