Add -reorder-basic-blocks option and fix nop insertion

src/IceCfg.h

Index: src/IceCfg.h
diff --git a/src/IceCfg.h b/src/IceCfg.h
index 08b4e979c2c07d993a56b38a2f3163627b45c1e1..4a6c5dc32013d5cbbb0b899126a52c0dbdef2b88 100644
--- a/src/IceCfg.h
+++ b/src/IceCfg.h
@@ -173,6 +173,7 @@ public:
   void deletePhis();
   void advancedPhiLowering();
   void reorderNodes();
+  void shuffleNodes();

[John, 2015/07/29 17:52:36]

What is the difference between shuffleNodes and reorderNodes? It seems to me
(just from their names) that they do related/similar/the same thing.

[qining, 2015/07/29 23:04:40]

They are doing different, but a little bit related things, IMO.

reorderNodes() (based on my understanding) is to 'adjust' the layout after
advancedPhiLowering. Advanced Phi Lowering will create new split basic blocks
and append them at the end of the basic block vector, this reorderNodes() moves
these split blocks to more appropriate places, like behind a predecessor or
before a successor.

   void doAddressOpt();
   void doArgLowering();
   void doNopInsertion();