PNaCl: Fix handling of va_arg on structs in simplification passes

test/Transforms/NaCl/pnacl-abi-simplify-preopt.ll

 ; RUN: opt %s -pnacl-abi-simplify-preopt -S | FileCheck %s
 
 ; "-pnacl-abi-simplify-preopt" runs various passes which are tested
 ; thoroughly in other *.ll files.  This file is a smoke test to check
 ; that "-pnacl-abi-simplify-preopt" runs what it's supposed to run.
 
 declare void @ext_func()
 
 
 define void @invoke_func() {
   invoke void @ext_func() to label %cont unwind label %lpad
 cont:
   ret void
 lpad:
   %lp = landingpad { i8*, i32 } personality i8* null cleanup
   ret void
 }
 ; CHECK-NOT: invoke void @ext_func()
 ; CHECK-NOT: landingpad
 
 
 define void @varargs_func(...) {
   ret void
 }
 ; CHECK-NOT: @varargs_func(...)
 
 
+%MyStruct = type { i32, i32 }
+
+; Checks that ExpandVarArgs and ExpandStructRegs are applied in the
+; right order.
+define void @get_struct_from_varargs(i8* %va_list, %MyStruct* %dest) {
+  %val = va_arg i8* %va_list, %MyStruct
+  store %MyStruct %val, %MyStruct* %dest
+  ret void
+}
+; CHECK-NOT: va_arg
+
+
 @llvm.global_ctors = appending global [0 x { i32, void ()* }] zeroinitializer
 ; CHECK-NOT: @llvm.global_ctors
 
 @tls_var = thread_local global i32 0
 ; CHECK-NOT: thread_local
 
 @alias = alias i32* @tls_var
 ; CHECK-NOT: @alias
 
 @weak_ref = extern_weak global i8*
 ; CHECK-NOT: extern_weak