From 2ed5a02fcca4da4acf4c8c3d7ee4c392fc18d948 Mon Sep 17 00:00:00 2001
From: Stan Lo <stan.lo@shopify.com>
Date: Thu, 2 Oct 2025 17:03:25 +0100
Subject: ZJIT: Add `NoSingletonClass` patch point (#14680)

* ZJIT: Add NoSingletonClass patch point

This patch point makes sure that when the object has a singleton class,
the JIT code is invalidated. As of now, this is only needed for C call
optimization.

In YJIT, the singleton class guard only applies to Array, Hash, and String.
But in ZJIT, we may optimize C calls from gems (e.g. `sqlite3`). So the
patch point needs to be applied to a broader range of classes.

* ZJIT: Only generate NoSingletonClass guard when the type can have singleton class

* ZJIT: Update or forget NoSingletonClass patch point when needed
---
 test/ruby/test_zjit.rb | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)

(limited to 'test/ruby')

diff --git a/test/ruby/test_zjit.rb b/test/ruby/test_zjit.rb
index 937cf44e19..83af7347d6 100644
--- a/test/ruby/test_zjit.rb
+++ b/test/ruby/test_zjit.rb
@@ -2912,6 +2912,65 @@ class TestZJIT < Test::Unit::TestCase
     }, call_threshold: 2, insns: [:opt_new]
   end
 
+  def test_singleton_class_invalidation_annotated_ccall
+    assert_compiles '[false, true]', %q{
+      def define_singleton(obj, define)
+        if define
+          # Wrap in C method frame to avoid exiting JIT on defineclass
+          [nil].reverse_each do
+            class << obj
+              def ==(_)
+                true
+              end
+            end
+          end
+        end
+        false
+      end
+
+      def test(define)
+        obj = BasicObject.new
+        # This == call gets compiled to a CCall
+        obj == define_singleton(obj, define)
+      end
+
+      result = []
+      result << test(false)  # Compiles BasicObject#==
+      result << test(true)   # Should use singleton#== now
+      result
+    }, call_threshold: 2
+  end
+
+  def test_singleton_class_invalidation_optimized_variadic_ccall
+    assert_compiles '[1, 1000]', %q{
+      def define_singleton(arr, define)
+        if define
+          # Wrap in C method frame to avoid exiting JIT on defineclass
+          [nil].reverse_each do
+            class << arr
+              def push(x)
+                super(x * 1000)
+              end
+            end
+          end
+        end
+        1
+      end
+
+      def test(define)
+        arr = []
+        val = define_singleton(arr, define)
+        arr.push(val)  # This CCall should be invalidated if singleton was defined
+        arr[0]
+      end
+
+      result = []
+      result << test(false)  # Compiles Array#push as CCall
+      result << test(true)   # Singleton defined, CCall should be invalidated
+      result
+    }, call_threshold: 2
+  end
+
   private
 
   # Assert that every method call in `test_script` can be compiled by ZJIT
-- 
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