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

[Pierre van Houtryve via llvm-commits]

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@@ -1974,6 +1983,12 @@ bool SITargetLowering::isTypeDesirableForOp(unsigned Op, EVT VT) const {
   // create setcc with i1 operands.  We don't have instructions for i1 setcc.
   if (VT == MVT::i1 && Op == ISD::SETCC)
     return false;
+  
+  // Avoiding legality check for reg type of v2i8 
+  // (do not need to addRegisterClass for v2i8)
+  // VT is result type, ensure the result type is v2i8
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Pierre-vh wrote:

Can shorten into something like "v2i8 is illegal and only allowed in specific cases" ?

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