[cpu-profiler] Expose parent pointer in a CpuProfileNode

Consumers can use this to derive the full stack from sampled leaf nodes
without having to flatten the tree.

Bug: v8:8999
Change-Id: I42c638dd2c757837b0c03514c204be0182653291
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1525877Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Alexei Filippov <alph@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60309}

include/v8-profiler.h

@@ -206,6 +206,9 @@ class V8_EXPORT CpuProfileNode {
   /** Retrieves a child node by index. */
   const CpuProfileNode* GetChild(int index) const;
 
+  /** Retrieves the ancestor node, or null if the root. */
+  const CpuProfileNode* GetParent() const;
+
   /** Retrieves deopt infos for the node. */
   const std::vector<CpuProfileDeoptInfo>& GetDeoptInfos() const;
 

src/api.cc

@@ -10038,6 +10038,11 @@ const CpuProfileNode* CpuProfileNode::GetChild(int index) const {
   return reinterpret_cast<const CpuProfileNode*>(child);
 }
 
+const CpuProfileNode* CpuProfileNode::GetParent() const {
+  const i::ProfileNode* parent =
+      reinterpret_cast<const i::ProfileNode*>(this)->parent();
+  return reinterpret_cast<const CpuProfileNode*>(parent);
+}
 
 const std::vector<CpuProfileDeoptInfo>& CpuProfileNode::GetDeoptInfos() const {
   const i::ProfileNode* node = reinterpret_cast<const i::ProfileNode*>(this);

test/cctest/test-cpu-profiler.cc

@@ -1880,7 +1880,8 @@ static void CheckFunctionDetails(v8::Isolate* isolate,
                                  const v8::CpuProfileNode* node,
                                  const char* name, const char* script_name,
                                  bool is_shared_cross_origin, int script_id,
-                                 int line, int column) {
+                                 int line, int column,
+                                 const v8::CpuProfileNode* parent) {
   v8::Local<v8::Context> context = isolate->GetCurrentContext();
   CHECK(v8_str(name)->Equals(context, node->GetFunctionName()).FromJust());
   CHECK_EQ(0, strcmp(name, node->GetFunctionNameStr()));
@@ -1891,6 +1892,7 @@ static void CheckFunctionDetails(v8::Isolate* isolate,
   CHECK_EQ(script_id, node->GetScriptId());
   CHECK_EQ(line, node->GetLineNumber());
   CHECK_EQ(column, node->GetColumnNumber());
+  CHECK_EQ(parent, node->GetParent());
 }
 
 TEST(FunctionDetails) {
@@ -1925,18 +1927,19 @@ TEST(FunctionDetails) {
   //  0        foo 18 #4 TryCatchStatement script_a:2
   //  1          bar 18 #5 no reason script_a:3
   const v8::CpuProfileNode* root = profile->GetTopDownRoot();
+  CHECK_EQ(root->GetParent(), nullptr);
   const v8::CpuProfileNode* script = GetChild(env, root, "");
   CheckFunctionDetails(env->GetIsolate(), script, "", "script_b", true,
-                       script_b->GetUnboundScript()->GetId(), 1, 1);
+                       script_b->GetUnboundScript()->GetId(), 1, 1, root);
   const v8::CpuProfileNode* baz = GetChild(env, script, "baz");
   CheckFunctionDetails(env->GetIsolate(), baz, "baz", "script_b", true,
-                       script_b->GetUnboundScript()->GetId(), 3, 16);
+                       script_b->GetUnboundScript()->GetId(), 3, 16, script);
   const v8::CpuProfileNode* foo = GetChild(env, baz, "foo");
   CheckFunctionDetails(env->GetIsolate(), foo, "foo", "script_a", false,
-                       script_a->GetUnboundScript()->GetId(), 4, 1);
+                       script_a->GetUnboundScript()->GetId(), 4, 1, baz);
   const v8::CpuProfileNode* bar = GetChild(env, foo, "bar");
   CheckFunctionDetails(env->GetIsolate(), bar, "bar", "script_a", false,
-                       script_a->GetUnboundScript()->GetId(), 5, 14);
+                       script_a->GetUnboundScript()->GetId(), 5, 14, foo);
 }
 
 TEST(FunctionDetailsInlining) {
@@ -2005,18 +2008,19 @@ TEST(FunctionDetailsInlining) {
   //  0      startProfiling 0 #3
 
   const v8::CpuProfileNode* root = profile->GetTopDownRoot();
+  CHECK_EQ(root->GetParent(), nullptr);
   const v8::CpuProfileNode* script = GetChild(env, root, "");
   CheckFunctionDetails(env->GetIsolate(), script, "", "script_a", false,
-                       script_a->GetUnboundScript()->GetId(), 1, 1);
+                       script_a->GetUnboundScript()->GetId(), 1, 1, root);
   const v8::CpuProfileNode* alpha = FindChild(env, script, "alpha");
   // Return early if profiling didn't sample alpha.
   if (!alpha) return;
   CheckFunctionDetails(env->GetIsolate(), alpha, "alpha", "script_a", false,
-                       script_a->GetUnboundScript()->GetId(), 1, 15);
+                       script_a->GetUnboundScript()->GetId(), 1, 15, script);
   const v8::CpuProfileNode* beta = FindChild(env, alpha, "beta");
   if (!beta) return;
   CheckFunctionDetails(env->GetIsolate(), beta, "beta", "script_b", true,
-                       script_b->GetUnboundScript()->GetId(), 1, 14);
+                       script_b->GetUnboundScript()->GetId(), 1, 14, alpha);
 }
 
 TEST(DontStopOnFinishedProfileDelete) {