Fix Win64 build after r16079.

src/runtime.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 8529 matching lines @@
     // The top JS function is this one, the PC is somewhere in the
     // unoptimized code.
     JavaScriptFrameIterator it(isolate);
     JavaScriptFrame* frame = it.frame();
     ASSERT(frame->function() == *function);
     ASSERT(frame->LookupCode() == *unoptimized);
     ASSERT(unoptimized->contains(frame->pc()));
 
     // Use linear search of the unoptimized code's back edge table to find
     // the AST id matching the PC.
-    uint32_t target_pc_offset = frame->pc() - unoptimized->instruction_start();
+    uint32_t target_pc_offset =
+      static_cast<uint32_t>(frame->pc() - unoptimized->instruction_start());
     uint32_t loop_depth = 0;
 
     for (FullCodeGenerator::BackEdgeTableIterator back_edges(*unoptimized);
          !back_edges.Done();
          back_edges.Next()) {
       if (back_edges.pc_offset() == target_pc_offset) {
         ast_id = back_edges.ast_id();
         loop_depth = back_edges.loop_depth();
         break;
       }
@@ skipping 5600 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal