Fix handling of constant global variable assignments.

BUG=347904
LOG=y
R=hpayer@chromium.org

Review URL: https://codereview.chromium.org/184303003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@19594 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen.cc

@@ -5909,12 +5909,20 @@ void HOptimizedGraphBuilder::HandleGlobalVariableAssignment(
     Handle<GlobalObject> global(current_info()->global_object());
     Handle<PropertyCell> cell(global->GetPropertyCell(&lookup));
     if (cell->type()->IsConstant()) {
+      Handle<Object> constant = cell->type()->AsConstant();
+      if (value->IsConstant()) {
+        HConstant* c_value = HConstant::cast(value);
+        if (!constant.is_identical_to(c_value->handle(isolate()))) {
+          Add<HDeoptimize>("Constant global variable assignment",
+                           Deoptimizer::EAGER);
+        }
+      } else {
+        HValue* c_constant = Add<HConstant>(constant);
         IfBuilder builder(this);
-      HValue* constant = Add<HConstant>(cell->type()->AsConstant());
-      if (cell->type()->AsConstant()->IsNumber()) {
-        builder.If<HCompareNumericAndBranch>(value, constant, Token::EQ);
+        if (constant->IsNumber()) {
+          builder.If<HCompareNumericAndBranch>(value, c_constant, Token::EQ);
         } else {
-        builder.If<HCompareObjectEqAndBranch>(value, constant);
+          builder.If<HCompareObjectEqAndBranch>(value, c_constant);
         }
         builder.Then();
         builder.Else();
@@ -5922,6 +5930,7 @@ void HOptimizedGraphBuilder::HandleGlobalVariableAssignment(
                          Deoptimizer::EAGER);
         builder.End();
       }
+    }
     HInstruction* instr =
         Add<HStoreGlobalCell>(value, cell, lookup.GetPropertyDetails());
     if (instr->HasObservableSideEffects()) {

test/mjsunit/regress/regress-347904.js

+// 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.
+
+// Flags: --allow-natives-syntax --stress-runs=2
+
+var v = /abc/;
+function f() {
+  v = 1578221999;
+};
+%OptimizeFunctionOnNextCall(f);
+f();