PNaCl: Add a pass to expand out Clang's use of registers of struct type

Clang's implementation of C++ method pointers generates IR that uses
LLVM registers with struct type -- specifically, loads and stores of
struct values, and extractvalue instructions.  See
lib/CodeGen/ItaniumCXXABI.cpp in Clang.  Add a pass, ExpandStructRegs,
which expands out those uses.

Factor out a function from ExpandArithWithOverflow so that the two
passes can share some code.

BUG=https://code.google.com/p/nativeclient/issues/detail?id=3343
TEST=*.ll tests + trybots + GCC torture tests

Review URL: https://codereview.chromium.org/15692014

1 files changed, 3 insertions, 0 deletions

diff --git a/lib/Transforms/NaCl/PNaClABISimplify.cpp b/lib/Transforms/NaCl/PNaClABISimplify.cpp
index 848d340e22..8c945800af 100644
--- a/lib/Transforms/NaCl/PNaClABISimplify.cpp
+++ b/lib/Transforms/NaCl/PNaClABISimplify.cpp
@@ -28,7 +28,10 @@ void llvm::PNaClABISimplifyAddPreOptPasses(PassManager &PM) {
   // Remove landingpad blocks made unreachable by LowerInvoke.
   PM.add(createCFGSimplificationPass());
 
+  // Expand out some uses of struct types.
   PM.add(createExpandArithWithOverflowPass());
+  PM.add(createExpandStructRegsPass());
+
   PM.add(createExpandVarArgsPass());
   PM.add(createExpandCtorsPass());
   PM.add(createResolveAliasesPass());