[llvm] [AMDGPU] selecting v_sat_pk instruction, version 2 (PR #123297)

[via llvm-commits]

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@@ -1982,8 +2004,10 @@ bool SITargetLowering::isTypeDesirableForOp(unsigned Op, EVT VT) const {
   if (VT == MVT::i1 && Op == ISD::SETCC)
     return false;
 
-  // v2i8 is illegal and only allowed in specific cases
-  if (VT == MVT::v2i8 && Op == ISD::TRUNCATE_SSAT_U)
+  // Special case for vNi8 handling where N is even
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Shoreshen wrote:

Hi @arsenm , yeah it is kind of weird logic. And what made it more strange is that to get into the ReplaceNodeResults function, it will check `TLI.getOperationAction(Opc, DstVT) == Custom`........

But if we want to change this, I think we also need to modify AArch64 backend....

https://github.com/llvm/llvm-project/pull/123297