[llvm] [mlir] [mlir][mesh] Add all-scatter operation (PR #81218)

[Lei Zhang via llvm-commits]

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@@ -341,6 +342,68 @@ def Mesh_AllReduceOp : Mesh_CollectiveCommunicationOpBase<"all_reduce", [
   let hasCanonicalizer = 1;
 }
 
+def Mesh_AllScatterOp : Mesh_CollectiveCommunicationOpBase<"all_scatter", [
+    Pure,
+    SameOperandsAndResultElementType,
+    SameOperandsAndResultRank
+  ]> {
+  let summary = "All-scatter over a device mesh. This is the inverse of all-gather.";
+  let description = [{
+    Scatter along the `scatter_axis` tensor axis.
+    This operation can be taught of as the inverse of all-gather.
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antiagainst wrote:

typo: s/taught/thought/ ?

https://github.com/llvm/llvm-project/pull/81218