extend rb_call_cache

Prior to this changeset, majority of inline cache mishits resulted
into the same method entry when rb_callable_method_entry() resolves
a method search.  Let's not call the function at the first place on
such situations.

In doing so we extend the struct rb_call_cache from 44 bytes (in
case of 64 bit machine) to 64 bytes, and fill the gap with
secondary class serial(s).  Call cache's class serials now behavies
as a LRU cache.

Calculating -------------------------------------
                           ours         2.7         2.6
vm2_poly_same_method     2.339M      1.744M      1.369M i/s - 6.000M times in 2.565086s 3.441329s 4.381386s

Comparison:
             vm2_poly_same_method
                ours:   2339103.0 i/s
                 2.7:   1743512.3 i/s - 1.34x  slower
                 2.6:   1369429.8 i/s - 1.71x  slower

1 files changed, 1 insertions, 1 deletions

diff --git a/vm_eval.c b/vm_eval.c
index 230b96b115..4c73d7337e 100644
--- a/vm_eval.c
+++ b/vm_eval.c
@@ -47,7 +47,7 @@ rb_vm_call0(rb_execution_context_t *ec, VALUE recv, ID id, int argc, const VALUE
 {
     struct rb_calling_info calling = { Qundef, recv, argc, kw_splat, };
     struct rb_call_info ci = { id, (kw_splat ? VM_CALL_KW_SPLAT : 0), argc, };
-    struct rb_call_cache cc = { 0, 0, me, me->def, vm_call_general, { 0, }, };
+    struct rb_call_cache cc = { 0, { 0, }, me, me->def, vm_call_general, { 0, }, };
     struct rb_call_data cd = { cc, ci, };
     return vm_call0_body(ec, &calling, &cd, argv);
 }