diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index d02c8df3eb2..88b45d8fffe 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2011-12-12  Jakub Jelinek  <jakub@redhat.com>
+
+	PR middle-end/51510
+	* calls.c (internal_arg_pointer_based_exp_scan): Don't use
+	VEC_safe_grow_cleared if idx is smaller than VEC_length.
+
 2011-12-12  Richard Sandiford  <richard.sandiford@linaro.org>
 
 	PR middle-end/50873
diff --git a/gcc/calls.c b/gcc/calls.c
index 95369b7baef..0ef0cad8d27 100644
--- a/gcc/calls.c
+++ b/gcc/calls.c
@@ -1705,9 +1705,11 @@ internal_arg_pointer_based_exp_scan (void)
 	    val = internal_arg_pointer_based_exp (SET_SRC (set), false);
 	  if (val != NULL_RTX)
 	    {
-	      VEC_safe_grow_cleared (rtx, heap,
-				     internal_arg_pointer_exp_state.cache,
-				     idx + 1);
+	      if (idx
+		  >= VEC_length (rtx, internal_arg_pointer_exp_state.cache))
+		VEC_safe_grow_cleared (rtx, heap,
+				       internal_arg_pointer_exp_state.cache,
+				       idx + 1);
 	      VEC_replace (rtx, internal_arg_pointer_exp_state.cache,
 			   idx, val);
 	    }