Introduce element-wise atomic memcpy intrinsic

This change adds a new intrinsic which is intended to provide memcpy functionality
with additional atomicity guarantees. Please refer to the review thread
or language reference for further details.

Differential Revision: https://reviews.llvm.org/D27133

llvm-svn: 290708

1 files changed, 45 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index da68fe87a32..cb803585282 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -4896,6 +4896,51 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
     updateDAGForMaybeTailCall(MM);
     return nullptr;
   }
+  case Intrinsic::memcpy_element_atomic: {
+    SDValue Dst = getValue(I.getArgOperand(0));
+    SDValue Src = getValue(I.getArgOperand(1));
+    SDValue NumElements = getValue(I.getArgOperand(2));
+    SDValue ElementSize = getValue(I.getArgOperand(3));
+
+    // Emit a library call.
+    TargetLowering::ArgListTy Args;
+    TargetLowering::ArgListEntry Entry;
+    Entry.Ty = DAG.getDataLayout().getIntPtrType(*DAG.getContext());
+    Entry.Node = Dst;
+    Args.push_back(Entry);
+
+    Entry.Node = Src;
+    Args.push_back(Entry);
+    
+    Entry.Ty = I.getArgOperand(2)->getType();
+    Entry.Node = NumElements;
+    Args.push_back(Entry);
+    
+    Entry.Ty = Type::getInt32Ty(*DAG.getContext());
+    Entry.Node = ElementSize;
+    Args.push_back(Entry);
+
+    uint64_t ElementSizeConstant =
+        cast<ConstantInt>(I.getArgOperand(3))->getZExtValue();
+    RTLIB::Libcall LibraryCall =
+        RTLIB::getMEMCPY_ELEMENT_ATOMIC(ElementSizeConstant);
+    if (LibraryCall == RTLIB::UNKNOWN_LIBCALL)
+      report_fatal_error("Unsupported element size");
+
+    TargetLowering::CallLoweringInfo CLI(DAG);
+    CLI.setDebugLoc(sdl)
+        .setChain(getRoot())
+        .setCallee(TLI.getLibcallCallingConv(LibraryCall),
+                   Type::getVoidTy(*DAG.getContext()),
+                   DAG.getExternalSymbol(
+                       TLI.getLibcallName(LibraryCall),
+                       TLI.getPointerTy(DAG.getDataLayout())),
+                   std::move(Args));
+
+    std::pair<SDValue, SDValue> CallResult = TLI.LowerCallTo(CLI);
+    DAG.setRoot(CallResult.second);
+    return nullptr;
+  }
   case Intrinsic::dbg_declare: {
     const DbgDeclareInst &DI = cast<DbgDeclareInst>(I);
     DILocalVariable *Variable = DI.getVariable();