PNaCl: Add two new passes: `-rewrite-aggregate-arguments && `-rewrite-aggregate-returns`.

lib/Transforms/NaCl/PNaClABISimplify.cpp

Index: lib/Transforms/NaCl/PNaClABISimplify.cpp
diff --git a/lib/Transforms/NaCl/PNaClABISimplify.cpp b/lib/Transforms/NaCl/PNaClABISimplify.cpp
index e758244a737d2ead200b9307e1ae38f93219b977..5172c259c1b9ce1806c29e7a89a768bd3a212970 100644
--- a/lib/Transforms/NaCl/PNaClABISimplify.cpp
+++ b/lib/Transforms/NaCl/PNaClABISimplify.cpp
@@ -92,6 +92,11 @@ void llvm::PNaClABISimplifyAddPreOptPasses(Triple *T, PassManagerBase &PM) {
   // "va_arg" instructions have been removed.
   PM.add(createExpandVarArgsPass());
 
+  // RewriteAgg(Arg|Ret) replaces aggregate arguments or return type with the
+  // pointer representation of the type. Needs to be before ExpandStructRegs.
+  PM.add(createRewriteAggArgPass());
+  PM.add(createRewriteAggRetPass());
+
   // TODO(mtrofin) Remove the following and only run it as a post-opt pass once
   //               the following bug is fixed.
   // https://code.google.com/p/nativeclient/issues/detail?id=3857