# Fix for #1844, affects avx512skx-x64 and avx512skx-x32.

# It's a port of 11.0 commit edcfb47ff6d5562e22207f364c65f84302aa346b

# https://reviews.llvm.org/D76312

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

index f88950fc872..7a68d18ef9b 100644

--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

@@ -11023,7 +11023,9 @@ SDValue DAGCombiner::visitTRUNCATE(SDNode *N) {

// Attempt to pre-truncate BUILD_VECTOR sources.

if (N0.getOpcode() == ISD::BUILD_VECTOR && !LegalOperations &&

- TLI.isTruncateFree(SrcVT.getScalarType(), VT.getScalarType())) {

+ TLI.isTruncateFree(SrcVT.getScalarType(), VT.getScalarType()) &&

+ // Avoid creating illegal types if running after type legalizer.

+ (!LegalTypes || TLI.isTypeLegal(VT.getScalarType()))) {

SDLoc DL(N);

EVT SVT = VT.getScalarType();

SmallVector<SDValue, 8> TruncOps;