Subzero: Prune unreachable nodes after constructing the Cfg.

src/IceConverter.cpp

Index: src/IceConverter.cpp
diff --git a/src/IceConverter.cpp b/src/IceConverter.cpp
index a078a676af870df2fd5087b83524d64dd548489f..6b83b1514f048241cf0bac2b4a68713c9de19819 100644
--- a/src/IceConverter.cpp
+++ b/src/IceConverter.cpp
@@ -113,7 +113,7 @@ public:
     for (const BasicBlock &BBI : *F)
       convertBasicBlock(&BBI);
     Func->setEntryNode(mapBasicBlockToNode(&F->getEntryBlock()));
-    Func->computePredecessors();
+    Func->computeInOutEdges();
 
     Ice::Cfg::setCurrentCfg(nullptr);
     Converter.translateFcn(std::move(Func));