Lower signatures exposing struct registers to byval struct pointers

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

Index: test/Transforms/NaCl/simplify-struct-reg-vararg-crash.ll
diff --git a/test/Transforms/NaCl/simplify-struct-reg-vararg-crash.ll b/test/Transforms/NaCl/simplify-struct-reg-vararg-crash.ll
new file mode 100644
index 0000000000000000000000000000000000000000..2b0e59fe8334eedf11a4a90c1fa86f808d843372
--- /dev/null
+++ b/test/Transforms/NaCl/simplify-struct-reg-vararg-crash.ll
@@ -0,0 +1,10 @@
+; RUN: not opt < %s -simplify-struct-reg-signatures -S
+
+%struct = type { i32, i32 }
+
+declare void @vararg_fct(...)
+
+define void @vararg_caller_with_agg(%struct %str) {
+  call void(...)* @vararg_fct(%struct %str)
+  ret void
+}