//
// 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 : Rob Schluntz
// Last Modified On : Fri May 29 15:57:12 2015
// Update Count     : 82
//

#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 );

		for ( std::list< Label >::iterator i = llabel.begin(); i != llabel.end(); i++ ) {
			if ( labelTable.find( *i ) == labelTable.end() ) { 
				// undefined and unused until now, add an entry
				labelTable[ *i ] =  new Entry( definition ); 
			} else if ( labelTable[ *i ]->defined() ) {\
				// defined twice, error
				throw SemanticError( "Duplicate definition of label: " + *i );
			}	else {
				// used previously, but undefined until now -> set its definition to this location
				labelTable[ *i ]->set_definition( definition );
			} // 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");
			}

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

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