source: src/GenPoly/Lvalue.cc @ 08fc48f

//
// 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.
//
// Lvalue.cc --
//
// Author           : Richard C. Bilson
// Created On       : Mon May 18 07:44:20 2015
// Last Modified By : Peter A. Buhr
// Last Modified On : Fri Mar 17 09:11:18 2017
// Update Count     : 5
//

#include <cassert>                       // for safe_dynamic_cast
#include <string>                        // for string

#include "Common/SemanticError.h"        // for SemanticError
#include "GenPoly.h"                     // for isPolyType
#include "Lvalue.h"
#include "Parser/LinkageSpec.h"          // for Spec, isBuiltin, Intrinsic
#include "ResolvExpr/TypeEnvironment.h"  // for AssertionSet, OpenVarSet
#include "ResolvExpr/Unify.h"            // for unify
#include "SymTab/Indexer.h"              // for Indexer
#include "SynTree/Declaration.h"         // for Declaration, FunctionDecl
#include "SynTree/Expression.h"          // for Expression, ConditionalExpr
#include "SynTree/Mutator.h"             // for mutateAll, Mutator
#include "SynTree/Statement.h"           // for ReturnStmt, Statement (ptr o...
#include "SynTree/Type.h"                // for PointerType, Type, FunctionType
#include "SynTree/Visitor.h"             // for Visitor, acceptAll

namespace GenPoly {
        namespace {
                /// Replace uses of lvalue returns with appropriate pointers
                class Pass1 : public Mutator {
                  public:
                        Pass1();

                        virtual Expression *mutate( ApplicationExpr *appExpr );
                        virtual Statement *mutate( ReturnStmt *appExpr );
                        virtual DeclarationWithType *mutate( FunctionDecl *funDecl );
                  private:
                        DeclarationWithType* retval;
                };

                /// Replace declarations of lvalue returns with appropriate pointers
                class Pass2 : public Visitor {
                  public:
                        virtual void visit( FunctionType *funType );
                  private:
                };

                /// GCC-like Generalized Lvalues (which have since been removed from GCC)
                /// https://gcc.gnu.org/onlinedocs/gcc-3.4.6/gcc/Lvalues.html#Lvalues
                /// Replaces &(a,b) with (a, &b), &(a ? b : c) with (a ? &b : &c)
                class GeneralizedLvalue : public Mutator {
                        typedef Mutator Parent;

                        virtual Expression * mutate( MemberExpr * memExpr );
                        virtual Expression * mutate( AddressExpr * addressExpr );

                        template<typename Func>
                        Expression * applyTransformation( Expression * expr, Expression * arg, Func mkExpr );
                };
        } // namespace

        void convertLvalue( std::list< Declaration* >& translationUnit ) {
                Pass1 p1;
                Pass2 p2;
                GeneralizedLvalue genLval;
                mutateAll( translationUnit, p1 );
                acceptAll( translationUnit, p2 );
                mutateAll( translationUnit, genLval );
        }

        Expression * generalizedLvalue( Expression * expr ) {
                GeneralizedLvalue genLval;
                return expr->acceptMutator( genLval );
        }

        namespace {
                Type* isLvalueRet( FunctionType *function ) {
                        if ( function->get_returnVals().empty() ) return 0;
                        Type *ty = function->get_returnVals().front()->get_type();
                        return ty->get_lvalue() ? ty : 0;
                }

                bool isIntrinsicApp( ApplicationExpr *appExpr ) {
                        if ( VariableExpr *varExpr = dynamic_cast< VariableExpr* >( appExpr->get_function() ) ) {
                                return varExpr->get_var()->get_linkage() == LinkageSpec::Intrinsic;
                        } else {
                                return false;
                        } // if
                }

                Pass1::Pass1() {
                }

                DeclarationWithType * Pass1::mutate( FunctionDecl *funcDecl ) {
                        if ( funcDecl->get_statements() ) {
                                DeclarationWithType* oldRetval = retval;
                                retval = 0;
                                if ( ! LinkageSpec::isBuiltin( funcDecl->get_linkage() ) && isLvalueRet( funcDecl->get_functionType() ) ) {
                                        retval = funcDecl->get_functionType()->get_returnVals().front();
                                }
                                // fix expressions and return statements in this function
                                funcDecl->set_statements( funcDecl->get_statements()->acceptMutator( *this ) );
                                retval = oldRetval;
                        } // if
                        return funcDecl;
                }

                Expression * Pass1::mutate( ApplicationExpr *appExpr ) {
                        appExpr->get_function()->acceptMutator( *this );
                        mutateAll( appExpr->get_args(), *this );

                        PointerType *pointer = safe_dynamic_cast< PointerType* >( appExpr->get_function()->get_result() );
                        FunctionType *function = safe_dynamic_cast< FunctionType* >( pointer->get_base() );

                        Type *funType = isLvalueRet( function );
                        if ( funType && ! isIntrinsicApp( appExpr ) ) {
                                Expression *expr = appExpr;
                                Type *appType = appExpr->get_result();
                                if ( isPolyType( funType ) && ! isPolyType( appType ) ) {
                                        // make sure cast for polymorphic type is inside dereference
                                        expr = new CastExpr( appExpr, new PointerType( Type::Qualifiers(), appType->clone() ) );
                                }
                                UntypedExpr *deref = new UntypedExpr( new NameExpr( "*?" ) );
                                deref->set_result( appType->clone() );
                                appExpr->set_result( new PointerType( Type::Qualifiers(), appType ) );
                                deref->get_args().push_back( expr );
                                return deref;
                        } else {
                                return appExpr;
                        } // if
                }

                Statement * Pass1::mutate(ReturnStmt *retStmt) {
                        if ( retval && retStmt->get_expr() ) {
                                if ( retStmt->get_expr()->get_result()->get_lvalue() ) {
                                        // ***** Code Removal ***** because casts may be stripped already

                                        // strip casts because not allowed to take address of cast
                                        // while ( CastExpr *castExpr = dynamic_cast< CastExpr* >( retStmt->get_expr() ) ) {
                                        //      retStmt->set_expr( castExpr->get_arg() );
                                        //      retStmt->get_expr()->set_env( castExpr->get_env() );
                                        //      castExpr->set_env( 0 );
                                        //      castExpr->set_arg( 0 );
                                        //      delete castExpr;
                                        // } // while
                                        retStmt->set_expr( new AddressExpr( retStmt->get_expr()->acceptMutator( *this ) ) );
                                } else {
                                        throw SemanticError( "Attempt to return non-lvalue from an lvalue-qualified function" );
                                } // if
                        } // if
                        return retStmt;
                }

                void Pass2::visit( FunctionType *funType ) {
                        std::string typeName;
                        if ( isLvalueRet( funType ) ) {
                                DeclarationWithType *retParm = funType->get_returnVals().front();

                                // make a new parameter that is a pointer to the type of the old return value
                                retParm->set_type( new PointerType( Type::Qualifiers(), retParm->get_type() ) );
                        } // if

                        Visitor::visit( funType );
                }

                template<typename Func>
                Expression * GeneralizedLvalue::applyTransformation( Expression * expr, Expression * arg, Func mkExpr ) {
                        if ( CommaExpr * commaExpr = dynamic_cast< CommaExpr * >( arg ) ) {
                                Expression * arg1 = commaExpr->get_arg1()->clone();
                                Expression * arg2 = commaExpr->get_arg2()->clone();
                                Expression * ret = new CommaExpr( arg1, mkExpr( arg2 ) );
                                ret->set_env( expr->get_env() );
                                expr->set_env( nullptr );
                                delete expr;
                                return ret->acceptMutator( *this );
                        } else if ( ConditionalExpr * condExpr = dynamic_cast< ConditionalExpr * >( arg ) ) {
                                Expression * arg1 = condExpr->get_arg1()->clone();
                                Expression * arg2 = condExpr->get_arg2()->clone();
                                Expression * arg3 = condExpr->get_arg3()->clone();
                                ConditionalExpr * ret = new ConditionalExpr( arg1, mkExpr( arg2 ), mkExpr( arg3 ) );
                                ret->set_env( expr->get_env() );
                                expr->set_env( nullptr );
                                delete expr;

                                // conditional expr type may not be either of the argument types, need to unify
                                using namespace ResolvExpr;
                                Type* commonType = nullptr;
                                TypeEnvironment newEnv;
                                AssertionSet needAssertions, haveAssertions;
                                OpenVarSet openVars;
                                unify( ret->get_arg2()->get_result(), ret->get_arg3()->get_result(), newEnv, needAssertions, haveAssertions, openVars, SymTab::Indexer(), commonType );
                                ret->set_result( commonType ? commonType : ret->get_arg2()->get_result()->clone() );
                                return ret->acceptMutator( *this );
                        }
                        return expr;
                }

                Expression * GeneralizedLvalue::mutate( MemberExpr * memExpr ) {
                        Parent::mutate( memExpr );
                        return applyTransformation( memExpr, memExpr->get_aggregate(), [=]( Expression * aggr ) { return new MemberExpr( memExpr->get_member(), aggr ); } );
                }

                Expression * GeneralizedLvalue::mutate( AddressExpr * addrExpr ) {
                        addrExpr = safe_dynamic_cast< AddressExpr * >( Parent::mutate( addrExpr ) );
                        return applyTransformation( addrExpr, addrExpr->get_arg(), []( Expression * arg ) { return new AddressExpr( arg ); } );
                }
        } // namespace
} // namespace GenPoly

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