[turbofan] Constant-fold concatenation of strings.

src/compiler/js-native-context-specialization.cc

 // Copyright 2015 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/js-native-context-specialization.h"
 
 #include "src/accessors.h"
 #include "src/code-factory.h"
 #include "src/compilation-dependencies.h"
 #include "src/compiler/access-builder.h"
@@ skipping 59 matching lines @@
       flags_(flags),
       global_object_(native_context->global_object()),
       global_proxy_(JSGlobalProxy::cast(native_context->global_proxy())),
       native_context_(native_context),
       dependencies_(dependencies),
       zone_(zone),
       type_cache_(TypeCache::Get()) {}
 
 Reduction JSNativeContextSpecialization::Reduce(Node* node) {
   switch (node->opcode()) {
+    case IrOpcode::kJSAdd:
+      return ReduceJSAdd(node);
     case IrOpcode::kJSGetSuperConstructor:
       return ReduceJSGetSuperConstructor(node);
     case IrOpcode::kJSInstanceOf:
       return ReduceJSInstanceOf(node);
     case IrOpcode::kJSOrdinaryHasInstance:
       return ReduceJSOrdinaryHasInstance(node);
     case IrOpcode::kJSLoadContext:
       return ReduceJSLoadContext(node);
     case IrOpcode::kJSLoadGlobal:
       return ReduceJSLoadGlobal(node);
@@ skipping 10 matching lines @@
     case IrOpcode::kJSStoreNamedOwn:
       return ReduceJSStoreNamedOwn(node);
     case IrOpcode::kJSStoreDataPropertyInLiteral:
       return ReduceJSStoreDataPropertyInLiteral(node);
     default:
       break;
   }
   return NoChange();
 }
 
+Reduction JSNativeContextSpecialization::ReduceJSAdd(Node* node) {
+  // TODO(turbofan): This has to run together with the inlining and
+  // native context specialization to be able to leverage the string
+  // constant-folding for optimizing property access, but we should
+  // nevertheless find a better home for this at some point.
+  DCHECK_EQ(IrOpcode::kJSAdd, node->opcode());
+
+  // Constant-fold string concatenation.
+  HeapObjectBinopMatcher m(node);
+  if (m.left().HasValue() && m.left().Value()->IsString() &&
+      m.right().HasValue() && m.right().Value()->IsString()) {
+    Handle<String> left = Handle<String>::cast(m.left().Value());
+    Handle<String> right = Handle<String>::cast(m.right().Value());
+    if (left->length() + right->length() <= String::kMaxLength) {
+      Handle<String> result =
+          factory()->NewConsString(left, right).ToHandleChecked();
+      Node* value = jsgraph()->HeapConstant(result);
+      ReplaceWithValue(node, value);
+      return Replace(value);
+    }
+  }
+  return NoChange();
+}
+
 Reduction JSNativeContextSpecialization::ReduceJSGetSuperConstructor(
     Node* node) {
   DCHECK_EQ(IrOpcode::kJSGetSuperConstructor, node->opcode());
   Node* constructor = NodeProperties::GetValueInput(node, 0);
 
   // If deoptimization is disabled, we cannot optimize.
   if (!(flags() & kDeoptimizationEnabled)) return NoChange();
 
   // Check if the input is a known JSFunction.
   HeapObjectMatcher m(constructor);
@@ skipping 2182 matching lines @@
   return jsgraph()->javascript();
 }
 
 SimplifiedOperatorBuilder* JSNativeContextSpecialization::simplified() const {
   return jsgraph()->simplified();
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8