re PR middle-end/54321 (ice in tree_low_cst at -O3)

	PR tree-optimization/54321
	* tree-ssa-forwprop.c (simplify_builtin_call): Pass 0 instead of 1
	as second argument to tree_low_cst call on val2.

	* gcc.c-torture/compile/pr54321.c: New test.

From-SVN: r190526

gcc/ChangeLog

+2012-08-20  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/54321
+	* tree-ssa-forwprop.c (simplify_builtin_call): Pass 0 instead of 1
+	as second argument to tree_low_cst call on val2.
+
 2012-08-20  Richard Guenther  <rguenther@suse.de>
 
 	* gimple.h (gimple_statement_base): Annotate with GTY chain_next.

gcc/testsuite/ChangeLog

+2012-08-20  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/54321
+	* gcc.c-torture/compile/pr54321.c: New test.
+
 2012-08-20  Tobias Burnus  <burnus@net-b.de>
 
 	PR fortran/54301

gcc/testsuite/gcc.c-torture/compile/pr54321.c

+/* PR tree-optimization/54321 */
+struct S { char s[0]; } *a;
+
+void
+foo (void)
+{
+  char *b = a->s;
+  int c = 0;
+  b[0] = 0;
+  while (++c < 9)
+    b[c] = 255;
+}

gcc/tree-ssa-forwprop.c

@@ -1554,7 +1554,7 @@ simplify_builtin_call (gimple_stmt_iterator *gsi_p, tree callee2)
 	  else
 	    src_buf[0] = tree_low_cst (src1, 0);
 	  memset (src_buf + tree_low_cst (diff, 1),
-		  tree_low_cst (val2, 1), tree_low_cst (len2, 1));
+		  tree_low_cst (val2, 0), tree_low_cst (len2, 1));
 	  src_buf[src_len] = '\0';
 	  /* Neither builtin_strncpy_read_str nor builtin_memcpy_read_str
 	     handle embedded '\0's.  */