Fixed two register allocator bugs (off-by-one error/failure propagation).

src/lithium-allocator.h

 // 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 409 matching lines @@
   const Vector<LiveRange*>* fixed_double_live_ranges() const {
     return &fixed_double_live_ranges_;
   }
 
   LPlatformChunk* chunk() const { return chunk_; }
   HGraph* graph() const { return graph_; }
   Isolate* isolate() const { return graph_->isolate(); }
   Zone* zone() const { return zone_; }
 
   int GetVirtualRegister() {
-    if (next_virtual_register_ > LUnallocated::kMaxVirtualRegisters) {
+    if (next_virtual_register_ >= LUnallocated::kMaxVirtualRegisters) {
       allocation_ok_ = false;
+      // Maintain the invariant that we return something below the maximum.
+      return 0;
     }
     return next_virtual_register_++;
   }
 
   bool AllocationOk() { return allocation_ok_; }
 
   void MarkAsOsrEntry() {
     // There can be only one.
     ASSERT(!has_osr_entry_);
     // Simply set a flag to find and process instruction later.
@@ skipping 172 matching lines @@
   // Indicates success or failure during register allocation.
   bool allocation_ok_;
 
   DISALLOW_COPY_AND_ASSIGN(LAllocator);
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_LITHIUM_ALLOCATOR_H_