re PR tree-optimization/77544 (segfault at -O0 - infinite loop in simplification)

2016-09-15  Richard Biener  <rguenther@suse.de>

	PR middle-end/77544
	* fold-const.c (split_tree): Do not split constant ~X.

	* c-c++-common/torture/pr77544.c: New testcase.

From-SVN: r240164

gcc/ChangeLog

+2016-09-15  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/77544
+	* fold-const.c (split_tree): Do not split constant ~X.
+
 2016-09-15  Jakub Jelinek  <jakub@redhat.com>
 
 	PR rtl-optimization/77425

gcc/fold-const.c

@@ -837,15 +837,16 @@ split_tree (location_t loc, tree in, tree type, enum tree_code code,
 	  var = negate_expr (var);
 	}
     }
+  else if (TREE_CONSTANT (in))
+    *conp = in;
   else if (TREE_CODE (in) == BIT_NOT_EXPR
 	   && code == PLUS_EXPR)
     {
-      /* -X - 1 is folded to ~X, undo that here.  */
+      /* -X - 1 is folded to ~X, undo that here.  Do _not_ do this
+         when IN is constant.  */
       *minus_litp = build_one_cst (TREE_TYPE (in));
       var = negate_expr (TREE_OPERAND (in, 0));
     }
-  else if (TREE_CONSTANT (in))
-    *conp = in;
   else
     var = in;
 

gcc/testsuite/ChangeLog

+2016-09-15  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/77544
+	* c-c++-common/torture/pr77544.c: New testcase.
+
 2016-09-15  Jakub Jelinek  <jakub@redhat.com>
 
 	PR middle-end/77475

gcc/testsuite/c-c++-common/torture/pr77544.c

+/* { dg-do compile } */
+
+struct {
+  long a : 17;
+} b;
+int c, d;
+void e() { b.a = d + c + ~(long)(302806U >> 0); }