[turbofan] Introduce TruncateTaggedToWord32 simplified operator.

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 f571898107c79ee08e1397232a3792b2ea272288..eed25f4b1c6b40657759262a0bc9ff46c5907edd 100644
--- a/test/unittests/compiler/simplified-operator-reducer-unittest.cc
+++ b/test/unittests/compiler/simplified-operator-reducer-unittest.cc
@@ -401,6 +401,28 @@ TEST_F(SimplifiedOperatorReducerTest, ChangeUint32ToTagged) {
   }
 }
 
+// -----------------------------------------------------------------------------
+// TruncateTaggedToWord32
+
+TEST_F(SimplifiedOperatorReducerTest,
+       TruncateTaggedToWord3WithChangeFloat64ToTagged) {
+  Node* param0 = Parameter(0);
+  Reduction reduction = Reduce(graph()->NewNode(
+      simplified()->TruncateTaggedToWord32(),
+      graph()->NewNode(simplified()->ChangeFloat64ToTagged(), param0)));
+  ASSERT_TRUE(reduction.Changed());
+  EXPECT_THAT(reduction.replacement(), IsTruncateFloat64ToWord32(param0));
+}
+
+TEST_F(SimplifiedOperatorReducerTest, TruncateTaggedToWord32WithConstant) {
+  TRACED_FOREACH(double, n, kFloat64Values) {
+    Reduction reduction = Reduce(graph()->NewNode(
+        simplified()->TruncateTaggedToWord32(), NumberConstant(n)));
+    ASSERT_TRUE(reduction.Changed());
+    EXPECT_THAT(reduction.replacement(), IsInt32Constant(DoubleToInt32(n)));
+  }
+}
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8