[llvm] [LLVM][SVE] Improve legalisation of fixed length get.active.lane.mask (PR #90213)

[David Sherwood via llvm-commits]

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@@ -25593,19 +25581,39 @@ void AArch64TargetLowering::ReplaceNodeResults(
       return;
     }
     case Intrinsic::aarch64_sve_lasta: {
+      assert((VT == MVT::i8 || VT == MVT::i16) &&
+             "custom lowering for unexpected type");
       SDLoc DL(N);
       auto V = DAG.getNode(AArch64ISD::LASTA, DL, MVT::i32,
                            N->getOperand(1), N->getOperand(2));
       Results.push_back(DAG.getNode(ISD::TRUNCATE, DL, VT, V));
       return;
     }
     case Intrinsic::aarch64_sve_lastb: {
+      assert((VT == MVT::i8 || VT == MVT::i16) &&
+             "custom lowering for unexpected type");
       SDLoc DL(N);
       auto V = DAG.getNode(AArch64ISD::LASTB, DL, MVT::i32,
                            N->getOperand(1), N->getOperand(2));
       Results.push_back(DAG.getNode(ISD::TRUNCATE, DL, VT, V));
       return;
     }
+    case Intrinsic::get_active_lane_mask: {
+      if (!VT.isFixedLengthVector())
+        return;
+      if (VT.getVectorElementType() != MVT::i1)
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david-arm wrote:

Maybe it looks neater to combine these two if statements into one?

https://github.com/llvm/llvm-project/pull/90213