strengthReduction.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 FRONTENDS_P4_STRENGTHREDUCTION_H_
#define FRONTENDS_P4_STRENGTHREDUCTION_H_
 
#include "frontends/common/resolveReferences/referenceMap.h"
#include "frontends/p4/sideEffects.h"
#include "frontends/p4/typeChecking/typeChecker.h"
#include "frontends/p4/typeMap.h"
#include "ir/ir.h"
 
namespace P4 {
 
using namespace literals;
 
class StrengthReductionPolicy {
 public:
    StrengthReductionPolicy() {}
    StrengthReductionPolicy(bool enableSubConstToAddTransform,
                            bool enableNarrowingCastToSliceTransform)
        : enableSubConstToAddTransform(enableSubConstToAddTransform),
          enableNarrowingCastToSliceTransform(enableNarrowingCastToSliceTransform) {}

    bool enableSubConstToAddTransform = true;

    bool enableNarrowingCastToSliceTransform = false;
};

class DoStrengthReduction final : public Transform {
 protected:
    TypeMap *typeMap = nullptr;
    StrengthReductionPolicy *policy;

    bool isOne(const IR::Expression *expr) const;
    bool isZero(const IR::Expression *expr) const;
    bool isTrue(const IR::Expression *expr) const;
    bool isFalse(const IR::Expression *expr) const;
    bool isAllOnes(const IR::Expression *expr) const;
    int isPowerOf2(const IR::Expression *expr) const;

    bool hasSideEffects(const IR::Expression *expr) const {
        return SideEffects::check(expr, this, nullptr, nullptr);
    }
 
 public:
    DoStrengthReduction(TypeMap *typeMap, StrengthReductionPolicy *policy)
        : typeMap(typeMap), policy(policy ? policy : new StrengthReductionPolicy()) {
        visitDagOnce = true;
        setName("StrengthReduction");
    }
 
    DoStrengthReduction() : DoStrengthReduction(nullptr, nullptr) {}
 
    using Transform::postorder;
 
    const IR::Node *postorder(IR::Cmpl *expr) override;
    const IR::Node *postorder(IR::BAnd *expr) override;
    const IR::Node *postorder(IR::BOr *expr) override;
    const IR::Node *postorder(IR::Equ *expr) override;
    const IR::Node *postorder(IR::Neq *expr) override;
    const IR::Node *relation(IR::Operation_Relation *expr, bool grt, bool eq);
    const IR::Node *postorder(IR::Geq *expr) override { return relation(expr, true, true); }
    const IR::Node *postorder(IR::Grt *expr) override { return relation(expr, true, false); }
    const IR::Node *postorder(IR::Leq *expr) override { return relation(expr, false, true); }
    const IR::Node *postorder(IR::Lss *expr) override { return relation(expr, false, false); }
    const IR::Node *postorder(IR::BXor *expr) override;
    const IR::Node *postorder(IR::LAnd *expr) override;
    const IR::Node *postorder(IR::LOr *expr) override;
    const IR::Node *postorder(IR::LNot *expr) override;
    const IR::Node *postorder(IR::Sub *expr) override;
    const IR::Node *postorder(IR::SubSat *expr) override;
    const IR::Node *postorder(IR::Add *expr) override;
    const IR::Node *postorder(IR::AddSat *expr) override;
    const IR::Node *postorder(IR::UPlus *expr) override;
    const IR::Node *postorder(IR::Shl *expr) override;
    const IR::Node *postorder(IR::Shr *expr) override;
    const IR::Node *postorder(IR::Mul *expr) override;
    const IR::Node *postorder(IR::Div *expr) override;
    const IR::Node *postorder(IR::Mod *expr) override;
    const IR::Node *postorder(IR::Mux *expr) override;
    const IR::Node *postorder(IR::Slice *expr) override;
    const IR::Node *postorder(IR::PlusSlice *expr) override;
    const IR::Node *postorder(IR::Cast *expr) override;
    const IR::Node *postorder(IR::Mask *expr) override;
    const IR::Node *postorder(IR::Range *expr) override;
    const IR::Node *postorder(IR::Concat *expr) override;
    const IR::Node *postorder(IR::ArrayIndex *expr) override;
 
    const IR::BlockStatement *preorder(IR::BlockStatement *bs) override {
        // FIXME: Do we need to check for expression, so we'd be able to fine tune, e.g.
        // @disable_optimization("strength_reduce")
        if (bs->hasAnnotation(IR::Annotation::disableOptimizationAnnotation)) prune();
        return bs;
    }
};
 
class StrengthReduction : public PassManager {
 public:
    explicit StrengthReduction(TypeMap *typeMap, TypeChecking *typeChecking = nullptr,
                               StrengthReductionPolicy *policy = nullptr) {
        if (typeMap != nullptr) {
            if (!typeChecking) typeChecking = new TypeChecking(nullptr, typeMap, true);
            passes.push_back(typeChecking);
        }
        passes.push_back(new DoStrengthReduction(typeMap, policy));
    }
 
    explicit StrengthReduction(TypeMap *typeMap, StrengthReductionPolicy *policy)
        : StrengthReduction(typeMap, nullptr, policy) {}
};
 
}  // namespace P4
 
#endif /* FRONTENDS_P4_STRENGTHREDUCTION_H_ */