Extend typed lowering to cover JSStrictEqual on differing types.

R=rossberg@chromium.org, titzer@chromium.org
TEST=unittests/JSTypedLoweringTest.JSStrictEqualWithTheHole

Review URL: https://codereview.chromium.org/722223003

Cr-Commit-Position: refs/heads/master@{#25359}

src/compiler/js-typed-lowering.cc

@@ -459,8 +459,15 @@ Reduction JSTypedLowering::ReduceJSStrictEqual(Node* node, bool invert) {
   if (r.left() == r.right()) {
     // x === x is always true if x != NaN
     if (!r.left_type()->Maybe(Type::NaN())) {
-      return ReplaceEagerly(node, invert ? jsgraph()->FalseConstant()
-                                         : jsgraph()->TrueConstant());
+      return ReplaceEagerly(node, jsgraph()->BooleanConstant(!invert));
+    }
+  }
+  Type* string_or_number = Type::Union(Type::String(), Type::Number(), zone());
+  if (r.OneInputCannotBe(string_or_number)) {
+    // For values with canonical representation (i.e. not string nor number) an
+    // empty type intersection means the values cannot be strictly equal.
+    if (!r.left_type()->Maybe(r.right_type())) {
+      return ReplaceEagerly(node, jsgraph()->BooleanConstant(invert));
     }
   }
   if (r.OneInputIs(Type::Undefined())) {

test/unittests/compiler/js-typed-lowering-unittest.cc

@@ -26,6 +26,10 @@ const ExternalArrayType kExternalArrayTypes[] = {
 };
 
 
+Type* const kJSTypes[] = {Type::Undefined(), Type::Null(),   Type::Boolean(),
+                          Type::Number(),    Type::String(), Type::Object()};
+
+
 const StrictMode kStrictModes[] = {SLOPPY, STRICT};
 
 }  // namespace
@@ -108,6 +112,25 @@ TEST_F(JSTypedLoweringTest, JSToBooleanWithOrderedNumberAndBoolean) {
 }
 
 
+// -----------------------------------------------------------------------------
+// JSStrictEqual
+
+
+TEST_F(JSTypedLoweringTest, JSStrictEqualWithTheHole) {
+  Node* const the_hole = HeapConstant(factory()->the_hole_value());
+  Node* const context = UndefinedConstant();
+  Node* const effect = graph()->start();
+  Node* const control = graph()->start();
+  TRACED_FOREACH(Type*, type, kJSTypes) {
+    Node* const lhs = Parameter(type);
+    Reduction r = Reduce(graph()->NewNode(javascript()->StrictEqual(), lhs,
+                                          the_hole, context, effect, control));
+    ASSERT_TRUE(r.Changed());
+    EXPECT_THAT(r.replacement(), IsFalseConstant());
+  }
+}
+
+
 // -----------------------------------------------------------------------------
 // JSShiftLeft