[X86][SSE] Minor regression fix for r225551

r225551 vector byte shuffle optimization caused an assertion as fully zeroable vectors can be produced under certain circumstances. This fix drops the assert and returns a zero vector where the assert would have failed.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225718 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index f455700d5ad290af6a0c9550b57b3c4135dd6ad2..c36bd52fc55ab5d102bf0d484578d03c2cefc8be 100644 (file)
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -9652,7 +9652,6 @@ static SDValue lowerV16I8VectorShuffle(SDValue Op, SDValue V1, SDValue V2,
         V2InUse |= (ZeroMask != V2Idx);
       }
     }
-    assert((V1InUse || V2InUse) && "Shuffling to a zeroable vector");
 
     if (V1InUse)
       V1 = DAG.getNode(X86ISD::PSHUFB, DL, MVT::v16i8, V1,
@@ -9668,6 +9667,8 @@ static SDValue lowerV16I8VectorShuffle(SDValue Op, SDValue V1, SDValue V2,
       return V1; // Single inputs are easy.
     if (V2InUse)
       return V2; // Single inputs are easy.
+    // Shuffling to a zeroable vector.
+    return getZeroVector(MVT::v16i8, Subtarget, DAG, DL);
   }
 
   // There are special ways we can lower some single-element blends.