1 files changed, 16 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 1820d5f944f..4ae22d69eaf 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -8779,6 +8779,22 @@ SDValue DAGCombiner::visitTRUNCATE(SDNode *N) {
     return DAG.getNode(N0.getOpcode(), SL, VTs, X, Y, N0.getOperand(2));
   }
 
+  // fold (truncate (extract_subvector(ext x))) ->
+  //      (extract_subvector x)
+  // TODO: This can be generalized to cover cases where the truncate and extract
+  // do not fully cancel each other out.
+  if (!LegalTypes && N0.getOpcode() == ISD::EXTRACT_SUBVECTOR) {
+    SDValue N00 = N0.getOperand(0);
+    if (N00.getOpcode() == ISD::SIGN_EXTEND ||
+        N00.getOpcode() == ISD::ZERO_EXTEND ||
+        N00.getOpcode() == ISD::ANY_EXTEND) {
+      if (N00.getOperand(0)->getValueType(0).getVectorElementType() ==
+          VT.getVectorElementType())
+        return DAG.getNode(ISD::EXTRACT_SUBVECTOR, SDLoc(N0->getOperand(0)), VT,
+                           N00.getOperand(0), N0.getOperand(1));
+    }
+  }
+
   if (SDValue NewVSel = matchVSelectOpSizesWithSetCC(N))
     return NewVSel;