[mlir][scf] Create constants for tiling in a parent with isolated region.

[olegshyshkov]

Summary

FuncOp is IsolatedFromAbove, so this change doesn't alter current behaviour, but the current code fails if the tile op is in an op with IsolatedFromAbove trait.

An alternative would be to create constant in the same region where they're used a rely on CSE to figure out where to move them.

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

 
 scf::SCFTilingOptions &
 scf::SCFTilingOptions::setTileSizes(ArrayRef<int64_t> ts) {
   assert(!tileSizeComputationFunction && "tile sizes already set");
   SmallVector<int64_t> tileSizes(ts.begin(), ts.end());
   tileSizeComputationFunction = [tileSizes](OpBuilder &b, Operation *op) {
     OpBuilder::InsertionGuard guard(b);
     b.setInsertionPointToStart(
-        &op->getParentOfType<func::FuncOp>().getBody().front());
+        &op->getParentWithTrait<OpTrait::IsIsolatedFromAbove>()
+             ->getRegion(0)
+             .front());
     return llvm::to_vector<4>(map_range(tileSizes, [&](int64_t s) {
       Value v = b.create<arith::ConstantIndexOp>(op->getLoc(), s);
       return v;
     }));
   };
   return *this;
 }