diff --git a/ChangeLog b/ChangeLog
index 38dec62e52..05038f5a43 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,16 @@
+Wed Sep 26 16:39:57 2012  Koichi Sasada  <ko1@atdot.net>
+
+	* insns.def: add new instruction `opt_empty_p' for optimize `empty?'
+	  method.  Apply a patch proposed at [ruby-dev:46120]
+	  [ruby-trunk - Feature #6972] by Glass_saga (Masaki Matsushita).
+
+	* compile.c (iseq_specialized_instruction), vm.c, vm_insnhelper.h:
+	  ditto.
+
+	* id.c, template/id.h.tmpl: ditto.
+
+	* test/ruby/test_optimization.rb: test for this changes.
+
 Tue Sep 25 09:59:26 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* insns.def (invokesuper): klass in cfp is not valid in at_exit and
diff --git a/compile.c b/compile.c
index 2f8cbb51cd..368e3cf6db 100644
--- a/compile.c
+++ b/compile.c
@@ -1872,6 +1872,7 @@ iseq_specialized_instruction(rb_iseq_t *iseq, INSN *iobj)
 		switch (mid) {
 		  case idLength: SP_INSN(length); break;
 		  case idSize:	 SP_INSN(size);	  break;
+		  case idEmptyP: SP_INSN(empty_p);break;
 		  case idSucc:	 SP_INSN(succ);	  break;
 		  case idNot:	 SP_INSN(not);	  break;
 		}
diff --git a/id.c b/id.c
index e5f971d3e2..b6143971a1 100644
--- a/id.c
+++ b/id.c
@@ -41,6 +41,7 @@ Init_id(void)
     REGISTER_SYMID(idEach, "each");
     REGISTER_SYMID(idLength, "length");
     REGISTER_SYMID(idSize, "size");
+    REGISTER_SYMID(idEmptyP, "empty?");
     REGISTER_SYMID(idLambda, "lambda");
     REGISTER_SYMID(idIntern, "intern");
     REGISTER_SYMID(idGets, "gets");
diff --git a/insns.def b/insns.def
index a1b8756d17..1dc4328d72 100644
--- a/insns.def
+++ b/insns.def
@@ -1992,6 +1992,44 @@ opt_size
     }
 }
 
+/**
+  @c optimize
+  @e optimized empty?
+  @j 最適化された recv.empty?()。
+ */
+DEFINE_INSN
+opt_empty_p
+(IC ic)
+(VALUE recv)
+(VALUE val)
+{
+    if (!SPECIAL_CONST_P(recv)) {
+	if (HEAP_CLASS_OF(recv) == rb_cString &&
+	    BASIC_OP_UNREDEFINED_P(BOP_EMPTY_P, STRING_REDEFINED_OP_FLAG)) {
+	    if (RSTRING_LEN(recv) == 0) val = Qtrue;
+	    else val = Qfalse;
+	}
+	else if (HEAP_CLASS_OF(recv) == rb_cArray &&
+		 BASIC_OP_UNREDEFINED_P(BOP_EMPTY_P, ARRAY_REDEFINED_OP_FLAG)) {
+	    if (RARRAY_LEN(recv) == 0) val = Qtrue;
+	    else val = Qfalse;
+	}
+	else if (HEAP_CLASS_OF(recv) == rb_cHash &&
+		 BASIC_OP_UNREDEFINED_P(BOP_EMPTY_P, HASH_REDEFINED_OP_FLAG)) {
+	    if (RHASH_EMPTY_P(recv)) val = Qtrue;
+	    else val = Qfalse;
+	}
+	else {
+	    goto INSN_LABEL(normal_dispatch);
+	}
+    }
+    else {
+      INSN_LABEL(normal_dispatch):
+	PUSH(recv);
+	CALL_SIMPLE_METHOD(0, idEmptyP, recv);
+    }
+}
+
 /**
   @c optimize
   @e optimized succ
diff --git a/template/id.h.tmpl b/template/id.h.tmpl
index 0e54e762f4..f7e764c123 100644
--- a/template/id.h.tmpl
+++ b/template/id.h.tmpl
@@ -20,6 +20,7 @@ method_ids = %w[
   MethodMissing
   Length
   Size
+  EmptyP
   Gets
   Succ
   Each
diff --git a/test/ruby/test_optimization.rb b/test/ruby/test_optimization.rb
index 1b0c730996..a3b4aedcdc 100644
--- a/test/ruby/test_optimization.rb
+++ b/test/ruby/test_optimization.rb
@@ -85,6 +85,14 @@ class TestRubyOptimization < Test::Unit::TestCase
     assert_equal 6, "string".length
   end
 
+  def test_string_empty?
+    assert_equal true, "".empty?
+    assert_equal false, "string".empty?
+    assert_nil redefine_method('String', 'empty?') { "string".empty? }
+    assert_equal true, "".empty?
+    assert_equal false, "string".empty?
+  end
+
   def test_string_plus
     assert_equal "", "" + ""
     assert_equal "x", "x" + ""
@@ -116,11 +124,21 @@ class TestRubyOptimization < Test::Unit::TestCase
     assert_equal 3, [1,2,3].length
   end
 
+  def test_array_empty?
+    assert_equal true, [].empty?
+    assert_equal false, [1,2,3].empty?
+  end
+
   def test_hash_length
     assert_equal 0, {}.length
     assert_equal 1, {1=>1}.length
   end
 
+  def test_hash_empty?
+    assert_equal true, {}.empty?
+    assert_equal false, {1=>1}.empty?
+  end
+
   class MyObj
     def ==(other)
       true
diff --git a/vm.c b/vm.c
index f842a6dfba..c59ef0b895 100644
--- a/vm.c
+++ b/vm.c
@@ -1005,6 +1005,7 @@ vm_init_redefined_flag(void)
     OP(ASET, ASET), (C(Array), C(Hash));
     OP(Length, LENGTH), (C(Array), C(String), C(Hash));
     OP(Size, SIZE), (C(Array), C(String), C(Hash));
+    OP(EmptyP, EMPTY_P), (C(Array), C(String), C(Hash));
     OP(Succ, SUCC), (C(Fixnum), C(String), C(Time));
 #undef C
 #undef OP
diff --git a/vm_insnhelper.h b/vm_insnhelper.h
index 4d5f0e36b6..7c7745ae60 100644
--- a/vm_insnhelper.h
+++ b/vm_insnhelper.h
@@ -49,6 +49,7 @@ enum {
   BOP_ASET,
   BOP_LENGTH,
   BOP_SIZE,
+  BOP_EMPTY_P,
   BOP_SUCC,
   BOP_GT,
   BOP_GE,