(__mpn_extract_long_double): Handle 80-bit denormalized numbers correct.

diff --git a/sysdeps/ieee754/ldbl2mpn.c b/sysdeps/ieee754/ldbl2mpn.c
index 29e8a3b..029a92a 100644 (file)
--- a/sysdeps/ieee754/ldbl2mpn.c
+++ b/sysdeps/ieee754/ldbl2mpn.c
@@ -64,6 +64,14 @@ __mpn_extract_long_double (mp_ptr res_ptr, mp_size_t size,
           /* It is a denormal number, meaning it has no implicit leading
             one bit, and its exponent is in fact the format minimum.  */
          int cnt;
+
+         /* One problem with Intel's 80-bit format is that the explicit
+            leading one in the normalized representation has to be zero
+            for denormalized number.  If it is one, the number is according
+            to Intel's specification an invalid number.  We make the
+            representation unique by explicitly clearing this bit.  */
+         res_ptr[N - 1] &= ~(1 << ((LDBL_MANT_DIG - 1) % BITS_PER_MP_LIMB));
+
          if (res_ptr[N - 1] != 0)
            {
              count_leading_zeros (cnt, res_ptr[N - 1]);
@@ -77,14 +85,14 @@ __mpn_extract_long_double (mp_ptr res_ptr, mp_size_t size,
                  res_ptr[N - 1] <<= cnt;
 #endif
                }
-             *expt = LDBL_MIN_EXP - 2 - cnt;
+             *expt = LDBL_MIN_EXP - 1 - cnt;
            }
          else
            {
              count_leading_zeros (cnt, res_ptr[0]);
              res_ptr[N - 1] = res_ptr[0] << cnt;
              res_ptr[0] = 0;
-             *expt = LDBL_MIN_EXP - 2 - BITS_PER_MP_LIMB - cnt;
+             *expt = LDBL_MIN_EXP - 1 - BITS_PER_MP_LIMB - cnt;
            }
        }
     }