From 2c90da465a7ff601007b324f5ab4959ef6277a89 Mon Sep 17 00:00:00 2001
From: Max Bernstein <ruby@bernsteinbear.com>
Date: Tue, 28 Oct 2025 10:36:37 -0400
Subject: ZJIT: Count GuardType instructions

We can measure how many we can remove by adding type information to C
functions, etc.
---
 zjit.rb             | 2 ++
 zjit/src/codegen.rs | 1 +
 zjit/src/stats.rs   | 3 +++
 3 files changed, 6 insertions(+)

diff --git a/zjit.rb b/zjit.rb
index 9ea83fe10f..b62d8e2b52 100644
--- a/zjit.rb
+++ b/zjit.rb
@@ -197,6 +197,8 @@ class << RubyVM::ZJIT
       :vm_write_to_parent_iseq_local_count,
       :vm_read_from_parent_iseq_local_count,
 
+      :guard_type_count,
+
       :code_region_bytes,
       :side_exit_count,
       :total_insn_count,
diff --git a/zjit/src/codegen.rs b/zjit/src/codegen.rs
index bfbc8e88b9..2b71be0e15 100644
--- a/zjit/src/codegen.rs
+++ b/zjit/src/codegen.rs
@@ -1595,6 +1595,7 @@ fn gen_test(asm: &mut Assembler, val: lir::Opnd) -> lir::Opnd {
 
 /// Compile a type check with a side exit
 fn gen_guard_type(jit: &mut JITState, asm: &mut Assembler, val: lir::Opnd, guard_type: Type, state: &FrameState) -> lir::Opnd {
+    gen_incr_counter(asm, Counter::guard_type_count);
     if guard_type.is_subtype(types::Fixnum) {
         asm.test(val, Opnd::UImm(RUBY_FIXNUM_FLAG as u64));
         asm.jz(side_exit(jit, state, GuardType(guard_type)));
diff --git a/zjit/src/stats.rs b/zjit/src/stats.rs
index 5ab81f9ac6..4874d0fe64 100644
--- a/zjit/src/stats.rs
+++ b/zjit/src/stats.rs
@@ -249,6 +249,9 @@ make_counters! {
     vm_read_from_parent_iseq_local_count,
     // TODO(max): Implement
     // vm_reify_stack_count,
+
+    // The number of times we ran a dynamic check
+    guard_type_count,
 }
 
 /// Increase a counter by a specified amount
-- 
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