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-rw-r--r--lib/CodeGen/SelectionDAG/DAGCombiner.cpp42
1 files changed, 42 insertions, 0 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 0c5cd3e6cab..f2d3a8d4fe9 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -5308,6 +5308,48 @@ SDValue DAGCombiner::visitTRUNCATE(SDNode *N) {
if (Reduced.getNode())
return Reduced;
}
+ // fold (trunc (concat ... x ...)) -> (concat ..., (trunc x), ...)),
+ // where ... are all 'undef'.
+ if (N0.getOpcode() == ISD::CONCAT_VECTORS && !LegalTypes) {
+ SmallVector<EVT, 8> VTs;
+ SDValue V;
+ unsigned Idx = 0;
+ unsigned NumDefs = 0;
+
+ for (unsigned i = 0, e = N0.getNumOperands(); i != e; ++i) {
+ SDValue X = N0.getOperand(i);
+ if (X.getOpcode() != ISD::UNDEF) {
+ V = X;
+ Idx = i;
+ NumDefs++;
+ }
+ // Stop if more than one members are non-undef.
+ if (NumDefs > 1)
+ break;
+ VTs.push_back(EVT::getVectorVT(*DAG.getContext(),
+ VT.getVectorElementType(),
+ X.getValueType().getVectorNumElements()));
+ }
+
+ if (NumDefs == 0)
+ return DAG.getUNDEF(VT);
+
+ if (NumDefs == 1) {
+ assert(V.getNode() && "The single defined operand is empty!");
+ SmallVector<SDValue, 8> Opnds;
+ for (unsigned i = 0, e = VTs.size(); i != e; ++i) {
+ if (i != Idx) {
+ Opnds.push_back(DAG.getUNDEF(VTs[i]));
+ continue;
+ }
+ SDValue NV = DAG.getNode(ISD::TRUNCATE, V.getDebugLoc(), VTs[i], V);
+ AddToWorkList(NV.getNode());
+ Opnds.push_back(NV);
+ }
+ return DAG.getNode(ISD::CONCAT_VECTORS, N->getDebugLoc(), VT,
+ &Opnds[0], Opnds.size());
+ }
+ }
// Simplify the operands using demanded-bits information.
if (!VT.isVector() &&