Subzero: Prune unreachable nodes after constructing the Cfg.

src/IceCfg.h

Index: src/IceCfg.h
diff --git a/src/IceCfg.h b/src/IceCfg.h
index b4c3748455829fb4e44a3325d6dc6f83d0953db2..8f74d07f1d434169c869f58359aa6bba2ccf621b 100644
--- a/src/IceCfg.h
+++ b/src/IceCfg.h
@@ -135,9 +135,9 @@ public:
   // Passes over the CFG.
   void translate();
   // After the CFG is fully constructed, iterate over the nodes and
-  // compute the predecessor edges, in the form of
-  // CfgNode::InEdges[].
-  void computePredecessors();
+  // compute the predecessor and successor edges, in the form of
+  // CfgNode::InEdges[] and CfgNode::OutEdges[].
+  void computeInOutEdges();
   void renumberInstructions();
   void placePhiLoads();
   void placePhiStores();