Re: [PATCH] tree: introduce range adaptor for TREE_VEC

[Jason Merrill via Gcc-patches]

On 5/11/22 15:20, Patrick Palka wrote:

This patch implements a simple tree wrapper, named tree_vec_range, which
lets us idiomatically iterate over all the elements of a TREE_VEC using
a C++11 range-based for loop:

   // v is a TREE_VEC
   for (tree e : tree_vec_range (v))
     ...

This is similar to the existing tree-based range adaptors ovl_range and
lkp_range added to the C++ frontend by r12-340-g3307b9a07a3c51.

This patch also converts some existing loops over TREE_VEC within the
C++ frontend to use tree_vec_range and range-for.

Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look
useful?

OK.

gcc/cp/ChangeLog:

        * constraint.cc (tsubst_parameter_mapping): Convert loop over
        TREE_VEC into a range-based for loop using tree_vec_range.
        * pt.cc (iterative_hash_template_arg): Likewise.
        (template_parms_level_to_args): Likewise (and simplify).
        (deducible_template_args): Likewise.
        (check_undeduced_parms): Likewise.
        (dependent_type_p_r): Likewise.
        (value_dependent_expression_p) <case NONTYPE_ARGUMENT_PACK>:
        Likewise.
        (dependent_template_arg_p): Likewise.
        * tree.cc (cp_walk_subtrees) <case NONTYPE_ARGUMENT_PACK>:
        Likewise.

gcc/ChangeLog:

        * tree.h (TREE_VEC_BEGIN): Define.
        (TREE_VEC_END): Correct access of length member.
        (class tree_vec_range): Define.
---
  gcc/cp/constraint.cc |  9 +++----
  gcc/cp/pt.cc         | 57 +++++++++++++++++---------------------------
  gcc/cp/tree.cc       |  5 ++--
  gcc/tree.h           | 15 +++++++++++-
  4 files changed, 41 insertions(+), 45 deletions(-)

diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 94f6222b436..591155cee22 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -2348,12 +2348,9 @@ tsubst_parameter_mapping (tree map, tree args, 
subst_info info)
        if (TREE_CODE (new_arg) == TYPE_ARGUMENT_PACK)
        {
          tree pack_args = ARGUMENT_PACK_ARGS (new_arg);
-         for (int i = 0; i < TREE_VEC_LENGTH (pack_args); i++)
-           {
-             tree& pack_arg = TREE_VEC_ELT (pack_args, i);
-             if (TYPE_P (pack_arg))
-               pack_arg = canonicalize_type_argument (pack_arg, complain);
-           }
+         for (tree& pack_arg : tree_vec_range (pack_args))
+           if (TYPE_P (pack_arg))
+             pack_arg = canonicalize_type_argument (pack_arg, complain);
        }
        if (new_arg == error_mark_node)
        return error_mark_node;
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 9932d861af6..2c7c5f8bb5d 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -1811,8 +1811,8 @@ iterative_hash_template_arg (tree arg, hashval_t val)
        return iterative_hash_object (IDENTIFIER_HASH_VALUE (arg), val);

case TREE_VEC:

-      for (int i = 0, len = TREE_VEC_LENGTH (arg); i < len; ++i)
-       val = iterative_hash_template_arg (TREE_VEC_ELT (arg, i), val);
+      for (tree elt : tree_vec_range (arg))
+       val = iterative_hash_template_arg (elt, val);
        return val;

case TYPE_PACK_EXPANSION:

@@ -4883,15 +4883,15 @@ template_parm_to_arg (tree t)
  tree
  template_parms_level_to_args (tree parms)
  {
-  tree a = copy_node (parms);
-  TREE_TYPE (a) = NULL_TREE;
-  for (int i = TREE_VEC_LENGTH (a) - 1; i >= 0; --i)
-    TREE_VEC_ELT (a, i) = template_parm_to_arg (TREE_VEC_ELT (a, i));
+  parms = copy_node (parms);
+  TREE_TYPE (parms) = NULL_TREE;
+  for (tree& parm : tree_vec_range (parms))
+    parm = template_parm_to_arg (parm);

if (CHECKING_P)

-    SET_NON_DEFAULT_TEMPLATE_ARGS_COUNT (a, TREE_VEC_LENGTH (a));
+    SET_NON_DEFAULT_TEMPLATE_ARGS_COUNT (parms, TREE_VEC_LENGTH (parms));

- return a;

+  return parms;
  }

/* Given a set of template parameters, return them as a set of template

@@ -22470,10 +22470,9 @@ deducible_array_bound (tree domain)
  static bool
  deducible_template_args (tree args)
  {
-  for (int i = 0; i < TREE_VEC_LENGTH (args); ++i)
+  for (tree elt : tree_vec_range (args))
      {
        bool deducible;
-      tree elt = TREE_VEC_ELT (args, i);
        if (ARGUMENT_PACK_P (elt))
        deducible = deducible_template_args (ARGUMENT_PACK_ARGS (elt));
        else
@@ -24844,12 +24843,11 @@ static bool
  check_undeduced_parms (tree targs, tree args, tree end)
  {
    bool found = false;
-  int i;
-  for (i = TREE_VEC_LENGTH (targs) - 1; i >= 0; --i)
-    if (TREE_VEC_ELT (targs, i) == NULL_TREE)
+  for (tree& targ : tree_vec_range (targs))
+    if (targ == NULL_TREE)
        {
        found = true;
-       TREE_VEC_ELT (targs, i) = error_mark_node;
+       targ = error_mark_node;
        }
    if (found)
      {
@@ -27288,10 +27286,9 @@ dependent_type_p_r (tree type)
    if (TREE_CODE (type) == TYPE_ARGUMENT_PACK)
      {
        tree args = ARGUMENT_PACK_ARGS (type);
-      int i, len = TREE_VEC_LENGTH (args);
-      for (i = 0; i < len; ++i)
-        if (dependent_template_arg_p (TREE_VEC_ELT (args, i)))
-          return true;
+      for (tree arg : tree_vec_range (args))
+       if (dependent_template_arg_p (arg))
+         return true;
      }

/* All TYPE_PACK_EXPANSIONs are dependent, because parameter packs must

@@ -27574,16 +27571,10 @@ value_dependent_expression_p (tree expression)
      case NONTYPE_ARGUMENT_PACK:
        /* A NONTYPE_ARGUMENT_PACK is value-dependent if any packed argument
           is value-dependent.  */
-      {
-        tree values = ARGUMENT_PACK_ARGS (expression);
-        int i, len = TREE_VEC_LENGTH (values);
-
-        for (i = 0; i < len; ++i)
-          if (value_dependent_expression_p (TREE_VEC_ELT (values, i)))
-            return true;
-
-        return false;
-      }
+      for (tree arg : tree_vec_range (ARGUMENT_PACK_ARGS (expression)))
+       if (value_dependent_expression_p (arg))
+         return true;
+      return false;

case TRAIT_EXPR:

        {
@@ -28209,13 +28200,9 @@ dependent_template_arg_p (tree arg)
    else if (ARGUMENT_PACK_P (arg))
      {
        tree args = ARGUMENT_PACK_ARGS (arg);
-      int i, len = TREE_VEC_LENGTH (args);
-      for (i = 0; i < len; ++i)
-        {
-          if (dependent_template_arg_p (TREE_VEC_ELT (args, i)))
-            return true;
-        }
-
+      for (tree arg : tree_vec_range (args))
+       if (dependent_template_arg_p (arg))
+         return true;
        return false;
      }
    else if (TYPE_P (arg))
diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc
index 633cc164a3a..bc38c8fbdbe 100644
--- a/gcc/cp/tree.cc
+++ b/gcc/cp/tree.cc
@@ -5414,9 +5414,8 @@ cp_walk_subtrees (tree *tp, int *walk_subtrees_p, 
walk_tree_fn func,
      case NONTYPE_ARGUMENT_PACK:
        {
          tree args = ARGUMENT_PACK_ARGS (*tp);
-        int i, len = TREE_VEC_LENGTH (args);
-        for (i = 0; i < len; i++)
-          WALK_SUBTREE (TREE_VEC_ELT (args, i));
+       for (tree arg : tree_vec_range (args))
+         WALK_SUBTREE (arg);
        }
        break;

diff --git a/gcc/tree.h b/gcc/tree.h

index 82eb8ba39d2..0c12c60ee7e 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -1107,8 +1107,9 @@ extern void omp_clause_range_check_failed (const_tree, 
const char *, int,

/* In a TREE_VEC node. */

  #define TREE_VEC_LENGTH(NODE) (TREE_VEC_CHECK (NODE)->base.u.length)
+#define TREE_VEC_BEGIN(NODE) (&TREE_VEC_CHECK (NODE)->vec.a[0])
  #define TREE_VEC_END(NODE) \
-  ((void) TREE_VEC_CHECK (NODE), &((NODE)->vec.a[(NODE)->vec.base.u.length]))
+  ((void) TREE_VEC_CHECK (NODE), &((NODE)->vec.a[(NODE)->base.u.length]))

#define TREE_VEC_ELT(NODE,I) TREE_VEC_ELT_CHECK (NODE, I) @@ -4481,6 +4482,18 @@ extern tree make_tree_vec (int CXX_MEM_STAT_INFO); extern tree grow_tree_vec (tree v, int CXX_MEM_STAT_INFO); +/* Treat a TREE_VEC as an range of trees, e.g.

+   for (tree e : tree_vec_range (v)) { ... }  */
+
+class tree_vec_range
+{
+  tree v;
+public:
+  tree_vec_range(tree v) : v(v) { }
+  tree *begin() { return TREE_VEC_BEGIN (v); }
+  tree *end() { return TREE_VEC_END (v); }
+};
+
  /* Construct various types of nodes.  */

extern tree build_nt (enum tree_code, ...);