CodeGen: Remove implicit ilist iterator conversions, NFC

Make ilist iterator conversions explicit in clangCodeGen.  Eventually
I'll remove them everywhere.

llvm-svn: 252358
diff --git a/clang/lib/CodeGen/CGVTables.cpp b/clang/lib/CodeGen/CGVTables.cpp
index 4c3202c..3d8c41c 100644
--- a/clang/lib/CodeGen/CGVTables.cpp
+++ b/clang/lib/CodeGen/CGVTables.cpp
@@ -175,14 +175,16 @@
   // Find the first store of "this", which will be to the alloca associated
   // with "this".
   Address ThisPtr(&*AI, CGM.getClassPointerAlignment(MD->getParent()));
-  llvm::BasicBlock *EntryBB = Fn->begin();
-  llvm::Instruction *ThisStore =
+  llvm::BasicBlock *EntryBB = &Fn->front();
+  llvm::BasicBlock::iterator ThisStore =
       std::find_if(EntryBB->begin(), EntryBB->end(), [&](llvm::Instruction &I) {
-    return isa<llvm::StoreInst>(I) && I.getOperand(0) == ThisPtr.getPointer();
-  });
-  assert(ThisStore && "Store of this should be in entry block?");
+        return isa<llvm::StoreInst>(I) &&
+               I.getOperand(0) == ThisPtr.getPointer();
+      });
+  assert(ThisStore != EntryBB->end() &&
+         "Store of this should be in entry block?");
   // Adjust "this", if necessary.
-  Builder.SetInsertPoint(ThisStore);
+  Builder.SetInsertPoint(&*ThisStore);
   llvm::Value *AdjustedThisPtr =
       CGM.getCXXABI().performThisAdjustment(*this, ThisPtr, Thunk.This);
   ThisStore->setOperand(0, AdjustedThisPtr);