Viewing file:  Use_def_counter.cpp (3.11 KB) -rw-rw-r--
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/*
* phc -- the open source PHP compiler
* See doc/license/README.license for licensing information
*
* HACK TODO: Remove.
* This is exactly the sort of hacky thing we wanted
* to remove. This would be much better done with a data-flow
* framework, but is much easier than cleaning up the passes, which
* would otherwise be necessary.
*
* Count the uses and defs of each variable. Of course, it is very
* imprecise, only works for very certain cases, doesn't use any
* sort of data-flow techniques, won't work in the general case in
* the presence of any sort of features, doesn't take references
* into account, etc. This is only barely usable for the hacky dead
* code elimination and copy propagation I've hacked into place.
*
*/
#include "Use_def_counter.h"
#include "HIR_visitor.h"
using namespace HIR;
using namespace std;
Use_def_counter::Use_def_counter ()
: analysis_defs ()
, analysis_occurences ()
{
}
/* The entry points are the php script, and method entries */
void Use_def_counter::init_analysis ()
{
analysis_defs.push (new Map<string, int>);
analysis_occurences.push (new Map<string, int>);
}
void Use_def_counter::children_php_script (PHP_script* in)
{
init_analysis ();
// continue the visitor
Visitor::children_php_script (in);
finish_analysis (in->statements);
}
void Use_def_counter::pre_method (Method* in)
{
init_analysis ();
}
/* Count defs and uses */
void Use_def_counter::pre_assign_var (Assign_var* in)
{
(*analysis_defs.top()) [*in->lhs->value] ++;
}
void Use_def_counter::pre_variable_name (VARIABLE_NAME* in)
{
(*analysis_occurences.top()) [*in->value] ++;
}
/* Exit points are after methods, and after the script completes */
void Use_def_counter::post_method (Method* in)
{
finish_analysis (in->statements);
}
class Add_attributes : public HIR::Visitor, public virtual GC_obj
{
private:
Map<string, int>* uses;
Map<string, int>* defs;
public:
Add_attributes (Map<string, int>* uses, Map<string, int>* defs)
: uses (uses)
, defs (defs)
{
}
void children_method (Method* in)
{
// Do not descend into functions
}
void pre_variable_name (VARIABLE_NAME* in)
{
in->attrs->set ("phc.use_defs.use_count", new Integer ((*uses) [*in->value]));
in->attrs->set ("phc.use_defs.def_count", new Integer ((*defs) [*in->value]));
}
};
void Use_def_counter::finish_analysis (HIR::Statement_list* in)
{
Map<string, int>* defs = analysis_defs.top ();
Map<string, int>* occurences = analysis_occurences.top ();
Map<string, int>* uses = new Map <string, int> ();
analysis_occurences.pop ();
analysis_defs.pop ();
// If either occurences or defs are missing a variable, add it.
Map<string, int>::const_iterator i;
for(i = defs->begin(); i != defs->end(); i++)
if (occurences->find ((*i).first) == defs->end ())
(*occurences) [(*i).first] = 0;
for(i = occurences->begin(); i != occurences->end(); i++)
if (defs->find ((*i).first) == defs->end ())
(*defs) [(*i).first] = 0;
for(i = occurences->begin(); i != occurences->end(); i++)
{
string key = (*i).first;
(*uses) [key] = (*occurences) [key] - (*defs) [key];
}
(new Add_attributes (uses, defs))->visit_statement_list (in);
}
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