[turbofan] Strength reduce CheckTaggedSigned/Pointer with checked inputs.

test/unittests/compiler/simplified-operator-reducer-unittest.cc

Index: test/unittests/compiler/simplified-operator-reducer-unittest.cc
diff --git a/test/unittests/compiler/simplified-operator-reducer-unittest.cc b/test/unittests/compiler/simplified-operator-reducer-unittest.cc
index 7f2835b2b2c9d3408f729e099ba8deaea1ff34cb..103b08182f1d8f3296b3eec43e88e6ed735b612d 100644
--- a/test/unittests/compiler/simplified-operator-reducer-unittest.cc
+++ b/test/unittests/compiler/simplified-operator-reducer-unittest.cc
@@ -378,6 +378,19 @@ TEST_F(SimplifiedOperatorReducerTest, CheckTaggedPointerWithHeapConstant) {
   }
 }
 
+TEST_F(SimplifiedOperatorReducerTest,
+       CheckTaggedPointerWithCheckTaggedPointer) {
+  Node* param0 = Parameter(0);
+  Node* effect = graph()->start();
+  Node* control = graph()->start();
+  Node* value = effect = graph()->NewNode(simplified()->CheckTaggedPointer(),
+                                          param0, effect, control);
+  Reduction reduction = Reduce(graph()->NewNode(
+      simplified()->CheckTaggedPointer(), value, effect, control));
+  ASSERT_TRUE(reduction.Changed());
+  EXPECT_EQ(value, reduction.replacement());
+}
+
 // -----------------------------------------------------------------------------
 // CheckTaggedSigned
 
@@ -404,6 +417,18 @@ TEST_F(SimplifiedOperatorReducerTest, CheckTaggedSignedWithNumberConstant) {
   EXPECT_EQ(value, reduction.replacement());
 }
 
+TEST_F(SimplifiedOperatorReducerTest, CheckTaggedSignedWithCheckTaggedSigned) {
+  Node* param0 = Parameter(0);
+  Node* effect = graph()->start();
+  Node* control = graph()->start();
+  Node* value = effect = graph()->NewNode(simplified()->CheckTaggedSigned(),
+                                          param0, effect, control);
+  Reduction reduction = Reduce(graph()->NewNode(
+      simplified()->CheckTaggedSigned(), value, effect, control));
+  ASSERT_TRUE(reduction.Changed());
+  EXPECT_EQ(value, reduction.replacement());
+}
+
 // -----------------------------------------------------------------------------
 // NumberAbs