//===- SimplifyAffineExpr.cpp - MLIR Affine Structures Class-----*- C++ -*-===//
//
// Copyright 2019 The MLIR Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// =============================================================================
//
// This file implements a pass to simplify affine expressions.
//
//===----------------------------------------------------------------------===//

#include "mlir/Analysis/AffineStructures.h"
#include "mlir/IR/AffineMap.h"
#include "mlir/IR/Attributes.h"
#include "mlir/IR/StmtVisitor.h"

#include "mlir/Transforms/Pass.h"
#include "mlir/Transforms/Passes.h"

using namespace mlir;
using llvm::report_fatal_error;

namespace {

/// Simplifies all affine expressions appearing in the operation statements of
/// the MLFunction. This is mainly to test the simplifyAffineExpr method.
//  TODO(someone): Gradually, extend this to all affine map references found in
//  ML functions and CFG functions.
struct SimplifyAffineExpr : public FunctionPass {
  explicit SimplifyAffineExpr() {}

  PassResult runOnMLFunction(MLFunction *f);
  // Does nothing on CFG functions for now. No reusable walkers/visitors exist
  // for this yet? TODO(someone).
  PassResult runOnCFGFunction(CFGFunction *f) { return success(); }
};

} // end anonymous namespace

FunctionPass *mlir::createSimplifyAffineExprPass() {
  return new SimplifyAffineExpr();
}

AffineMap *MutableAffineMap::getAffineMap() {
  return AffineMap::get(numDims, numSymbols, results, rangeSizes, context);
}

PassResult SimplifyAffineExpr::runOnMLFunction(MLFunction *f) {
  struct MapSimplifier : public StmtWalker<MapSimplifier> {
    MLIRContext *context;
    MapSimplifier(MLIRContext *context) : context(context) {}

    void visitOperationStmt(OperationStmt *opStmt) {
      for (auto attr : opStmt->getAttrs()) {
        if (auto *mapAttr = dyn_cast<AffineMapAttr>(attr.second)) {
          MutableAffineMap mMap(mapAttr->getValue(), context);
          mMap.simplify();
          auto *map = mMap.getAffineMap();
          opStmt->setAttr(attr.first, AffineMapAttr::get(map, context));
        }
      }
    }
  };

  MapSimplifier v(f->getContext());
  v.walkPostOrder(f);
  return success();
}