Fix MJIT's ISEQ_BODY macro usage at 5f10bd6

Author: k0kubun

mjit_compile.c

@@ -370,7 +370,7 @@ mjit_compile_body(FILE *f, const rb_iseq_t *iseq, struct compile_status *status)
     if (body->param.flags.has_opt) {
         int i;
         fprintf(f, "\n");
-        fprintf(f, "    switch (reg_cfp->pc - reg_cfp->ISEQ_BODY(iseq)->iseq_encoded) {\n");
+        fprintf(f, "    switch (reg_cfp->pc - ISEQ_BODY(reg_cfp->iseq)->iseq_encoded) {\n");
         for (i = 0; i <= body->param.opt_num; i++) {
             VALUE pc_offset = body->param.opt_table[i];
             fprintf(f, "      case %"PRIdVALUE":\n", pc_offset);

test/ruby/test_mjit.rb

@@ -621,6 +621,16 @@ def test_compile_insn_checkmatch
     end;
   end
 
+  def test_compile_opt_pc
+    assert_eval_with_jit("#{<<~"begin;"}\n#{<<~"end;"}", stdout: 'hello', success_count: 1)
+    begin;
+      def test(arg = 'hello')
+        print arg
+      end
+      test
+    end;
+  end
+
   def test_mjit_output
     out, err = eval_with_jit('5.times { puts "MJIT" }', verbose: 1, min_calls: 5)
     assert_equal("MJIT\n" * 5, out)