[PATCH] Refactor AtomicExpandPass and add a generic isAtomic() method to Instruction

[JF Bastien]

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Comment at: lib/CodeGen/AtomicExpandPass.cpp:150
@@ -149,1 +149,3 @@
+  // If getInsertFencesForAtomic() returns true, then the target does not want
+  // to
   // deal with memory orders, and emitLeading/TrailingFence should take care of
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Something got messed up here and below.

http://reviews.llvm.org/D5035