unusedDeclarations.h

/*
Copyright 2013-present Barefoot Networks, Inc.
 
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.
*/
 
#ifndef P4_UNUSEDDECLARATIONS_H_
#define P4_UNUSEDDECLARATIONS_H_
 
#include "../common/resolveReferences/resolveReferences.h"
#include "ir/ir.h"
#include "ir/pass_manager.h"
 
namespace P4 {
 
class RemoveUnusedDeclarations;
 
class RemoveUnusedPolicy {
 public:
    virtual RemoveUnusedDeclarations *getRemoveUnusedDeclarationsPass(const ReferenceMap *refMap,
                                                                      bool warn = false) const;
};

class RemoveUnusedDeclarations : public Transform {
 protected:
    const ReferenceMap *refMap;

    std::set<const IR::Node *> *warned;

    bool giveWarning(const IR::Node *node);
    const IR::Node *process(const IR::IDeclaration *decl);
    const IR::Node *warnIfUnused(const IR::Node *node);
 
    // Prevent direct instantiations of this class.
    friend class RemoveUnusedPolicy;
    RemoveUnusedDeclarations(const ReferenceMap *refMap, bool warn)
        : refMap(refMap), warned(warn ? new std::set<const IR::Node *> : nullptr) {
        CHECK_NULL(refMap);
        setName("RemoveUnusedDeclarations");
    }
 
 public:
    using Transform::init_apply;
    using Transform::postorder;
    using Transform::preorder;
 
    Visitor::profile_t init_apply(const IR::Node *root) override;
 
    const IR::Node *preorder(IR::P4Control *cont) override;
    const IR::Node *preorder(IR::P4Parser *cont) override;
    const IR::Node *preorder(IR::P4Table *cont) override;
    const IR::Node *preorder(IR::ParserState *state) override;
    const IR::Node *preorder(IR::Type_Enum *type) override;
    const IR::Node *preorder(IR::Type_SerEnum *type) override;
 
    const IR::Node *preorder(IR::Declaration_Instance *decl) override;
    const IR::Node *preorder(IR::Method *decl) override;
 
    // The following kinds of nodes are not deleted even if they are unreferenced
    const IR::Node *preorder(IR::Type_Error *type) override {
        prune();
        return type;
    }
    const IR::Node *preorder(IR::Declaration_MatchKind *decl) override {
        prune();
        return decl;
    }
    const IR::Node *preorder(IR::Type_StructLike *type) override {
        visit(type->typeParameters);
        prune();
        return type;
    }
    const IR::Node *preorder(IR::Type_Extern *type) override {
        visit(type->typeParameters);
        prune();
        return type;
    }
    const IR::Node *preorder(IR::Type_Method *type) override {
        visit(type->typeParameters);
        prune();
        return type;
    }
    const IR::Node *preorder(IR::Parameter *param) override;
    const IR::Node *preorder(IR::NamedExpression *ne) override { return ne; }  // never dead
    const IR::Node *preorder(IR::Type_Var *p) override {
        prune();
        return warnIfUnused(p);
    }
 
    const IR::Node *preorder(IR::Declaration_Variable *decl) override;
    const IR::Node *preorder(IR::Declaration *decl) override { return process(decl); }
    const IR::Node *preorder(IR::Type_Declaration *decl) override { return process(decl); }
    cstring ifSystemFile(const IR::Node *node);  // return file containing node if system file
};

class RemoveAllUnusedDeclarations : public PassRepeated {
 public:
    RemoveAllUnusedDeclarations(ReferenceMap *refMap, const RemoveUnusedPolicy &policy,
                                bool warn = false)
        : PassManager({new ResolveReferences(refMap),
                       policy.getRemoveUnusedDeclarationsPass(refMap, warn)}) {
        // Unused extern instances are not removed but may still trigger
        // warnings.  The @warned set keeps track of warnings emitted in
        // previous iterations to avoid emitting duplicate warnings.
        CHECK_NULL(refMap);
        setName("RemoveAllUnusedDeclarations");
        setStopOnError(true);
    }
};
 
}  // namespace P4
 
#endif /* P4_UNUSEDDECLARATIONS_H_ */