[llvm] [LoongArch] Add demanded bits support for [X]VMSKLTZ (PR #143528)

[Lu Weining via llvm-commits]

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@@ -8192,3 +8210,56 @@ unsigned LoongArchTargetLowering::getNumRegistersForCallingConv(
 
   return TargetLowering::getNumRegistersForCallingConv(Context, CC, VT);
 }
+
+bool LoongArchTargetLowering::SimplifyDemandedBitsForTargetNode(
+    SDValue Op, const APInt &OriginalDemandedBits,
+    const APInt &OriginalDemandedElts, KnownBits &Known, TargetLoweringOpt &TLO,
+    unsigned Depth) const {
+  EVT VT = Op.getValueType();
+  unsigned BitWidth = OriginalDemandedBits.getBitWidth();
+  unsigned Opc = Op.getOpcode();
+  switch (Opc) {
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SixWeining wrote:

Add a `default` branch to avoid compiler warning?

https://github.com/llvm/llvm-project/pull/143528