Viewing file:  If_simplification.cpp (2.28 KB) -rw-rw-r--
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#include "If_simplification.h"
#include "process_ir/General.h"
#include "Def_use_web.h"
#include "wpa/Context.h"
#include "wpa/Def_use.h"
#include "wpa/Points_to.h"
#include <iostream>
using namespace MIR;
void
If_simplification::visit_branch_block (Branch_block* bb)
{
/* Turn
*
* if (!$x) goto L1; else goto L2;
*
* into
*
* if ($x) goto L2; else goto L1;
*/
Context* cx = Context::non_contextual (bb);
string ns = cx->symtable_name ();
// Extract the correct use from the branch
SSA_use* use = NULL;
bool simplify = false;
foreach (SSA_use* temp, *bb->cfg->duw->get_block_uses (bb))
{
if (temp->type_flag != SSA_PHI)
{
string s = temp->name->get_name ();
Index_node name (ns, *bb->branch->variable_name->value);
if (s == name.get_starred_name()->str())
{
use = temp;
simplify = true;
}
}
}
if (simplify)
{
SSA_def_list* defs = use->get_defs ();
if (defs->size () == 1)
{
Statement_block* sb;
if ((sb = dynamic_cast<Statement_block*> (defs->front()->bb)))
{
Assign_var* ass_var;
Unary_op* un_op;
if ((ass_var = dynamic_cast<Assign_var*> (sb->statement)))
{
if ((un_op = dynamic_cast<Unary_op*> (ass_var->rhs)))
{
if (*un_op->op->value == "!")
{
// I don't like this, I don't think I should need it....
if (*un_op->variable_name->value != *bb->branch->variable_name->value)
{
bb->branch->variable_name = un_op->variable_name->clone ();
bb->switch_successors ();
// Fix def-use information. We won't fix Def_use_web since it will be
// destroyed after this pass.
Def_use *du = bb->cfg->duw->get_def_use();
foreach (const Index_node *use, *du->get_uses(bb))
du->remove_use(bb, use);
Basic_block *correct_bb = defs->front()->bb;
Index_node *correct_index = IN(ns, *un_op->variable_name->value);
// FIXME: Could I add the correct index node directly?
// du->insert_use(bb, correct_index);
// Let's be conservative and add the previously known Index_node pointer.
foreach (const Index_node *use, *du->get_uses(correct_bb)) {
if (*use == *correct_index)
du->insert_use(bb, use);
}
}
}
}
}
}
}
else
{
phc_unreachable ();
}
}
}
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