PR middle-end/21781

	* real.c (real_from_string): If the mantissa is zero, don't bother
	parsing the exponent as the result should always be zero.

	* gcc.dg/real-const-1.c: New test case.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@112136 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 9 insertions, 0 deletions

diff --git a/gcc/real.c b/gcc/real.c
index c4b6479067f..1e1083f9abe 100644
--- a/gcc/real.c
+++ b/gcc/real.c
@@ -1862,6 +1862,11 @@ real_from_string (REAL_VALUE_TYPE *r, const char *str)
 	      str++;
 	    }
 	}
+
+      /* If the mantissa is zero, ignore the exponent.  */
+      if (!cmp_significand_0 (r))
+	goto underflow;
+
       if (*str == 'p' || *str == 'P')
 	{
 	  bool exp_neg = false;
@@ -1934,6 +1939,10 @@ real_from_string (REAL_VALUE_TYPE *r, const char *str)
 	    }
 	}
 
+      /* If the mantissa is zero, ignore the exponent.  */
+      if (r->cl == rvc_zero)
+	goto underflow;
+
       if (*str == 'e' || *str == 'E')
 	{
 	  bool exp_neg = false;