[turbofan] Constant-fold ToNumber conversions.

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/code-factory.h"
 #include "src/compilation-dependencies.h"
 #include "src/compiler/access-builder.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/js-typed-lowering.h"
 #include "src/compiler/linkage.h"
@@ skipping 762 matching lines @@
     Node* vfalse = NodeProperties::GetValueInput(input, 2);
     Type* vfalse_type = NodeProperties::GetType(vfalse);
     if (vtrue_type->Is(Type::Undefined()) && vfalse_type->Is(Type::Number())) {
       if (check->opcode() == IrOpcode::kNumberIsHoleNaN &&
           check->InputAt(0) == vfalse) {
         // JSToNumber(Select(NumberIsHoleNaN(x), y:undefined, x:number)) => x
         return Replace(vfalse);
       }
     }
   }
-  // Check if we have a cached conversion.
+  // Try constant-folding of JSToNumber with constant inputs.
   Type* input_type = NodeProperties::GetType(input);
+  if (input_type->IsConstant()) {
+    Handle<Object> input_value = input_type->AsConstant()->Value();
+    if (input_value->IsString()) {
+      return Replace(jsgraph()->Constant(
+          String::ToNumber(Handle<String>::cast(input_value))));
+    } else if (input_value->IsOddball()) {
+      return Replace(jsgraph()->Constant(
+          Oddball::ToNumber(Handle<Oddball>::cast(input_value))));
+    }
+  }
   if (input_type->Is(Type::Number())) {
     // JSToNumber(x:number) => x
     return Changed(input);
   }
   if (input_type->Is(Type::Undefined())) {
     // JSToNumber(undefined) => #NaN
     return Replace(jsgraph()->NaNConstant());
   }
   if (input_type->Is(Type::Null())) {
     // JSToNumber(null) => #0
@@ skipping 1876 matching lines @@
 }
 
 
 CompilationDependencies* JSTypedLowering::dependencies() const {
   return dependencies_;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8