[DAGCombiner] Avoid calling method 'isShuffleMaskLegal' on illegal vector types.

This patch fixes a crasher in method 'DAGCombiner::visitOR' due to an invalid
call to method 'isShuffleMaskLegal'. On x86, method 'isShuffleMaskLegal'
always expects a legal vector value type in input.

With this patch, we immediately check if the input OR dag node has a legal
vector type; we only try to fold a OR dag node into a single shufflevector
if we know that the resulting shuffle will have a legal type.
This is to avoid calling method 'isShuffleMaskLegal' on a potentially
illegal vector value type.

Added a new test-case to file 'CodeGen/X86/combine-or.ll' to verify that
DAGCombiner doesn't crash in the attempt to check/combine an OR between shuffles
with illegal types.

llvm-svn: 213020

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index a1dd8bf5cb2..9d91b3e6443 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3255,6 +3255,8 @@ SDValue DAGCombiner::visitOR(SDNode *N) {
     // Do this only if the resulting shuffle is legal.
     if (isa<ShuffleVectorSDNode>(N0) &&
         isa<ShuffleVectorSDNode>(N1) &&
+        // Avoid folding a node with illegal type.
+        TLI.isTypeLegal(VT) &&
         N0->getOperand(1) == N1->getOperand(1) &&
         ISD::isBuildVectorAllZeros(N0.getOperand(1).getNode())) {
       bool CanFold = true;