libctf: map from old to corresponding newly-added types in ctf_add_type

This lets you call ctf_type_mapping (dest_fp, src_fp, src_type_id)
and get told what type ID the corresponding type has in the target
ctf_file_t.  This works even if it was added by a recursive call, and
because it is stored in the target ctf_file_t it works even if we
had to add one type to multiple ctf_file_t's as part of conflicting
type handling.

We empty out this mapping after every archive is linked: because it maps
input to output fps, and we only visit each input fp once, its contents
are rendered entirely useless every time the source fp changes.

v3: add several missing mapping additions.  Add ctf_dynhash_empty, and
    empty after every input archive.
v5: fix tabdamage.

libctf/
	* ctf-impl.h (ctf_file_t): New field ctf_link_type_mapping.
	(struct ctf_link_type_mapping_key): New.
	(ctf_hash_type_mapping_key): Likewise.
	(ctf_hash_eq_type_mapping_key): Likewise.
	(ctf_add_type_mapping): Likewise.
	(ctf_type_mapping): Likewise.
	(ctf_dynhash_empty): Likewise.
	* ctf-open.c (ctf_file_close): Update accordingly.
	* ctf-create.c (ctf_update): Likewise.
	(ctf_add_type): Populate the mapping.
	* ctf-hash.c (ctf_hash_type_mapping_key): Hash a type mapping key.
	(ctf_hash_eq_type_mapping_key): Check the key for equality.
	(ctf_dynhash_insert): Fix comment typo.
	(ctf_dynhash_empty): New.
	* ctf-link.c (ctf_add_type_mapping): New.
	(ctf_type_mapping): Likewise.
	(empty_link_type_mapping): New.
	(ctf_link_one_input_archive): Call it.

libctf/ctf-link.c

@@ -20,6 +20,104 @@
 #include <ctf-impl.h>
 #include <string.h>
 
+/* Type tracking machinery.  */
+
+/* Record the correspondence between a source and ctf_add_type()-added
+   destination type: both types are translated into parent type IDs if need be,
+   so they relate to the actual container they are in.  Outside controlled
+   circumstances (like linking) it is probably not useful to do more than
+   compare these pointers, since there is nothing stopping the user closing the
+   source container whenever they want to.
+
+   Our OOM handling here is just to not do anything, because this is called deep
+   enough in the call stack that doing anything useful is painfully difficult:
+   the worst consequence if we do OOM is a bit of type duplication anyway.  */
+
+void
+ctf_add_type_mapping (ctf_file_t *src_fp, ctf_id_t src_type,
+		      ctf_file_t *dst_fp, ctf_id_t dst_type)
+{
+  if (LCTF_TYPE_ISPARENT (src_fp, src_type) && src_fp->ctf_parent)
+    src_fp = src_fp->ctf_parent;
+
+  src_type = LCTF_TYPE_TO_INDEX(src_fp, src_type);
+
+  if (LCTF_TYPE_ISPARENT (dst_fp, dst_type) && dst_fp->ctf_parent)
+    dst_fp = dst_fp->ctf_parent;
+
+  dst_type = LCTF_TYPE_TO_INDEX(dst_fp, dst_type);
+
+  /* This dynhash is a bit tricky: it has a multivalued (structural) key, so we
+     need to use the sized-hash machinery to generate key hashing and equality
+     functions.  */
+
+  if (dst_fp->ctf_link_type_mapping == NULL)
+    {
+      ctf_hash_fun f = ctf_hash_type_mapping_key;
+      ctf_hash_eq_fun e = ctf_hash_eq_type_mapping_key;
+
+      if ((dst_fp->ctf_link_type_mapping = ctf_dynhash_create (f, e, free,
+							       NULL)) == NULL)
+	return;
+    }
+
+  ctf_link_type_mapping_key_t *key;
+  key = calloc (1, sizeof (struct ctf_link_type_mapping_key));
+  if (!key)
+    return;
+
+  key->cltm_fp = src_fp;
+  key->cltm_idx = src_type;
+
+  ctf_dynhash_insert (dst_fp->ctf_link_type_mapping, key,
+		      (void *) (uintptr_t) dst_type);
+}
+
+/* Look up a type mapping: return 0 if none.  The DST_FP is modified to point to
+   the parent if need be.  The ID returned is from the dst_fp's perspective.  */
+ctf_id_t
+ctf_type_mapping (ctf_file_t *src_fp, ctf_id_t src_type, ctf_file_t **dst_fp)
+{
+  ctf_link_type_mapping_key_t key;
+  ctf_file_t *target_fp = *dst_fp;
+  ctf_id_t dst_type = 0;
+
+  if (LCTF_TYPE_ISPARENT (src_fp, src_type) && src_fp->ctf_parent)
+    src_fp = src_fp->ctf_parent;
+
+  src_type = LCTF_TYPE_TO_INDEX(src_fp, src_type);
+  key.cltm_fp = src_fp;
+  key.cltm_idx = src_type;
+
+  if (target_fp->ctf_link_type_mapping)
+    dst_type = (uintptr_t) ctf_dynhash_lookup (target_fp->ctf_link_type_mapping,
+					       &key);
+
+  if (dst_type != 0)
+    {
+      dst_type = LCTF_INDEX_TO_TYPE (target_fp, dst_type,
+				     target_fp->ctf_parent != NULL);
+      *dst_fp = target_fp;
+      return dst_type;
+    }
+
+  if (target_fp->ctf_parent)
+    target_fp = target_fp->ctf_parent;
+  else
+    return 0;
+
+  if (target_fp->ctf_link_type_mapping)
+    dst_type = (uintptr_t) ctf_dynhash_lookup (target_fp->ctf_link_type_mapping,
+					       &key);
+
+  if (dst_type)
+    dst_type = LCTF_INDEX_TO_TYPE (target_fp, dst_type,
+				   target_fp->ctf_parent != NULL);
+
+  *dst_fp = target_fp;
+  return dst_type;
+}
+
 /* Linker machinery.
 
    CTF linking consists of adding CTF archives full of content to be merged into
@@ -229,6 +327,17 @@ ctf_link_one_input_archive_member (ctf_file_t *in_fp, const char *name, void *ar
   return 0;
 }
 
+/* Dump the unnecessary link type mapping after one input file is processed.  */
+static void
+empty_link_type_mapping (void *key _libctf_unused_, void *value,
+			 void *arg _libctf_unused_)
+{
+  ctf_file_t *fp = (ctf_file_t *) value;
+
+  if (fp->ctf_link_type_mapping)
+    ctf_dynhash_empty (fp->ctf_link_type_mapping);
+}
+
 /* Link one input file's types into the output file.  */
 static void
 ctf_link_one_input_archive (void *key, void *value, void *arg_)
@@ -267,6 +376,11 @@ ctf_link_one_input_archive (void *key, void *value, void *arg_)
       ctf_set_errno (arg->out_fp, 0);
     }
   ctf_file_close (arg->main_input_fp);
+
+  /* Discard the now-unnecessary mapping table data.  */
+  if (arg->out_fp->ctf_link_type_mapping)
+    ctf_dynhash_empty (arg->out_fp->ctf_link_type_mapping);
+  ctf_dynhash_iter (arg->out_fp->ctf_link_outputs, empty_link_type_mapping, NULL);
 }
 
 /* Merge types and variable sections in all files added to the link