Optimize away call data refs in JIT-ed method calls

According to ko1, `cd->cc != cc` was for GC.compact guard.
As we pin cc by rb_gc_mark(), we don't need the check.

```
$ benchmark-driver benchmark.yml -v --rbenv 'before --jit;after --jit' --repeat-count=12 --output=all
before --jit: ruby 2.8.0dev (2020-03-11T05:36:48Z master da69487) +JIT [x86_64-linux]
after --jit: ruby 2.8.0dev (2020-03-11T06:26:34Z master 36b20b8b4a) +JIT [x86_64-linux]
Calculating -------------------------------------
                                 before --jit           after --jit
Optcarrot Lan_Master.nes    74.03480698689405     71.63404803273507 fps
                            74.15085286586992     73.43923328104295
                            75.51738277744781     75.75465268365384
                            76.24922600109410     76.74071607861318
                            76.45513422802325     77.47521029238116
                            76.86617230739330     78.14759496269018
                            77.71509137131933     79.14051571125866
                            77.72839157096146     79.35884822673313
                            78.25218904561633     79.92538876408051
                            78.72521071333249     79.98075556706726
                            78.79950460165091     80.51747831497875
                            79.43884960720381     80.97973166525254
```

iseq.c

@@ -364,7 +364,8 @@ 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) {
-                    rb_gc_mark((VALUE)cc); // pindown
+                    // Pin cc against GC.compact as the the address may be written in JIT-ed code.
+                    rb_gc_mark((VALUE)cc);
                 }
             }
         }

tool/ruby_vm/views/_mjit_compile_send.erb

@@ -38,9 +38,8 @@
             }
 
 % # JIT: Invalidate call cache if it requires vm_search_method. This allows to inline some of following things.
-            fprintf(f, "    const struct rb_call_data *cd = (const struct rb_callcache *)0x%"PRIxVALUE";\n", (VALUE)cd);
             fprintf(f, "    const struct rb_callcache *cc = (const struct rb_callcache *)0x%"PRIxVALUE";\n", (VALUE)captured_cc);
-            fprintf(f, "    if (UNLIKELY(cd->cc != cc || !vm_cc_valid_p(cc, CLASS_OF(stack[%d])))) {\n", b->stack_size - 1 - argc);
+            fprintf(f, "    if (UNLIKELY(!vm_cc_valid_p(cc, 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");
@@ -63,7 +62,7 @@
                 fprintf(f, "    {\n");
                 fprintf(f, "        struct rb_calling_info calling;\n");
 % if insn.name == 'send'
-                fprintf(f, "        calling.block_handler = vm_caller_setup_arg_block(ec, reg_cfp, cd->ci, (rb_iseq_t *)0x%"PRIxVALUE", FALSE);\n", (VALUE)blockiseq);
+                fprintf(f, "        calling.block_handler = vm_caller_setup_arg_block(ec, reg_cfp, (const struct rb_callinfo *)0x%"PRIxVALUE", (rb_iseq_t *)0x%"PRIxVALUE", FALSE);\n", (VALUE)ci, (VALUE)blockiseq);
 % else
                 fprintf(f, "        calling.block_handler = VM_BLOCK_HANDLER_NONE;\n");
 % end