Avoid creating unnecessary branches in Hydrogen

src/hydrogen.cc

 // Copyright 2012 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 3597 matching lines @@
 
 void TestContext::BuildBranch(HValue* value) {
   // We expect the graph to be in edge-split form: there is no edge that
   // connects a branch node to a join node.  We conservatively ensure that
   // property by always adding an empty block on the outgoing edges of this
   // branch.
   HOptimizedGraphBuilder* builder = owner();
   if (value != NULL && value->CheckFlag(HValue::kIsArguments)) {
     builder->Bailout("arguments object value in a test context");
   }
+  if (value->IsConstant()) {
+    HConstant* constant_value = HConstant::cast(value);
+    if (constant_value->ToBoolean()) {
+      builder->current_block()->Goto(if_true(), builder->function_state());
+    } else {
+      builder->current_block()->Goto(if_false(), builder->function_state());
+    }
+    builder->set_current_block(NULL);
+    return;
+  }
   HBasicBlock* empty_true = builder->graph()->CreateBasicBlock();
   HBasicBlock* empty_false = builder->graph()->CreateBasicBlock();
   TypeFeedbackId test_id = condition()->test_id();
   ToBooleanStub::Types expected(oracle()->ToBooleanTypes(test_id));
   HBranch* test = new(zone()) HBranch(value, empty_true, empty_false, expected);
   builder->current_block()->Finish(test);
 
-  empty_true->Goto(if_true(), owner()->function_state());
-  empty_false->Goto(if_false(), owner()->function_state());
+  empty_true->Goto(if_true(), builder->function_state());
+  empty_false->Goto(if_false(), builder->function_state());
   builder->set_current_block(NULL);
 }
 
 
 // HOptimizedGraphBuilder infrastructure for bailing out and checking bailouts.
 #define CHECK_BAILOUT(call)                     \
   do {                                          \
     call;                                       \
     if (HasStackOverflow()) return;             \
   } while (false)
@@ skipping 5383 matching lines @@
     // context as the entire expression.
     if (eval_right->HasPredecessor()) {
       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->ToBoolean()) ||
+          (!is_logical_and && !left_constant->ToBoolean())) {
+        Drop(1);  // left_value.
+        CHECK_BAILOUT(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();
     TypeFeedbackId test_id = expr->left()->test_id();
     ToBooleanStub::Types expected(oracle()->ToBooleanTypes(test_id));
     HBranch* test = is_logical_and
-      ? new(zone()) HBranch(Top(), eval_right, empty_block, expected)
-      : new(zone()) HBranch(Top(), empty_block, eval_right, expected);
+      ? new(zone()) HBranch(left_value, eval_right, empty_block, expected)
+      : new(zone()) HBranch(left_value, empty_block, eval_right, expected);
     current_block()->Finish(test);
 
     set_current_block(eval_right);
     Drop(1);  // Value of the left subexpression.
     CHECK_BAILOUT(VisitForValue(expr->right()));
 
     HBasicBlock* join_block =
       CreateJoin(empty_block, current_block(), expr->id());
     set_current_block(join_block);
     return ast_context()->ReturnValue(Pop());
@@ skipping 1618 matching lines @@
     }
   }
 
 #ifdef DEBUG
   if (graph_ != NULL) graph_->Verify(false);  // No full verify.
   if (allocator_ != NULL) allocator_->Verify();
 #endif
 }
 
 } }  // namespace v8::internal