[PATCH v2 10/11] OpenMP: Use OMP_ARRAY_SECTION instead of TREE_LIST for array sections in C FE

[Julian Brown <julian@codesourcery.com>]

This patch uses the new OMP_ARRAY_SECTION tree code to represent OpenMP
array sections, rather than TREE_LIST.  As for the C++ FE, using TREE_LIST
becomes unwieldy when the array-section representation sticks around
for longer due to adding "declare mapper" support.

We must be a little careful here because OMP_CLAUSE_DEPEND and
OMP_CLAUSE_AFFINITY also use TREE_LIST for their own purposes, and we're
not changing those ones.

No behavioural changes should be introduced by this patch.

2022-03-04  Julian Brown  <julian@codesourcery.com>

gcc/c/
	* c-parser.cc (c_parser_omp_variable_list): Use OMP_ARRAY_SECTION
	instead of TREE_LIST for array sections.
	(c_parser_omp_clause_reduction): Likewise.
	* c-typeck.cc (handle_omp_array_sections_1, handle_omp_array_sections,
	c_oacc_check_attachments, c_finish_omp_clauses): Likewise.
---
 gcc/c/c-parser.cc | 21 +++++++++++++++------
 gcc/c/c-typeck.cc | 37 +++++++++++++++++++------------------
 2 files changed, 34 insertions(+), 24 deletions(-)

diff --git a/gcc/c/c-parser.cc b/gcc/c/c-parser.cc
index cc590e56e75..1ca03b6a632 100644
--- a/gcc/c/c-parser.cc
+++ b/gcc/c/c-parser.cc
@@ -13165,16 +13165,20 @@ c_parser_omp_variable_list (c_parser *parser,
 		}
 
 	      for (int i = dims.length () - 1; i >= 0; i--)
-		decl = tree_cons (dims[i].low_bound, dims[i].length, decl);
+		decl = build3_loc (loc, OMP_ARRAY_SECTION, TREE_TYPE (decl),
+				   decl, dims[i].low_bound, dims[i].length);
 	    }
 	  else if (TREE_CODE (decl) == INDIRECT_REF)
 	    {
+	      tree type = TREE_TYPE (decl);
+
 	      /* Turn *foo into the representation previously used for
 		 foo[0].  */
 	      decl = TREE_OPERAND (decl, 0);
 	      STRIP_NOPS (decl);
 
-	      decl = tree_cons (integer_zero_node, integer_one_node, decl);
+	      decl = build3_loc (loc, OMP_ARRAY_SECTION, type, decl,
+				 integer_zero_node, integer_one_node);
 	    }
 	  else if (TREE_CODE (decl) == ARRAY_REF)
 	    {
@@ -13183,7 +13187,8 @@ c_parser_omp_variable_list (c_parser *parser,
 	      decl = TREE_OPERAND (decl, 0);
 	      STRIP_NOPS (decl);
 
-	      decl = tree_cons (idx, integer_one_node, decl);
+	      decl = build3_loc (loc, OMP_ARRAY_SECTION, TREE_TYPE (decl),
+				 decl, idx, integer_one_node);
 	    }
 	  else if (TREE_CODE (decl) == NON_LVALUE_EXPR
 		   || CONVERT_EXPR_P (decl))
@@ -13345,7 +13350,9 @@ c_parser_omp_variable_list (c_parser *parser,
 		    }
 		  else
 		    for (unsigned i = 0; i < dims.length (); i++)
-		      t = tree_cons (dims[i].low_bound, dims[i].length, t);
+		      t = build3_loc (clause_loc, OMP_ARRAY_SECTION,
+				      TREE_TYPE (t), t, dims[i].low_bound,
+				      dims[i].length);
 		}
 
 	      if ((kind == OMP_CLAUSE_DEPEND || kind == OMP_CLAUSE_AFFINITY)
@@ -15061,13 +15068,15 @@ c_parser_omp_clause_reduction (c_parser *parser, enum omp_clause_code kind,
 	  for (c = nl; c != list; c = OMP_CLAUSE_CHAIN (c))
 	    {
 	      tree d = OMP_CLAUSE_DECL (c), type;
-	      if (TREE_CODE (d) != TREE_LIST)
+	      if (TREE_CODE (d) != OMP_ARRAY_SECTION)
 		type = TREE_TYPE (d);
 	      else
 		{
 		  int cnt = 0;
 		  tree t;
-		  for (t = d; TREE_CODE (t) == TREE_LIST; t = TREE_CHAIN (t))
+		  for (t = d;
+		      TREE_CODE (t) == OMP_ARRAY_SECTION;
+		      t = TREE_OPERAND (t, 0))
 		    cnt++;
 		  type = TREE_TYPE (t);
 		  while (cnt > 0)
diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
index 162ed0a18a2..98212c6b7f5 100644
--- a/gcc/c/c-typeck.cc
+++ b/gcc/c/c-typeck.cc
@@ -13218,7 +13218,7 @@ handle_omp_array_sections_1 (tree c, tree t, vec<tree> &types,
 			     enum c_omp_region_type ort)
 {
   tree ret, low_bound, length, type;
-  if (TREE_CODE (t) != TREE_LIST)
+  if (TREE_CODE (t) != OMP_ARRAY_SECTION)
     {
       if (error_operand_p (t))
 	return error_mark_node;
@@ -13293,14 +13293,14 @@ handle_omp_array_sections_1 (tree c, tree t, vec<tree> &types,
       return ret;
     }
 
-  ret = handle_omp_array_sections_1 (c, TREE_CHAIN (t), types,
+  ret = handle_omp_array_sections_1 (c, TREE_OPERAND (t, 0), types,
 				     maybe_zero_len, first_non_one, ort);
   if (ret == error_mark_node || ret == NULL_TREE)
     return ret;
 
   type = TREE_TYPE (ret);
-  low_bound = TREE_PURPOSE (t);
-  length = TREE_VALUE (t);
+  low_bound = TREE_OPERAND (t, 1);
+  length = TREE_OPERAND (t, 2);
 
   if (low_bound == error_mark_node || length == error_mark_node)
     return error_mark_node;
@@ -13493,7 +13493,7 @@ handle_omp_array_sections_1 (tree c, tree t, vec<tree> &types,
 	  tree lb = save_expr (low_bound);
 	  if (lb != low_bound)
 	    {
-	      TREE_PURPOSE (t) = lb;
+	      TREE_OPERAND (t, 1) = lb;
 	      low_bound = lb;
 	    }
 	}
@@ -13524,14 +13524,15 @@ handle_omp_array_sections_1 (tree c, tree t, vec<tree> &types,
 	 array-section-subscript, the array section could be non-contiguous.  */
       if (OMP_CLAUSE_CODE (c) != OMP_CLAUSE_DEPEND
 	  && OMP_CLAUSE_CODE (c) != OMP_CLAUSE_AFFINITY
-	  && TREE_CODE (TREE_CHAIN (t)) == TREE_LIST)
+	  && TREE_CODE (TREE_OPERAND (t, 0)) == OMP_ARRAY_SECTION)
 	{
 	  /* If any prior dimension has a non-one length, then deem this
 	     array section as non-contiguous.  */
-	  for (tree d = TREE_CHAIN (t); TREE_CODE (d) == TREE_LIST;
-	       d = TREE_CHAIN (d))
+	  for (tree d = TREE_OPERAND (t, 0);
+	       TREE_CODE (d) == OMP_ARRAY_SECTION;
+	       d = TREE_OPERAND (d, 0))
 	    {
-	      tree d_length = TREE_VALUE (d);
+	      tree d_length = TREE_OPERAND (d, 2);
 	      if (d_length == NULL_TREE || !integer_onep (d_length))
 		{
 		  error_at (OMP_CLAUSE_LOCATION (c),
@@ -13554,7 +13555,7 @@ handle_omp_array_sections_1 (tree c, tree t, vec<tree> &types,
   tree lb = save_expr (low_bound);
   if (lb != low_bound)
     {
-      TREE_PURPOSE (t) = lb;
+      TREE_OPERAND (t, 1) = lb;
       low_bound = lb;
     }
   ret = build_array_ref (OMP_CLAUSE_LOCATION (c), ret, low_bound);
@@ -13617,10 +13618,10 @@ handle_omp_array_sections (tree c, enum c_omp_region_type ort)
 	maybe_zero_len = true;
 
       for (i = num, t = OMP_CLAUSE_DECL (c); i > 0;
-	   t = TREE_CHAIN (t))
+	   t = TREE_OPERAND (t, 0))
 	{
-	  tree low_bound = TREE_PURPOSE (t);
-	  tree length = TREE_VALUE (t);
+	  tree low_bound = TREE_OPERAND (t, 1);
+	  tree length = TREE_OPERAND (t, 2);
 
 	  i--;
 	  if (low_bound
@@ -14069,8 +14070,8 @@ c_oacc_check_attachments (tree c)
     {
       tree t = OMP_CLAUSE_DECL (c);
 
-      while (TREE_CODE (t) == TREE_LIST)
-	t = TREE_CHAIN (t);
+      while (TREE_CODE (t) == OMP_ARRAY_SECTION)
+	t = TREE_OPERAND (t, 0);
 
       if (TREE_CODE (TREE_TYPE (t)) != POINTER_TYPE)
 	{
@@ -14170,7 +14171,7 @@ c_finish_omp_clauses (tree clauses, enum c_omp_region_type ort)
 	case OMP_CLAUSE_TASK_REDUCTION:
 	  need_implicitly_determined = true;
 	  t = OMP_CLAUSE_DECL (c);
-	  if (TREE_CODE (t) == TREE_LIST)
+	  if (TREE_CODE (t) == OMP_ARRAY_SECTION)
 	    {
 	      if (handle_omp_array_sections (c, ort))
 		{
@@ -14790,7 +14791,7 @@ c_finish_omp_clauses (tree clauses, enum c_omp_region_type ort)
 	    }
 	  else
 	    last_iterators = NULL_TREE;
-	  if (TREE_CODE (t) == TREE_LIST)
+	  if (TREE_CODE (t) == OMP_ARRAY_SECTION)
 	    {
 	      if (handle_omp_array_sections (c, ort))
 		remove = true;
@@ -14876,7 +14877,7 @@ c_finish_omp_clauses (tree clauses, enum c_omp_region_type ort)
 	case OMP_CLAUSE_FROM:
 	case OMP_CLAUSE__CACHE_:
 	  t = OMP_CLAUSE_DECL (c);
-	  if (TREE_CODE (t) == TREE_LIST)
+	  if (TREE_CODE (t) == OMP_ARRAY_SECTION)
 	    {
 	      if (handle_omp_array_sections (c, ort))
 		remove = true;
-- 
2.29.2