source: src/ControlStruct/LabelFixer.cc@ 94e0864d

//
// 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.
//
// LabelFixer.cc -- 
//
// Author           : Rodolfo G. Esteves
// Created On       : Mon May 18 07:44:20 2015
// Last Modified By : Peter A. Buhr
// Last Modified On : Tue Jun 23 12:42:23 2015
// Update Count     : 96
//

#include <list>
#include <cassert>

#include "LabelFixer.h"
#include "MLEMutator.h"
#include "SynTree/Statement.h"
#include "SynTree/Declaration.h"
#include "utility.h"

#include <iostream>

namespace ControlStruct {
        LabelFixer::Entry::Entry( Statement *to, BranchStmt *from ) : definition ( to ) {
                if ( from != 0 )
                        usage.push_back( from );
        }

        bool LabelFixer::Entry::insideLoop() {
                return ( dynamic_cast< ForStmt * > ( definition ) ||
                        dynamic_cast< WhileStmt * > ( definition )  );
        }

        LabelFixer::LabelFixer( LabelGenerator *gen ) : generator ( gen ) {
                if ( generator == 0 )
                        generator = LabelGenerator::getGenerator();
        }

        void LabelFixer::visit( FunctionDecl *functionDecl ) {
                maybeAccept( functionDecl->get_statements(), *this );

                MLEMutator mlemut( resolveJumps(), generator );
                functionDecl->acceptMutator( mlemut );
        }

        // prune to at most one label definition for each statement
        void LabelFixer::visit( Statement *stmt ) {
                std::list< Label > &labels = stmt->get_labels();

                if ( ! labels.empty() ) {
                        // only remember one label for each statement
                        Label current = setLabelsDef( labels, stmt );
                        labels.clear();
                        labels.push_front( current );
                } // if
        }

        void LabelFixer::visit( BranchStmt *branchStmt ) {
                visit ( ( Statement * )branchStmt );

                // for labeled branches, add an entry to the label table
                Label target = branchStmt->get_target();
                if ( target != "" ) {
                        setLabelsUsg( target, branchStmt );
                }
        }

        // sets the definition of the labelTable entry to be the provided 
        // statement for every label in the list parameter. Happens for every kind of statement
        Label LabelFixer::setLabelsDef( std::list< Label > &llabel, Statement *definition ) {
                assert( definition != 0 );
                assert( llabel.size() > 0 );

                Entry * e = new Entry( definition );

                for ( std::list< Label >::iterator i = llabel.begin(); i != llabel.end(); i++ ) {
                        if ( labelTable.find( *i ) == labelTable.end() ) {
                                // all labels on this statement need to use the same entry, so this should only be created once
                                // undefined and unused until now, add an entry
                                labelTable[ *i ] =  e;
                        } else if ( labelTable[ *i ]->defined() ) {
                                // defined twice, error
                                throw SemanticError( "Duplicate definition of label: " + *i );
                        }       else {
                                // used previously, but undefined until now -> link with this entry
                                Entry * oldEntry = labelTable[ *i ];
                                e->add_uses( oldEntry->get_uses() );
                                labelTable[ *i ] = e;
                        } // if
                } // for

                // produce one of the labels attached to this statement to be 
                // temporarily used as the canonical label
                return labelTable[ llabel.front() ]->get_label();
        }

        // Remember all uses of a label.
        void LabelFixer::setLabelsUsg( Label orgValue, BranchStmt *use ) {
                assert( use != 0 );

                if ( labelTable.find( orgValue ) != labelTable.end() ) {
                        // the label has been defined or used before
                        labelTable[ orgValue ]->add_use( use );
                } else {
                        labelTable[ orgValue ] = new Entry( 0, use );
                }
        }

        // Ultimately builds a table that maps a label to its defining statement.
        // In the process, 
        std::map<Label, Statement * > *LabelFixer::resolveJumps() throw ( SemanticError ) {
                std::map< Statement *, Entry * > def_us;

                // combine the entries for all labels that target the same location
                for ( std::map< Label, Entry *>::iterator i = labelTable.begin(); i != labelTable.end(); ++i ) {
                        Entry *e = i->second;

                        if ( def_us.find ( e->get_definition() ) == def_us.end() ) {
                                def_us[ e->get_definition() ] = e;                              
                        } else if ( e->used() ) {
                                def_us[ e->get_definition() ]->add_uses( e->get_uses() );
                        }
                }

                // create a unique label for each target location. 
                for ( std::map< Statement *, Entry * >::iterator i = def_us.begin(); i != def_us.end(); ++i ) {
                        Statement *to = (*i).first;
                        Entry * entry = (*i).second;
                        std::list< BranchStmt *> &from = entry->get_uses();

                        // no label definition found
                        if ( to == 0 ) {
                                Label undef = from.back()->get_target();
                                throw SemanticError ( "'" + undef + "' label not defined");
                        } // if

                        // generate a new label, and attach it to its defining statement as the only label on that statement
                        Label finalLabel = generator->newLabel( to->get_labels().back() );
                        entry->set_label( finalLabel );

                        to->get_labels().clear();
                        to->get_labels().push_back( finalLabel );

                        // redirect each of the source branch statements to the new target label
                        for ( std::list< BranchStmt *>::iterator j = from.begin(); j != from.end(); ++j ) {
                                BranchStmt *jump = *j;
                                assert( jump != 0 );
                                jump->set_target( finalLabel );
                        } // for
                } // for

                // create a table where each label maps to its defining statement
                std::map< Label, Statement * > *ret = new std::map< Label, Statement * >();
                for ( std::map< Statement *, Entry * >::iterator i = def_us.begin(); i != def_us.end(); ++i ) {
                        (*ret)[ (*i).second->get_label() ] = (*i).first;
                }

                return ret;
        }
}  // namespace ControlStruct

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