Lower signatures exposing struct registers to byval struct pointers

lib/Transforms/NaCl/PNaClABISimplify.cpp

 //===-- PNaClABISimplify.cpp - Lists PNaCl ABI simplification passes ------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the meta-passes "-pnacl-abi-simplify-preopt"
@@ skipping 133 matching lines @@
   // atomics: a ``fence seq_cst`` surrounded by ``asm("":::"memory")``
   // has special meaning and is translated differently.
   PM.add(createRemoveAsmMemoryPass());
 
   PM.add(createSimplifyAllocasPass());
 
   // ReplacePtrsWithInts assumes that getelementptr instructions and
   // ConstantExprs have already been expanded out.
   PM.add(createReplacePtrsWithIntsPass());
 
+  // Convert struct reg function params to struct* byval
+  PM.add(createSimplifyStructRegSignaturesPass());
+
   // The atomic cmpxchg instruction returns a struct, and is rewritten to an
   // intrinsic as a post-opt pass, we therefore need to expand struct regs one
   // last time.
   PM.add(createExpandStructRegsPass());
 
   // We place StripAttributes after optimization passes because many
   // analyses add attributes to reflect their results.
   // StripAttributes must come after ExpandByVal and
   // ExpandSmallArguments.
   PM.add(createStripAttributesPass());
 
   // Strip dead prototytes to appease the intrinsic ABI checks.
   // ExpandVarArgs leaves around vararg intrinsics, and
   // ReplacePtrsWithInts leaves the lifetime.start/end intrinsics.
   PM.add(createStripDeadPrototypesPass());
 
   // Eliminate simple dead code that the post-opt passes could have
   // created.
   PM.add(createDeadInstEliminationPass());
   PM.add(createDeadCodeEliminationPass());
 }