source: src/Tuples/TupleExpansion.cc @ cedb545

//
// Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// TupleAssignment.cc --
//
// Author           : Rodolfo G. Esteves
// Created On       : Mon May 18 07:44:20 2015
// Last Modified By : Peter A. Buhr
// Last Modified On : Wed Feb 13 18:14:12 2019
// Update Count     : 21
//

#include <stddef.h>               // for size_t
#include <cassert>                // for assert
#include <list>                   // for list

#include "Common/PassVisitor.h"   // for PassVisitor, WithDeclsToAdd, WithGu...
#include "Common/ScopedMap.h"     // for ScopedMap
#include "Common/utility.h"       // for CodeLocation
#include "InitTweak/InitTweak.h"  // for getFunction
#include "Parser/LinkageSpec.h"   // for Spec, C, Intrinsic
#include "SynTree/Constant.h"     // for Constant
#include "SynTree/Declaration.h"  // for StructDecl, DeclarationWithType
#include "SynTree/Expression.h"   // for UntypedMemberExpr, Expression, Uniq...
#include "SynTree/Label.h"        // for operator==, Label
#include "SynTree/Mutator.h"      // for Mutator
#include "SynTree/Type.h"         // for Type, Type::Qualifiers, TupleType
#include "SynTree/Visitor.h"      // for Visitor
#include "Tuples.h"

class CompoundStmt;
class TypeSubstitution;

namespace Tuples {
        namespace {
                struct MemberTupleExpander final : public WithShortCircuiting, public WithVisitorRef<MemberTupleExpander> {
                        void premutate( UntypedMemberExpr * ) { visit_children = false; }
                        Expression * postmutate( UntypedMemberExpr * memberExpr );
                };

                struct UniqueExprExpander final : public WithDeclsToAdd {
                        Expression * postmutate( UniqueExpr * unqExpr );

                        std::map< int, Expression * > decls; // not vector, because order added may not be increasing order

                        ~UniqueExprExpander() {
                                for ( std::pair<const int, Expression *> & p : decls ) {
                                        delete p.second;
                                }
                        }
                };

                struct TupleAssignExpander {
                        Expression * postmutate( TupleAssignExpr * tupleExpr );
                };

                struct TupleTypeReplacer : public WithDeclsToAdd, public WithGuards, public WithConstTypeSubstitution {
                        Type * postmutate( TupleType * tupleType );

                        void premutate( CompoundStmt * ) {
                                GuardScope( typeMap );
                        }
                  private:
                        ScopedMap< int, StructDecl * > typeMap;
                };

                struct TupleIndexExpander {
                        Expression * postmutate( TupleIndexExpr * tupleExpr );
                };

                struct TupleExprExpander final {
                        Expression * postmutate( TupleExpr * tupleExpr );
                };
        }

        void expandMemberTuples( std::list< Declaration * > & translationUnit ) {
                PassVisitor<MemberTupleExpander> expander;
                mutateAll( translationUnit, expander );
        }

        void expandUniqueExpr( std::list< Declaration * > & translationUnit ) {
                PassVisitor<UniqueExprExpander> unqExpander;
                mutateAll( translationUnit, unqExpander );
        }

        void expandTuples( std::list< Declaration * > & translationUnit ) {
                PassVisitor<TupleAssignExpander> assnExpander;
                mutateAll( translationUnit, assnExpander );

                PassVisitor<TupleTypeReplacer> replacer;
                mutateAll( translationUnit, replacer );

                PassVisitor<TupleIndexExpander> idxExpander;
                mutateAll( translationUnit, idxExpander );

                PassVisitor<TupleExprExpander> exprExpander;
                mutateAll( translationUnit, exprExpander );
        }

        namespace {
                /// given a expression representing the member and an expression representing the aggregate,
                /// reconstructs a flattened UntypedMemberExpr with the right precedence
                Expression * reconstructMemberExpr( Expression * member, Expression * aggr, CodeLocation & loc ) {
                        if ( UntypedMemberExpr * memberExpr = dynamic_cast< UntypedMemberExpr * >( member ) ) {
                                // construct a new UntypedMemberExpr with the correct structure , and recursively
                                // expand that member expression.
                                PassVisitor<MemberTupleExpander> expander;
                                UntypedMemberExpr * inner = new UntypedMemberExpr( memberExpr->aggregate, aggr->clone() );
                                UntypedMemberExpr * newMemberExpr = new UntypedMemberExpr( memberExpr->member, inner );
                                inner->location = newMemberExpr->location = loc;
                                memberExpr->member = nullptr;
                                memberExpr->aggregate = nullptr;
                                delete memberExpr;
                                return newMemberExpr->acceptMutator( expander );
                        } else {
                                // not a member expression, so there is nothing to do but attach and return
                                UntypedMemberExpr * newMemberExpr = new UntypedMemberExpr( member, aggr->clone() );
                                newMemberExpr->location = loc;
                                return newMemberExpr;
                        }
                }
        }

        Expression * MemberTupleExpander::postmutate( UntypedMemberExpr * memberExpr ) {
                if ( UntypedTupleExpr * tupleExpr = dynamic_cast< UntypedTupleExpr * > ( memberExpr->member ) ) {
                        Expression * aggr = memberExpr->aggregate->clone()->acceptMutator( *visitor );
                        // aggregate expressions which might be impure must be wrapped in unique expressions
                        if ( Tuples::maybeImpureIgnoreUnique( memberExpr->aggregate ) ) aggr = new UniqueExpr( aggr );
                        for ( Expression *& expr : tupleExpr->exprs ) {
                                expr = reconstructMemberExpr( expr, aggr, memberExpr->location );
                                expr->location = memberExpr->location;
                        }
                        delete aggr;
                        tupleExpr->location = memberExpr->location;
                        return tupleExpr;
                } else {
                        // there may be a tuple expr buried in the aggregate
                        // xxx - this is a memory leak
                        UntypedMemberExpr * newMemberExpr = new UntypedMemberExpr( memberExpr->member->clone(), memberExpr->aggregate->acceptMutator( *visitor ) );
                        newMemberExpr->location = memberExpr->location;
                        return newMemberExpr;
                }
        }

        Expression * UniqueExprExpander::postmutate( UniqueExpr * unqExpr ) {
                const int id = unqExpr->get_id();

                // on first time visiting a unique expr with a particular ID, generate the expression that replaces all UniqueExprs with that ID,
                // and lookup on subsequent hits. This ensures that all unique exprs with the same ID reference the same variable.
                if ( ! decls.count( id ) ) {
                        Expression * assignUnq;
                        Expression * var = unqExpr->get_var();
                        if ( unqExpr->get_object() ) {
                                // an object was generated to represent this unique expression -- it should be added to the list of declarations now
                                declsToAddBefore.push_back( unqExpr->get_object() );
                                unqExpr->set_object( nullptr );
                                // steal the expr from the unqExpr
                                assignUnq = UntypedExpr::createAssign( unqExpr->get_var()->clone(), unqExpr->get_expr() );
                                unqExpr->set_expr( nullptr );
                        } else {
                                // steal the already generated assignment to var from the unqExpr - this has been generated by FixInit
                                Expression * expr = unqExpr->get_expr();
                                CommaExpr * commaExpr = strict_dynamic_cast< CommaExpr * >( expr );
                                assignUnq = commaExpr->get_arg1();
                                commaExpr->set_arg1( nullptr );
                        }
                        ObjectDecl * finished = new ObjectDecl( toString( "_unq", id, "_finished_" ), Type::StorageClasses(), LinkageSpec::Cforall, nullptr, new BasicType( Type::Qualifiers(), BasicType::Bool ),
                                                                                                        new SingleInit( new ConstantExpr( Constant::from_int( 0 ) ) ) );
                        declsToAddBefore.push_back( finished );
                        // (finished ? _unq_expr_N : (_unq_expr_N = <unqExpr->get_expr()>, finished = 1, _unq_expr_N))
                        // This pattern ensures that each unique expression is evaluated once, regardless of evaluation order of the generated C code.
                        Expression * assignFinished = UntypedExpr::createAssign( new VariableExpr(finished), new ConstantExpr( Constant::from_int( 1 ) ) );
                        ConditionalExpr * condExpr = new ConditionalExpr( new VariableExpr( finished ), var->clone(),
                                new CommaExpr( new CommaExpr( assignUnq, assignFinished ), var->clone() ) );
                        condExpr->set_result( var->get_result()->clone() );
                        condExpr->set_env( maybeClone( unqExpr->get_env() ) );
                        decls[id] = condExpr;
                }
                delete unqExpr;
                return decls[id]->clone();
        }

        Expression * TupleAssignExpander::postmutate( TupleAssignExpr * assnExpr ) {
                StmtExpr * ret = assnExpr->get_stmtExpr();
                assnExpr->set_stmtExpr( nullptr );
                // move env to StmtExpr
                ret->set_env( assnExpr->get_env() );
                assnExpr->set_env( nullptr );
                delete assnExpr;
                return ret;
        }

        Type * TupleTypeReplacer::postmutate( TupleType * tupleType ) {
                unsigned tupleSize = tupleType->size();
                if ( ! typeMap.count( tupleSize ) ) {
                        // generate struct type to replace tuple type based on the number of components in the tuple
                        StructDecl * decl = new StructDecl( toString( "_tuple", tupleSize, "_" ) );
                        decl->location = tupleType->location;
                        decl->set_body( true );
                        for ( size_t i = 0; i < tupleSize; ++i ) {
                                TypeDecl * tyParam = new TypeDecl( toString( "tuple_param_", tupleSize, "_", i ), Type::StorageClasses(), nullptr, TypeDecl::Dtype, true );
                                decl->get_members().push_back( new ObjectDecl( toString("field_", i ), Type::StorageClasses(), LinkageSpec::C, nullptr, new TypeInstType( Type::Qualifiers(), tyParam->get_name(), tyParam ), nullptr ) );
                                decl->get_parameters().push_back( tyParam );
                        }
                        if ( tupleSize == 0 ) {
                                // empty structs are not standard C. Add a dummy field to empty tuples to silence warnings when a compound literal Tuple0 is created.
                                decl->get_members().push_back( new ObjectDecl( "dummy", Type::StorageClasses(), LinkageSpec::C, nullptr, new BasicType( Type::Qualifiers(), BasicType::SignedInt ), nullptr ) );
                        }
                        typeMap[tupleSize] = decl;
                        declsToAddBefore.push_back( decl );
                }
                Type::Qualifiers qualifiers = tupleType->get_qualifiers();

                StructDecl * decl = typeMap[tupleSize];
                StructInstType * newType = new StructInstType( qualifiers, decl );
                for ( auto p : group_iterate( tupleType->get_types(), decl->get_parameters() ) ) {
                        Type * t = std::get<0>(p);
                        newType->get_parameters().push_back( new TypeExpr( t->clone() ) );
                }
                delete tupleType;
                return newType;
        }

        Expression * TupleIndexExpander::postmutate( TupleIndexExpr * tupleExpr ) {
                Expression * tuple = tupleExpr->tuple;
                assert( tuple );
                tupleExpr->tuple = nullptr;
                unsigned int idx = tupleExpr->index;
                TypeSubstitution * env = tupleExpr->env;
                tupleExpr->env = nullptr;
                delete tupleExpr;

                if ( TupleExpr * tupleExpr = dynamic_cast< TupleExpr * > ( tuple ) ) {
                        if ( ! maybeImpureIgnoreUnique( tupleExpr ) ) {
                                // optimization: definitely pure tuple expr => can reduce to the only relevant component.
                                assert( tupleExpr->exprs.size() > idx );
                                Expression *& expr = *std::next(tupleExpr->exprs.begin(), idx);
                                Expression * ret = expr;
                                ret->env = env;
                                expr = nullptr; // remove from list so it can safely be deleted
                                delete tupleExpr;
                                return ret;
                        }
                }

                StructInstType * type = strict_dynamic_cast< StructInstType * >( tuple->result );
                StructDecl * structDecl = type->baseStruct;
                assert( structDecl->members.size() > idx );
                Declaration * member = *std::next(structDecl->members.begin(), idx);
                MemberExpr * memExpr = new MemberExpr( strict_dynamic_cast< DeclarationWithType * >( member ), tuple );
                memExpr->env = env;
                return memExpr;
        }

        Expression * replaceTupleExpr( Type * result, const std::list< Expression * > & exprs, TypeSubstitution * env ) {
                if ( result->isVoid() ) {
                        // void result - don't need to produce a value for cascading - just output a chain of comma exprs
                        assert( ! exprs.empty() );
                        std::list< Expression * >::const_iterator iter = exprs.begin();
                        Expression * expr = new CastExpr( *iter++ );
                        for ( ; iter != exprs.end(); ++iter ) {
                                expr = new CommaExpr( expr, new CastExpr( *iter ) );
                        }
                        expr->set_env( env );
                        return expr;
                } else {
                        // typed tuple expression - produce a compound literal which performs each of the expressions
                        // as a distinct part of its initializer - the produced compound literal may be used as part of
                        // another expression
                        std::list< Initializer * > inits;
                        for ( Expression * expr : exprs ) {
                                inits.push_back( new SingleInit( expr ) );
                        }
                        Expression * expr = new CompoundLiteralExpr( result, new ListInit( inits ) );
                        expr->set_env( env );
                        return expr;
                }
        }

        Expression * TupleExprExpander::postmutate( TupleExpr * tupleExpr ) {
                Type * result = tupleExpr->get_result();
                std::list< Expression * > exprs = tupleExpr->get_exprs();
                assert( result );
                TypeSubstitution * env = tupleExpr->get_env();

                // remove data from shell and delete it
                tupleExpr->set_result( nullptr );
                tupleExpr->get_exprs().clear();
                tupleExpr->set_env( nullptr );
                delete tupleExpr;

                return replaceTupleExpr( result, exprs, env );
        }

        Type * makeTupleType( const std::list< Expression * > & exprs ) {
                // produce the TupleType which aggregates the types of the exprs
                std::list< Type * > types;
                Type::Qualifiers qualifiers( Type::Const | Type::Volatile | Type::Restrict | Type::Lvalue | Type::Atomic | Type::Mutex );
                for ( Expression * expr : exprs ) {
                        assert( expr->get_result() );
                        if ( expr->get_result()->isVoid() ) {
                                // if the type of any expr is void, the type of the entire tuple is void
                                return new VoidType( Type::Qualifiers() );
                        }
                        Type * type = expr->get_result()->clone();
                        types.push_back( type );
                        // the qualifiers on the tuple type are the qualifiers that exist on all component types
                        qualifiers &= type->get_qualifiers();
                } // for
                if ( exprs.empty() ) qualifiers = Type::Qualifiers();
                return new TupleType( qualifiers, types );
        }

        TypeInstType * isTtype( Type * type ) {
                if ( TypeInstType * inst = dynamic_cast< TypeInstType * >( type ) ) {
                        if ( inst->get_baseType() && inst->get_baseType()->get_kind() == TypeDecl::Ttype ) {
                                return inst;
                        }
                }
                return nullptr;
        }

        namespace {
                /// determines if impurity (read: side-effects) may exist in a piece of code. Currently gives a very crude approximation, wherein any function call expression means the code may be impure
                struct ImpurityDetector : public WithShortCircuiting {
                        ImpurityDetector( bool ignoreUnique ) : ignoreUnique( ignoreUnique ) {}

                        void previsit( ApplicationExpr * appExpr ) {
                                visit_children = false;
                                if ( DeclarationWithType * function = InitTweak::getFunction( appExpr ) ) {
                                        if ( function->get_linkage() == LinkageSpec::Intrinsic ) {
                                                if ( function->get_name() == "*?" || function->get_name() == "?[?]" ) {
                                                        // intrinsic dereference, subscript are pure, but need to recursively look for impurity
                                                        visit_children = true;
                                                        return;
                                                }
                                        }
                                }
                                maybeImpure = true;
                        }
                        void previsit( UntypedExpr * ) { maybeImpure = true; visit_children = false; }
                        void previsit( UniqueExpr * ) {
                                if ( ignoreUnique ) {
                                        // bottom out at unique expression.
                                        // The existence of a unique expression doesn't change the purity of an expression.
                                        // That is, even if the wrapped expression is impure, the wrapper protects the rest of the expression.
                                        visit_children = false;
                                        return;
                                }
                        }

                        bool maybeImpure = false;
                        bool ignoreUnique;
                };
        } // namespace

        bool maybeImpure( Expression * expr ) {
                PassVisitor<ImpurityDetector> detector( false );
                expr->accept( detector );
                return detector.pass.maybeImpure;
        }

        bool maybeImpureIgnoreUnique( Expression * expr ) {
                PassVisitor<ImpurityDetector> detector( true );
                expr->accept( detector );
                return detector.pass.maybeImpure;
        }
} // namespace Tuples

// Local Variables: //
// tab-width: 4 //
// mode: c++ //
// compile-command: "make install" //
// End: //