Subzero: Validate phi instructions after CFG construction.

src/IceCfg.cpp

Index: src/IceCfg.cpp
diff --git a/src/IceCfg.cpp b/src/IceCfg.cpp
index 57f216ff39d582b903f22ecf87e98e2500c70763..ed60abb74088d09d96bbac3f4a97acc66be954c4 100644
--- a/src/IceCfg.cpp
+++ b/src/IceCfg.cpp
@@ -232,6 +232,10 @@ void Cfg::computeInOutEdges() {
     }
   }
   Nodes.resize(Dest);
+
+  TimerMarker T(TimerStack::TT_phiValidation, this);
+  for (CfgNode *Node : Nodes)
+    Node->validatePhis();
 }
 
 void Cfg::renumberInstructions() {