From 8db30094fce210cd193b571d7c4b7e5702ed1ca9 Mon Sep 17 00:00:00 2001
From: Alan Wu <XrXr@users.noreply.github.com>
Date: Fri, 31 Oct 2025 18:58:21 -0400
Subject: ZJIT: Fix incorrect elision of call to BasicObject#!=

rb_obj_not_equal() uses rb_funcall(), so it's not `no_gc`, `leaf`, nor
`elidable`.
---
 zjit/src/cruby_methods.rs |  2 +-
 zjit/src/hir/opt_tests.rs | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/zjit/src/cruby_methods.rs b/zjit/src/cruby_methods.rs
index bd3409ff07..0af3be1819 100644
--- a/zjit/src/cruby_methods.rs
+++ b/zjit/src/cruby_methods.rs
@@ -221,7 +221,7 @@ pub fn init() -> Annotations {
     annotate!(rb_mKernel, "respond_to?", inline_kernel_respond_to_p);
     annotate!(rb_cBasicObject, "==", inline_basic_object_eq, types::BoolExact, no_gc, leaf, elidable);
     annotate!(rb_cBasicObject, "!", types::BoolExact, no_gc, leaf, elidable);
-    annotate!(rb_cBasicObject, "!=", inline_basic_object_neq, types::BoolExact, no_gc, leaf, elidable);
+    annotate!(rb_cBasicObject, "!=", inline_basic_object_neq, types::BoolExact);
     annotate!(rb_cBasicObject, "initialize", inline_basic_object_initialize);
     annotate!(rb_cInteger, "succ", inline_integer_succ);
     annotate!(rb_cInteger, "^", inline_integer_xor);
diff --git a/zjit/src/hir/opt_tests.rs b/zjit/src/hir/opt_tests.rs
index 8a9acb59bb..d0b3203ac1 100644
--- a/zjit/src/hir/opt_tests.rs
+++ b/zjit/src/hir/opt_tests.rs
@@ -502,6 +502,52 @@ mod hir_opt_tests {
         ");
     }
 
+    #[test]
+    fn neq_with_side_effect_not_elided () {
+        let result = eval("
+            class CustomEq
+              attr_reader :count
+
+              def ==(o)
+                @count = @count.to_i + 1
+                self.equal?(o)
+              end
+            end
+
+            def test(object)
+              # intentionally unused, but also can't assign to underscore
+              object != object
+              nil
+            end
+
+            custom = CustomEq.new
+            test(custom)
+            test(custom)
+
+            custom.count
+        ");
+        assert_eq!(VALUE::fixnum_from_usize(2), result);
+        assert_snapshot!(hir_string("test"), @r"
+        fn test@<compiled>:13:
+        bb0():
+          EntryPoint interpreter
+          v1:BasicObject = LoadSelf
+          v2:BasicObject = GetLocal l0, SP@4
+          Jump bb2(v1, v2)
+        bb1(v5:BasicObject, v6:BasicObject):
+          EntryPoint JIT(0)
+          Jump bb2(v5, v6)
+        bb2(v8:BasicObject, v9:BasicObject):
+          PatchPoint MethodRedefined(CustomEq@0x1000, !=@0x1008, cme:0x1010)
+          PatchPoint NoSingletonClass(CustomEq@0x1000)
+          v28:HeapObject[class_exact:CustomEq] = GuardType v9, HeapObject[class_exact:CustomEq]
+          v29:BoolExact = CCallWithFrame !=@0x1038, v28, v9
+          v19:NilClass = Const Value(nil)
+          CheckInterrupts
+          Return v19
+        ");
+    }
+
     #[test]
     fn test_replace_guard_if_known_fixnum() {
         eval("
-- 
cgit v1.2.3