IR: add a second ordering operand to cmpxhg for failure

The syntax for "cmpxchg" should now look something like:

	cmpxchg i32* %addr, i32 42, i32 3 acquire monotonic

where the second ordering argument gives the required semantics in the case
that no exchange takes place. It should be no stronger than the first ordering
constraint and cannot be either "release" or "acq_rel" (since no store will
have taken place).

rdar://problem/15996804

llvm-svn: 203559

1 files changed, 33 insertions, 1 deletions

diff --git a/llvm/lib/IR/AsmWriter.cpp b/llvm/lib/IR/AsmWriter.cpp
index c9ea49b2224..a528e5f326b 100644
--- a/llvm/lib/IR/AsmWriter.cpp
+++ b/llvm/lib/IR/AsmWriter.cpp
@@ -1226,6 +1226,37 @@ void AssemblyWriter::writeAtomic(AtomicOrdering Ordering,
   }
 }
 
+void AssemblyWriter::writeAtomicCmpXchg(AtomicOrdering SuccessOrdering,
+                                        AtomicOrdering FailureOrdering,
+                                        SynchronizationScope SynchScope) {
+  assert(SuccessOrdering != NotAtomic && FailureOrdering != NotAtomic);
+
+  switch (SynchScope) {
+  case SingleThread: Out << " singlethread"; break;
+  case CrossThread: break;
+  }
+
+  switch (SuccessOrdering) {
+  default: Out << " <bad ordering " << int(SuccessOrdering) << ">"; break;
+  case Unordered: Out << " unordered"; break;
+  case Monotonic: Out << " monotonic"; break;
+  case Acquire: Out << " acquire"; break;
+  case Release: Out << " release"; break;
+  case AcquireRelease: Out << " acq_rel"; break;
+  case SequentiallyConsistent: Out << " seq_cst"; break;
+  }
+
+  switch (FailureOrdering) {
+  default: Out << " <bad ordering " << int(FailureOrdering) << ">"; break;
+  case Unordered: Out << " unordered"; break;
+  case Monotonic: Out << " monotonic"; break;
+  case Acquire: Out << " acquire"; break;
+  case Release: Out << " release"; break;
+  case AcquireRelease: Out << " acq_rel"; break;
+  case SequentiallyConsistent: Out << " seq_cst"; break;
+  }
+}
+
 void AssemblyWriter::writeParamOperand(const Value *Operand,
                                        AttributeSet Attrs, unsigned Idx) {
   if (Operand == 0) {
@@ -2018,7 +2049,8 @@ void AssemblyWriter::printInstruction(const Instruction &I) {
     if (SI->getAlignment())
       Out << ", align " << SI->getAlignment();
   } else if (const AtomicCmpXchgInst *CXI = dyn_cast<AtomicCmpXchgInst>(&I)) {
-    writeAtomic(CXI->getOrdering(), CXI->getSynchScope());
+    writeAtomicCmpXchg(CXI->getSuccessOrdering(), CXI->getFailureOrdering(),
+                       CXI->getSynchScope());
   } else if (const AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(&I)) {
     writeAtomic(RMWI->getOrdering(), RMWI->getSynchScope());
   } else if (const FenceInst *FI = dyn_cast<FenceInst>(&I)) {