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

gcc/ChangeLog

+2005-07-29  Joseph S. Myers  <joseph@codesourcery.com>
+
+	PR c/21720
+	* real.c (real_from_string): Set last bit if there is a nonzero
+	hex digit beyond GCC's internal precision.
+
 2005-07-28  Richard Henderson  <rth@redhat.com>
 
 	PR rtl-opt/22619

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++;
 	}

gcc/testsuite/ChangeLog

+2005-07-29  Joseph S. Myers  <joseph@codesourcery.com>
+
+	PR c/21720
+	* gcc.dg/hex-round-1.c: New test.
+
 2005-07-28  Jan Hubicka  <jh@suse.cz>
 
 	* inliner-1.c: Do not dump everything.

gcc/testsuite/gcc.dg/hex-round-1.c

+/* Test for hexadecimal float rounding: bug 21720.  */
+/* { dg-do link } */
+/* { dg-options "-O -std=gnu99" } */
+
+#include <float.h>
+
+extern void link_failure (void);
+
+int
+main (void)
+{
+#if FLT_RADIX == 2 && FLT_MANT_DIG == 24
+  if (0x1.000001000000000000000000000000000001p0f == 1)
+    link_failure ();
+  if (0x1.0000010000000000000000000000000000001p0f == 1)
+    link_failure ();
+  if (0x1.00000100000000000000000000000000000001p0f == 1)
+    link_failure ();
+  if (0x1.000001000000000000000000000000000000001p0f == 1)
+    link_failure ();
+  if (0x1.0000010000000000000000000000000000000001p0f == 1)
+    link_failure ();
+  if (0x1.00000100000000000000000000000000000000001p0f == 1)
+    link_failure ();
+  if (0x1.000001000000000000000000000000000000000001p0f == 1)
+    link_failure ();
+  if (0x1.0000010000000000000000000000000000000000001p0f == 1)
+    link_failure ();
+#endif
+  return 0;
+}