//===- ValueBoundsOpInterfaceImpl.cpp - Impl. of ValueBoundsOpInterface ---===//
//
// 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 "mlir/Dialect/Affine/IR/ValueBoundsOpInterfaceImpl.h"

#include "mlir/Dialect/Affine/IR/AffineOps.h"
#include "mlir/Interfaces/ValueBoundsOpInterface.h"

using namespace mlir;
using namespace mlir::affine;

namespace mlir {
namespace {

struct AffineApplyOpInterface
    : public ValueBoundsOpInterface::ExternalModel<AffineApplyOpInterface,
                                                   AffineApplyOp> {
  void populateBoundsForIndexValue(Operation *op, Value value,
                                   ValueBoundsConstraintSet &cstr) const {
    auto applyOp = cast<AffineApplyOp>(op);
    assert(value == applyOp.getResult() && "invalid value");
    assert(applyOp.getAffineMap().getNumResults() == 1 &&
           "expected single result");

    // Fully compose this affine.apply with other ops because the folding logic
    // can see opportunities for simplifying the affine map that
    // `FlatLinearConstraints` can currently not see.
    AffineMap map = applyOp.getAffineMap();
    SmallVector<Value> operands = llvm::to_vector(applyOp.getOperands());
    fullyComposeAffineMapAndOperands(&map, &operands);

    // Align affine map result with dims/symbols in the constraint set.
    AffineExpr expr = map.getResult(0);
    SmallVector<AffineExpr> dimReplacements, symReplacements;
    for (int64_t i = 0, e = map.getNumDims(); i < e; ++i)
      dimReplacements.push_back(cstr.getExpr(operands[i]));
    for (int64_t i = map.getNumDims(),
                 e = map.getNumDims() + map.getNumSymbols();
         i < e; ++i)
      symReplacements.push_back(cstr.getExpr(operands[i]));
    AffineExpr bound =
        expr.replaceDimsAndSymbols(dimReplacements, symReplacements);
    cstr.bound(value) == bound;
  }
};

struct AffineMinOpInterface
    : public ValueBoundsOpInterface::ExternalModel<AffineMinOpInterface,
                                                   AffineMinOp> {
  void populateBoundsForIndexValue(Operation *op, Value value,
                                   ValueBoundsConstraintSet &cstr) const {
    auto minOp = cast<AffineMinOp>(op);
    assert(value == minOp.getResult() && "invalid value");

    // Align affine map results with dims/symbols in the constraint set.
    for (AffineExpr expr : minOp.getAffineMap().getResults()) {
      SmallVector<AffineExpr> dimReplacements = llvm::to_vector(llvm::map_range(
          minOp.getDimOperands(), [&](Value v) { return cstr.getExpr(v); }));
      SmallVector<AffineExpr> symReplacements = llvm::to_vector(llvm::map_range(
          minOp.getSymbolOperands(), [&](Value v) { return cstr.getExpr(v); }));
      AffineExpr bound =
          expr.replaceDimsAndSymbols(dimReplacements, symReplacements);
      cstr.bound(value) <= bound;
    }
  };
};

struct AffineMaxOpInterface
    : public ValueBoundsOpInterface::ExternalModel<AffineMaxOpInterface,
                                                   AffineMaxOp> {
  void populateBoundsForIndexValue(Operation *op, Value value,
                                   ValueBoundsConstraintSet &cstr) const {
    auto maxOp = cast<AffineMaxOp>(op);
    assert(value == maxOp.getResult() && "invalid value");

    // Align affine map results with dims/symbols in the constraint set.
    for (AffineExpr expr : maxOp.getAffineMap().getResults()) {
      SmallVector<AffineExpr> dimReplacements = llvm::to_vector(llvm::map_range(
          maxOp.getDimOperands(), [&](Value v) { return cstr.getExpr(v); }));
      SmallVector<AffineExpr> symReplacements = llvm::to_vector(llvm::map_range(
          maxOp.getSymbolOperands(), [&](Value v) { return cstr.getExpr(v); }));
      AffineExpr bound =
          expr.replaceDimsAndSymbols(dimReplacements, symReplacements);
      cstr.bound(value) >= bound;
    }
  };
};

} // namespace
} // namespace mlir

void mlir::affine::registerValueBoundsOpInterfaceExternalModels(
    DialectRegistry &registry) {
  registry.addExtension(+[](MLIRContext *ctx, AffineDialect *dialect) {
    AffineApplyOp::attachInterface<AffineApplyOpInterface>(*ctx);
    AffineMaxOp::attachInterface<AffineMaxOpInterface>(*ctx);
    AffineMinOp::attachInterface<AffineMinOpInterface>(*ctx);
  });
}

FailureOr<int64_t>
mlir::affine::fullyComposeAndComputeConstantDelta(Value value1, Value value2) {
  assert(value1.getType().isIndex() && "expected index type");
  assert(value2.getType().isIndex() && "expected index type");

  // Subtract the two values/dimensions from each other. If the result is 0,
  // both are equal.
  Builder b(value1.getContext());
  AffineMap map = AffineMap::get(/*dimCount=*/2, /*symbolCount=*/0,
                                 b.getAffineDimExpr(0) - b.getAffineDimExpr(1));
  // Fully compose the affine map with other ops because the folding logic
  // can see opportunities for simplifying the affine map that
  // `FlatLinearConstraints` can currently not see.
  SmallVector<Value> mapOperands;
  mapOperands.push_back(value1);
  mapOperands.push_back(value2);
  affine::fullyComposeAffineMapAndOperands(&map, &mapOperands);
  ValueDimList valueDims;
  for (Value v : mapOperands)
    valueDims.push_back({v, std::nullopt});
  return ValueBoundsConstraintSet::computeConstantBound(
      presburger::BoundType::EQ, map, valueDims);
}