[turbofan] Optimize silent hole checks on legacy const context slots.

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

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/common-operator.h"
 #include "src/compiler/common-operator-reducer.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/js-operator.h"
 #include "src/compiler/machine-operator.h"
 #include "src/compiler/machine-type.h"
@@ skipping 203 matching lines @@
     TRACED_FOREACH(MachineType, type, kMachineTypes) {
       Reduction r = Reduce(
           graph()->NewNode(common()->Select(type, hint), input, input, input));
       ASSERT_TRUE(r.Changed());
       EXPECT_EQ(input, r.replacement());
     }
   }
 }
 
 
+TEST_F(CommonOperatorReducerTest, SelectWithFalseConstant) {
+  Node* p0 = Parameter(0);
+  Node* p1 = Parameter(1);
+  Node* select = graph()->NewNode(common()->Select(kMachAnyTagged),
+                                  FalseConstant(), p0, p1);
+  Reduction r = Reduce(select);
+  ASSERT_TRUE(r.Changed());
+  EXPECT_EQ(p1, r.replacement());
+}
+
+
+TEST_F(CommonOperatorReducerTest, SelectWithTrueConstant) {
+  Node* p0 = Parameter(0);
+  Node* p1 = Parameter(1);
+  Node* select = graph()->NewNode(common()->Select(kMachAnyTagged),
+                                  TrueConstant(), p0, p1);
+  Reduction r = Reduce(select);
+  ASSERT_TRUE(r.Changed());
+  EXPECT_EQ(p0, r.replacement());
+}
+
+
 TEST_F(CommonOperatorReducerTest, SelectToFloat32Abs) {
   Node* p0 = Parameter(0);
   Node* c0 = Float32Constant(0.0);
   Node* check = graph()->NewNode(machine()->Float32LessThan(), c0, p0);
   Node* select =
       graph()->NewNode(common()->Select(kMachFloat32), check, p0,
                        graph()->NewNode(machine()->Float32Sub(), c0, p0));
   Reduction r = Reduce(select, MachineOperatorBuilder::kFloat32Abs);
   ASSERT_TRUE(r.Changed());
   EXPECT_THAT(r.replacement(), IsFloat32Abs(p0));
@@ skipping 56 matching lines @@
   Node* select =
       graph()->NewNode(common()->Select(kMachFloat64), check, p0, p1);
   Reduction r = Reduce(select, MachineOperatorBuilder::kFloat64Min);
   ASSERT_TRUE(r.Changed());
   EXPECT_THAT(r.replacement(), IsFloat64Min(p0, p1));
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8