Lower signatures exposing struct registers to byval struct pointers

test/Transforms/NaCl/simplify-struct-reg-resume-crash.ll

+; RUN: not opt < %s -simplify-struct-reg-signatures -S
+
+%struct = type { i8*, void(%struct)* }
+
+declare i32 @__gxx_personality_v0(...)
+declare void @something_to_invoke()
+
+; landingpad with struct
+define void @landingpad_is_struct(%struct %str) {
+  invoke void @something_to_invoke()
+    to label %OK unwind label %Err
+
+OK:
+  ret void
+
+Err:
+  %exn = landingpad {i8*, i32} personality i32 (...)* @__gxx_personality_v0
+    cleanup
+  resume %struct %str
+}