delete unnecessary branch

At last, not only myself but also your compiler are fully confident
that the method entries pointed from call caches are immutable.  We
don't have to worry about silent updates.  Just delete the branch
that is now always false.

Calculating -------------------------------------
                           ours       trunk
vm2_poly_same_method     2.142M      2.070M i/s -      6.000M times in 2.801148s 2.898994s

Comparison:
             vm2_poly_same_method
                ours:   2141979.2 i/s
               trunk:   2069683.8 i/s - 1.03x  slower

3 files changed, 1 insertions, 7 deletions

diff --git a/insns.def b/insns.def
index f365106e2c..e3edc5e29f 100644
--- a/insns.def
+++ b/insns.def
@@ -911,7 +911,7 @@ invokeblock
 // attr rb_snum_t sp_inc = sp_inc_of_invokeblock(ci);
 {
     static struct rb_call_cache cc = {
-        0, 0, NULL, NULL, vm_invokeblock_i,
+        0, 0, NULL, vm_invokeblock_i,
     };
 
     VALUE bh = VM_BLOCK_HANDLER_NONE;
diff --git a/internal.h b/internal.h
index 2346703d68..dee7775d95 100644
--- a/internal.h
+++ b/internal.h
@@ -2330,7 +2330,6 @@ enum method_missing_reason {
     MISSING_NONE      = 0x40
 };
 struct rb_callable_method_entry_struct;
-struct rb_method_definition_struct;
 struct rb_execution_context_struct;
 struct rb_control_frame_struct;
 struct rb_calling_info;
@@ -2342,7 +2341,6 @@ struct rb_call_cache {
 
     /* inline cache: values */
     const struct rb_callable_method_entry_struct *me;
-    const struct rb_method_definition_struct *def;
 
     VALUE (*call)(struct rb_execution_context_struct *ec,
                   struct rb_control_frame_struct *cfp,
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index 197e100607..545fba2dfe 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -1386,9 +1386,6 @@ calccall(const struct rb_call_info *ci, const struct rb_call_cache *cc, const rb
     else if (LIKELY(cc->me != me)) {
         return vm_call_general; /* normal cases */
     }
-    else if (UNLIKELY(cc->def != me->def)) {
-        return vm_call_general;  /* cc->me was refined elsewhere */
-    }
     /* "Calling a formerly-public method, which is now privatised, with an
      * explicit receiver" is the only situation we have to check here.  A
      * formerly-private method now publicised is an absolutely safe thing.
@@ -1411,7 +1408,6 @@ rb_vm_search_method_slowpath(const struct rb_call_info *ci, struct rb_call_cache
         GET_GLOBAL_METHOD_STATE(),
         RCLASS_SERIAL(klass),
         me,
-        me ? me->def : NULL,
         calccall(ci, cc, me),
     };
     VM_ASSERT(callable_method_entry_p(cc->me));