tree.def: Improve RAW_DATA_CST documentation

In PR117262 David was asking for better documentation of RAW_DATA_CST
and in the review of the PR119076 patch Jason was asking for that as well.

Here is an attempt to do so.

2025-03-12  Jakub Jelinek  <jakub@redhat.com>

	* tree.def (RAW_DATA_CST): Document meaning of NULL RAW_DATA_OWNER.
	(CONSTRUCTOR): Document meaning of RAW_DATA_CST used as element
	value.

diff --git a/gcc/tree.def b/gcc/tree.def
index 9d31fee845458aab3b6a90500a61e791182f5803..c4ad8d08f10ce61326657c3647b4fbfcd0f04875 100644 (file)
--- a/gcc/tree.def
+++ b/gcc/tree.def
@@ -313,7 +313,9 @@ DEFTREECODE (STRING_CST, "string_cst", tcc_constant, 0)
    of the raw data, plus RAW_DATA_OWNER for owner of the
    data.  That can be either a STRING_CST, used e.g. when writing
    PCH header, or another RAW_DATA_CST representing data owned by
-   libcpp and representing the original range (if possible).
+   libcpp and representing the original range (if possible)
+   or NULL_TREE if it is the RAW_DATA_OWNER of other RAW_DATA_CST
+   nodes (and represents data owned by libcpp).
    TREE_TYPE is the type of each of the RAW_DATA_LENGTH elements.  */
 DEFTREECODE (RAW_DATA_CST, "raw_data_cst", tcc_constant, 0)
 
@@ -505,6 +507,14 @@ DEFTREECODE (OBJ_TYPE_REF, "obj_type_ref", tcc_expression, 3)
    one for each index in the range.  (If the corresponding field VALUE
    has side-effects, they are evaluated once for each element.  Wrap the
    value in a SAVE_EXPR if you want to evaluate side effects only once.)
+   If the index is INTEGER_CST or NULL_TREE and value RAW_DATA_CST, it is
+   a short-hand for RAW_DATA_LENGTH consecutive nodes, first at the given
+   index or current location, each node being
+   build_int_cst (TREE_TYPE (value), TYPE_UNSIGNED (TREE_TYPE (value))
+                 ? (HOST_WIDE_INT) RAW_DATA_UCHAR_ELT (value, n)
+                 : (HOST_WIDE_INT) RAW_DATA_SCHAR_ELT (value, n)) at index
+   tree_to_uhwi (index) + n (or current location + n) for n from 0 to
+   RAW_DATA_LENGTH (value) - 1.
 
    Components that aren't present are cleared as per the C semantics,
    unless the CONSTRUCTOR_NO_CLEARING flag is set, in which case their