Fix for a smi stores optimization on x64 with a test case.

BUG=338425
LOG=N
R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/152923006

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19288 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/flag-definitions.h

@@ -234,7 +234,6 @@ DEFINE_implication(track_double_fields, track_fields)
 DEFINE_implication(track_heap_object_fields, track_fields)
 DEFINE_implication(track_computed_fields, track_fields)
 DEFINE_bool(smi_binop, true, "support smi representation in binary operations")
-DEFINE_bool(smi_x64_store_opt, false, "optimized stores of smi on x64")
 
 // Flags for optimization types.
 DEFINE_bool(optimize_for_size, false,

src/hydrogen-instructions.h

@@ -6516,7 +6516,6 @@ class HStoreNamedField V8_FINAL : public HTemplateInstruction<3> {
         write_barrier_mode_(UPDATE_WRITE_BARRIER),
         has_transition_(false),
         store_mode_(store_mode) {
-    if (!FLAG_smi_x64_store_opt) store_mode_ = INITIALIZING_STORE;
     // Stores to a non existing in-object property are allowed only to the
     // newly allocated objects (via HAllocate or HInnerAllocatedObject).
     ASSERT(!access.IsInobject() || access.existing_inobject_property() ||
@@ -6705,7 +6704,6 @@ class HStoreKeyed V8_FINAL
       is_uninitialized_(false),
       store_mode_(store_mode),
       new_space_dominator_(NULL) {
-    if (!FLAG_smi_x64_store_opt) store_mode_ = INITIALIZING_STORE;
     SetOperandAt(0, obj);
     SetOperandAt(1, key);
     SetOperandAt(2, val);

src/hydrogen.cc

@@ -9816,6 +9816,8 @@ void HOptimizedGraphBuilder::BuildEmitInObjectProperties(
         value_instruction = double_box;
       } else if (representation.IsSmi() && value->IsUninitialized()) {
         value_instruction = graph()->GetConstant0();
+        // Ensure that Constant0 is stored as smi.
+        access = access.WithRepresentation(representation);
       } else {
         value_instruction = Add<HConstant>(value);
       }

src/x64/lithium-codegen-x64.cc

@@ -3928,6 +3928,10 @@ void LCodeGen::DoStoreNamedField(LStoreNamedField* instr) {
   if (representation.IsSmi() &&
       hinstr->value()->representation().IsInteger32()) {
     ASSERT(hinstr->store_mode() == STORE_TO_INITIALIZED_ENTRY);
+#ifdef DEBUG
+    __ movq(kScratchRegister, FieldOperand(write_register, offset));
+    __ AssertSmi(kScratchRegister);
+#endif
     // Store int value directly to upper half of the smi.
     STATIC_ASSERT(kSmiTag == 0);
     STATIC_ASSERT(kSmiTagSize + kSmiShiftSize == 32);

test/mjsunit/compiler/smi-stores-opt.js

+// Copyright 2014 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: --allow-natives-syntax
+
+var o = {a:1.5};
+o.a = 0;
+var a = o.a;
+
+function g() {
+  return 1;
+}
+
+var o2 = {a:{}};
+
+function f() {
+  var result = {a: a};
+  var literal = {x:g()};
+  return [result, literal];
+}
+
+f();
+f();
+%OptimizeFunctionOnNextCall(f);
+assertEquals(1, f()[1].x);