YJIT: Fix Struct accessors not firing tracing events

Reading and writing to structs should fire `c_call` and `c_return`, but
YJIT wasn't correctly dropping those calls when tracing.
This has been missing since this functionality was added in 3081c83,
but the added test only fails when ran in isolation with
`--yjit-call-threshold=1`. The test sometimes failed on CI.

bootstraptest/test_yjit.rb

@@ -4964,3 +4964,19 @@ class NilClass
 
   results << test
 } unless rjit_enabled? # Not yet working on RJIT
+
+# test struct accessors fire c_call events
+assert_equal '[[:c_call, :x=], [:c_call, :x]]', %q{
+  c = Struct.new(:x)
+  obj = c.new
+
+  events = []
+  TracePoint.new(:c_call) do
+    events << [_1.event, _1.method_id]
+  end.enable do
+    obj.x = 100
+    obj.x
+  end
+
+  events
+}

yjit/src/codegen.rs

@@ -8309,6 +8309,13 @@ fn gen_struct_aref(
         }
     }
 
+    if c_method_tracing_currently_enabled(jit) {
+        // Struct accesses need fire c_call and c_return events, which we can't support
+        // See :attr-tracing:
+        gen_counter_incr(asm, Counter::send_cfunc_tracing);
+        return None;
+    }
+
     // This is a .send call and we need to adjust the stack
     if flags & VM_CALL_OPT_SEND != 0 {
         handle_opt_send_shift_stack(asm, argc);
@@ -8353,6 +8360,13 @@ fn gen_struct_aset(
         return None;
     }
 
+    if c_method_tracing_currently_enabled(jit) {
+        // Struct accesses need fire c_call and c_return events, which we can't support
+        // See :attr-tracing:
+        gen_counter_incr(asm, Counter::send_cfunc_tracing);
+        return None;
+    }
+
     // This is a .send call and we need to adjust the stack
     if flags & VM_CALL_OPT_SEND != 0 {
         handle_opt_send_shift_stack(asm, argc);
@@ -8619,10 +8633,8 @@ fn gen_send_general(
                     // Handling the C method tracing events for attr_accessor
                     // methods is easier than regular C methods as we know the
                     // "method" we are calling into never enables those tracing
-                    // events. Once global invalidation runs, the code for the
-                    // attr_accessor is invalidated and we exit at the closest
-                    // instruction boundary which is always outside of the body of
-                    // the attr_accessor code.
+                    // events. We are never inside the code that needs to be
+                    // invalidated when invalidation happens.
                     gen_counter_incr(asm, Counter::send_cfunc_tracing);
                     return None;
                 }