+/* Index into a template parameter list. The TEMPLATE_PARM_IDX gives
+ the index (from 0) of the parameter, while the TEMPLATE_PARM_LEVEL
+ gives the level (from 1) of the parameter.
+
+ Here's an example:
+
+ template <class T> // Index 0, Level 1.
+ struct S
+ {
+ template <class U, // Index 0, Level 2.
+ class V> // Index 1, Level 2.
+ void f();
+ };
+
+ The DESCENDANTS will be a chain of TEMPLATE_PARM_INDEXs descended
+ from this one. The first descendant will have the same IDX, but
+ its LEVEL will be one less. The TREE_CHAIN field is used to chain
+ together the descendants. The TEMPLATE_PARM_DECL is the
+ declaration of this parameter, either a TYPE_DECL or CONST_DECL.
+ The TEMPLATE_PARM_ORIG_LEVEL is the LEVEL of the most distant
+ parent, i.e., the LEVEL that the parameter originally had when it
+ was declared. For example, if we instantiate S<int>, we will have:
+
+ struct S<int>
+ {
+ template <class U, // Index 0, Level 1, Orig Level 2
+ class V> // Index 1, Level 1, Orig Level 2
+ void f();
+ };
+
+ The LEVEL is the level of the parameter when we are worrying about
+ the types of things; the ORIG_LEVEL is the level when we are
+ worrying about instantiating things. */
+DEFTREECODE (TEMPLATE_PARM_INDEX, "template_parm_index", 'x',
+ /* The addition of (sizeof(tree) - 1) in the next expression
+ is to handle the case when padding pushes us past an even
+ multiple of sizeof(tree). */
+ /* We used to try to calculate this using
+ 1+3*sizeof(HOST_WIDE_INT), but that fails if alignment
+ makes it bigger. */
+ ((sizeof (template_parm_index) - sizeof (struct tree_common))
+ + sizeof (tree) - 1)
+ / sizeof (tree))
+