[PATCH 1/3] perf dwarf-aux: Add die_is_compound_type() to handle C++ class types

[Yanbo Zhao]

Introduce the die_is_compound_type() helper which checks for
DW_TAG_structure_type, DW_TAG_union_type, and DW_TAG_class_type, and
convert all the existing open-coded struct/union tag checks to use it:
- die_get_member_type() in dwarf-aux.c.
- __add_member_cb(), is_compound_type(), and set_stack_state() in
  annotate-data.c.

Also accept DW_TAG_inheritance in the member lookup callbacks
(__die_find_member_offset_cb() and __add_member_cb()) so that member
lookup by offset descends into C++ base class subobjects.

This extends the existing member type resolution and data type
profiling state handling to C++ classes with inheritance without
changing behavior for C struct/union types.

Signed-off-by: Yanbo Zhao <yzhao62@xxxxxxxx>
---
 tools/perf/util/annotate-data.c | 29 ++++++-----------------------
 tools/perf/util/dwarf-aux.c     | 17 ++++++++++++-----
 tools/perf/util/dwarf-aux.h     |  3 +++
 3 files changed, 21 insertions(+), 28 deletions(-)

diff --git a/tools/perf/util/annotate-data.c b/tools/perf/util/annotate-data.c
index 4e4c58764082..ee6bd2d0012d 100644
--- a/tools/perf/util/annotate-data.c
+++ b/tools/perf/util/annotate-data.c
@@ -230,9 +230,9 @@ static int __add_member_cb(Dwarf_Die *die, void *arg)
 	Dwarf_Word size, loc, bit_size = 0;
 	Dwarf_Attribute attr;
 	struct strbuf sb;
-	int tag;
+	int tag = dwarf_tag(die);
 
-	if (dwarf_tag(die) != DW_TAG_member)
+	if (tag != DW_TAG_member && tag != DW_TAG_inheritance)
 		return DIE_FIND_CB_SIBLING;
 
 	member = zalloc(sizeof(*member));
@@ -292,15 +292,8 @@ static int __add_member_cb(Dwarf_Die *die, void *arg)
 	INIT_LIST_HEAD(&member->children);
 	list_add_tail(&member->node, &parent->children);
 
-	tag = dwarf_tag(&die_mem);
-	switch (tag) {
-	case DW_TAG_structure_type:
-	case DW_TAG_union_type:
+	if (die_is_compound_type(&die_mem))
 		die_find_child(&die_mem, __add_member_cb, member, &die_mem);
-		break;
-	default:
-		break;
-	}
 	return DIE_FIND_CB_SIBLING;
 }
 
@@ -464,9 +457,7 @@ static const char *match_result_str(enum type_match_result tmr)
 
 static bool is_compound_type(Dwarf_Die *type_die)
 {
-	int tag = dwarf_tag(type_die);
-
-	return tag == DW_TAG_structure_type || tag == DW_TAG_union_type;
+	return die_is_compound_type(type_die);
 }
 
 /* returns if Type B has better information than Type A */
@@ -584,7 +575,6 @@ struct type_state_stack *find_stack_state(struct type_state *state,
 void set_stack_state(struct type_state_stack *stack, int offset, u8 kind,
 			    Dwarf_Die *type_die, int ptr_offset)
 {
-	int tag;
 	Dwarf_Word size;
 
 	if (kind == TSR_KIND_POINTER) {
@@ -605,17 +595,10 @@ void set_stack_state(struct type_state_stack *stack, int offset, u8 kind,
 		return;
 	}
 
-	tag = dwarf_tag(type_die);
-
-	switch (tag) {
-	case DW_TAG_structure_type:
-	case DW_TAG_union_type:
+	if (die_is_compound_type(type_die))
 		stack->compound = (kind != TSR_KIND_PERCPU_POINTER);
-		break;
-	default:
+	else
 		stack->compound = false;
-		break;
-	}
 }
 
 struct type_state_stack *findnew_stack_state(struct type_state *state,
diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index d7160f87ac7d..88ba0ec23a68 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -60,6 +60,14 @@ const char *cu_get_comp_dir(Dwarf_Die *cu_die)
 	return dwarf_formstring(&attr);
 }
 
+bool die_is_compound_type(Dwarf_Die *type_die)
+{
+	int tag = dwarf_tag(type_die);
+
+	return tag == DW_TAG_structure_type || tag == DW_TAG_union_type ||
+	       tag == DW_TAG_class_type;
+}
+
 /* Unlike dwarf_getsrc_die(), cu_getsrc_die() only returns statement line */
 static Dwarf_Line *cu_getsrc_die(Dwarf_Die *cu_die, Dwarf_Addr addr)
 {
@@ -2053,7 +2061,7 @@ static int __die_find_member_offset_cb(Dwarf_Die *die_mem, void *arg)
 	Dwarf_Word offset = (long)arg;
 	int tag = dwarf_tag(die_mem);
 
-	if (tag != DW_TAG_member)
+	if (tag != DW_TAG_member && tag != DW_TAG_inheritance)
 		return DIE_FIND_CB_SIBLING;
 
 	/* Unions might not have location */
@@ -2104,7 +2112,7 @@ Dwarf_Die *die_get_member_type(Dwarf_Die *type_die, int offset,
 
 	tag = dwarf_tag(type_die);
 	/* If it's not a compound type, return the type directly */
-	if (tag != DW_TAG_structure_type && tag != DW_TAG_union_type) {
+	if (!die_is_compound_type(type_die)) {
 		Dwarf_Word size;
 
 		if (dwarf_aggregate_size(type_die, &size) < 0)
@@ -2119,7 +2127,7 @@ Dwarf_Die *die_get_member_type(Dwarf_Die *type_die, int offset,
 
 	mb_type = *type_die;
 	/* TODO: Handle union types better? */
-	while (tag == DW_TAG_structure_type || tag == DW_TAG_union_type) {
+	while (die_is_compound_type(&mb_type)) {
 		member = die_find_child(&mb_type, __die_find_member_offset_cb,
 					(void *)(long)offset, die_mem);
 		if (member == NULL)
@@ -2130,8 +2138,7 @@ Dwarf_Die *die_get_member_type(Dwarf_Die *type_die, int offset,
 
 		tag = dwarf_tag(&mb_type);
 
-		if (tag == DW_TAG_structure_type || tag == DW_TAG_union_type ||
-		    tag == DW_TAG_array_type) {
+		if (die_is_compound_type(&mb_type) || tag == DW_TAG_array_type) {
 			Dwarf_Word loc;
 
 			/* Update offset for the start of the member struct */
diff --git a/tools/perf/util/dwarf-aux.h b/tools/perf/util/dwarf-aux.h
index 161f0bf980b6..855c45fec5bb 100644
--- a/tools/perf/util/dwarf-aux.h
+++ b/tools/perf/util/dwarf-aux.h
@@ -23,6 +23,9 @@ const char *cu_find_realpath(Dwarf_Die *cu_die, const char *fname);
 /* Get DW_AT_comp_dir (should be NULL with older gcc) */
 const char *cu_get_comp_dir(Dwarf_Die *cu_die);
 
+/* Check if DIE is a compound type (structure, union, or class) */
+bool die_is_compound_type(Dwarf_Die *type_die);
+
 /* Get a line number and file name for given address */
 int cu_find_lineinfo(Dwarf_Die *cudie, Dwarf_Addr addr,
 		     const char **fname, int *lineno);
-- 
2.25.1