Merged r19031 into 3.23 branch.

src/hydrogen.cc

 // 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
@@ skipping 8985 matching lines @@
       eval_right->SetJoinId(expr->RightId());
       set_current_block(eval_right);
       Visit(expr->right());
     }
 
   } else if (ast_context()->IsValue()) {
     CHECK_ALIVE(VisitForValue(expr->left()));
     ASSERT(current_block() != NULL);
     HValue* left_value = Top();
 
-    if (left_value->IsConstant()) {
-      HConstant* left_constant = HConstant::cast(left_value);
-      if ((is_logical_and && left_constant->BooleanValue()) ||
-          (!is_logical_and && !left_constant->BooleanValue())) {
-        Drop(1);  // left_value.
+    // Short-circuit left values that always evaluate to the same boolean value.
+    if (expr->left()->ToBooleanIsTrue() || expr->left()->ToBooleanIsFalse()) {
+      // l (evals true)  && r -> r
+      // l (evals true)  || r -> l
+      // l (evals false) && r -> l
+      // l (evals false) || r -> r
+      if (is_logical_and == expr->left()->ToBooleanIsTrue()) {
+        Drop(1);
         CHECK_ALIVE(VisitForValue(expr->right()));
       }
       return ast_context()->ReturnValue(Pop());
     }
 
     // We need an extra block to maintain edge-split form.
     HBasicBlock* empty_block = graph()->CreateBasicBlock();
     HBasicBlock* eval_right = graph()->CreateBasicBlock();
     ToBooleanStub::Types expected(expr->left()->to_boolean_types());
     HBranch* test = is_logical_and
@@ skipping 1787 matching lines @@
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 } }  // namespace v8::internal