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/mjit_compile.c b/mjit_compile.c
index 27ea836ef4..bf5143f6ed 100644
--- a/mjit_compile.c
+++ b/mjit_compile.c
@@ -87,7 +87,7 @@ has_valid_method_type(CALL_CACHE cc)
 {
     extern bool mjit_valid_class_serial_p(rb_serial_t class_serial);
     return GET_GLOBAL_METHOD_STATE() == cc->method_state
-        && mjit_valid_class_serial_p(cc->class_serial) && cc->me;
+        && mjit_valid_class_serial_p(cc->class_serial[0]) && cc->me;
 }
 
 // Returns true if iseq can use fastpath for setup, otherwise NULL. This becomes true in the same condition