diff --git a/src/arm/full-codegen-arm.cc b/src/arm/full-codegen-arm.cc
index 8ad62b0cfd..5f5de3a9f9 100644
--- a/src/arm/full-codegen-arm.cc
+++ b/src/arm/full-codegen-arm.cc
@@ -3977,71 +3977,52 @@ bool FullCodeGenerator::TryLiteralCompare(Token::Value op,
   PrepareForBailoutBeforeSplit(TOS_REG, true, if_true, if_false);
 
   if (check->Equals(Heap::number_symbol())) {
-    __ tst(r0, Operand(kSmiTagMask));
-    __ b(eq, if_true);
+    __ JumpIfSmi(r0, if_true);
     __ ldr(r0, FieldMemOperand(r0, HeapObject::kMapOffset));
     __ LoadRoot(ip, Heap::kHeapNumberMapRootIndex);
     __ cmp(r0, ip);
     Split(eq, if_true, if_false, fall_through);
   } else if (check->Equals(Heap::string_symbol())) {
-    __ tst(r0, Operand(kSmiTagMask));
-    __ b(eq, if_false);
+    __ JumpIfSmi(r0, if_false);
     // Check for undetectable objects => false.
-    __ ldr(r0, FieldMemOperand(r0, HeapObject::kMapOffset));
+    __ CompareObjectType(r0, r0, r1, FIRST_NONSTRING_TYPE);
+    __ b(ge, if_false);
     __ ldrb(r1, FieldMemOperand(r0, Map::kBitFieldOffset));
-    __ and_(r1, r1, Operand(1 << Map::kIsUndetectable));
-    __ cmp(r1, Operand(1 << Map::kIsUndetectable));
-    __ b(eq, if_false);
-    __ ldrb(r1, FieldMemOperand(r0, Map::kInstanceTypeOffset));
-    __ cmp(r1, Operand(FIRST_NONSTRING_TYPE));
-    Split(lt, if_true, if_false, fall_through);
+    __ tst(r1, Operand(1 << Map::kIsUndetectable));
+    Split(eq, if_true, if_false, fall_through);
   } else if (check->Equals(Heap::boolean_symbol())) {
-    __ LoadRoot(ip, Heap::kTrueValueRootIndex);
-    __ cmp(r0, ip);
+    __ CompareRoot(r0, Heap::kTrueValueRootIndex);
     __ b(eq, if_true);
-    __ LoadRoot(ip, Heap::kFalseValueRootIndex);
-    __ cmp(r0, ip);
+    __ CompareRoot(r0, Heap::kFalseValueRootIndex);
     Split(eq, if_true, if_false, fall_through);
   } else if (check->Equals(Heap::undefined_symbol())) {
-    __ LoadRoot(ip, Heap::kUndefinedValueRootIndex);
-    __ cmp(r0, ip);
+    __ CompareRoot(r0, Heap::kUndefinedValueRootIndex);
     __ b(eq, if_true);
-    __ tst(r0, Operand(kSmiTagMask));
-    __ b(eq, if_false);
+    __ JumpIfSmi(r0, if_false);
     // Check for undetectable objects => true.
     __ ldr(r0, FieldMemOperand(r0, HeapObject::kMapOffset));
     __ ldrb(r1, FieldMemOperand(r0, Map::kBitFieldOffset));
-    __ and_(r1, r1, Operand(1 << Map::kIsUndetectable));
-    __ cmp(r1, Operand(1 << Map::kIsUndetectable));
-    Split(eq, if_true, if_false, fall_through);
+    __ tst(r1, Operand(1 << Map::kIsUndetectable));
+    Split(ne, if_true, if_false, fall_through);
+
   } else if (check->Equals(Heap::function_symbol())) {
-    __ tst(r0, Operand(kSmiTagMask));
-    __ b(eq, if_false);
-    __ CompareObjectType(r0, r1, r0, JS_FUNCTION_TYPE);
-    __ b(eq, if_true);
-    // Regular expressions => 'function' (they are callable).
-    __ CompareInstanceType(r1, r0, JS_REGEXP_TYPE);
-    Split(eq, if_true, if_false, fall_through);
+    __ JumpIfSmi(r0, if_false);
+    __ CompareObjectType(r0, r1, r0, FIRST_FUNCTION_CLASS_TYPE);
+    Split(ge, if_true, if_false, fall_through);
+
   } else if (check->Equals(Heap::object_symbol())) {
-    __ tst(r0, Operand(kSmiTagMask));
-    __ b(eq, if_false);
-    __ LoadRoot(ip, Heap::kNullValueRootIndex);
-    __ cmp(r0, ip);
+    __ JumpIfSmi(r0, if_false);
+    __ CompareRoot(r0, Heap::kNullValueRootIndex);
     __ b(eq, if_true);
-    // Regular expressions => 'function', not 'object'.
-    __ CompareObjectType(r0, r1, r0, JS_REGEXP_TYPE);
-    __ b(eq, if_false);
-    // Check for undetectable objects => false.
-    __ ldrb(r0, FieldMemOperand(r1, Map::kBitFieldOffset));
-    __ and_(r0, r0, Operand(1 << Map::kIsUndetectable));
-    __ cmp(r0, Operand(1 << Map::kIsUndetectable));
-    __ b(eq, if_false);
     // Check for JS objects => true.
-    __ ldrb(r0, FieldMemOperand(r1, Map::kInstanceTypeOffset));
-    __ cmp(r0, Operand(FIRST_JS_OBJECT_TYPE));
-    __ b(lt, if_false);
-    __ cmp(r0, Operand(LAST_JS_OBJECT_TYPE));
-    Split(le, if_true, if_false, fall_through);
+    __ CompareObjectType(r0, r0, r1, FIRST_JS_OBJECT_TYPE);
+    __ b(lo, if_false);
+    __ CompareInstanceType(r0, r1, FIRST_FUNCTION_CLASS_TYPE);
+    __ b(hs, if_false);
+    // Check for undetectable objects => false.
+    __ ldrb(r1, FieldMemOperand(r0, Map::kBitFieldOffset));
+    __ tst(r1, Operand(1 << Map::kIsUndetectable));
+    Split(eq, if_true, if_false, fall_through);
   } else {
     if (if_false != fall_through) __ jmp(if_false);
   }
diff --git a/src/arm/lithium-codegen-arm.cc b/src/arm/lithium-codegen-arm.cc
index 9e046e74f7..ab58600bbf 100644
--- a/src/arm/lithium-codegen-arm.cc
+++ b/src/arm/lithium-codegen-arm.cc
@@ -3672,37 +3672,30 @@ Condition LCodeGen::EmitTypeofIs(Label* true_label,
   Condition final_branch_condition = kNoCondition;
   Register scratch = scratch0();
   if (type_name->Equals(Heap::number_symbol())) {
-    __ tst(input, Operand(kSmiTagMask));
-    __ b(eq, true_label);
+    __ JumpIfSmi(input, true_label);
     __ ldr(input, FieldMemOperand(input, HeapObject::kMapOffset));
     __ LoadRoot(ip, Heap::kHeapNumberMapRootIndex);
     __ cmp(input, Operand(ip));
     final_branch_condition = eq;
 
   } else if (type_name->Equals(Heap::string_symbol())) {
-    __ tst(input, Operand(kSmiTagMask));
-    __ b(eq, false_label);
-    __ ldr(input, FieldMemOperand(input, HeapObject::kMapOffset));
+    __ JumpIfSmi(input, false_label);
+    __ CompareObjectType(input, input, scratch, FIRST_NONSTRING_TYPE);
+    __ b(ge, false_label);
     __ ldrb(ip, FieldMemOperand(input, Map::kBitFieldOffset));
     __ tst(ip, Operand(1 << Map::kIsUndetectable));
-    __ b(ne, false_label);
-    __ CompareInstanceType(input, scratch, FIRST_NONSTRING_TYPE);
-    final_branch_condition = lo;
+    final_branch_condition = eq;
 
   } else if (type_name->Equals(Heap::boolean_symbol())) {
-    __ LoadRoot(ip, Heap::kTrueValueRootIndex);
-    __ cmp(input, ip);
+    __ CompareRoot(input, Heap::kTrueValueRootIndex);
     __ b(eq, true_label);
-    __ LoadRoot(ip, Heap::kFalseValueRootIndex);
-    __ cmp(input, ip);
+    __ CompareRoot(input, Heap::kFalseValueRootIndex);
     final_branch_condition = eq;
 
   } else if (type_name->Equals(Heap::undefined_symbol())) {
-    __ LoadRoot(ip, Heap::kUndefinedValueRootIndex);
-    __ cmp(input, ip);
+    __ CompareRoot(input, Heap::kUndefinedValueRootIndex);
     __ b(eq, true_label);
-    __ tst(input, Operand(kSmiTagMask));
-    __ b(eq, false_label);
+    __ JumpIfSmi(input, false_label);
     // Check for undetectable objects => true.
     __ ldr(input, FieldMemOperand(input, HeapObject::kMapOffset));
     __ ldrb(ip, FieldMemOperand(input, Map::kBitFieldOffset));
@@ -3710,32 +3703,22 @@ Condition LCodeGen::EmitTypeofIs(Label* true_label,
     final_branch_condition = ne;
 
   } else if (type_name->Equals(Heap::function_symbol())) {
-    __ tst(input, Operand(kSmiTagMask));
-    __ b(eq, false_label);
-    __ CompareObjectType(input, input, scratch, JS_FUNCTION_TYPE);
-    __ b(eq, true_label);
-    // Regular expressions => 'function' (they are callable).
-    __ CompareInstanceType(input, scratch, JS_REGEXP_TYPE);
-    final_branch_condition = eq;
+    __ JumpIfSmi(input, false_label);
+    __ CompareObjectType(input, input, scratch, FIRST_FUNCTION_CLASS_TYPE);
+    final_branch_condition = ge;
 
   } else if (type_name->Equals(Heap::object_symbol())) {
-    __ tst(input, Operand(kSmiTagMask));
-    __ b(eq, false_label);
-    __ LoadRoot(ip, Heap::kNullValueRootIndex);
-    __ cmp(input, ip);
+    __ JumpIfSmi(input, false_label);
+    __ CompareRoot(input, Heap::kNullValueRootIndex);
     __ b(eq, true_label);
-    // Regular expressions => 'function', not 'object'.
-    __ CompareObjectType(input, input, scratch, JS_REGEXP_TYPE);
-    __ b(eq, false_label);
+    __ CompareObjectType(input, input, scratch, FIRST_JS_OBJECT_TYPE);
+    __ b(lo, false_label);
+    __ CompareInstanceType(input, scratch, FIRST_FUNCTION_CLASS_TYPE);
+    __ b(hs, false_label);
     // Check for undetectable objects => false.
     __ ldrb(ip, FieldMemOperand(input, Map::kBitFieldOffset));
     __ tst(ip, Operand(1 << Map::kIsUndetectable));
-    __ b(ne, false_label);
-    // Check for JS objects => true.
-    __ CompareInstanceType(input, scratch, FIRST_JS_OBJECT_TYPE);
-    __ b(lo, false_label);
-    __ CompareInstanceType(input, scratch, LAST_JS_OBJECT_TYPE);
-    final_branch_condition = ls;
+    final_branch_condition = eq;
 
   } else {
     final_branch_condition = ne;
diff --git a/src/ia32/full-codegen-ia32.cc b/src/ia32/full-codegen-ia32.cc
index 67e0e8fac9..9a7d41ada2 100644
--- a/src/ia32/full-codegen-ia32.cc
+++ b/src/ia32/full-codegen-ia32.cc
@@ -3936,21 +3936,18 @@ bool FullCodeGenerator::TryLiteralCompare(Token::Value op,
   PrepareForBailoutBeforeSplit(TOS_REG, true, if_true, if_false);
 
   if (check->Equals(Heap::number_symbol())) {
-    __ test(eax, Immediate(kSmiTagMask));
-    __ j(zero, if_true);
+    __ JumpIfSmi(eax, if_true);
     __ cmp(FieldOperand(eax, HeapObject::kMapOffset),
            Factory::heap_number_map());
     Split(equal, if_true, if_false, fall_through);
   } else if (check->Equals(Heap::string_symbol())) {
-    __ test(eax, Immediate(kSmiTagMask));
-    __ j(zero, if_false);
+    __ JumpIfSmi(eax, if_false);
+    __ CmpObjectType(eax, FIRST_NONSTRING_TYPE, edx);
+    __ j(above_equal, if_false);
     // Check for undetectable objects => false.
-    __ mov(edx, FieldOperand(eax, HeapObject::kMapOffset));
-    __ movzx_b(ecx, FieldOperand(edx, Map::kBitFieldOffset));
-    __ test(ecx, Immediate(1 << Map::kIsUndetectable));
-    __ j(not_zero, if_false);
-    __ CmpInstanceType(edx, FIRST_NONSTRING_TYPE);
-    Split(below, if_true, if_false, fall_through);
+    __ test_b(FieldOperand(edx, Map::kBitFieldOffset),
+              1 << Map::kIsUndetectable);
+    Split(zero, if_true, if_false, fall_through);
   } else if (check->Equals(Heap::boolean_symbol())) {
     __ cmp(eax, Factory::true_value());
     __ j(equal, if_true);
@@ -3959,39 +3956,28 @@ bool FullCodeGenerator::TryLiteralCompare(Token::Value op,
   } else if (check->Equals(Heap::undefined_symbol())) {
     __ cmp(eax, Factory::undefined_value());
     __ j(equal, if_true);
-    __ test(eax, Immediate(kSmiTagMask));
-    __ j(zero, if_false);
+    __ JumpIfSmi(eax, if_false);
     // Check for undetectable objects => true.
     __ mov(edx, FieldOperand(eax, HeapObject::kMapOffset));
     __ movzx_b(ecx, FieldOperand(edx, Map::kBitFieldOffset));
     __ test(ecx, Immediate(1 << Map::kIsUndetectable));
     Split(not_zero, if_true, if_false, fall_through);
   } else if (check->Equals(Heap::function_symbol())) {
-    __ test(eax, Immediate(kSmiTagMask));
-    __ j(zero, if_false);
-    __ CmpObjectType(eax, JS_FUNCTION_TYPE, edx);
-    __ j(equal, if_true);
-    // Regular expressions => 'function' (they are callable).
-    __ CmpInstanceType(edx, JS_REGEXP_TYPE);
-    Split(equal, if_true, if_false, fall_through);
+    __ JumpIfSmi(eax, if_false);
+    __ CmpObjectType(eax, FIRST_FUNCTION_CLASS_TYPE, edx);
+    Split(above_equal, if_true, if_false, fall_through);
   } else if (check->Equals(Heap::object_symbol())) {
-    __ test(eax, Immediate(kSmiTagMask));
-    __ j(zero, if_false);
+    __ JumpIfSmi(eax, if_false);
     __ cmp(eax, Factory::null_value());
     __ j(equal, if_true);
-    // Regular expressions => 'function', not 'object'.
-    __ CmpObjectType(eax, JS_REGEXP_TYPE, edx);
-    __ j(equal, if_false);
+    __ CmpObjectType(eax, FIRST_JS_OBJECT_TYPE, edx);
+    __ j(below, if_false);
+    __ CmpInstanceType(edx, FIRST_FUNCTION_CLASS_TYPE);
+    __ j(above_equal, if_false);
     // Check for undetectable objects => false.
-    __ movzx_b(ecx, FieldOperand(edx, Map::kBitFieldOffset));
-    __ test(ecx, Immediate(1 << Map::kIsUndetectable));
-    __ j(not_zero, if_false);
-    // Check for JS objects => true.
-    __ movzx_b(ecx, FieldOperand(edx, Map::kInstanceTypeOffset));
-    __ cmp(ecx, FIRST_JS_OBJECT_TYPE);
-    __ j(less, if_false);
-    __ cmp(ecx, LAST_JS_OBJECT_TYPE);
-    Split(less_equal, if_true, if_false, fall_through);
+    __ test_b(FieldOperand(edx, Map::kBitFieldOffset),
+              1 << Map::kIsUndetectable);
+    Split(zero, if_true, if_false, fall_through);
   } else {
     if (if_false != fall_through) __ jmp(if_false);
   }
diff --git a/src/ia32/lithium-codegen-ia32.cc b/src/ia32/lithium-codegen-ia32.cc
index d84354f66c..6c34394e19 100644
--- a/src/ia32/lithium-codegen-ia32.cc
+++ b/src/ia32/lithium-codegen-ia32.cc
@@ -3702,21 +3702,18 @@ Condition LCodeGen::EmitTypeofIs(Label* true_label,
                                  Handle<String> type_name) {
   Condition final_branch_condition = no_condition;
   if (type_name->Equals(Heap::number_symbol())) {
-    __ test(input, Immediate(kSmiTagMask));
-    __ j(zero, true_label);
+    __ JumpIfSmi(input, true_label);
     __ cmp(FieldOperand(input, HeapObject::kMapOffset),
            Factory::heap_number_map());
     final_branch_condition = equal;
 
   } else if (type_name->Equals(Heap::string_symbol())) {
-    __ test(input, Immediate(kSmiTagMask));
-    __ j(zero, false_label);
-    __ mov(input, FieldOperand(input, HeapObject::kMapOffset));
+    __ JumpIfSmi(input, false_label);
+    __ CmpObjectType(input, FIRST_NONSTRING_TYPE, input);
+    __ j(above_equal, false_label);
     __ test_b(FieldOperand(input, Map::kBitFieldOffset),
               1 << Map::kIsUndetectable);
-    __ j(not_zero, false_label);
-    __ CmpInstanceType(input, FIRST_NONSTRING_TYPE);
-    final_branch_condition = below;
+    final_branch_condition = zero;
 
   } else if (type_name->Equals(Heap::boolean_symbol())) {
     __ cmp(input, Factory::true_value());
@@ -3727,8 +3724,7 @@ Condition LCodeGen::EmitTypeofIs(Label* true_label,
   } else if (type_name->Equals(Heap::undefined_symbol())) {
     __ cmp(input, Factory::undefined_value());
     __ j(equal, true_label);
-    __ test(input, Immediate(kSmiTagMask));
-    __ j(zero, false_label);
+    __ JumpIfSmi(input, false_label);
     // Check for undetectable objects => true.
     __ mov(input, FieldOperand(input, HeapObject::kMapOffset));
     __ test_b(FieldOperand(input, Map::kBitFieldOffset),
@@ -3736,8 +3732,7 @@ Condition LCodeGen::EmitTypeofIs(Label* true_label,
     final_branch_condition = not_zero;
 
   } else if (type_name->Equals(Heap::function_symbol())) {
-    __ test(input, Immediate(kSmiTagMask));
-    __ j(zero, false_label);
+    __ JumpIfSmi(input, false_label);
     __ CmpObjectType(input, JS_FUNCTION_TYPE, input);
     __ j(equal, true_label);
     // Regular expressions => 'function' (they are callable).
@@ -3745,22 +3740,18 @@ Condition LCodeGen::EmitTypeofIs(Label* true_label,
     final_branch_condition = equal;
 
   } else if (type_name->Equals(Heap::object_symbol())) {
-    __ test(input, Immediate(kSmiTagMask));
-    __ j(zero, false_label);
+    __ JumpIfSmi(input, false_label);
     __ cmp(input, Factory::null_value());
     __ j(equal, true_label);
     // Regular expressions => 'function', not 'object'.
-    __ CmpObjectType(input, JS_REGEXP_TYPE, input);
-    __ j(equal, false_label);
+    __ CmpObjectType(input, FIRST_JS_OBJECT_TYPE, input);
+    __ j(below, false_label);
+    __ CmpInstanceType(input, FIRST_FUNCTION_CLASS_TYPE);
+    __ j(above_equal, false_label);
     // Check for undetectable objects => false.
     __ test_b(FieldOperand(input, Map::kBitFieldOffset),
               1 << Map::kIsUndetectable);
-    __ j(not_zero, false_label);
-    // Check for JS objects => true.
-    __ CmpInstanceType(input, FIRST_JS_OBJECT_TYPE);
-    __ j(below, false_label);
-    __ CmpInstanceType(input, LAST_JS_OBJECT_TYPE);
-    final_branch_condition = below_equal;
+    final_branch_condition = zero;
 
   } else {
     final_branch_condition = not_equal;
diff --git a/src/x64/full-codegen-x64.cc b/src/x64/full-codegen-x64.cc
index 0ad6ec2376..780f4b027f 100644
--- a/src/x64/full-codegen-x64.cc
+++ b/src/x64/full-codegen-x64.cc
@@ -3640,21 +3640,18 @@ bool FullCodeGenerator::TryLiteralCompare(Token::Value op,
   PrepareForBailoutBeforeSplit(TOS_REG, true, if_true, if_false);
 
   if (check->Equals(Heap::number_symbol())) {
-    Condition is_smi = masm_->CheckSmi(rax);
-    __ j(is_smi, if_true);
+    __ JumpIfSmi(rax, if_true);
     __ movq(rax, FieldOperand(rax, HeapObject::kMapOffset));
     __ CompareRoot(rax, Heap::kHeapNumberMapRootIndex);
     Split(equal, if_true, if_false, fall_through);
   } else if (check->Equals(Heap::string_symbol())) {
-    Condition is_smi = masm_->CheckSmi(rax);
-    __ j(is_smi, if_false);
+    __ JumpIfSmi(rax, if_false);
     // Check for undetectable objects => false.
-    __ movq(rdx, FieldOperand(rax, HeapObject::kMapOffset));
+    __ CmpObjectType(rax, FIRST_NONSTRING_TYPE, rdx);
+    __ j(above_equal, if_false);
     __ testb(FieldOperand(rdx, Map::kBitFieldOffset),
              Immediate(1 << Map::kIsUndetectable));
-    __ j(not_zero, if_false);
-    __ CmpInstanceType(rdx, FIRST_NONSTRING_TYPE);
-    Split(below, if_true, if_false, fall_through);
+    Split(zero, if_true, if_false, fall_through);
   } else if (check->Equals(Heap::boolean_symbol())) {
     __ CompareRoot(rax, Heap::kTrueValueRootIndex);
     __ j(equal, if_true);
@@ -3663,38 +3660,28 @@ bool FullCodeGenerator::TryLiteralCompare(Token::Value op,
   } else if (check->Equals(Heap::undefined_symbol())) {
     __ CompareRoot(rax, Heap::kUndefinedValueRootIndex);
     __ j(equal, if_true);
-    Condition is_smi = masm_->CheckSmi(rax);
-    __ j(is_smi, if_false);
+    __ JumpIfSmi(rax, if_false);
     // Check for undetectable objects => true.
     __ movq(rdx, FieldOperand(rax, HeapObject::kMapOffset));
     __ testb(FieldOperand(rdx, Map::kBitFieldOffset),
              Immediate(1 << Map::kIsUndetectable));
     Split(not_zero, if_true, if_false, fall_through);
   } else if (check->Equals(Heap::function_symbol())) {
-    Condition is_smi = masm_->CheckSmi(rax);
-    __ j(is_smi, if_false);
-    __ CmpObjectType(rax, JS_FUNCTION_TYPE, rdx);
-    __ j(equal, if_true);
-    // Regular expressions => 'function' (they are callable).
-    __ CmpInstanceType(rdx, JS_REGEXP_TYPE);
-    Split(equal, if_true, if_false, fall_through);
+    __ JumpIfSmi(rax, if_false);
+    __ CmpObjectType(rax, FIRST_FUNCTION_CLASS_TYPE, rdx);
+    Split(above_equal, if_true, if_false, fall_through);
   } else if (check->Equals(Heap::object_symbol())) {
-    Condition is_smi = masm_->CheckSmi(rax);
-    __ j(is_smi, if_false);
+    __ JumpIfSmi(rax, if_false);
     __ CompareRoot(rax, Heap::kNullValueRootIndex);
     __ j(equal, if_true);
-    // Regular expressions => 'function', not 'object'.
-    __ CmpObjectType(rax, JS_REGEXP_TYPE, rdx);
-    __ j(equal, if_false);
+    __ CmpObjectType(rax, FIRST_JS_OBJECT_TYPE, rdx);
+    __ j(below, if_false);
+    __ CmpInstanceType(rdx, FIRST_FUNCTION_CLASS_TYPE);
+    __ j(above_equal, if_false);
     // Check for undetectable objects => false.
     __ testb(FieldOperand(rdx, Map::kBitFieldOffset),
              Immediate(1 << Map::kIsUndetectable));
-    __ j(not_zero, if_false);
-    // Check for JS objects => true.
-    __ CmpInstanceType(rdx, FIRST_JS_OBJECT_TYPE);
-    __ j(below, if_false);
-    __ CmpInstanceType(rdx, LAST_JS_OBJECT_TYPE);
-    Split(below_equal, if_true, if_false, fall_through);
+    Split(zero, if_true, if_false, fall_through);
   } else {
     if (if_false != fall_through) __ jmp(if_false);
   }
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 2cbab4bf05..1007784e41 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -3480,12 +3480,11 @@ Condition LCodeGen::EmitTypeofIs(Label* true_label,
 
   } else if (type_name->Equals(Heap::string_symbol())) {
     __ JumpIfSmi(input, false_label);
-    __ movq(input, FieldOperand(input, HeapObject::kMapOffset));
+    __ CmpObjectType(input, FIRST_NONSTRING_TYPE, input);
+    __ j(above_equal, false_label);
     __ testb(FieldOperand(input, Map::kBitFieldOffset),
              Immediate(1 << Map::kIsUndetectable));
-    __ j(not_zero, false_label);
-    __ CmpInstanceType(input, FIRST_NONSTRING_TYPE);
-    final_branch_condition = below;
+    final_branch_condition = zero;
 
   } else if (type_name->Equals(Heap::boolean_symbol())) {
     __ CompareRoot(input, Heap::kTrueValueRootIndex);
@@ -3510,17 +3509,16 @@ Condition LCodeGen::EmitTypeofIs(Label* true_label,
 
   } else if (type_name->Equals(Heap::object_symbol())) {
     __ JumpIfSmi(input, false_label);
-    __ Cmp(input, Factory::null_value());
+    __ CompareRoot(input, Heap::kNullValueRootIndex);
     __ j(equal, true_label);
+    __ CmpObjectType(input, FIRST_JS_OBJECT_TYPE, input);
+    __ j(below, false_label);
+    __ CmpInstanceType(input, FIRST_FUNCTION_CLASS_TYPE);
+    __ j(above_equal, false_label);
     // Check for undetectable objects => false.
     __ testb(FieldOperand(input, Map::kBitFieldOffset),
              Immediate(1 << Map::kIsUndetectable));
-    __ j(not_zero, false_label);
-    // Check for JS objects that are not RegExp or Function => true.
-    __ CmpInstanceType(input, FIRST_JS_OBJECT_TYPE);
-    __ j(below, false_label);
-    __ CmpInstanceType(input, FIRST_FUNCTION_CLASS_TYPE);
-    final_branch_condition = below_equal;
+    final_branch_condition = zero;
 
   } else {
     final_branch_condition = never;