[PAHOLE v5 2/5] dwarf_loader: Extract die__add_btf_type_tag() helper [NFC]

NFC change preparing for DW_TAG_GNU_annotation support.
Extract the btf_type_tag annotation creation logic into helper
die__add_btf_type_tag().

Signed-off-by: Vineet Gupta <[email protected]>
Acked-by: Yonghong Song <[email protected]>
Reviewed-by: Emil Tsalapatis <[email protected]>
---
Changes since v [4]
 - Collected the review tags [Emil, Yonghong]

Changes since v3 [3]
 - Fix comment to kernel style [Arnaldo]

Changes since v2 [2]
 - die__add_btf_type_tag() returns pointer not error code [Alan]

Changes since v1 [1]
 - NFC reinstate some original comments

[4] https://lore.kernel.org/bpf/[email protected]/
[3] https://lore.kernel.org/bpf/[email protected]/
[2] https://lore.kernel.org/bpf/[email protected]/
[1] https://lore.kernel.org/bpf/[email protected]/
---
 dwarf_loader.c | 58 +++++++++++++++++++++++++++++---------------------
 1 file changed, 34 insertions(+), 24 deletions(-)

diff --git a/dwarf_loader.c b/dwarf_loader.c
index 16fb7becffee..42a0f3f74ce3 100644
--- a/dwarf_loader.c
+++ b/dwarf_loader.c
@@ -1600,14 +1600,44 @@ static struct btf_type_tag_type *die__create_new_btf_type_tag_type(Dwarf_Die *di
 	return tag;
 }
 
+static struct btf_type_tag_ptr_type *die__add_btf_type_tag(struct btf_type_tag_ptr_type *tag,
+							    Dwarf_Die *die, Dwarf_Die *adie,
+							    struct cu *cu, struct conf_load *conf)
+{
+	struct btf_type_tag_type *annot;
+	uint32_t id;
+
+	if (tag == NULL) {
+		tag = die__create_new_btf_type_tag_ptr_type(die, cu);
+		if (!tag)
+			return NULL;
+	}
+
+	annot = die__create_new_btf_type_tag_type(adie, cu, conf);
+	if (annot == NULL)
+		return NULL;
+
+	if (cu__table_add_tag(cu, &annot->tag, &id) < 0)
+		return NULL;
+
+	struct dwarf_tag *dtag = tag__dwarf(&annot->tag);
+	dtag->small_id = id;
+	cu__hash(cu, &annot->tag);
+
+	/*
+	 * Prepends: for annotations tag1 -> tag2 -> tag3,
+	 * the tag->tags list ends up as tag3 -> tag2 -> tag1.
+	 */
+	list_add(&annot->node, &tag->tags);
+	return tag;
+}
+
 static struct tag *die__create_new_pointer_tag(Dwarf_Die *die, struct cu *cu,
 					       struct conf_load *conf)
 {
 	struct btf_type_tag_ptr_type *tag = NULL;
-	struct btf_type_tag_type *annot;
 	Dwarf_Die *cdie, child;
 	const char *name;
-	uint32_t id;
 
 	/* If no child tags or skipping btf_type_tag encoding, just create a new tag
 	 * and return
@@ -1627,29 +1657,9 @@ static struct tag *die__create_new_pointer_tag(Dwarf_Die *die, struct cu *cu,
 		if (strcmp(name, "btf_type_tag") != 0)
 			continue;
 
-		if (tag == NULL) {
-			/* Create a btf_type_tag_ptr type. */
-			tag = die__create_new_btf_type_tag_ptr_type(die, cu);
-			if (!tag)
-				return NULL;
-		}
-
-		/* Create a btf_type_tag type for this annotation. */
-		annot = die__create_new_btf_type_tag_type(cdie, cu, conf);
-		if (annot == NULL)
-			return NULL;
-
-		if (cu__table_add_tag(cu, &annot->tag, &id) < 0)
+		tag = die__add_btf_type_tag(tag, die, cdie, cu, conf);
+		if (tag == NULL)
 			return NULL;
-
-		struct dwarf_tag *dtag = tag__dwarf(&annot->tag);
-		dtag->small_id = id;
-		cu__hash(cu, &annot->tag);
-
-		/* For a list of DW_TAG_LLVM_annotation like tag1 -> tag2 -> tag3,
-		 * the tag->tags contains tag3 -> tag2 -> tag1.
-		 */
-		list_add(&annot->node, &tag->tags);
 	} while (dwarf_siblingof(cdie, cdie) == 0);
 
 	return tag ? &tag->tag : tag__new(die, cu);
-- 
2.54.0