* mpz/get_d_2exp.c, mpf/get_d_2exp.c: Avoid res==1.0 when floats round

	upwards.

1 files changed, 22 insertions, 2 deletions

diff --git a/mpf/get_d_2exp.c b/mpf/get_d_2exp.c
index c16752b7d..3ba97f647 100644
--- a/mpf/get_d_2exp.c
+++ b/mpf/get_d_2exp.c
@@ -1,6 +1,6 @@
 /* double mpf_get_d_2exp (signed long int *exp, mpf_t src).
 
-Copyright 2001, 2002 Free Software Foundation, Inc.
+Copyright 2001, 2002, 2003 Free Software Foundation, Inc.
 
 This file is part of the GNU MP Library.
 
@@ -31,6 +31,7 @@ mpf_get_d_2exp (signed long int *exp2, mpf_srcptr src)
   int negative;
   mp_ptr qp;
   int cnt;
+  long exp;
 
   size = SIZ(src);
   if (size == 0)
@@ -49,8 +50,27 @@ mpf_get_d_2exp (signed long int *exp2, mpf_srcptr src)
   for (i = 1; i < n_limbs_to_use; i++)
     res = (res + qp[i]) / MP_BASE_AS_DOUBLE;
   count_leading_zeros (cnt, qp[n_limbs_to_use - 1]);
-  *exp2 = EXP(src) * GMP_NUMB_BITS - cnt + GMP_NAIL_BITS;
+  exp = EXP(src) * GMP_NUMB_BITS - cnt + GMP_NAIL_BITS;
   res = res * ((mp_limb_t) 1 << cnt);
 
+  /* gcc on m68k and x86 holds floats in the coprocessor, which may mean
+     "res" has extra precision.  Force it through memory to ensure any
+     rounding takes place now and won't become 1.0 in the caller.  */
+#if (HAVE_HOST_CPU_FAMILY_m68k || HAVE_HOST_CPU_FAMILY_x86)     \
+  && defined (__GNUC__)
+  asm ("" : "=m" (res) : "0" (res));
+#endif
+
+  /* if hardware floats are in round upwards mode then res may be 1.0 */
+  if (UNLIKELY (res >= 1.0))
+    {
+      res *= 0.5;
+      exp++;
+    }
+
+  ASSERT (res >= 0.5);
+  ASSERT (res < 1.0);
+
+  *exp2 = exp;
   return negative ? -res : res;
 }