Avoid generating jmp +0.

When a block branches to a non-following block, but blocks
in-between do branch to it, we can avoid doing the branch.

Change-Id: I9b343f662a4efc718cd4b58168f93162a24e1219
diff --git a/compiler/optimizing/code_generator_x86_64.h b/compiler/optimizing/code_generator_x86_64.h
index dbdbf86..707c999 100644
--- a/compiler/optimizing/code_generator_x86_64.h
+++ b/compiler/optimizing/code_generator_x86_64.h
@@ -232,7 +232,7 @@
   void LoadCurrentMethod(CpuRegister reg);
 
   Label* GetLabelOf(HBasicBlock* block) const {
-    return block_labels_.GetRawStorage() + block->GetBlockId();
+    return CommonGetLabelOf<Label>(block_labels_.GetRawStorage(), block);
   }
 
   void Initialize() OVERRIDE {