[mlir][vector] Add vector.to_elements unrolling

mlir/lib/Dialect/Vector/Transforms/LowerVectorToElements.cpp

@@ -34,8 +34,7 @@ struct UnrollToElements final : public OpRewritePattern<vector::ToElementsOp> {
     }
     SmallVector<Value> vectors = *result;
 
-    // May be a large vector.
-    SmallVector<Value, 0> results;
+    SmallVector<Value> results;
     for (const Value &vector : vectors) {
       auto subElements =
           vector::ToElementsOp::create(rewriter, op.getLoc(), vector);

mlir/test/Dialect/Vector/lit.local.cfg

@@ -0,0 +1,2 @@
+# Skip the directory with input TD sequences
+config.excludes = ["td"]

mlir/test/Dialect/Vector/td/unroll-elements.mlir

@@ -0,0 +1,11 @@
+module attributes {transform.with_named_sequence} {
+  transform.named_sequence @unroll_to_elements(%module_op: !transform.any_op {transform.readonly}) {
+    %f = transform.structured.match ops{["func.func"]} in %module_op
+      : (!transform.any_op) -> !transform.any_op
+    transform.apply_patterns to %f {
+      transform.apply_patterns.vector.transfer_permutation_patterns
+      transform.apply_patterns.vector.unroll_to_elements
+    } : !transform.any_op
+    transform.yield
+  }
+}

mlir/test/Dialect/Vector/vector-to-elements-lowering.mlir

@@ -1,4 +1,6 @@
 // RUN: mlir-opt %s -test-unroll-vector-to-elements -split-input-file | FileCheck %s
+// RUN: mlir-opt %s -transform-preload-library='transform-library-paths=%p/td/unroll-elements.mlir' \
+// RUN: -transform-interpreter=entry-point=unroll_to_elements | FileCheck %s
 
 // CHECK-LABEL: func.func @to_elements_1d(
 // CHECK-SAME:    %[[ARG0:.+]]: vector<2xf32>