Viewing file:  ESSA.cpp (3.22 KB) -rw-rw-r--
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#include "optimize/ssa/HSSA.h"
#include "optimize/ssa/Phi.h"
#include "optimize/ssa/SSA_ops.h"
#include "optimize/wpa/Aliasing.h"
#include "optimize/wpa/Whole_program.h"
#include "optimize/Basic_block.h"
#include "optimize/Def_use_web.h"
#include "ESSA.h"
using namespace MIR;
ESSA::ESSA(Whole_program* wp, CFG* cfg) : HSSA(wp, cfg) {
}
void ESSA::insert_nodes() {
// Insert sigma nodes only once for conditional branches.
insert_sigma_nodes();
// Always try to insert phi nodes.
insert_phi_nodes();
}
bool ESSA::insert_sigma_nodes() {
bool changed = false;
foreach (Basic_block *bb, *cfg->get_all_bbs()) {
if (Branch_block *br = dynamic_cast<Branch_block *>(bb)) {
// Obtain where the variables was defined.
SSA_def *def = find_variable(br, br->branch->variable_name);
// May have legitimate cases where the def is unknown.
if (!def)
continue;
SSA_name_list *sigmas = collect_vars(def->bb);
// Adding sigmas for collected uses on the branch block.
foreach (SSA_name *add, *sigmas) {
// Add the sigma node.
if (!br->has_sigma_node(*add)) {
br->add_sigma_node(*add);
changed = true;
}
}
}
}
return changed;
}
SSA_def *ESSA::find_variable(Basic_block *bb, VARIABLE_NAME *var_name) {
Context* cx = Context::non_contextual(bb);
string ns = cx->symtable_name();
Index_node name(ns, *var_name->value);
string starred_name = name.get_starred_name()->str();
SSA_use *use = NULL;
foreach (SSA_use *tmp, *cfg->duw->get_block_uses(bb)) {
// Not interested in phi and sigma nodes.
if (tmp->type_flag == SSA_PHI || tmp->type_flag == SSI_SIGMA)
continue;
string s = tmp->name->get_name();
if (s == starred_name) {
// Found the use.
use = tmp;
break;
}
}
if (!use)
return NULL;
SSA_def_list *defs = use->get_defs();
// The def-use may be outdated and a use may have more than 1 def.
// If this is the case, let's skip it.
if (defs->size() != 1)
return NULL;
return defs->front();
}
SSA_name_list *ESSA::collect_vars(Basic_block *bb) {
SSA_name_list *names = new SSA_name_list;
Statement_block *stmt = dynamic_cast<Statement_block *>(bb);
if (!stmt)
return names;
// TODO: Should we handle casts here?
// Add sigma for variables referenced by the casts.
foreach (SSA_use *use, *cfg->duw->get_block_uses(stmt)) {
// Ugly hack to see if the use is a starred index node.
if (!use->name->is_starred())
continue;
// Checking the type of the used variable.
Context *ctx = Context::non_contextual(use->bb);
Index_node *in = use->name->reverse();
VARIABLE_NAME *var = new VARIABLE_NAME(s(in->index));
const Abstract_value *absval = wp->get_abstract_value(ctx, R_OUT, var);
// If a variable's type is not a string, it's not a source of problem.
if (!absval->types->has("string"))
continue;
names->push_back(use->name);
// Find its variable names alias.
cReference_list *refs = wp->aliasing->get_references(ctx, R_OUT, in, PTG_ALL);
foreach (const Reference *ref, *refs) {
Index_node *starred = ref->index->get_starred_name();
names->push_back(new SSA_name(starred->str()));
}
}
return names;
}
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