Small cleanups to type(of: self) handling in DI

Should be NFC

Author: jckarter

lib/SILOptimizer/Mandatory/DefiniteInitialization.cpp

@@ -857,8 +857,7 @@ void LifetimeChecker::handleLoadForTypeOfSelfUse(const DIMemoryUse &Use) {
         break;
     }
     assert(valueMetatype);
-    auto metatypeArgument = load->getFunction()->getEntryBlock()->getArguments()
-      .back();
+    auto metatypeArgument = load->getFunction()->getSelfMetadataArgument();
     replaceAllSimplifiedUsesAndErase(valueMetatype, metatypeArgument,
                                      [](SILInstruction*) { });
   }

test/SILOptimizer/definite_init_type_of_self_in_convenience_init.swift

@@ -0,0 +1,40 @@
+// RUN: %target-swift-emit-sil -verify %s
+
+// Integration test to ensure that `type(of: self)` keeps working in
+// class convenience initializers, even though they are now implemented as
+// allocating entry points.
+
+class C {
+  init() { }
+  init(throwingDesignated: ()) throws {}
+
+  convenience init(normal: ()) {
+    _ = (type(of: self), type(of: self))
+    self.init()
+    _ = (type(of: self), type(of: self))
+  }
+
+  convenience init(throwing: ()) throws {
+    do {
+      _ = (type(of: self), type(of: self))
+      try self.init(throwingDesignated: ())
+      _ = (type(of: self), type(of: self))
+    } catch {
+      _ = (type(of: self), type(of: self))
+      throw error
+    }
+    _ = (type(of: self), type(of: self))
+  }
+
+  convenience init?(optional: Bool) {
+    _ = (type(of: self), type(of: self))
+    if optional {
+      _ = (type(of: self), type(of: self))
+      self.init()
+    } else {
+      _ = (type(of: self), type(of: self))
+      return nil
+    }
+    _ = (type(of: self), type(of: self))
+  }
+}