Pin and inline cme in JIT-ed method calls

```
$ benchmark-driver benchmark.yml -v --rbenv 'before --jit;after --jit' --repeat-count=12 --output=all
before --jit: ruby 2.8.0dev (2020-03-11T07:43:12Z master e89ebdcb87) +JIT [x86_64-linux]
after --jit: ruby 2.8.0dev (2020-03-11T07:54:18Z master 143776a0da) +JIT [x86_64-linux]
Calculating -------------------------------------
                                 before --jit           after --jit
Optcarrot Lan_Master.nes    73.86976729561439     77.20184819316513 fps
                            74.46997176460742     78.43493030231805
                            77.59686308754307     78.55714131655935
                            78.53693921126656     79.08984255596820
                            80.10158944910573     79.17751731838183
                            80.12254974411167     79.60853122429181
                            80.28678655204945     79.74674066871896
                            80.38690681095379     79.90624544440300
                            80.79223498756919     80.57881084206193
                            80.82857188422419     80.70677614429169
                            81.06447745878245     81.03868541295149
                            81.21620802278490     82.16354660940607
```

iseq.c

@@ -364,8 +364,9 @@ rb_iseq_mark(const rb_iseq_t *iseq)
             for (unsigned int i=0; i<body->ci_size; i++) {
                 const struct rb_callcache *cc = cc_entries[i];
                 if (cc != NULL) {
-                    // Pin cc against GC.compact as the the address may be written in JIT-ed code.
+                    // Pin `cc` and `cc->cme` against GC.compact as their addresses may be written in JIT-ed code.
                     rb_gc_mark((VALUE)cc);
+                    rb_gc_mark((VALUE)vm_cc_cme(cc));
                 }
             }
         }

tool/ruby_vm/views/_mjit_compile_send.erb

@@ -39,7 +39,8 @@
 
 % # JIT: Invalidate call cache if it requires vm_search_method. This allows to inline some of following things.
             fprintf(f, "    const struct rb_callcache *cc = (const struct rb_callcache *)0x%"PRIxVALUE";\n", (VALUE)captured_cc);
-            fprintf(f, "    if (UNLIKELY(!vm_cc_valid_p(cc, CLASS_OF(stack[%d])))) {\n", b->stack_size - 1 - argc);
+            fprintf(f, "    const rb_callable_method_entry_t *cc_cme = (const rb_callable_method_entry_t *)0x%"PRIxVALUE";\n", (VALUE)vm_cc_cme(captured_cc));
+            fprintf(f, "    if (UNLIKELY(!vm_cc_valid_p(cc, cc_cme, CLASS_OF(stack[%d])))) {\n", b->stack_size - 1 - argc);
             fprintf(f, "        reg_cfp->pc = original_body_iseq + %d;\n", pos);
             fprintf(f, "        reg_cfp->sp = vm_base_ptr(reg_cfp) + %d;\n", b->stack_size);
             fprintf(f, "        goto send_cancel;\n");
@@ -72,7 +73,7 @@
 % # JIT: Special CALL_METHOD. Bypass captured_cc->call and inline vm_call_iseq_setup_normal for vm_call_iseq_setup_func FASTPATH.
                 fprintf(f, "        {\n");
                 fprintf(f, "            VALUE v;\n");
-                fprintf(f, "            vm_call_iseq_setup_normal(ec, reg_cfp, &calling, vm_cc_cme(cc), 0, %d, %d);\n",
+                fprintf(f, "            vm_call_iseq_setup_normal(ec, reg_cfp, &calling, cc_cme, 0, %d, %d);\n",
                            param_size, iseq->body->local_table_size); // fastpath_applied_iseq_p checks rb_simple_iseq_p, which ensures has_opt == FALSE
                 if (iseq->body->catch_except_p) {
                     fprintf(f, "            VM_ENV_FLAGS_SET(ec->cfp->ep, VM_FRAME_FLAG_FINISH);\n");

vm_callinfo.h

@@ -316,11 +316,12 @@ vm_cc_markable(const struct rb_callcache *cc)
     return FL_TEST_RAW(cc, VM_CALLCACHE_UNMARKABLE) == 0;
 }
 
+// For MJIT. cc_cme is supposed to have inlined `vm_cc_cme(cc)`.
 static inline bool
-vm_cc_valid_p(const struct rb_callcache *cc, VALUE klass)
+vm_cc_valid_p(const struct rb_callcache *cc, const rb_callable_method_entry_t *cc_cme, VALUE klass)
 {
     VM_ASSERT(IMEMO_TYPE_P(cc, imemo_callcache));
-    if (cc->klass == klass && !METHOD_ENTRY_INVALIDATED(vm_cc_cme(cc))) {
+    if (cc->klass == klass && !METHOD_ENTRY_INVALIDATED(cc_cme)) {
         return 1;
     }
     else {