Index: src/ControlStruct/LabelFixer.cc =================================================================== --- src/ControlStruct/LabelFixer.cc (revision 00cc023285120a85a7e80e417220f36483ebd413) +++ src/ControlStruct/LabelFixer.cc (revision 76934fbc18afbcbc97f690da75e4e77dd42659af) @@ -10,6 +10,6 @@ // Created On : Mon May 18 07:44:20 2015 // Last Modified By : Rob Schluntz -// Last Modified On : Wed May 27 16:16:14 2015 -// Update Count : 4 +// Last Modified On : Fri May 29 15:57:12 2015 +// Update Count : 82 // @@ -23,6 +23,8 @@ #include "utility.h" +#include + namespace ControlStruct { - LabelFixer::Entry::Entry( Statement *to, Statement *from ) : definition ( to ) { + LabelFixer::Entry::Entry( Statement *to, BranchStmt *from ) : definition ( to ) { if ( from != 0 ) usage.push_back( from ); @@ -31,5 +33,5 @@ bool LabelFixer::Entry::insideLoop() { return ( dynamic_cast< ForStmt * > ( definition ) || - dynamic_cast< WhileStmt * > ( definition ) ); + dynamic_cast< WhileStmt * > ( definition ) ); } @@ -46,8 +48,10 @@ } + // 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(); @@ -57,85 +61,98 @@ void LabelFixer::visit( BranchStmt *branchStmt ) { - visit ( ( Statement * )branchStmt ); // the labels this statement might have + visit ( ( Statement * )branchStmt ); - Label target; - if ( (target = branchStmt->get_target()) != "" ) { + // for labeled branches, add an entry to the label table + Label target = branchStmt->get_target(); + if ( target != "" ) { setLabelsUsg( target, branchStmt ); - } //else /* computed goto or normal exit-loop statements */ + } } + // 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 ); - Entry *entry = new Entry( definition ); - bool used = false; + assert( llabel.size() > 0 ); - for ( std::list< Label >::iterator i = llabel.begin(); i != llabel.end(); i++ ) - if ( labelTable.find( *i ) == labelTable.end() ) - { used = true; labelTable[ *i ] = entry; } // undefined and unused - else - if ( labelTable[ *i ]->defined() ) - throw SemanticError( "Duplicate definition of label: " + *i ); - else - labelTable[ *i ]->set_definition( definition ); + 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 - if ( ! used ) delete entry; - - return labelTable[ llabel.front() ]->get_label(); // this *must* exist + // produce one of the labels attached to this statement to be + // temporarily used as the canonical label + return labelTable[ llabel.front() ]->get_label(); } - Label LabelFixer::setLabelsUsg( Label orgValue, Statement *use ) { + // Remember all uses of a label. + void LabelFixer::setLabelsUsg( Label orgValue, BranchStmt *use ) { assert( use != 0 ); - if ( labelTable.find( orgValue ) != labelTable.end() ) - labelTable[ orgValue ]->add_use( use ); // the label has been defined or used before - else + 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 ); - - return labelTable[ orgValue ]->get_label(); + } } + // Ultimately builds a table that maps a label to its defining statement. + // In the process, std::map *LabelFixer::resolveJumps() throw ( SemanticError ) { std::map< Statement *, Entry * > def_us; - for ( std::map< Label, Entry *>::iterator i = labelTable.begin(); i != labelTable.end(); i++ ) { + // 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() ); + } else if ( e->used() ) { + def_us[ e->get_definition() ]->add_uses( e->get_uses() ); } } - // get rid of labelTable - for ( std::map< Statement *, Entry * >::iterator i = def_us.begin(); i != def_us.end(); i++ ) { + // 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; - std::list< Statement *> &from = (*i).second->get_uses(); - Label finalLabel = generator->newLabel(); - (*i).second->set_label( finalLabel ); + Entry * entry = (*i).second; + std::list< BranchStmt *> &from = entry->get_uses(); + // no label definition found if ( to == 0 ) { - BranchStmt *first_use = dynamic_cast(from.back()); - Label undef(""); - if ( first_use != 0 ) - undef = first_use->get_target(); + 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 ); - for ( std::list< Statement *>::iterator j = from.begin(); j != from.end(); j++ ) { - BranchStmt *jumpTo = dynamic_cast< BranchStmt * > ( *j ); - assert( jumpTo != 0 ); - jumpTo->set_target( 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 - // reverse table + // 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++ ) + for ( std::map< Statement *, Entry * >::iterator i = def_us.begin(); i != def_us.end(); ++i ) { (*ret)[ (*i).second->get_label() ] = (*i).first; + } return ret; Index: src/ControlStruct/LabelFixer.h =================================================================== --- src/ControlStruct/LabelFixer.h (revision 00cc023285120a85a7e80e417220f36483ebd413) +++ src/ControlStruct/LabelFixer.h (revision 76934fbc18afbcbc97f690da75e4e77dd42659af) @@ -10,6 +10,6 @@ // Created On : Mon May 18 07:44:20 2015 // Last Modified By : Rob Schluntz -// Last Modified On : Tue May 26 12:55:10 2015 -// Update Count : 4 +// Last Modified On : Fri May 29 15:25:55 2015 +// Update Count : 11 // @@ -55,10 +55,10 @@ Label setLabelsDef( std::list< Label > &, Statement *definition ); - Label setLabelsUsg( Label, Statement *usage = 0 ); + void setLabelsUsg( Label, BranchStmt *usage = 0 ); private: class Entry { public: - Entry( Statement *to = 0, Statement *from = 0 ); + Entry( Statement *to = 0, BranchStmt *from = 0 ); bool used() { return ( usage.empty() ); } bool defined() { return ( definition != 0 ); } @@ -71,11 +71,11 @@ void set_definition( Statement *def ) { definition = def; } - std::list< Statement *> &get_uses() { return usage; } - void add_use ( Statement *use ) { usage.push_back( use ); } - void add_uses ( std::list uses ) { usage.insert( usage.end(), uses.begin(), uses.end() ); } + std::list< BranchStmt *> &get_uses() { return usage; } + void add_use ( BranchStmt *use ) { usage.push_back( use ); } + void add_uses ( std::list uses ) { usage.insert( usage.end(), uses.begin(), uses.end() ); } private: Label label; Statement *definition; - std::list usage; + std::list usage; };