From 0f54cc9c63842ddfa921530cb499743cafc9b177 Mon Sep 17 00:00:00 2001
From: Jason Merrill <jason@redhat.com>
Date: Fri, 2 Apr 2021 22:20:43 -0400
Subject: tree-iterator: C++11 range-for and tree_stmt_iterator

Like my recent patch to add ovl_range and lkp_range in the C++ front end,
this patch adds the tsi_range adaptor for using C++11 range-based 'for' with
a STATEMENT_LIST, e.g.

  for (tree stmt : tsi_range (stmt_list)) { ... }

This also involves adding some operators to tree_stmt_iterator that are
needed for range-for iterators, and should also be useful in code that uses
the iterators directly.

The patch updates the suitable loops in the C++ front end, but does not
touch any loops elsewhere in the compiler.

gcc/ChangeLog:

	* tree-iterator.h (struct tree_stmt_iterator): Add operator++,
	operator--, operator*, operator==, and operator!=.
	(class tsi_range): New.

gcc/cp/ChangeLog:

	* constexpr.c (build_data_member_initialization): Use tsi_range.
	(build_constexpr_constructor_member_initializers): Likewise.
	(constexpr_fn_retval, cxx_eval_statement_list): Likewise.
	(potential_constant_expression_1): Likewise.
	* coroutines.cc (await_statement_expander): Likewise.
	(await_statement_walker): Likewise.
	* module.cc (trees_out::core_vals): Likewise.
	* pt.c (tsubst_expr): Likewise.
	* semantics.c (set_cleanup_locs): Likewise.
---
 gcc/tree-iterator.h | 36 +++++++++++++++++++++++++++++++-----
 1 file changed, 31 insertions(+), 5 deletions(-)

(limited to 'gcc/tree-iterator.h')

diff --git a/gcc/tree-iterator.h b/gcc/tree-iterator.h
index 076fff8..a72d0d3 100644
--- a/gcc/tree-iterator.h
+++ b/gcc/tree-iterator.h
@@ -1,4 +1,4 @@
-/* Iterator routines for manipulating GENERIC tree statement list.
+/* Iterator routines for manipulating GENERIC tree statement list. -*- C++ -*-
    Copyright (C) 2003-2021 Free Software Foundation, Inc.
    Contributed by Andrew MacLeod  <amacleod@redhat.com>
 
@@ -32,6 +32,21 @@ along with GCC; see the file COPYING3.  If not see
 struct tree_stmt_iterator {
   struct tree_statement_list_node *ptr;
   tree container;
+
+  /* No need for user-defined constructors, the implicit definitions (or
+     aggregate initialization) are fine.  */
+
+  bool operator== (tree_stmt_iterator b) const
+    { return b.ptr == ptr && b.container == container; }
+  bool operator!= (tree_stmt_iterator b) const { return !(*this == b); }
+  tree_stmt_iterator &operator++ () { ptr = ptr->next; return *this; }
+  tree_stmt_iterator &operator-- () { ptr = ptr->prev; return *this; }
+  tree_stmt_iterator operator++ (int)
+    { tree_stmt_iterator x = *this; ++*this; return x; }
+  tree_stmt_iterator operator-- (int)
+    { tree_stmt_iterator x = *this; --*this; return x; }
+  tree &operator* () { return ptr->stmt; }
+  tree operator* () const { return ptr->stmt; }
 };
 
 static inline tree_stmt_iterator
@@ -71,27 +86,38 @@ tsi_one_before_end_p (tree_stmt_iterator i)
 static inline void
 tsi_next (tree_stmt_iterator *i)
 {
-  i->ptr = i->ptr->next;
+  ++(*i);
 }
 
 static inline void
 tsi_prev (tree_stmt_iterator *i)
 {
-  i->ptr = i->ptr->prev;
+  --(*i);
 }
 
 static inline tree *
 tsi_stmt_ptr (tree_stmt_iterator i)
 {
-  return &i.ptr->stmt;
+  return &(*i);
 }
 
 static inline tree
 tsi_stmt (tree_stmt_iterator i)
 {
-  return i.ptr->stmt;
+  return *i;
 }
 
+/* Make tree_stmt_iterator work as a C++ range, e.g.
+   for (tree stmt : tsi_range (stmt_list)) { ... }  */
+class tsi_range
+{
+  tree t;
+ public:
+  tsi_range (tree t): t(t) { }
+  tree_stmt_iterator begin() const { return tsi_start (t); }
+  tree_stmt_iterator end() const { return { nullptr, t }; }
+};
+
 enum tsi_iterator_update
 {
   TSI_NEW_STMT,		/* Only valid when single statement is added, move
-- 
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