[X86] Lower blended PACKUSes using appropriate types.

When lowering two blended PACKUS, we used to disregard the types
of the PACKUS inputs, indiscriminately generating a v16i8 PACKUS.

This leads to non-selectable things like:
    (v16i8 (PACKUS (v4i32 v0), (v4i32 v1)))

Instead, check that the PACKUSes have the same type, and use that
as the final result type.

llvm-svn: 274138

1 files changed, 14 insertions, 11 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 859c27afe44..7d6f5c578fb 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -8943,22 +8943,25 @@ static SDValue lowerV2I64VectorShuffle(const SDLoc &DL, ArrayRef<int> Mask,
   assert(Mask[0] < 2 && "We sort V1 to be the first input.");
   assert(Mask[1] >= 2 && "We sort V2 to be the second input.");
 
-  // If we have a blend of two PACKUS operations an the blend aligns with the
-  // low and half halves, we can just merge the PACKUS operations. This is
-  // particularly important as it lets us merge shuffles that this routine itself
-  // creates.
+  // If we have a blend of two same-type PACKUS operations and the blend aligns
+  // with the low and high halves, we can just merge the PACKUS operations.
+  // This is particularly important as it lets us merge shuffles that this
+  // routine itself creates.
   auto GetPackNode = [](SDValue V) {
     V = peekThroughBitcasts(V);
     return V.getOpcode() == X86ISD::PACKUS ? V : SDValue();
   };
   if (SDValue V1Pack = GetPackNode(V1))
-    if (SDValue V2Pack = GetPackNode(V2))
-      return DAG.getBitcast(MVT::v2i64,
-                            DAG.getNode(X86ISD::PACKUS, DL, MVT::v16i8,
-                                        Mask[0] == 0 ? V1Pack.getOperand(0)
-                                                     : V1Pack.getOperand(1),
-                                        Mask[1] == 2 ? V2Pack.getOperand(0)
-                                                     : V2Pack.getOperand(1)));
+    if (SDValue V2Pack = GetPackNode(V2)) {
+      EVT PackVT = V1Pack.getValueType();
+      if (PackVT == V2Pack.getValueType())
+        return DAG.getBitcast(MVT::v2i64,
+                              DAG.getNode(X86ISD::PACKUS, DL, PackVT,
+                                          Mask[0] == 0 ? V1Pack.getOperand(0)
+                                                       : V1Pack.getOperand(1),
+                                          Mask[1] == 2 ? V2Pack.getOperand(0)
+                                                       : V2Pack.getOperand(1)));
+    }
 
   // Try to use shift instructions.
   if (SDValue Shift = lowerVectorShuffleAsShift(DL, MVT::v2i64, V1, V2, Mask,