[mlir] [VectorOps] refined description of vector.contract

[aartbik]

Summary

A few details were missing in the description. These
changes makes the documented code "compile".

[merge_guards_bot]

Unit tests: fail. 62357 tests passed, 1 failed and 839 were skipped.

failed: libc++.std/containers/sequences/array/array_creation/to_array.fail.cpp

clang-tidy: pass.

clang-format: pass.

Build artifacts: diff.json, clang-tidy.txt, clang-format.patch, CMakeCache.txt, console-log.txt, test-results.xml

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[nicolasvasilache]

Thanks Aart!

[andydavis1]

Thanks Aart

mlir/include/mlir/Dialect/VectorOps/VectorOps.td

let description = [{
     An indexing map attribute list must be specified with an entry for lhs, rhs
     and acc arguments. An indexing map attribute specifies a mapping from each
     iterator in the iterator type list, to each dimension of an N-D vector.
 
     Examples:
 
       // 2D vector contraction with one contracting dimension (matmul).
       #contraction_accesses = [
-        (i, j, k) -> (i, k),
-        (i, j, k) -> (k, j),
-        (i, j, k) -> (i, j)
+        affine_map<(i, j, k) -> (i, k)>,
+        affine_map<(i, j, k) -> (k, j)>,
+        affine_map<(i, j, k) -> (i, j)>
       ]
       #contraction_trait = {
         indexing_maps = #contraction_accesses,
-        iterator_types = [parallel, parallel, reduction]
+        iterator_types = ["parallel", "parallel", "reduction"]
       }
 
       %3 = vector.contract #contraction_trait %0, %1, %2
         : vector<4x3xf32>, vector<3x7xf32> into vector<4x7xf32>
 
       // 4D to 3D vector contraction with two contracting dimensions and
       // one batch dimension.
       #contraction_accesses = [
-        (b0, f0, f1, c0, c1) -> (c0, b0, c1, f0),
-        (b0, f0, f1, c0, c1) -> (b0, c1, c0, f1),
-        (b0, f0, f1, c0, c1) -> (b0, f0, f1)
+        affine_map<(b0, f0, f1, c0, c1) -> (c0, b0, c1, f0)>,
+        affine_map<(b0, f0, f1, c0, c1) -> (b0, c1, c0, f1)>,
+        affine_map<(b0, f0, f1, c0, c1) -> (b0, f0, f1)>
       ]
       #contraction_trait = {
         indexing_maps = #contraction_accesses,
-        iterator_types = [parallel, parallel, parallel reduction, reduction]
+        iterator_types = ["parallel", "parallel", "parallel",
+                    "reduction", "reduction"]
       }
 
       %4 = vector.contract #contraction_trait %0, %1, %2
           : vector<7x8x16x15xf32>, vector<8x16x7x5xf32> into vector<8x15x5xf32>
 
       // 4D vector contraction with two contracting dimensions and optional
       // vector mask arguments.
       %lhs_mask = vector.constant_mask [7, 8, 16, 15] : vector<7x8x16x15xi1>