[ARM] Factor out two-result shuffle matching. NFCI.

In preparation for a future patch: makes it easier to do the same
matching to generate different nodes, without duplication.

llvm-svn: 240116

1 files changed, 35 insertions, 26 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 25da08b3227..e00e338bd28 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -5063,6 +5063,30 @@ static bool isVZIP_v_undef_Mask(ArrayRef<int> M, EVT VT, unsigned &WhichResult){
   return true;
 }
 
+/// Check if \p ShuffleMask is a NEON two-result shuffle (VZIP, VUZP, VTRN),
+/// and return the corresponding ARMISD opcode if it is, or 0 if it isn't.
+static unsigned isNEONTwoResultShuffleMask(ArrayRef<int> ShuffleMask, EVT VT,
+                                           unsigned &WhichResult,
+                                           bool &isV_UNDEF) {
+  isV_UNDEF = false;
+  if (isVTRNMask(ShuffleMask, VT, WhichResult))
+    return ARMISD::VTRN;
+  if (isVUZPMask(ShuffleMask, VT, WhichResult))
+    return ARMISD::VUZP;
+  if (isVZIPMask(ShuffleMask, VT, WhichResult))
+    return ARMISD::VZIP;
+
+  isV_UNDEF = true;
+  if (isVTRN_v_undef_Mask(ShuffleMask, VT, WhichResult))
+    return ARMISD::VTRN;
+  if (isVUZP_v_undef_Mask(ShuffleMask, VT, WhichResult))
+    return ARMISD::VUZP;
+  if (isVZIP_v_undef_Mask(ShuffleMask, VT, WhichResult))
+    return ARMISD::VZIP;
+
+  return 0;
+}
+
 /// \return true if this is a reverse operation on an vector.
 static bool isReverseMask(ArrayRef<int> M, EVT VT) {
   unsigned NumElts = VT.getVectorNumElements();
@@ -5479,7 +5503,7 @@ ARMTargetLowering::isShuffleMaskLegal(const SmallVectorImpl<int> &M,
       return true;
   }
 
-  bool ReverseVEXT;
+  bool ReverseVEXT, isV_UNDEF;
   unsigned Imm, WhichResult;
 
   unsigned EltSize = VT.getVectorElementType().getSizeInBits();
@@ -5490,12 +5514,7 @@ ARMTargetLowering::isShuffleMaskLegal(const SmallVectorImpl<int> &M,
           isVREVMask(M, VT, 16) ||
           isVEXTMask(M, VT, ReverseVEXT, Imm) ||
           isVTBLMask(M, VT) ||
-          isVTRNMask(M, VT, WhichResult) ||
-          isVUZPMask(M, VT, WhichResult) ||
-          isVZIPMask(M, VT, WhichResult) ||
-          isVTRN_v_undef_Mask(M, VT, WhichResult) ||
-          isVUZP_v_undef_Mask(M, VT, WhichResult) ||
-          isVZIP_v_undef_Mask(M, VT, WhichResult) ||
+          isNEONTwoResultShuffleMask(M, VT, WhichResult, isV_UNDEF) ||
           ((VT == MVT::v8i16 || VT == MVT::v16i8) && isReverseMask(M, VT)));
 }
 
@@ -5687,25 +5706,15 @@ static SDValue LowerVECTOR_SHUFFLE(SDValue Op, SelectionDAG &DAG) {
     // these operations, DAG memoization will ensure that a single node is
     // used for both shuffles.
     unsigned WhichResult;
-    if (isVTRNMask(ShuffleMask, VT, WhichResult))
-      return DAG.getNode(ARMISD::VTRN, dl, DAG.getVTList(VT, VT),
-                         V1, V2).getValue(WhichResult);
-    if (isVUZPMask(ShuffleMask, VT, WhichResult))
-      return DAG.getNode(ARMISD::VUZP, dl, DAG.getVTList(VT, VT),
-                         V1, V2).getValue(WhichResult);
-    if (isVZIPMask(ShuffleMask, VT, WhichResult))
-      return DAG.getNode(ARMISD::VZIP, dl, DAG.getVTList(VT, VT),
-                         V1, V2).getValue(WhichResult);
-
-    if (isVTRN_v_undef_Mask(ShuffleMask, VT, WhichResult))
-      return DAG.getNode(ARMISD::VTRN, dl, DAG.getVTList(VT, VT),
-                         V1, V1).getValue(WhichResult);
-    if (isVUZP_v_undef_Mask(ShuffleMask, VT, WhichResult))
-      return DAG.getNode(ARMISD::VUZP, dl, DAG.getVTList(VT, VT),
-                         V1, V1).getValue(WhichResult);
-    if (isVZIP_v_undef_Mask(ShuffleMask, VT, WhichResult))
-      return DAG.getNode(ARMISD::VZIP, dl, DAG.getVTList(VT, VT),
-                         V1, V1).getValue(WhichResult);
+    bool isV_UNDEF;
+    if (unsigned ShuffleOpc = isNEONTwoResultShuffleMask(
+            ShuffleMask, VT, WhichResult, isV_UNDEF)) {
+      if (isV_UNDEF)
+        V2 = V1;
+      return DAG.getNode(ShuffleOpc, dl, DAG.getVTList(VT, VT), V1, V2)
+          .getValue(WhichResult);
+    }
+
   }
 
   // If the shuffle is not directly supported and it has 4 elements, use