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

[Pierre van Houtryve via llvm-commits]

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@@ -6615,6 +6640,44 @@ void SITargetLowering::ReplaceNodeResults(SDNode *N,
     Results.push_back(lowerFSQRTF16(SDValue(N, 0), DAG));
     break;
   }
+  case ISD::TRUNCATE_SSAT_U: {
+    SDLoc SL(N);
+    SDValue Src = N->getOperand(0);
+    EVT SrcVT = Src.getValueType();
+    EVT DstVT = N->getValueType(0);
+
+    assert(SrcVT.isVector() && DstVT.isVector());
+    assert(DstVT.getVectorElementType() == MVT::i8);
+    assert(SrcVT.getVectorElementType() == MVT::i16);
+
+    unsigned EleNo = SrcVT.getVectorNumElements();
+    assert(EleNo == DstVT.getVectorNumElements());
+
+    if (EleNo == 2) {
+      SDValue Op = DAG.getNode(AMDGPUISD::SAT_PK_CAST, SL, MVT::i16, Src);
+      Op = DAG.getNode(ISD::BITCAST, SL, N->getValueType(0), Op);
+      Results.push_back(Op);
+    } else {
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Pierre-vh wrote:

nit: You could just `break` at the end of that condition and avoid the `else` to remove a layer of nesting, which always helps readability


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