[X86][SSE] Add support for lowering unary shuffles to PACKSS/PACKUS

Extension to D38472

llvm-svn: 314901

1 files changed, 24 insertions, 12 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index a6cd747999c..08c944ca696 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -8683,24 +8683,36 @@ static SDValue lowerVectorShuffleWithPACK(const SDLoc &DL, MVT VT,
   MVT PackSVT = MVT::getIntegerVT(BitSize * 2);
   MVT PackVT = MVT::getVectorVT(PackSVT, NumElts / 2);
 
-  // TODO - Add support for unary packs.
-  SmallVector<int, 32> BinaryMask;
-  createPackShuffleMask(VT, BinaryMask, false);
-
-  if (isShuffleEquivalent(V1, V2, Mask, BinaryMask)) {
-    SDValue VV1 = DAG.getBitcast(PackVT, V1);
-    SDValue VV2 = DAG.getBitcast(PackVT, V2);
-    if ((V1.isUndef() || DAG.ComputeNumSignBits(VV1) > BitSize) &&
-        (V2.isUndef() || DAG.ComputeNumSignBits(VV2) > BitSize))
+  auto LowerWithPACK = [&](SDValue N1, SDValue N2) {
+    SDValue VV1 = DAG.getBitcast(PackVT, N1);
+    SDValue VV2 = DAG.getBitcast(PackVT, N2);
+    if ((N1.isUndef() || DAG.ComputeNumSignBits(VV1) > BitSize) &&
+        (N2.isUndef() || DAG.ComputeNumSignBits(VV2) > BitSize))
       return DAG.getNode(X86ISD::PACKSS, DL, VT, VV1, VV2);
 
     if (Subtarget.hasSSE41() || PackSVT == MVT::i16) {
       APInt ZeroMask = APInt::getHighBitsSet(BitSize * 2, BitSize);
-      if ((V1.isUndef() || DAG.MaskedValueIsZero(VV1, ZeroMask)) &&
-          (V2.isUndef() || DAG.MaskedValueIsZero(VV2, ZeroMask)))
+      if ((N1.isUndef() || DAG.MaskedValueIsZero(VV1, ZeroMask)) &&
+          (N2.isUndef() || DAG.MaskedValueIsZero(VV2, ZeroMask)))
         return DAG.getNode(X86ISD::PACKUS, DL, VT, VV1, VV2);
     }
-  }
+
+    return SDValue();
+  };
+
+  // Try binary shuffle.
+  SmallVector<int, 32> BinaryMask;
+  createPackShuffleMask(VT, BinaryMask, false);
+  if (isShuffleEquivalent(V1, V2, Mask, BinaryMask))
+    if (SDValue Pack = LowerWithPACK(V1, V2))
+      return Pack;
+
+  // Try unary shuffle.
+  SmallVector<int, 32> UnaryMask;
+  createPackShuffleMask(VT, UnaryMask, true);
+  if (isShuffleEquivalent(V1, V2, Mask, UnaryMask))
+    if (SDValue Pack = LowerWithPACK(V1, V1))
+      return Pack;
 
   return SDValue();
 }