[DAGCombine] Bail out if can't create a vector with at least two elements

Summary:

Fixes pr32278

Reviewers: igorb, craig.topper, RKSimon, spatel, hfinkel

Reviewed By: RKSimon

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D30978

llvm-svn: 297878

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -14098,8 +14098,11 @@ SDValue DAGCombiner::visitCONCAT_VECTORS(SDNode *N) {
       if (!SclTy.isFloatingPoint() && !SclTy.isInteger())
         return SDValue();
 
-      EVT NVT = EVT::getVectorVT(*DAG.getContext(), SclTy,
-                                 VT.getSizeInBits() / SclTy.getSizeInBits());
+      unsigned VNTNumElms = VT.getSizeInBits() / SclTy.getSizeInBits();
+      if (VNTNumElms < 2)
+        return SDValue();
+
+      EVT NVT = EVT::getVectorVT(*DAG.getContext(), SclTy, VNTNumElms);
       if (!TLI.isTypeLegal(NVT) || !TLI.isTypeLegal(Scalar.getValueType()))
         return SDValue();
 

llvm/test/CodeGen/Generic/pr32278.ll

@@ -1,6 +1,4 @@
 ; PR32278
-; XFAIL: *
-; REQUIRES: asserts
 
 ; RUN: llc < %s