d452e67ee7
This patch enables tiling in flang. In MLIR tiling is handled by changing the the omp.loop_nest op to be able to represent both collapse and tiling, so the flang front-end will combine the nested constructs into a single MLIR op. The MLIR->LLVM-IR lowering of the LoopNestOp is enhanced to first do the tiling if present, then collapse.