diff --git a/compiler/optimizing/code_generator_arm.cc b/compiler/optimizing/code_generator_arm.cc
index 507b3cd..c506be1 100644
--- a/compiler/optimizing/code_generator_arm.cc
+++ b/compiler/optimizing/code_generator_arm.cc
@@ -3874,9 +3874,11 @@
   SlowPathCodeARM* slow_path = nullptr;
 
   // Return 0 if `obj` is null.
-  // TODO: avoid this check if we know obj is not null.
-  __ cmp(obj, ShifterOperand(0));
-  __ b(&zero, EQ);
+  // avoid null check if we know obj is not null.
+  if (instruction->MustDoNullCheck()) {
+    __ cmp(obj, ShifterOperand(0));
+    __ b(&zero, EQ);
+  }
   // Compare the class of `obj` with `cls`.
   __ LoadFromOffset(kLoadWord, out, obj, class_offset);
   __ cmp(out, ShifterOperand(cls));
@@ -3895,8 +3897,12 @@
     __ LoadImmediate(out, 1);
     __ b(&done);
   }
-  __ Bind(&zero);
-  __ LoadImmediate(out, 0);
+
+  if (instruction->MustDoNullCheck() || instruction->IsClassFinal()) {
+    __ Bind(&zero);
+    __ LoadImmediate(out, 0);
+  }
+
   if (slow_path != nullptr) {
     __ Bind(slow_path->GetExitLabel());
   }
@@ -3922,9 +3928,11 @@
       instruction, locations->InAt(1), locations->GetTemp(0), instruction->GetDexPc());
   codegen_->AddSlowPath(slow_path);
 
-  // TODO: avoid this check if we know obj is not null.
-  __ cmp(obj, ShifterOperand(0));
-  __ b(slow_path->GetExitLabel(), EQ);
+  // avoid null check if we know obj is not null.
+  if (instruction->MustDoNullCheck()) {
+    __ cmp(obj, ShifterOperand(0));
+    __ b(slow_path->GetExitLabel(), EQ);
+  }
   // Compare the class of `obj` with `cls`.
   __ LoadFromOffset(kLoadWord, temp, obj, class_offset);
   __ cmp(temp, ShifterOperand(cls));
diff --git a/compiler/optimizing/code_generator_arm64.cc b/compiler/optimizing/code_generator_arm64.cc
index f6ec729..3619656 100644
--- a/compiler/optimizing/code_generator_arm64.cc
+++ b/compiler/optimizing/code_generator_arm64.cc
@@ -1373,8 +1373,10 @@
       instruction, locations->InAt(1), LocationFrom(obj_cls), instruction->GetDexPc());
   codegen_->AddSlowPath(slow_path);
 
-  // TODO: avoid this check if we know obj is not null.
-  __ Cbz(obj, slow_path->GetExitLabel());
+  // Avoid null check if we know obj is not null.
+  if (instruction->MustDoNullCheck()) {
+    __ Cbz(obj, slow_path->GetExitLabel());
+  }
   // Compare the class of `obj` with `cls`.
   __ Ldr(obj_cls, HeapOperand(obj, mirror::Object::ClassOffset()));
   __ Cmp(obj_cls, cls);
@@ -1821,9 +1823,11 @@
   vixl::Label done;
 
   // Return 0 if `obj` is null.
-  // TODO: Avoid this check if we know `obj` is not null.
-  __ Mov(out, 0);
-  __ Cbz(obj, &done);
+  // Avoid null check if we know `obj` is not null.
+  if (instruction->MustDoNullCheck()) {
+    __ Mov(out, 0);
+    __ Cbz(obj, &done);
+  }
 
   // Compare the class of `obj` with `cls`.
   __ Ldr(out, HeapOperand(obj, mirror::Object::ClassOffset()));
diff --git a/compiler/optimizing/code_generator_x86.cc b/compiler/optimizing/code_generator_x86.cc
index 0cc377c..b48a4d5 100644
--- a/compiler/optimizing/code_generator_x86.cc
+++ b/compiler/optimizing/code_generator_x86.cc
@@ -4225,9 +4225,11 @@
   SlowPathCodeX86* slow_path = nullptr;
 
   // Return 0 if `obj` is null.
-  // TODO: avoid this check if we know obj is not null.
-  __ testl(obj, obj);
-  __ j(kEqual, &zero);
+  // Avoid null check if we know obj is not null.
+  if (instruction->MustDoNullCheck()) {
+    __ testl(obj, obj);
+    __ j(kEqual, &zero);
+  }
   __ movl(out, Address(obj, class_offset));
   // Compare the class of `obj` with `cls`.
   if (cls.IsRegister()) {
@@ -4252,8 +4254,12 @@
     __ movl(out, Immediate(1));
     __ jmp(&done);
   }
-  __ Bind(&zero);
-  __ movl(out, Immediate(0));
+
+  if (instruction->MustDoNullCheck() || instruction->IsClassFinal()) {
+    __ Bind(&zero);
+    __ movl(out, Immediate(0));
+  }
+
   if (slow_path != nullptr) {
     __ Bind(slow_path->GetExitLabel());
   }
@@ -4278,11 +4284,13 @@
       instruction, locations->InAt(1), locations->GetTemp(0), instruction->GetDexPc());
   codegen_->AddSlowPath(slow_path);
 
-  // TODO: avoid this check if we know obj is not null.
-  __ testl(obj, obj);
-  __ j(kEqual, slow_path->GetExitLabel());
-  __ movl(temp, Address(obj, class_offset));
+  // Avoid null check if we know obj is not null.
+  if (instruction->MustDoNullCheck()) {
+    __ testl(obj, obj);
+    __ j(kEqual, slow_path->GetExitLabel());
+  }
 
+  __ movl(temp, Address(obj, class_offset));
   // Compare the class of `obj` with `cls`.
   if (cls.IsRegister()) {
     __ cmpl(temp, cls.AsRegister<Register>());
diff --git a/compiler/optimizing/code_generator_x86_64.cc b/compiler/optimizing/code_generator_x86_64.cc
index fb0f4ca..4e5aaf5 100644
--- a/compiler/optimizing/code_generator_x86_64.cc
+++ b/compiler/optimizing/code_generator_x86_64.cc
@@ -4033,9 +4033,11 @@
   SlowPathCodeX86_64* slow_path = nullptr;
 
   // Return 0 if `obj` is null.
-  // TODO: avoid this check if we know obj is not null.
-  __ testl(obj, obj);
-  __ j(kEqual, &zero);
+  // Avoid null check if we know obj is not null.
+  if (instruction->MustDoNullCheck()) {
+    __ testl(obj, obj);
+    __ j(kEqual, &zero);
+  }
   // Compare the class of `obj` with `cls`.
   __ movl(out, Address(obj, class_offset));
   if (cls.IsRegister()) {
@@ -4059,8 +4061,12 @@
     __ movl(out, Immediate(1));
     __ jmp(&done);
   }
-  __ Bind(&zero);
-  __ movl(out, Immediate(0));
+
+  if (instruction->MustDoNullCheck() || instruction->IsClassFinal()) {
+    __ Bind(&zero);
+    __ movl(out, Immediate(0));
+  }
+
   if (slow_path != nullptr) {
     __ Bind(slow_path->GetExitLabel());
   }
@@ -4085,9 +4091,11 @@
       instruction, locations->InAt(1), locations->GetTemp(0), instruction->GetDexPc());
   codegen_->AddSlowPath(slow_path);
 
-  // TODO: avoid this check if we know obj is not null.
-  __ testl(obj, obj);
-  __ j(kEqual, slow_path->GetExitLabel());
+  // Avoid null check if we know obj is not null.
+  if (instruction->MustDoNullCheck()) {
+    __ testl(obj, obj);
+    __ j(kEqual, slow_path->GetExitLabel());
+  }
   // Compare the class of `obj` with `cls`.
   __ movl(temp, Address(obj, class_offset));
   if (cls.IsRegister()) {
diff --git a/compiler/optimizing/instruction_simplifier.cc b/compiler/optimizing/instruction_simplifier.cc
index afbc490..40ff098 100644
--- a/compiler/optimizing/instruction_simplifier.cc
+++ b/compiler/optimizing/instruction_simplifier.cc
@@ -60,6 +60,7 @@
   void VisitSub(HSub* instruction) OVERRIDE;
   void VisitUShr(HUShr* instruction) OVERRIDE;
   void VisitXor(HXor* instruction) OVERRIDE;
+  void VisitInstanceOf(HInstanceOf* instruction) OVERRIDE;
 
   OptimizingCompilerStats* stats_;
   bool simplification_occurred_ = false;
@@ -161,6 +162,10 @@
 
 void InstructionSimplifierVisitor::VisitCheckCast(HCheckCast* check_cast) {
   HLoadClass* load_class = check_cast->InputAt(1)->AsLoadClass();
+  if (!check_cast->InputAt(0)->CanBeNull()) {
+    check_cast->ClearMustDoNullCheck();
+  }
+
   if (!load_class->IsResolved()) {
     // If the class couldn't be resolve it's not safe to compare against it. It's
     // default type would be Top which might be wider that the actual class type
@@ -178,6 +183,12 @@
   }
 }
 
+void InstructionSimplifierVisitor::VisitInstanceOf(HInstanceOf* instruction) {
+  if (!instruction->InputAt(0)->CanBeNull()) {
+    instruction->ClearMustDoNullCheck();
+  }
+}
+
 void InstructionSimplifierVisitor::VisitSuspendCheck(HSuspendCheck* check) {
   HBasicBlock* block = check->GetBlock();
   // Currently always keep the suspend check at entry.
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index fe47939..db1e505 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -3329,6 +3329,7 @@
               uint32_t dex_pc)
       : HExpression(Primitive::kPrimBoolean, SideEffects::None()),
         class_is_final_(class_is_final),
+        must_do_null_check_(true),
         dex_pc_(dex_pc) {
     SetRawInputAt(0, object);
     SetRawInputAt(1, constant);
@@ -3348,10 +3349,15 @@
 
   bool IsClassFinal() const { return class_is_final_; }
 
+  // Used only in code generation.
+  bool MustDoNullCheck() const { return must_do_null_check_; }
+  void ClearMustDoNullCheck() { must_do_null_check_ = false; }
+
   DECLARE_INSTRUCTION(InstanceOf);
 
  private:
   const bool class_is_final_;
+  bool must_do_null_check_;
   const uint32_t dex_pc_;
 
   DISALLOW_COPY_AND_ASSIGN(HInstanceOf);
@@ -3392,6 +3398,7 @@
              uint32_t dex_pc)
       : HTemplateInstruction(SideEffects::None()),
         class_is_final_(class_is_final),
+        must_do_null_check_(true),
         dex_pc_(dex_pc) {
     SetRawInputAt(0, object);
     SetRawInputAt(1, constant);
@@ -3410,6 +3417,9 @@
 
   bool CanThrow() const OVERRIDE { return true; }
 
+  bool MustDoNullCheck() const { return must_do_null_check_; }
+  void ClearMustDoNullCheck() { must_do_null_check_ = false; }
+
   uint32_t GetDexPc() const { return dex_pc_; }
 
   bool IsClassFinal() const { return class_is_final_; }
@@ -3418,6 +3428,7 @@
 
  private:
   const bool class_is_final_;
+  bool must_do_null_check_;
   const uint32_t dex_pc_;
 
   DISALLOW_COPY_AND_ASSIGN(HCheckCast);