[llvm] Perform bitreverse using AVX512 GFNI for i32 and i64. (PR #81764)

[Phoebe Wang via llvm-commits]

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@@ -31040,17 +31044,63 @@ static SDValue LowerBITREVERSE_XOP(SDValue Op, SelectionDAG &DAG) {
   return DAG.getBitcast(VT, Res);
 }
 
+static auto createBSWAPShuffleMask(EVT VT) {
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phoebewang wrote:

Style: We avoid to use `auto` in function definition. And it's better to pass a `SmallVectorImpl<int> &ShuffleMask` to avoid copy.

https://github.com/llvm/llvm-project/pull/81764