Concurrency support for PNaCl ABI

Add portable support for concurrency in PNaCl's ABI:
 - Promote volatile to atomic.
 - Promote all memory ordering to sequential consistency.
 - Rewrite all atomic operations to frozen NaCl intrinsics for pexe.
 - Rewrite atomic intrinsics to LLVM instructions for translation.

This change also adds documentation to the PNaCl language reference, as
well as tests where it makes sense.

A future CL could clean up more of our code which mentions atomics,
volatiles, memory orderings.

Multiple reviewers because this is a big patch:
 - eliben: LLVM-fu and ResolvePNaClIntrinsics.
 - dschuff: ABI stability.
 - mseaborn: ABI stability.
 - sehr: Tron-duty (fight for the user's programs to work).

BUG= https://code.google.com/p/nativeclient/issues/detail?id=3475
R=dschuff@chromium.org, eliben@chromium.org, sehr@google.com
TEST= (cd ./pnacl/build/llvm_x86_64; ninja check-all) && ./pnacl/test.sh test-x86-32 && ./pnacl/test.sh test-x86-64 && ./pnacl/test.sh test-arm && ./pnacl/test.sh test-x86-32-sbtc && ./pnacl/test.sh test-x86-64-sbtc && ./pnacl/test.sh test-arm-sbtc

Review URL: https://codereview.chromium.org/17777004

1 files changed, 2 insertions, 0 deletions

diff --git a/lib/Transforms/NaCl/PNaClABISimplify.cpp b/lib/Transforms/NaCl/PNaClABISimplify.cpp
index f8f78135a8..189d87f2cb 100644
--- a/lib/Transforms/NaCl/PNaClABISimplify.cpp
+++ b/lib/Transforms/NaCl/PNaClABISimplify.cpp
@@ -94,6 +94,8 @@ void llvm::PNaClABISimplifyAddPostOptPasses(PassManager &PM) {
   // ExpandGetElementPtr must follow ExpandConstantExpr to expand the
   // getelementptr instructions it creates.
   PM.add(createExpandGetElementPtrPass());
+  // Rewrite atomic and volatile instructions with intrinsic calls.
+  PM.add(createRewriteAtomicsPass());
   // ReplacePtrsWithInts assumes that getelementptr instructions and
   // ConstantExprs have already been expanded out.
   PM.add(createReplacePtrsWithIntsPass());