[DAG] Fix crash in build_vector -> vector_shuffle combine

Fixes a crash in the build_vector -> vector_shuffle combine
when the first vector input is twice as wide as the output,
and the second input vector is even wider.

llvm-svn: 283953

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index b8dad384f6c..57cee4706d8 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -12955,6 +12955,11 @@ SDValue DAGCombiner::createBuildVecShuffle(SDLoc DL, SDNode *N,
           VecIn2 = DAG.getNode(ISD::INSERT_SUBVECTOR, DL, InVT1,
                                DAG.getUNDEF(InVT1), VecIn2, ZeroIdx);
         ShuffleNumElems = NumElems * 2;
+      } else {
+        // Both VecIn1 and VecIn2 are wider than the output, and VecIn2 is wider
+        // than VecIn1. We can't handle this for now - this case will disappear
+        // when we start sorting the vectors by type.
+        return SDValue();
       }
     } else {
       // TODO: Support cases where the length mismatch isn't exactly by a