[mlir] Return scf.parallel ops resulted from tiling.

[pifon2a]

use pair not vector

[herhut]

Thanks!

mlir/include/mlir/Dialect/SCF/Transforms.h

 /// into
 ///   scf.parallel (%i0, %i1) = (%arg0, %arg1) to (%arg2, %arg3)
 ///                                             step (%arg4*tileSize[0],
 ///                                                   %arg5*tileSize[1])
 ///     scf.parallel (%j0, %j1) = (0, 0) to (min(tileSize[0], %arg2-%j0)
 ///                                           min(tileSize[1], %arg3-%j1))
 ///                                        step (%arg4, %arg5)
 /// The old loop is replaced with the new one.
-void tileParallelLoop(ParallelOp op, llvm::ArrayRef<int64_t> tileSizes);
+///
+/// The function returns the resulting ParallelOps, i.e. {outer_loop_op,
+/// inner_loop_op}.
+std::pair<ParallelOp, ParallelOp>
+tileParallelLoop(ParallelOp op, llvm::ArrayRef<int64_t> tileSizes);
 
 /// Populates patterns for SCF structural type conversions and sets up the
 /// provided ConversionTarget with the appropriate legality configuration for
 /// the ops to get converted properly.
 ///
 /// A "structural" type conversion is one where the underlying ops are
 /// completely agnostic to the actual types involved and simply need to update
 /// their types. An example of this is scf.if -- the scf.if op and the

mlir/lib/Dialect/SCF/Transforms/ParallelLoopTiling.cpp

 ///     scf.parallel (%j0, %j1) = (0, 0) to (min(%arg4*tileSize[0], %arg2-%i0)
 ///                                          min(%arg5*tileSize[1], %arg3-%i1))
 ///                                      step (%arg4, %arg5)
 ///
 /// where the uses of %i0 and %i1 in the loop body are replaced by
 /// %i0 + j0 and %i1 + %j1.
 //
 /// The old loop is replaced with the new one.
-void mlir::scf::tileParallelLoop(ParallelOp op, ArrayRef<int64_t> tileSizes) {
+std::pair<ParallelOp, ParallelOp>
+mlir::scf::tileParallelLoop(ParallelOp op, ArrayRef<int64_t> tileSizes) {
   OpBuilder b(op);
   auto zero = b.create<ConstantIndexOp>(op.getLoc(), 0);
   SmallVector<Value, 2> tileSizeConstants;
   tileSizeConstants.reserve(op.upperBound().size());
   for (size_t i = 0, end = op.upperBound().size(); i != end; ++i) {
     if (i < tileSizes.size())
       tileSizeConstants.push_back(
           b.create<ConstantIndexOp>(op.getLoc(), tileSizes[i]));
for (auto ivs :
     Value inner_index = std::get<0>(ivs);
     AddIOp newIndex =
         b.create<AddIOp>(op.getLoc(), std::get<0>(ivs), std::get<1>(ivs));
     inner_index.replaceAllUsesExcept(
         newIndex, SmallPtrSet<Operation *, 1>{newIndex.getOperation()});
   }
 
   op.erase();
+  return std::make_pair(outerLoop, innerLoop);
 }
 
 namespace {
 struct ParallelLoopTiling
     : public SCFParallelLoopTilingBase<ParallelLoopTiling> {
   ParallelLoopTiling() = default;
   explicit ParallelLoopTiling(ArrayRef<int64_t> tileSizes) {
     this->tileSizes = tileSizes;