Short-circuit embedded cons strings.

R=mstarzinger@chromium.org
BUG=

Review URL: https://codereview.chromium.org/17418003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15263 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/assembler-arm-inl.h

@@ -149,6 +149,7 @@ Object** RelocInfo::target_object_address() {
 
 void RelocInfo::set_target_object(Object* target, WriteBarrierMode mode) {
   ASSERT(IsCodeTarget(rmode_) || rmode_ == EMBEDDED_OBJECT);
+  ASSERT(!target->IsConsString());
   Assembler::set_target_pointer_at(pc_, reinterpret_cast<Address>(target));
   if (mode == UPDATE_WRITE_BARRIER &&
       host() != NULL &&

src/factory.cc

@@ -259,6 +259,32 @@ Handle<String> Factory::NewConsString(Handle<String> first,
 }
 
 
+template<typename SinkChar, typename StringType>
+Handle<String> ConcatStringContent(Handle<StringType> result,
+                                   Handle<String> first,
+                                   Handle<String> second) {
+  DisallowHeapAllocation pointer_stays_valid;
+  SinkChar* sink = result->GetChars();
+  String::WriteToFlat(*first, sink, 0, first->length());
+  String::WriteToFlat(*second, sink + first->length(), 0, second->length());
+  return result;
+}
+
+
+Handle<String> Factory::NewFlatConcatString(Handle<String> first,
+                                            Handle<String> second) {
+  int total_length = first->length() + second->length();
+  if (first->IsOneByteRepresentationUnderneath() &&
+      second->IsOneByteRepresentationUnderneath()) {
+    return ConcatStringContent<uint8_t>(
+        NewRawOneByteString(total_length), first, second);
+  } else {
+    return ConcatStringContent<uc16>(
+        NewRawTwoByteString(total_length), first, second);
+  }
+}
+
+
 Handle<String> Factory::NewSubString(Handle<String> str,
                                      int begin,
                                      int end) {

src/factory.h

@@ -152,6 +152,10 @@ class Factory {
   Handle<String> NewConsString(Handle<String> first,
                                Handle<String> second);
 
+  // Create a new sequential string containing the concatenation of the inputs.
+  Handle<String> NewFlatConcatString(Handle<String> first,
+                                     Handle<String> second);
+
   // Create a new string object which holds a substring of a string.
   Handle<String> NewSubString(Handle<String> str,
                               int begin,

src/hydrogen-instructions.cc

@@ -3338,10 +3338,9 @@ HInstruction* HStringAdd::New(
     HConstant* c_right = HConstant::cast(right);
     HConstant* c_left = HConstant::cast(left);
     if (c_left->HasStringValue() && c_right->HasStringValue()) {
-      Factory* factory = Isolate::Current()->factory();
-      return new(zone) HConstant(factory->NewConsString(c_left->StringValue(),
-                                                        c_right->StringValue()),
-                                 Representation::Tagged());
+      Handle<String> concat = zone->isolate()->factory()->NewFlatConcatString(
+          c_left->StringValue(), c_right->StringValue());
+      return new(zone) HConstant(concat, Representation::Tagged());
     }
   }
   return new(zone) HStringAdd(context, left, right);

src/ia32/assembler-ia32-inl.h

@@ -132,6 +132,7 @@ Object** RelocInfo::target_object_address() {
 
 void RelocInfo::set_target_object(Object* target, WriteBarrierMode mode) {
   ASSERT(IsCodeTarget(rmode_) || rmode_ == EMBEDDED_OBJECT);
+  ASSERT(!target->IsConsString());
   Memory::Object_at(pc_) = target;
   CPU::FlushICache(pc_, sizeof(Address));
   if (mode == UPDATE_WRITE_BARRIER &&

src/mips/assembler-mips-inl.h

@@ -202,6 +202,7 @@ Object** RelocInfo::target_object_address() {
 
 void RelocInfo::set_target_object(Object* target, WriteBarrierMode mode) {
   ASSERT(IsCodeTarget(rmode_) || rmode_ == EMBEDDED_OBJECT);
+  ASSERT(!target->IsConsString());
   Assembler::set_target_address_at(pc_, reinterpret_cast<Address>(target));
   if (mode == UPDATE_WRITE_BARRIER &&
       host() != NULL &&

src/x64/assembler-x64-inl.h

@@ -308,6 +308,7 @@ Address* RelocInfo::target_reference_address() {
 
 void RelocInfo::set_target_object(Object* target, WriteBarrierMode mode) {
   ASSERT(IsCodeTarget(rmode_) || rmode_ == EMBEDDED_OBJECT);
+  ASSERT(!target->IsConsString());
   Memory::Object_at(pc_) = target;
   CPU::FlushICache(pc_, sizeof(Address));
   if (mode == UPDATE_WRITE_BARRIER &&

test/mjsunit/regress/regress-embedded-cons-string.js

@@ -0,0 +1,66 @@
+// Copyright 2013 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --fold-constants --nodead-code-elimination
+// Flags: --expose-gc --allow-natives-syntax
+// Flags: --parallel-recompilation --parallel-recompilation-delay=300
+
+if (!%IsParallelRecompilationSupported()) {
+  print("Parallel recompilation is disabled. Skipping this test.");
+  quit();
+}
+
+function assertUnoptimized(fun) {
+  assertTrue(%GetOptimizationStatus(fun) != 1);
+}
+
+function test(fun) {
+  fun();
+  fun();
+  %OptimizeFunctionOnNextCall(fun, "parallel");
+  fun();  // Trigger optimization in the background.
+  gc();   // Tenure cons string.
+  assertUnoptimized(fun);      // Compilation not complete yet.
+  %CompleteOptimization(fun);  // Compilation embeds tenured cons string.
+  gc();   // Visit embedded cons string during mark compact.
+}
+
+function f() {
+  return "abcdefghijklmn" + "123456789";
+}
+
+function g() {
+  return "abcdefghijklmn\u2603" + "123456789";
+}
+
+function h() {
+  return "abcdefghijklmn\u2603" + "123456789\u2604";
+}
+
+test(f);
+test(g);
+test(h);