"mant(c) != 1/2" test was broken.

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@1127 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 4 insertions, 5 deletions

diff --git a/add.c b/add.c
index b079b2b42..e50d3162e 100644
--- a/add.c
+++ b/add.c
@@ -117,11 +117,10 @@ mpfr_add1 (a, b, c, rnd_mode, diff_exp)
 	    /* c is not zero */
 	    /* check whether mant(c)=1/2 or not */
 
-	    cc = *cp - (ONE<<(BITS_PER_MP_LIMB-1));
-	    if (cc==0) {
-	      bp = cp+(MPFR_PREC(c)-1)/BITS_PER_MP_LIMB;
-	      while (cp<bp && cc==0) cc = *++cp;
-	    }
+            mp_limb_t *cp2 = cp + (cn-1);  /* highest limb */
+
+	    cc = *cp2 - MP_LIMB_T_HIGHBIT;
+            while (cc == 0 && cp2 > cp) cc = *--cp2;
 
 	    if (cc || ((ap[0] >> sh) & ONE)) goto add_one_ulp;
 	    /* mant(c) != 1/2 or mant(c) = 1/2: add 1 iff lsb(a)=1 */