Initial implementation of 'fence' instruction, the new C++0x-style replacement for llvm.memory.barrier.

This is just a LangRef entry and reading/writing/memory representation; optimizer+codegen support coming soon.

llvm-svn: 136009
diff --git a/llvm/lib/VMCore/Verifier.cpp b/llvm/lib/VMCore/Verifier.cpp
index c6b14c0..2b2b815 100644
--- a/llvm/lib/VMCore/Verifier.cpp
+++ b/llvm/lib/VMCore/Verifier.cpp
@@ -278,6 +278,7 @@
     void visitUserOp1(Instruction &I);
     void visitUserOp2(Instruction &I) { visitUserOp1(I); }
     void visitIntrinsicFunctionCall(Intrinsic::ID ID, CallInst &CI);
+    void visitFenceInst(FenceInst &FI);
     void visitAllocaInst(AllocaInst &AI);
     void visitExtractValueInst(ExtractValueInst &EVI);
     void visitInsertValueInst(InsertValueInst &IVI);
@@ -1315,6 +1316,15 @@
   visitInstruction(AI);
 }
 
+void Verifier::visitFenceInst(FenceInst &FI) {
+  const AtomicOrdering Ordering = FI.getOrdering();
+  Assert1(Ordering == Acquire || Ordering == Release ||
+          Ordering == AcquireRelease || Ordering == SequentiallyConsistent,
+          "fence instructions may only have "
+          " acquire, release, acq_rel, or seq_cst ordering.", &FI);
+  visitInstruction(FI);
+}
+
 void Verifier::visitExtractValueInst(ExtractValueInst &EVI) {
   Assert1(ExtractValueInst::getIndexedType(EVI.getAggregateOperand()->getType(),
                                            EVI.getIndices()) ==