Reland "Refine expression typing, esp. by propagating range information."

src/compiler/js-typed-lowering.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/access-builder.h"
 #include "src/compiler/graph-inl.h"
 #include "src/compiler/js-builtin-reducer.h"
 #include "src/compiler/js-typed-lowering.h"
 #include "src/compiler/node-aux-data-inl.h"
 #include "src/compiler/node-properties-inl.h"
@@ skipping 365 matching lines @@
 
 Reduction JSTypedLowering::ReduceJSStrictEqual(Node* node, bool invert) {
   JSBinopReduction r(this, node);
   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());
     }
   }
-  /* TODO(neis): This is currently unsound.
-  if (!r.left_type()->Maybe(r.right_type())) {
-    // Type intersection is empty; === is always false unless both
-    // inputs could be strings (one internalized and one not).
-    if (r.OneInputCannotBe(Type::String())) {
-      return ReplaceEagerly(node, invert ? jsgraph()->TrueConstant()
-                                         : jsgraph()->FalseConstant());
-    }
-  }
-  */
   if (r.OneInputIs(Type::Undefined())) {
     return r.ChangeToPureOperator(
         simplified()->ReferenceEqual(Type::Undefined()), invert);
   }
   if (r.OneInputIs(Type::Null())) {
     return r.ChangeToPureOperator(simplified()->ReferenceEqual(Type::Null()),
                                   invert);
   }
   if (r.OneInputIs(Type::Boolean())) {
     return r.ChangeToPureOperator(simplified()->ReferenceEqual(Type::Boolean()),
@@ skipping 285 matching lines @@
       return JSBuiltinReducer(jsgraph()).Reduce(node);
     default:
       break;
   }
   return NoChange();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8