Quick: Rewrite Phi node insertion.

Delay Phi node insertion to the SSAConversion pass to allow
updating the vreg_to_ssa_map_ with INVALID_SREG when we omit
a Phi in the pruned SSA form.

Change-Id: I450dee21f7dc4353d25fc66f4d0ee01671de6e0e
diff --git a/compiler/dex/post_opt_passes.h b/compiler/dex/post_opt_passes.h
index a3dbc5a..1ab8625 100644
--- a/compiler/dex/post_opt_passes.h
+++ b/compiler/dex/post_opt_passes.h
@@ -189,19 +189,19 @@
 };
 
 /**
- * @class CreatePhiNodes
- * @brief Pass to create the phi nodes after SSA calculation
+ * @class FindPhiNodeBlocksPass
+ * @brief Pass to find out where we need to insert the phi nodes for the SSA conversion.
  */
-class CreatePhiNodes : public PassMEMirSsaRep {
+class FindPhiNodeBlocksPass : public PassMEMirSsaRep {
  public:
-  CreatePhiNodes() : PassMEMirSsaRep("CreatePhiNodes", kNoNodes) {
+  FindPhiNodeBlocksPass() : PassMEMirSsaRep("FindPhiNodeBlocks", kNoNodes) {
   }
 
   void Start(PassDataHolder* data) const {
     DCHECK(data != nullptr);
     CompilationUnit* c_unit = down_cast<PassMEDataHolder*>(data)->c_unit;
     DCHECK(c_unit != nullptr);
-    c_unit->mir_graph.get()->InsertPhiNodes();
+    c_unit->mir_graph.get()->FindPhiNodeBlocks();
   }
 };