[flang-commits] [flang] [flang][OpenMP] Rewrite `omp.loop` to semantically equivalent ops (PR #115443)

[Kiran Chandramohan via flang-commits]

================
@@ -0,0 +1,168 @@
+//===- GenericLoopConversion.cpp ------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "flang/Common/OpenMP-utils.h"
+#include "flang/Optimizer/Dialect/FIRDialect.h"
+#include "flang/Optimizer/HLFIR/HLFIRDialect.h"
+#include "flang/Optimizer/OpenMP/Passes.h"
+#include "flang/Semantics/symbol.h"
+
+#include "mlir/Dialect/ControlFlow/IR/ControlFlowOps.h"
+#include "mlir/Dialect/Math/IR/Math.h"
+#include "mlir/Dialect/OpenMP/OpenMPDialect.h"
+#include "mlir/IR/IRMapping.h"
+#include "mlir/Transforms/DialectConversion.h"
+
+#include <memory>
+
+namespace flangomp {
+#define GEN_PASS_DEF_GENERICLOOPCONVERSIONPASS
+#include "flang/Optimizer/OpenMP/Passes.h.inc"
+} // namespace flangomp
+
+namespace {
+
+/// A conversion pattern to handle various combined forms of `omp.loop`. For how
+/// combined/composite directive are handled see:
+/// https://discourse.llvm.org/t/rfc-representing-combined-composite-constructs-in-the-openmp-dialect/76986.
----------------
kiranchandramohan wrote:

Handling in a separate PR is fine with me.

>  I agree with you though, we could probably move pretty much everything under flang/lib/Optimizer/OpenMP/ to the dialect directory under mlir

I am not fully sure about this. Generic transformations should go to MLIR. But there could be some transformations that are Flang specific where for ease of lowering we lower in one way but immediately correct in a pass to the right form.

https://github.com/llvm/llvm-project/pull/115443