[llvm] [AArch64][SVE] Implement demanded bits for @llvm.aarch64.sve.cntp (PR #168714)

[Benjamin Maxwell via llvm-commits]

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@@ -19459,6 +19459,32 @@ static std::optional<unsigned> IsSVECntIntrinsic(SDValue S) {
   return {};
 }
 
+// Returns the element size associated with an SVE cnt[bhwdp] intrinsic. For
+// cntp (predicate), the element size corresponds to the legal (packed) SVE
+// vector type associated with the predicate. E.g. nxv4i1 returns 32.
+static std::optional<unsigned> GetSVECntElementSize(SDValue Op) {
+  if (auto ElementSize = IsSVECntIntrinsic(Op))
+    return ElementSize;
+  Intrinsic::ID IID = getIntrinsicID(Op.getNode());
+  if (IID != Intrinsic::aarch64_sve_cntp)
+    return {};
+  EVT PredVT = Op.getOperand(Op.getNumOperands() - 1).getValueType();
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MacDue wrote:

1 or 2 works (0 is the IID)

https://github.com/llvm/llvm-project/pull/168714