[X86] Clarify PSHUFB+blend lowering function name. NFC.

Also guard against v32i8 users.

llvm-svn: 271024

1 files changed, 11 insertions, 9 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index d4a631673e8..d11cd5221ba 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -9637,11 +9637,13 @@ static SDValue lowerV8I16GeneralSingleInputVectorShuffle(
   return V;
 }
 
-/// \brief Helper to form a PSHUFB-based shuffle+blend.
-static SDValue lowerVectorShuffleAsPSHUFB(SDLoc DL, MVT VT, SDValue V1,
-                                          SDValue V2, ArrayRef<int> Mask,
-                                          SelectionDAG &DAG, bool &V1InUse,
-                                          bool &V2InUse) {
+/// Helper to form a PSHUFB-based shuffle+blend, opportunistically avoiding the
+/// blend if only one input is used.
+static SDValue
+lowerVectorShuffleAsBlendOfPSHUFBs(SDLoc DL, MVT VT, SDValue V1, SDValue V2,
+                                   ArrayRef<int> Mask, SelectionDAG &DAG,
+                                   bool &V1InUse, bool &V2InUse) {
+  assert(VT.is128BitVector() && "v32i8 VPSHUFB blend not implemented yet!");
   SmallBitVector Zeroable = computeZeroableShuffleElements(Mask, V1, V2);
   SDValue V1Mask[16];
   SDValue V2Mask[16];
@@ -9807,8 +9809,8 @@ static SDValue lowerV8I16VectorShuffle(SDValue Op, SDValue V1, SDValue V2,
   // can both shuffle and set up the inefficient blend.
   if (!IsBlendSupported && Subtarget.hasSSSE3()) {
     bool V1InUse, V2InUse;
-    return lowerVectorShuffleAsPSHUFB(DL, MVT::v8i16, V1, V2, Mask, DAG,
-                                      V1InUse, V2InUse);
+    return lowerVectorShuffleAsBlendOfPSHUFBs(DL, MVT::v8i16, V1, V2, Mask, DAG,
+                                              V1InUse, V2InUse);
   }
 
   // We can always bit-blend if we have to so the fallback strategy is to
@@ -10050,8 +10052,8 @@ static SDValue lowerV16I8VectorShuffle(SDValue Op, SDValue V1, SDValue V2,
     bool V1InUse = false;
     bool V2InUse = false;
 
-    SDValue PSHUFB = lowerVectorShuffleAsPSHUFB(DL, MVT::v16i8, V1, V2, Mask,
-                                                DAG, V1InUse, V2InUse);
+    SDValue PSHUFB = lowerVectorShuffleAsBlendOfPSHUFBs(
+        DL, MVT::v16i8, V1, V2, Mask, DAG, V1InUse, V2InUse);
 
     // If both V1 and V2 are in use and we can use a direct blend or an unpack,
     // do so. This avoids using them to handle blends-with-zero which is