Skip back edge creation for "do ... while(false)" loops

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 4301 matching lines @@
   ASSERT(current_block() != NULL);
   HBasicBlock* loop_entry = BuildLoopEntry(stmt);
 
   BreakAndContinueInfo break_info(stmt);
   CHECK_BAILOUT(VisitLoopBody(stmt, loop_entry, &break_info));
   HBasicBlock* body_exit =
       JoinContinue(stmt, current_block(), break_info.continue_block());
   HBasicBlock* loop_successor = NULL;
   if (body_exit != NULL && !stmt->cond()->ToBooleanIsTrue()) {
     set_current_block(body_exit);
-    // The block for a true condition, the actual predecessor block of the
-    // back edge.
-    body_exit = graph()->CreateBasicBlock();
     loop_successor = graph()->CreateBasicBlock();
-    CHECK_BAILOUT(VisitForControl(stmt->cond(), body_exit, loop_successor));
-    if (body_exit->HasPredecessor()) {
+    if (stmt->cond()->ToBooleanIsFalse()) {
+      Goto(loop_successor);
+      body_exit = NULL;
+    } else {
+      // The block for a true condition, the actual predecessor block of the
+      // back edge.
+      body_exit = graph()->CreateBasicBlock();
+      CHECK_BAILOUT(VisitForControl(stmt->cond(), body_exit, loop_successor));
+    }
+    if (body_exit != NULL && body_exit->HasPredecessor()) {
       body_exit->SetJoinId(stmt->BackEdgeId());
     } else {
       body_exit = NULL;
     }
     if (loop_successor->HasPredecessor()) {
       loop_successor->SetJoinId(stmt->ExitId());
     } else {
       loop_successor = NULL;
     }
   }
@@ skipping 6606 matching lines @@
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 } }  // namespace v8::internal