Concurrency support for PNaCl ABI

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 64 matching lines @@
 
   // We should not place arbitrary passes after ExpandConstantExpr
   // because they might reintroduce ConstantExprs.
   PM.add(createExpandConstantExprPass());
   // PromoteIntegersPass does not handle constexprs and creates GEPs,
   // so it goes between those passes.
   PM.add(createPromoteIntegersPass());
   // 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());

[Mark Seaborn, 2013/07/02 19:16:02]

It would be better to place this before ExpandConstantExpr.  The passes from
ExpandConstantExpr onwards have subtle ordering constraints, but RewriteAtomics
doesn't, so can go earlier.

   // ReplacePtrsWithInts assumes that getelementptr instructions and
   // ConstantExprs have already been expanded out.
   PM.add(createReplacePtrsWithIntsPass());
 
   // 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());
 }