[COFF, ARM64] Add _InterlockedAdd intrinsic

Reviewers: rnk, mstorsjo, compnerd, TomTan, haripul, javed.absar, efriedma

Reviewed By: efriedma

Subscribers: efriedma, kristof.beyls, chrib, jfb, cfe-commits

Differential Revision: https://reviews.llvm.org/D52811

llvm-svn: 343894
diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 8e23b22..18b300b 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -8517,6 +8517,15 @@
     return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedDecrement, E);
   case AArch64::BI_InterlockedIncrement64:
     return EmitMSVCBuiltinExpr(MSVCIntrin::_InterlockedIncrement, E);
+
+  case AArch64::BI_InterlockedAdd: {
+    Value *Arg0 = EmitScalarExpr(E->getArg(0));
+    Value *Arg1 = EmitScalarExpr(E->getArg(1));
+    AtomicRMWInst *RMWI = Builder.CreateAtomicRMW(
+      AtomicRMWInst::Add, Arg0, Arg1,
+      llvm::AtomicOrdering::SequentiallyConsistent);
+    return Builder.CreateAdd(RMWI, Arg1);
+  }
   }
 }