Support tracing of attr_reader and attr_writer

In vm_call_method_each_type, check for c_call and c_return events before
dispatching to vm_call_ivar and vm_call_attrset.  With this approach, the
call cache will still dispatch directly to those functions, so this
change will only decrease performance for the first (uncached) call, and
even then, the performance decrease is very minimal.

This approach requires that we clear the call caches when tracing is
enabled or disabled.  The approach currently switches all vm_call_ivar
and vm_call_attrset call caches to vm_call_general any time tracing is
enabled or disabled. So it could theoretically result in a slowdown for
code that constantly enables or disables tracing.

This approach does not handle targeted tracepoints, but from my testing,
c_call and c_return events are not supported for targeted tracepoints,
so that shouldn't matter.

This includes a benchmark showing the performance decrease is minimal
if detectable at all.

Fixes [Bug #16383]
Fixes [Bug #10470]

Co-authored-by: Takashi Kokubun <takashikkbn@gmail.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/iseq.c b/iseq.c
index b08f1bb497..3dd7beaf0d 100644
--- a/iseq.c
+++ b/iseq.c
@@ -3407,6 +3407,32 @@ rb_iseq_trace_set(const rb_iseq_t *iseq, rb_event_flag_t turnon_events)
     }
 }
 
+bool rb_vm_call_ivar_attrset_p(const vm_call_handler ch);
+void rb_vm_cc_general(const struct rb_callcache *cc);
+
+static int
+clear_attr_ccs_i(void *vstart, void *vend, size_t stride, void *data)
+{
+    VALUE v = (VALUE)vstart;
+    for (; v != (VALUE)vend; v += stride) {
+        void *ptr = asan_poisoned_object_p(v);
+        asan_unpoison_object(v, false);
+
+        if (imemo_type_p(v, imemo_callcache) && rb_vm_call_ivar_attrset_p(((const struct rb_callcache *)v)->call_)) {
+            rb_vm_cc_general((struct rb_callcache *)v);
+        }
+
+        asan_poison_object_if(ptr, v);
+    }
+    return 0;
+}
+
+void
+rb_clear_attr_ccs(void)
+{
+    rb_objspace_each_objects(clear_attr_ccs_i, NULL);
+}
+
 static int
 trace_set_i(void *vstart, void *vend, size_t stride, void *data)
 {
@@ -3420,6 +3446,9 @@ trace_set_i(void *vstart, void *vend, size_t stride, void *data)
 	if (rb_obj_is_iseq(v)) {
 	    rb_iseq_trace_set(rb_iseq_check((rb_iseq_t *)v), turnon_events);
 	}
+        else if (imemo_type_p(v, imemo_callcache) && rb_vm_call_ivar_attrset_p(((const struct rb_callcache *)v)->call_)) {
+            rb_vm_cc_general((struct rb_callcache *)v);
+        }
 
         asan_poison_object_if(ptr, v);
     }