PNaCl: Fix handling of va_arg on structs in simplification passes

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 39 matching lines @@
   // Expand out computed gotos (indirectbr and blockaddresses) into switches.
   PM.add(createExpandIndirectBrPass());
 
   // LowerExpect converts Intrinsic::expect into branch weights,
   // which can then be removed after BlockPlacement.
   PM.add(createLowerExpectIntrinsicPass());
   // Rewrite unsupported intrinsics to simpler and portable constructs.
   PM.add(createRewriteLLVMIntrinsicsPass());
 
   // Expand out some uses of struct types.
+  PM.add(createExpandVarArgsPass());
   PM.add(createExpandArithWithOverflowPass());
   // ExpandStructRegs must be run after ExpandArithWithOverflow to
   // expand out the insertvalue instructions that
-  // ExpandArithWithOverflow introduces.
+  // ExpandArithWithOverflow introduces.  ExpandStructRegs must be run
+  // after ExpandVarArgs so that struct-typed "va_arg" instructions
+  // have been removed.
   PM.add(createExpandStructRegsPass());
 
-  PM.add(createExpandVarArgsPass());
   PM.add(createExpandCtorsPass());
   PM.add(createResolveAliasesPass());
   PM.add(createExpandTlsPass());
   // GlobalCleanup needs to run after ExpandTls because
   // __tls_template_start etc. are extern_weak before expansion
   PM.add(createGlobalCleanupPass());
 }
 
 void llvm::PNaClABISimplifyAddPostOptPasses(PassManager &PM) {
   PM.add(createRewritePNaClLibraryCallsPass());
@@ skipping 54 matching lines @@
   // 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());
 }