[mlir][amx] add doc to AMX dialect

[aartbik]

Summary

Making sure the AMX dialect webpage reads better with a short introduction on the purpose of this dialect.

[bondhugula]

mlir/include/mlir/Dialect/AMX/AMX.td

47

Nit: IR details of AMX -> IR support for AMX ?

[aartbik]

addressed comment, added link

mlir/include/mlir/Dialect/AMX/AMX.td

 //===-- AMX.td - AMX dialect operation definitions *- tablegen -*----------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file defines the basic operations for the AMX dialect.
 //
-// The Intel Advanced Matrix Extensions (AMX) provides a tile matrix
+// The Intel Advanced Matrix Extensions (AMX) provide a tile matrix
 // multiply unit (TMUL), a tile control register (TILECFG), and eight
 // tile registers TMM0 through TMM7 (TILEDATA).
 //
 // The AMX dialect provides a bridge between MLIR concepts, such as
 // 2-d vector, operations, and memrefs, and the lower level details
 // of Intel AMX, such as configuration setup, tile sizes, instructions,
 // and tile release.
 //

 
 //===----------------------------------------------------------------------===//
 // AMX dialect definition.
 //===----------------------------------------------------------------------===//
 
 def AMX_Dialect : Dialect {
   let name = "amx";
   let cppNamespace = "::mlir::amx";
+  let description = [{
+    The Intel Advanced Matrix Extensions (AMX) provide a tile matrix
+    multiply unit (TMUL), a tile control register (TILECFG), and eight
+    tile registers TMM0 through TMM7 (TILEDATA).
+
+    This `AMX` dialect provides a bridge between MLIR concepts such as
+    vectors and memrefs and the lower level LLVM IR support of AMX.
+    The dialect is split into user-facing AMX ops (AMX_Op) and
+    backend-facing intrinsic ops (AMX_IntrOp).
+
+    Note that since configuration changes (implicit at dialect level) are
+    costly, it is highly recommended to use the AMX dialect on same-shaped
+    vectors, at least within a single method.
+
+    For details, see the Intel documentation:
+    https://software.intel.com/content/www/us/en/develop/articles/intel-sdm.html
+  }];
 }
 
 //===----------------------------------------------------------------------===//
 // AMX Op and IntrOp definitions.
 //===----------------------------------------------------------------------===//
 
 class AMX_Op<string mnemonic, list<OpTrait> traits = []> :
   Op<AMX_Dialect, mnemonic, traits> {}
let description = [{
     source operand tiles; the zero or sign extension is specified with
     the attributes and default to sign extended). The operation is eventually
     lowered into one of the "tdpbssd", "tdpbsud", "tdpbusd", or "tdpbuud"
     instructions with the corresponding tile configuration.
 
     Example:
 
     ```mlir
-      %0 = amx.tile_muli %a zext, %b zext, %c 
+      %0 = amx.tile_muli %a zext, %b zext, %c
         : vector<16x64xi8>, vector<16x64xi8>, vector<16x16xi32>
     ```
   }];
   let verifier = [{ return ::verify(*this); }];
   let arguments = (ins VectorOfRankAndType<[2], [I32, I8]>:$lhs,
                        VectorOfRankAndType<[2], [I32, I8]>:$rhs,
                        VectorOfRankAndType<[2], [I32, I8]>:$acc,
                        UnitAttr:$isZextLhs,