stmt_functor.h

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 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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
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#ifndef TVM_TIR_STMT_FUNCTOR_H_
#define TVM_TIR_STMT_FUNCTOR_H_

#include <tvm/node/functor.h>
#include <tvm/tir/expr.h>
#include <tvm/tir/expr_functor.h>
#include <tvm/tir/stmt.h>

#include <unordered_map>
#include <utility>

namespace tvm {
namespace tir {
template <typename FType>
class StmtFunctor;

#define STMT_FUNCTOR_DEFAULT \
  { return VisitStmtDefault_(op, std::forward<Args>(args)...); }

#define IR_STMT_FUNCTOR_DISPATCH(OP)                                                       \
  vtable.template set_dispatch<OP>([](const ObjectRef& n, TSelf* self, Args... args) {     \
    return self->VisitStmt_(static_cast<const OP*>(n.get()), std::forward<Args>(args)...); \
  });

template <typename R, typename... Args>
class StmtFunctor<R(const Stmt& n, Args... args)> {
 private:
  using TSelf = StmtFunctor<R(const Stmt& n, Args... args)>;
  using FType = NodeFunctor<R(const ObjectRef& n, TSelf* self, Args... args)>;

 public:
  using result_type = R;
  virtual ~StmtFunctor() {}
  R operator()(const Stmt& n, Args... args) { return VisitStmt(n, std::forward<Args>(args)...); }
  virtual R VisitStmt(const Stmt& n, Args... args) {
    static FType vtable = InitVTable();
    return vtable(n, this, std::forward<Args>(args)...);
  }
  // Functions that can be overriden by subclass
  virtual R VisitStmt_(const LetStmtNode* op, Args... args) STMT_FUNCTOR_DEFAULT;
  virtual R VisitStmt_(const AttrStmtNode* op, Args... args) STMT_FUNCTOR_DEFAULT;
  virtual R VisitStmt_(const IfThenElseNode* op, Args... args) STMT_FUNCTOR_DEFAULT;
  virtual R VisitStmt_(const ForNode* op, Args... args) STMT_FUNCTOR_DEFAULT;
  virtual R VisitStmt_(const WhileNode* op, Args... args) STMT_FUNCTOR_DEFAULT;
  virtual R VisitStmt_(const AllocateNode* op, Args... args) STMT_FUNCTOR_DEFAULT;
  virtual R VisitStmt_(const StoreNode* op, Args... args) STMT_FUNCTOR_DEFAULT;
  virtual R VisitStmt_(const BufferStoreNode* op, Args... args) STMT_FUNCTOR_DEFAULT;
  virtual R VisitStmt_(const BufferRealizeNode* op, Args... args) STMT_FUNCTOR_DEFAULT;
  virtual R VisitStmt_(const AssertStmtNode* op, Args... args) STMT_FUNCTOR_DEFAULT;
  virtual R VisitStmt_(const ProducerStoreNode* op, Args... args) STMT_FUNCTOR_DEFAULT;
  virtual R VisitStmt_(const ProducerRealizeNode* op, Args... args) STMT_FUNCTOR_DEFAULT;
  virtual R VisitStmt_(const PrefetchNode* op, Args... args) STMT_FUNCTOR_DEFAULT;
  virtual R VisitStmt_(const SeqStmtNode* op, Args... args) STMT_FUNCTOR_DEFAULT;
  virtual R VisitStmt_(const EvaluateNode* op, Args... args) STMT_FUNCTOR_DEFAULT;
  virtual R VisitStmt_(const BlockNode* op, Args... args) STMT_FUNCTOR_DEFAULT;
  virtual R VisitStmt_(const BlockRealizeNode* op, Args... args) STMT_FUNCTOR_DEFAULT;
  virtual R VisitStmtDefault_(const Object* op, Args...) {
    LOG(FATAL) << "Do not have a default for " << op->GetTypeKey();
    return R();
  }

 private:
  // initialize the vtable.
  static FType InitVTable() {
    FType vtable;
    IR_STMT_FUNCTOR_DISPATCH(LetStmtNode);
    IR_STMT_FUNCTOR_DISPATCH(AttrStmtNode);
    IR_STMT_FUNCTOR_DISPATCH(IfThenElseNode);
    IR_STMT_FUNCTOR_DISPATCH(ForNode);
    IR_STMT_FUNCTOR_DISPATCH(WhileNode);
    IR_STMT_FUNCTOR_DISPATCH(AllocateNode);
    IR_STMT_FUNCTOR_DISPATCH(StoreNode);
    IR_STMT_FUNCTOR_DISPATCH(AssertStmtNode);
    IR_STMT_FUNCTOR_DISPATCH(ProducerStoreNode);
    IR_STMT_FUNCTOR_DISPATCH(ProducerRealizeNode);
    IR_STMT_FUNCTOR_DISPATCH(PrefetchNode);
    IR_STMT_FUNCTOR_DISPATCH(SeqStmtNode);
    IR_STMT_FUNCTOR_DISPATCH(EvaluateNode);
    IR_STMT_FUNCTOR_DISPATCH(BufferStoreNode);
    IR_STMT_FUNCTOR_DISPATCH(BufferRealizeNode);
    IR_STMT_FUNCTOR_DISPATCH(BlockNode);
    IR_STMT_FUNCTOR_DISPATCH(BlockRealizeNode);
    return vtable;
  }
};

#undef IR_STMT_FUNCTOR_DISPATCH
#undef STMT_FUNCTOR_DEFAULT

class TVM_DLL StmtVisitor : protected StmtFunctor<void(const Stmt&)> {
 public:
  using StmtFunctor::operator();

 protected:
  using StmtFunctor::VisitStmt;
  virtual void VisitExpr(const PrimExpr& e) {}
  // statement visitor
  void VisitStmt_(const AttrStmtNode* op) override;
  void VisitStmt_(const IfThenElseNode* op) override;
  void VisitStmt_(const LetStmtNode* op) override;
  void VisitStmt_(const ForNode* op) override;
  void VisitStmt_(const WhileNode* op) override;
  void VisitStmt_(const AllocateNode* op) override;
  void VisitStmt_(const StoreNode* op) override;
  void VisitStmt_(const BufferStoreNode* op) override;
  void VisitStmt_(const BufferRealizeNode* op) override;
  void VisitStmt_(const AssertStmtNode* op) override;
  void VisitStmt_(const ProducerStoreNode* op) override;
  void VisitStmt_(const ProducerRealizeNode* op) override;
  void VisitStmt_(const PrefetchNode* op) override;
  void VisitStmt_(const SeqStmtNode* op) override;
  void VisitStmt_(const EvaluateNode* op) override;
  void VisitStmt_(const BlockNode* op) override;
  void VisitStmt_(const BlockRealizeNode* op) override;
};

class TVM_DLL StmtMutator : protected StmtFunctor<Stmt(const Stmt&)> {
 public:
  Stmt operator()(Stmt stmt) {
    allow_copy_on_write_ = true;
    return VisitStmt(stmt);
  }

 protected:
  // We perform copy on write optimizations on the StmtMutator
  // so that an unique copy of parent can be mutated inplace
  // when some of its children changed.
  // We only do such optimization for Stmt nests(instead of Exprs) for now
  // as Stmt's parent state is more likely remain unchanged when one of
  // its child block changes.
  bool allow_copy_on_write_{false};
  template <typename TNode>
  ObjectPtr<TNode> CopyOnWrite(const TNode* node) {
    static_assert(std::is_base_of<StmtNode, TNode>::value,
                  "StmtMutator:: CopyOnWrite requires us to track uniqueness of all parent "
                  "nodes during the recursion. Because the child classes do not necessarily "
                  "check the Array, Expr and other structures during the visit, it is only safe to "
                  "call this function with StmtNodes for now. "
                  "Please create a new node directly in other cases.");
    if (allow_copy_on_write_) {
      // return the old node.
      return runtime::GetObjectPtr<TNode>(const_cast<TNode*>(node));
    } else {
      // Make a new copy of the node.
      // need to rely on the default copy constructor
      return runtime::make_object<TNode>(*node);
    }
  }
  Stmt VisitStmt(const Stmt& stmt) override {
    if (allow_copy_on_write_ && !stmt.unique()) {
      allow_copy_on_write_ = false;
      Stmt ret = StmtFunctor::VisitStmt(stmt);
      allow_copy_on_write_ = true;
      return ret;
    } else {
      return StmtFunctor::VisitStmt(stmt);
    }
  }
  virtual PrimExpr VisitExpr(const PrimExpr& e) { return e; }
  // statement visitor
  Stmt VisitStmt_(const AttrStmtNode* op) override;
  Stmt VisitStmt_(const IfThenElseNode* op) override;
  Stmt VisitStmt_(const LetStmtNode* op) override;
  Stmt VisitStmt_(const ForNode* op) override;
  Stmt VisitStmt_(const WhileNode* op) override;
  Stmt VisitStmt_(const AllocateNode* op) override;
  Stmt VisitStmt_(const StoreNode* op) override;
  Stmt VisitStmt_(const BufferStoreNode* op) override;
  Stmt VisitStmt_(const BufferRealizeNode* op) override;
  Stmt VisitStmt_(const AssertStmtNode* op) override;
  Stmt VisitStmt_(const ProducerStoreNode* op) override;
  Stmt VisitStmt_(const ProducerRealizeNode* op) override;
  Stmt VisitStmt_(const PrefetchNode* op) override;
  Stmt VisitStmt_(const SeqStmtNode* op) override;
  Stmt VisitStmt_(const EvaluateNode* op) override;
  Stmt VisitStmt_(const BlockNode* op) override;
  Stmt VisitStmt_(const BlockRealizeNode* op) override;
  Stmt VisitSeqStmt_(const SeqStmtNode* op, bool flatten_before_visit,
                     std::function<Stmt(const Stmt&)> fmutate = nullptr);
  // internal helper.
  class Internal;
};

class StmtExprVisitor : public StmtVisitor, public ExprVisitor {
 public:
  using StmtVisitor::operator();
  using ExprVisitor::operator();

 protected:
  using ExprVisitor::VisitExpr;
  using StmtVisitor::VisitStmt;

  void VisitExpr(const PrimExpr& e) override { return ExprVisitor::VisitExpr(e); }
};

class StmtExprMutator : public StmtMutator, public ExprMutator {
 public:
  using StmtMutator::operator();
  using ExprMutator::operator();

 protected:
  using ExprMutator::VisitExpr;
  using StmtMutator::VisitExpr;

  PrimExpr VisitExpr(const PrimExpr& e) override { return ExprMutator::VisitExpr(e); }
};

TVM_DLL Stmt IRTransform(Stmt stmt, const runtime::PackedFunc& preorder,
                         const runtime::PackedFunc& postorder,
                         Optional<Array<String>> only_enable = NullOpt);

TVM_DLL void PostOrderVisit(const ObjectRef& node, std::function<void(const ObjectRef&)> fvisit);

TVM_DLL Stmt Substitute(Stmt stmt, std::function<Optional<PrimExpr>(const Var& var)> vmap);

TVM_DLL PrimExpr Substitute(PrimExpr expr, std::function<Optional<PrimExpr>(const Var& var)> vmap);

TVM_DLL Array<Range> Substitute(const Array<Range>& region, const Map<Var, PrimExpr>& vmap);

template <typename T>
inline auto Substitute(T input, const Map<Var, PrimExpr>& value_map) {
  auto vmap = [&](const Var& var) -> Optional<PrimExpr> {
    auto it = value_map.find(var);
    if (it != value_map.end()) return (*it).second;
    return Optional<PrimExpr>(nullptr);
  };
  return Substitute(std::move(input), vmap);
}

template <typename T>
inline T Substitute(T input, const std::unordered_map<const VarNode*, PrimExpr>& value_map) {
  auto vmap = [&](const Var& var) -> Optional<PrimExpr> {
    auto it = value_map.find(var.get());
    if (it != value_map.end()) return (*it).second;
    return Optional<PrimExpr>(nullptr);
  };
  return Substitute(std::move(input), vmap);
}

TVM_DLL void PreOrderVisit(const ObjectRef& stmt_or_expr,
                           const std::function<bool(const ObjectRef&)>& fvisit);
}  // namespace tir
}  // namespace tvm

#endif  // TVM_TIR_STMT_FUNCTOR_H_