[SystemZ] Use MVC for memcpy

Use MVC for memcpy in cases where a single MVC is enough.  Using MVC is
a win for longer copies too, but I'll leave that for later.

llvm-svn: 185802

1 files changed, 46 insertions, 0 deletions

diff --git a/llvm/lib/Target/SystemZ/SystemZSelectionDAGInfo.cpp b/llvm/lib/Target/SystemZ/SystemZSelectionDAGInfo.cpp
new file mode 100644
index 00000000000..d2da9d2a03a
--- /dev/null
+++ b/llvm/lib/Target/SystemZ/SystemZSelectionDAGInfo.cpp
@@ -0,0 +1,46 @@
+//===-- SystemZSelectionDAGInfo.cpp - SystemZ SelectionDAG Info -----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the SystemZSelectionDAGInfo class.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "systemz-selectiondag-info"
+#include "SystemZTargetMachine.h"
+#include "llvm/CodeGen/SelectionDAG.h"
+
+using namespace llvm;
+
+SystemZSelectionDAGInfo::
+SystemZSelectionDAGInfo(const SystemZTargetMachine &TM)
+  : TargetSelectionDAGInfo(TM) {
+}
+
+SystemZSelectionDAGInfo::~SystemZSelectionDAGInfo() {
+}
+
+SDValue SystemZSelectionDAGInfo::
+EmitTargetCodeForMemcpy(SelectionDAG &DAG, SDLoc DL, SDValue Chain,
+                        SDValue Dst, SDValue Src, SDValue Size, unsigned Align,
+                        bool IsVolatile, bool AlwaysInline,
+                        MachinePointerInfo DstPtrInfo,
+                        MachinePointerInfo SrcPtrInfo) const {
+  if (IsVolatile)
+    return SDValue();
+
+  if (ConstantSDNode *CSize = dyn_cast<ConstantSDNode>(Size)) {
+    uint64_t Bytes = CSize->getZExtValue();
+    if (Bytes >= 1 && Bytes <= 0x100) {
+      // A single MVC.
+      return DAG.getNode(SystemZISD::MVC, DL, MVT::Other,
+                         Chain, Dst, Src, Size);
+    }
+  }
+  return SDValue();
+}