Viewing file:  Dead_temp_cleanup.cpp (1.71 KB) -rw-rw-r--
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/*
* phc -- the open source PHP compiler
* See doc/license/README.license for licensing information
*
* The lowering passes introduce a lot of unnecessary copies, which
* add extra reference counts, resulting in extra copying and poor
* performance.
*
* This removes assignments from simple variables to compiler-generated
* temporaries, so long as the temporary is never used.
*
* 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.
*
*/
#include "Dead_temp_cleanup.h"
#include "Use_def_counter.h"
#include "process_ir/General.h"
#include "HIR_visitor.h"
using namespace HIR;
Dead_temp_cleanup::Dead_temp_cleanup ()
{
}
void Dead_temp_cleanup::children_php_script (PHP_script* in)
{
in->visit (new Use_def_counter ());
Transform::children_php_script (in);
in->visit (new Clear_use_defs);
}
void Dead_temp_cleanup::pre_assign_var (Assign_var* in, Statement_list* out)
{
// get useful variables
VARIABLE_NAME *lhs = in->lhs;
if (!isa<HIR::VARIABLE_NAME> (in->rhs))
{
out->push_back (in);
return;
}
VARIABLE_NAME *rhs = dyc<HIR::VARIABLE_NAME> (in->rhs);
DEBUG ("is simple assignment");
xdebug (lhs);
xdebug (rhs);
// Remove statement
if (lhs->attrs->is_true ("phc.codegen.compiler_generated")
&& lhs->attrs->get_integer ("phc.use_defs.use_count")->value() == 0
&& lhs->attrs->get_integer ("phc.use_defs.def_count")->value() == 1)
{
DEBUG ("removing statement");
// note lack of out->push_back (in);
iterate_again = true;
return;
}
else
{
DEBUG ("Not removing: ");
debug (in);
}
out->push_back (in);
}
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