re PR middle-end/21720 (GCC incorrectly rounds hex floats)

	PR c/21720
	* real.c (real_from_string): Set last bit if there is a nonzero
	hex digit beyond GCC's internal precision.

testsuite:
	* gcc.dg/hex-round-1.c: New test.

From-SVN: r102539

1 files changed, 4 insertions, 0 deletions

diff --git a/gcc/real.c b/gcc/real.c
index 9099f41..045a803 100644
--- a/gcc/real.c
+++ b/gcc/real.c
@@ -1789,6 +1789,10 @@ real_from_string (REAL_VALUE_TYPE *r, const char *str)
 		|= (unsigned long) d << (pos % HOST_BITS_PER_LONG);
 	      pos -= 4;
 	    }
+	  else if (d)
+	    /* Ensure correct rounding by setting last bit if there is
+	       a subsequent nonzero digit.  */
+	    r->sig[0] |= 1;
 	  exp += 4;
 	  str++;
 	}