sideEffects.h

/*
Copyright 2016 VMware, 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_SIDEEFFECTS_H_
#define FRONTENDS_P4_SIDEEFFECTS_H_
 
/* makes explicit side effect ordering */
 
#include "frontends/common/resolveReferences/referenceMap.h"
#include "frontends/common/resolveReferences/resolveReferences.h"
#include "frontends/p4/methodInstance.h"
#include "frontends/p4/typeChecking/typeChecker.h"
#include "ir/ir.h"
 
namespace P4 {

class HasTableApply : public Inspector, public ResolutionContext {
    TypeMap *typeMap;
 
 public:
    const IR::P4Table *table;
    const IR::MethodCallExpression *call;
    explicit HasTableApply(TypeMap *typeMap) : typeMap(typeMap), table(nullptr), call(nullptr) {
        CHECK_NULL(typeMap);
        setName("HasTableApply");
    }
 
    void postorder(const IR::MethodCallExpression *expression) override {
        auto mi = MethodInstance::resolve(expression, this, typeMap);
        if (!mi->isApply()) return;
        auto am = mi->to<P4::ApplyMethod>();
        if (!am->object->is<IR::P4Table>()) return;
        BUG_CHECK(table == nullptr, "%1% and %2%: multiple table applications in one expression",
                  table, am->object);
        table = am->object->to<IR::P4Table>();
        call = expression;
        LOG3("Invoked table is " << dbp(table));
    }
};

class SideEffects : public Inspector, public ResolutionContext {
 private:
    TypeMap *typeMap;
 
 public:
    const IR::Node *nodeWithSideEffect = nullptr;

    unsigned sideEffectCount = 0;
 
    void postorder(const IR::MethodCallExpression *mce) override {
        if (mayHaveSideEffect(mce, this, typeMap)) {
            sideEffectCount++;
            nodeWithSideEffect = mce;
        }
    }
 
    void postorder(const IR::ConstructorCallExpression *cce) override {
        sideEffectCount++;
        nodeWithSideEffect = cce;
    }

    explicit SideEffects(TypeMap *typeMap) : typeMap(typeMap) { setName("SideEffects"); }

    static bool check(const IR::Expression *expression, const Visitor *calledBy,
                      TypeMap *typeMap = nullptr, const Visitor::Context *ctxt = nullptr) {
        SideEffects se(typeMap);
        se.setCalledBy(calledBy);
        if (calledBy && !ctxt) ctxt = calledBy->getChildContext();
        expression->apply(se, ctxt);
        return se.nodeWithSideEffect != nullptr;
    }

    static bool mayHaveSideEffect(const IR::MethodCallExpression *mce, DeclarationLookup *refMap,
                                  TypeMap *typeMap) {
        // mce does not produce a side effect in few cases:
        //  * isValid()
        //  * function, extern function, or extern method with noSideEffects annotation
        auto mi = MethodInstance::resolve(mce, refMap, typeMap, !typeMap);
        if (!mi) return true;
        if (const auto *ec = mi->to<P4::ExternCall>())
            return !ec->method->hasAnnotation(IR::Annotation::noSideEffectsAnnotation);
        if (const auto *ef = mi->to<P4::FunctionCall>())
            return !ef->function->hasAnnotation(IR::Annotation::noSideEffectsAnnotation);
        if (const auto *bim = mi->to<BuiltInMethod>()) return bim->name != IR::Type_Header::isValid;
        return true;
    }
};

class DoSimplifyExpressions : public Transform, P4WriteContext, public ResolutionContext {
    MinimalNameGenerator nameGen;
    TypeMap *typeMap;
    // Expressions holding temporaries that are already added.
    std::set<const IR::Expression *> *added;
 
    IR::IndexedVector<IR::Declaration> toInsert;  // temporaries
    IR::IndexedVector<IR::StatOrDecl> statements;
    std::set<const IR::Expression *> temporaries;
 
    cstring createTemporary(const IR::Type *type);
    const IR::Expression *addAssignment(Util::SourceInfo srcInfo, cstring varName,
                                        const IR::Expression *expression);
    bool mayAlias(const IR::Expression *left, const IR::Expression *right,
                  const Visitor::Context *ctxt) const;
    bool containsHeaderType(const IR::Type *type);
 
 public:
    DoSimplifyExpressions(TypeMap *typeMap, std::set<const IR::Expression *> *added)
        : typeMap(typeMap), added(added) {
        CHECK_NULL(typeMap);
        setName("DoSimplifyExpressions");
    }
 
    const IR::Node *postorder(IR::Expression *expression) override;
    const IR::Node *preorder(IR::StructExpression *expression) override;
    const IR::Node *preorder(IR::ListExpression *expression) override;
    const IR::Node *preorder(IR::Literal *expression) override;
    const IR::Node *preorder(IR::ArrayIndex *expression) override;
    const IR::Node *preorder(IR::Member *expression) override;
    const IR::Node *preorder(IR::SelectExpression *expression) override;
    const IR::Node *preorder(IR::Operation_Unary *expression) override;
    const IR::Node *preorder(IR::Operation_Binary *expression) override;
    const IR::Node *shortCircuit(IR::Operation_Binary *expression);
    const IR::Node *preorder(IR::Mux *expression) override;
    const IR::Node *preorder(IR::LAnd *expression) override;
    const IR::Node *preorder(IR::LOr *expression) override;
    const IR::Node *preorder(IR::MethodCallExpression *mce) override;
 
    const IR::Node *preorder(IR::ConstructorCallExpression *cce) override {
        prune();
        return cce;
    }
    const IR::Node *preorder(IR::Property *prop) override {
        prune();
        return prop;
    }
    const IR::Node *preorder(IR::Annotation *anno) override {
        prune();
        return anno;
    }
 
    const IR::Node *postorder(IR::P4Parser *parser) override;
    const IR::Node *postorder(IR::Function *function) override;
    const IR::Node *postorder(IR::P4Control *control) override;
    const IR::Node *postorder(IR::P4Action *action) override;
    const IR::Node *postorder(IR::ParserState *state) override;
    const IR::Node *postorder(IR::BaseAssignmentStatement *statement) override;
    const IR::Node *postorder(IR::MethodCallStatement *statement) override;
    const IR::Node *postorder(IR::ReturnStatement *statement) override;
    const IR::Node *preorder(IR::SwitchStatement *statement) override;
    const IR::Node *preorder(IR::IfStatement *statement) override;
    const IR::Node *preorder(IR::ForStatement *statement) override;
    const IR::Node *preorder(IR::ForInStatement *statement) override;
 
    profile_t init_apply(const IR::Node *node) override;
    void end_apply(const IR::Node *) override;
};
 
class TableInsertions {
 public:
    std::vector<const IR::Declaration_Variable *> declarations;
    std::vector<const IR::BaseAssignmentStatement *> statements;
};

class KeySideEffect : public Transform, public ResolutionContext {
 protected:
    MinimalNameGenerator nameGen;
    TypeMap *typeMap;
    std::map<const IR::P4Table *, TableInsertions *> toInsert;
    std::set<const IR::P4Table *> *invokedInKey;
 
 public:
    KeySideEffect(TypeMap *typeMap, std::set<const IR::P4Table *> *invokedInKey)
        : typeMap(typeMap), invokedInKey(invokedInKey) {
        CHECK_NULL(typeMap);
        CHECK_NULL(invokedInKey);
        setName("KeySideEffect");
    }
 
    profile_t init_apply(const IR::Node *node) override;
 
    virtual const IR::Node *doStatement(const IR::Statement *statement,
                                        const IR::Expression *expression,
                                        const Visitor::Context *ctxt);
 
    const IR::Node *preorder(IR::Key *key) override;
 
    // These should be all kinds of statements that may contain a table apply
    // after the program has been simplified
    const IR::Node *postorder(IR::MethodCallStatement *statement) override {
        return doStatement(statement, statement->methodCall, getContext());
    }
    const IR::Node *postorder(IR::IfStatement *statement) override {
        return doStatement(statement, statement->condition, getContext());
    }
    const IR::Node *postorder(IR::SwitchStatement *statement) override {
        return doStatement(statement, statement->expression, getContext());
    }
    const IR::Node *postorder(IR::BaseAssignmentStatement *statement) override {
        return doStatement(statement, statement->right, getContext());
    }
    const IR::Node *postorder(IR::KeyElement *element) override;
    const IR::Node *postorder(IR::P4Table *table) override;
    const IR::Node *preorder(IR::P4Table *table) override;
};

class TablesInKeys : public Inspector {
    TypeMap *typeMap;
    std::set<const IR::P4Table *> *invokedInKey;
 
 public:
    TablesInKeys(TypeMap *typeMap, std::set<const IR::P4Table *> *invokedInKey)
        : typeMap(typeMap), invokedInKey(invokedInKey) {
        CHECK_NULL(invokedInKey);
        setName("TableInKeys");
    }
    Visitor::profile_t init_apply(const IR::Node *node) override {
        invokedInKey->clear();
        return Inspector::init_apply(node);
    }
    void postorder(const IR::MethodCallExpression *mce) override {
        if (!isInContext<IR::Key>()) return;
        HasTableApply hta(typeMap);
        hta.setCalledBy(this);
        (void)mce->apply(hta, getContext());
        if (hta.table != nullptr) {
            LOG2("Table " << hta.table << " invoked in key of another table");
            invokedInKey->emplace(hta.table);
        }
    }
};

class TablesInActions : public Inspector {
    TypeMap *typeMap;
 
 public:
    explicit TablesInActions(TypeMap *typeMap) : typeMap(typeMap) {}
    void postorder(const IR::MethodCallExpression *expression) override {
        if (isInContext<IR::ActionList>()) {
            HasTableApply hta(typeMap);
            hta.setCalledBy(this);
            (void)expression->apply(hta, getContext());
            if (hta.table != nullptr) {
                ::P4::error(ErrorType::ERR_UNSUPPORTED, "%1%: table invocation in action argument",
                            expression);
            }
        }
    }
};
 
class SideEffectOrdering : public PassRepeated {
    // Contains all tables that are invoked within key
    // computations for other tables.  The keys for these
    // inner tables cannot be expanded until the keys of
    // the caller tables have been expanded.
    std::set<const IR::P4Table *> invokedInKey;
    // Temporaries that were added
    std::set<const IR::Expression *> added;
 
 public:
    SideEffectOrdering(TypeMap *typeMap, bool skipSideEffectOrdering,
                       TypeChecking *typeChecking = nullptr) {
        if (!typeChecking) typeChecking = new TypeChecking(nullptr, typeMap);
        if (!skipSideEffectOrdering) {
            passes.push_back(new TypeChecking(nullptr, typeMap));
            passes.push_back(new DoSimplifyExpressions(typeMap, &added));
            passes.push_back(typeChecking);
            passes.push_back(new TablesInActions(typeMap));
            passes.push_back(new TablesInKeys(typeMap, &invokedInKey));
            passes.push_back(new KeySideEffect(typeMap, &invokedInKey));
        }
        setName("SideEffectOrdering");
    }
};
 
}  // namespace P4
 
#endif /* FRONTENDS_P4_SIDEEFFECTS_H_ */