mul.c: added missing case of exactly one underflow to mpfr_fmma;

   commented out test case in sqr.dat now passes when artificially forcing
   naive squaring


git-svn-id: svn://scm.gforge.inria.fr/svn/mpc/trunk@1136 211d60ee-9f03-0410-a15a-8952a2c7a4e4

1 files changed, 8 insertions, 0 deletions

diff --git a/src/mul.c b/src/mul.c
index 842d0ef..ff220e5 100644
--- a/src/mul.c
+++ b/src/mul.c
@@ -201,6 +201,14 @@ mpfr_fmma (mpfr_ptr z, mpfr_srcptr a, mpfr_srcptr b, mpfr_srcptr c,
       mpfr_set_si (z, (mpfr_signbit (z) ? -1 : 1), GMP_RNDN);
       inex = mpfr_mul_2ui (z, z, mpfr_get_emax (), rnd);
    }
+   else if (mpfr_zero_p (u) && !mpfr_zero_p (v)) {
+      /* exactly u underflowed, determine inexact flag */
+      inex = (mpfr_signbit (u) ? 1 : -1);
+   }
+   else if (mpfr_zero_p (v) && !mpfr_zero_p (u)) {
+      /* exactly v underflowed, determine inexact flag */
+      inex = (mpfr_signbit (v) ? 1 : -1);
+   }
    else if (mpfr_nan_p (z) || (mpfr_zero_p (u) && mpfr_zero_p (v))) {
       /* In the first case, u and v are infinities with opposite signs.
          In the second case, u and v are zeroes; their sum may be 0 or the