optimized-String#freeze.diff

diff --git a/compile.c b/compile.c
index 2285d28..02044f3 100644
--- a/compile.c
+++ b/compile.c
@@ -4311,6 +4311,13 @@ iseq_compile_each(rb_iseq_t *iseq, LINK_ANCHOR *ret, NODE * node, int poped)
   break;
       }
       case NODE_CALL:
+	if (nd_type(node->nd_recv) == NODE_STR && node->nd_mid == idFreeze && node->nd_args == NULL) {
+	    ADD_INSN1(ret, line, opt_str_freeze, rb_fstring(node->nd_recv->nd_lit));
+	    if (poped) {
+		ADD_INSN(ret, line, pop);
+	    }
+	    break;
+	}
       case NODE_FCALL:
       case NODE_VCALL:{		/* VCALL: variable or call */
 	/*
diff --git a/defs/id.def b/defs/id.def
index 57c0ae9..53ed377 100644
--- a/defs/id.def
+++ b/defs/id.def
@@ -1,5 +1,6 @@
 # -*- mode: ruby; coding: us-ascii -*-
 firstline, predefined = __LINE__+1, %[\
+  freeze
   inspect
   intern
   object_id
diff --git a/insns.def b/insns.def
index 740ff5d..e8deedb 100644
--- a/insns.def
+++ b/insns.def
@@ -1002,6 +1002,20 @@ send
     CALL_METHOD(ci);
 }
 
+DEFINE_INSN
+opt_str_freeze
+(VALUE str)
+()
+(VALUE val)
+{
+    if (BASIC_OP_UNREDEFINED_P(BOP_FREEZE, STRING_REDEFINED_OP_FLAG)) {
+	val = str;
+    }
+    else {
+	val = rb_funcall(rb_str_resurrect(str), idFreeze, 0);
+    }
+}
+
 /**
   @c optimize
   @e Invoke method without block, splat
diff --git a/string.c b/string.c
index 7bf4006..be1cee7 100644
--- a/string.c
+++ b/string.c
@@ -8738,6 +8738,7 @@ Init_String(void)
     rb_define_method(rb_cString, "byteslice", rb_str_byteslice, -1);
     rb_define_method(rb_cString, "scrub", rb_str_scrub, -1);
     rb_define_method(rb_cString, "scrub!", str_scrub_bang, -1);
+    rb_define_method(rb_cString, "freeze", rb_obj_freeze, 0);
 
     rb_define_method(rb_cString, "to_i", rb_str_to_i, -1);
     rb_define_method(rb_cString, "to_f", rb_str_to_f, 0);
diff --git a/vm.c b/vm.c
index a43f3d6..62bb89b 100644
--- a/vm.c
+++ b/vm.c
@@ -1096,6 +1096,7 @@ vm_init_redefined_flag(void)
     OP(EmptyP, EMPTY_P), (C(Array), C(String), C(Hash));
     OP(Succ, SUCC), (C(Fixnum), C(String), C(Time));
     OP(EqTilde, MATCH), (C(Regexp), C(String));
+    OP(Freeze, FREEZE), (C(String));
 #undef C
 #undef OP
 }
diff --git a/vm_insnhelper.h b/vm_insnhelper.h
index 73e88e5..8978ea0 100644
--- a/vm_insnhelper.h
+++ b/vm_insnhelper.h
@@ -56,6 +56,7 @@ enum {
   BOP_NOT,
   BOP_NEQ,
   BOP_MATCH,
+  BOP_FREEZE,
 
   BOP_LAST_
 };

poped my favorite typo!

I think it is a religious reference :)