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

[Pierre van Houtryve via llvm-commits]

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@@ -865,6 +865,15 @@ SITargetLowering::SITargetLowering(const TargetMachine &TM,
       setOperationAction({ISD::FMAXIMUM, ISD::FMINIMUM}, MVT::v2f16, Legal);
   }
 
+  // special dealing for v_sat_pk instruction
+  if (AMDGPU::isGFX9(STI) || AMDGPU::isGFX11(STI) || AMDGPU::isGFX12(STI)) {
+    // In foldToSaturated during DAG combine
+    // 1. isOperationLegalOrCustom(Opc, SrcVT) getOperationAction(Op, SrcVT) == Custom
+    // 2. isTypeDesirableForOp checks regclass for v2i8 (hooked now checking DstVT == v2i8)
+    // In CustomLowerNode during legalizing, checks getOperationAction(Op, DstVT) == Custom
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Pierre-vh wrote:

Leftover debug comments?

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