From 7371388e1d09e401783c42c95ce1013e5f67de33 Mon Sep 17 00:00:00 2001
From: Robert O'Callahan <robert@ocallahan.org>
Date: Fri, 17 Oct 2025 12:15:53 +1300
Subject: [PATCH] Add timing stats for IdString garbage collection

---
 kernel/driver.cc   | 2 ++
 kernel/register.cc | 5 +++++
 kernel/register.h  | 2 ++
 kernel/rtlil.cc    | 8 ++++++++
 kernel/rtlil.h     | 5 +++++
 5 files changed, 22 insertions(+)

diff --git a/kernel/driver.cc b/kernel/driver.cc
index 795fd9fc5..eae9c5276 100644
--- a/kernel/driver.cc
+++ b/kernel/driver.cc
@@ -709,6 +709,8 @@ int main(int argc, char **argv)
 				total_ns += it.second->runtime_ns + 1;
 				timedat.insert(make_tuple(it.second->runtime_ns + 1, it.second->call_counter, it.first));
 			}
+		timedat.insert(make_tuple(RTLIL::OwningIdString::garbage_collection_ns() + 1,
+				RTLIL::OwningIdString::garbage_collection_count(), "id_gc"));
 
 		if (timing_details)
 		{
diff --git a/kernel/register.cc b/kernel/register.cc
index 1f8e4a9a5..3f5aa49ca 100644
--- a/kernel/register.cc
+++ b/kernel/register.cc
@@ -129,6 +129,11 @@ void Pass::post_execute(Pass::pre_post_exec_state_t state)
 	int64_t time_ns = PerformanceTimer::query() - state.begin_ns;
 	runtime_ns += time_ns;
 	current_pass = state.parent_pass;
+	subtract_from_current_runtime_ns(time_ns);
+}
+
+void Pass::subtract_from_current_runtime_ns(int64_t time_ns)
+{
 	if (current_pass)
 		current_pass->runtime_ns -= time_ns;
 }
diff --git a/kernel/register.h b/kernel/register.h
index b9c709dc1..78f9b430d 100644
--- a/kernel/register.h
+++ b/kernel/register.h
@@ -95,6 +95,8 @@ struct Pass
 	bool experimental_flag = false;
 	bool internal_flag = false;
 
+	static void subtract_from_current_runtime_ns(int64_t time_ns);
+
 	void experimental() {
 		experimental_flag = true;
 	}
diff --git a/kernel/rtlil.cc b/kernel/rtlil.cc
index b6cb8fec5..bcb10fad2 100644
--- a/kernel/rtlil.cc
+++ b/kernel/rtlil.cc
@@ -243,8 +243,12 @@ struct IdStringCollector {
 	std::unordered_set<int> live;
 };
 
+int64_t RTLIL::OwningIdString::gc_ns;
+int RTLIL::OwningIdString::gc_count;
+
 void RTLIL::OwningIdString::collect_garbage()
 {
+	int64_t start = PerformanceTimer::query();
 #ifndef YOSYS_NO_IDS_REFCNT
 	IdStringCollector collector;
 	for (auto &[idx, design] : *RTLIL::Design::get_all_designs()) {
@@ -288,6 +292,10 @@ void RTLIL::OwningIdString::collect_garbage()
 		it = global_autoidx_id_prefix_storage_.erase(it);
 	}
 #endif
+	int64_t time_ns = PerformanceTimer::query() - start;
+	Pass::subtract_from_current_runtime_ns(time_ns);
+	gc_ns += time_ns;
+	++gc_count;
 }
 
 dict<std::string, std::string> RTLIL::constpad;
diff --git a/kernel/rtlil.h b/kernel/rtlil.h
index 1d07b6296..ff98ee500 100644
--- a/kernel/rtlil.h
+++ b/kernel/rtlil.h
@@ -578,6 +578,8 @@ struct RTLIL::OwningIdString : public RTLIL::IdString {
 
 	// Collect all non-owning references.
 	static void collect_garbage();
+	static int64_t garbage_collection_ns() { return gc_ns; }
+	static int garbage_collection_count() { return gc_count; }
 
 	// Used by the ID() macro to create an IdString with no destructor whose string will
 	// never be released. If ID() creates a closure-static `OwningIdString` then
@@ -589,6 +591,9 @@ struct RTLIL::OwningIdString : public RTLIL::IdString {
 		return result;
 	}
 private:
+	static int64_t gc_ns;
+	static int gc_count;
+
 	void get_reference()
 	{
 		get_reference(index_);