PR tree-optimization/45522 (missed constand folding in VRP)

[Jan Hubicka]

Hi
this patch fixes missed folding of tree_code_type[6] into 2 in the testcase
attached.  The problem is that the constant is discovered by VRP, not CCP and
gimple_fold makes no attempt to fold the constant vars references into
constants except for string.

Moving code folding strings into fold_const_aggregate_ref is also needed
to avoid one missed constant folding during Ada bootstrap I don't know how
to produce testcase for.

Bootstrapped/regtested x86_64-linux, OK?

Honza

/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-optimized" } */
typedef const union tree_node *const_tree;
typedef struct
{
}
double_int;
double_int double_int_zext (double_int, unsigned);
enum tree_code
{ ERROR_MARK, IDENTIFIER_NODE, TREE_LIST, BLOCK, ENUMERAL_TYPE, BOOLEAN_TYPE,
    INTEGER_TYPE, ARRAY_TYPE, INTEGER_CST, VAR_DECL, PARM_DECL, RESULT_DECL,
  };
enum tree_code_class
{ tcc_exceptional, tcc_constant, tcc_type, tcc_declaration, tcc_reference, };
struct tree_base
{
  __extension__ enum tree_code code:16;
  unsigned unsigned_flag:1;
};
struct tree_type
{
  unsigned int precision:10;
  union tree_type_symtab
  {
  } symtab;
};
union tree_node
{
  struct tree_base base;
  struct tree_type type;
};
const enum tree_code_class tree_code_type[] =
{ tcc_exceptional, 1, 0, 0, 0, 0, 2, };

int_fits_type_p (const_tree c, const_tree type)
{
  double_int dc, dd;
  {
    if (((enum tree_code) (type)->base.code) == INTEGER_TYPE && ((
								   {
								   __typeof
								   (type) __t
								   = (type);
								   if
								   (tree_code_type
								    [(int)
								     (((enum
									tree_code)
								       (__t)->
								       base.
								       code))]
								    !=
								    (tcc_type))
								   tree_class_check_failed
								   (__t,
								    __FUNCTION__);
								   __t;})->
								 base.
								 unsigned_flag))
      dd = double_int_zext (dd, ((
				   {
				   __typeof (type) __t = (type);
				   if (tree_code_type
				       [(int)
					(((enum tree_code) (__t)->base.
					  code))] !=
				       (tcc_type))
				   tree_class_check_failed (__t,
							    __FUNCTION__);
				   __t;}
				 )->type.precision));
}
}
/* The switch should be switch converted and later constant propagated.  */
/* { dg-final { scan-tree-dump-not "tree_code_type.6" "optimized"} } */
/* { dg-final { cleanup-tree-dump "optimized" } } */

	* gimple-fold.c (maybe_fold_reference): Use fold_const_aggregate_ref.
	* tree-ssa-ccp.c (fold_const_aggregate_ref): Use
	fold_read_from_constant_string.
Index: gimple-fold.c
===================================================================
--- gimple-fold.c	(revision 163859)
+++ gimple-fold.c	(working copy)
@@ -462,14 +474,11 @@ static tree
 maybe_fold_reference (tree expr, bool is_lhs)
 {
   tree *t = &expr;
+  tree result;
 
-  if (TREE_CODE (expr) == ARRAY_REF
-      && !is_lhs)
-    {
-      tree tem = fold_read_from_constant_string (expr);
-      if (tem)
-	return tem;
-    }
+  if (!is_lhs
+      && (result = fold_const_aggregate_ref (expr)))
+    return result;
 
   /* ???  We might want to open-code the relevant remaining cases
      to avoid using the generic fold.  */
Index: tree-ssa-ccp.c
===================================================================
--- tree-ssa-ccp.c	(revision 163859)
+++ tree-ssa-ccp.c	(working copy)
@@ -1325,6 +1325,10 @@ fold_const_aggregate_ref (tree t)
   if (TREE_CODE_CLASS (TREE_CODE (t)) == tcc_declaration)
     return get_symbol_constant_value (t);
 
+  tem = fold_read_from_constant_string (t);
+  if (tem)
+    return tem;
+
   switch (TREE_CODE (t))
     {
     case ARRAY_REF: