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// Metaprogram's revision differentiator implementation
// Copyright 2023 Nguyễn Gia Phong
//
// This file is distributed under the University of Illinois
// Open Source License. See LICENSE.TXT for details.
#include "Differentiator.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/CommandLine.h"
#include <spawn.h>
llvm::cl::opt<std::string>
InputProgram{llvm::cl::desc("<input program>"),
llvm::cl::Positional, llvm::cl::Required};
using namespace klee;
ExprCmbnVisitor::ExprCmbnVisitor(char rev, ArrayCache& ac)
: revision(rev), arrayCache(ac)
{}
ExprVisitor::Action
ExprCmbnVisitor::visitExprPost(const Expr& e)
{
if (e.getKind() != Expr::Read)
return ExprVisitor::Action::doChildren();
const auto load = dyn_cast<ReadExpr>(&e);
const auto orig = load->updates.root;
if (!Differentiator::isSymOut(orig->name))
return ExprVisitor::Action::doChildren();
const auto a = this->arrayCache.CreateArray(
orig->name + '!' + this->revision,
orig->size, 0, 0, orig->domain, orig->range);
const auto replacement = ReadExpr::create({a, load->updates.head},
load->index);
this->outVars[orig->name][load->index] = dyn_cast<ReadExpr>(replacement.get());
return ExprVisitor::Action::changeTo(replacement);
}
bool
Differentiator::isSymArg(const std::string& name)
{
return (name.size() == 5 // string::starts_with requires C++20
&& name[0] == 'a' && name[1] == 'r' && name[2] == 'g'
&& '0' <= name[3] && name[3] <= '9'
&& '0' <= name[4] && name[4] <= '9');
}
bool
Differentiator::isSymOut(const std::string& name)
{
// string::starts_with requires C++20
return (name[0] == 'o' && name[1] == 'u' && name[2] == 't' && name[3] == '!'
&& '0' <= name[name.size() - 1] && name[name.size() - 1] <= '9');
}
Differentiator::Differentiator(std::unique_ptr<TimingSolver>* s,
time::Span& t, ArrayCache& ac)
: envs{{0, ""}}, prog{InputProgram}, solver{s}, solverTimeout{t},
arrayCache{ac}, visitorA{'a', ac}, visitorB{'b', ac}
{}
void
Differentiator::extract(ExecutionState* a, ExecutionState* b,
const std::vector<const Array*>& objects,
const std::vector<Bytes>& values)
{
TestArgs argv;
TestOuts outputs;
{
std::map<std::uint8_t, Bytes> args;
for (unsigned i = 0; i < objects.size(); ++i) {
const auto& name = objects[i]->name;
if (isSymArg(name)) {
args[std::atoi(name.c_str() + 3)] = values[i];
args[std::atoi(name.c_str() + 3)].push_back(0); // null termination
} else if (isSymOut(name.substr(0, name.size() - 2))) {
const auto rev = ((name[name.size() - 1] == 'a') ? a : b)->patchNo;
outputs[rev].first[name.substr(4, name.size() - 6)] = values[i];
}
}
uint8_t last = 0;
for (const auto& p : args) {
assert(p.first == last);
argv.push_back(p.second);
last++;
}
}
char buffer[128]; // output buffer for concrete execution
for (const auto& rev : this->envs) {
auto& envs = rev.second;
pid_t pid;
std::vector<const char*> argp {this->prog.c_str()};
for (const auto& v : argv)
argp.push_back((const char *) v.data());
argp.push_back(NULL);
int fildes[2];
auto err = pipe(fildes);
assert(!err);
posix_spawn_file_actions_t action;
posix_spawn_file_actions_init(&action);
posix_spawn_file_actions_addclose(&action, fildes[0]);
posix_spawn_file_actions_adddup2(&action, fildes[1], 1);
char *const envp[] = {const_cast<char* const>(envs.c_str()), NULL};
err = posix_spawn(&pid, this->prog.c_str(), &action, NULL,
const_cast<char* const *>(argp.data()),
envs.empty() ? NULL : envp);
assert(!err);
close(fildes[1]);
for (unsigned char n; n = read(fildes[0], buffer, sizeof(buffer));) {
assert(n >= 0);
for (unsigned char i = 0; i < n; ++i)
outputs[rev.first].second.push_back(buffer[i]);
}
outputs[rev.first].second.push_back(0); // null termination
posix_spawn_file_actions_destroy(&action);
}
this->tests[argv] = outputs;
// :var :val cluster
std::map<std::string, std::map<Bytes, std::set<std::uint64_t>>> revOut;
for (auto& o : outputs) {
for (auto& var : o.second.first)
revOut[var.first][var.second].insert(o.first);
revOut[""][o.second.second].insert(o.first); // stdout
}
for (auto& vp : revOut)
for (auto& p : vp.second)
for (auto& q : vp.second) {
if (&p == &q)
continue;
for (std::uint64_t i : p.second)
for (std::uint64_t j : q.second)
if (i < j)
this->done.emplace(std::make_pair(i, j), &this->tests[argv]);
}
}
void
Differentiator::search(ExecutionState* latest)
{
if (!this->exits[latest->patchNo].insert(latest).second)
return; // skip when seen before
for (const auto& rev : this->exits) {
if (rev.first == latest->patchNo)
continue;
if (rev.first < latest->patchNo) {
if (this->done.find(std::make_pair(rev.first, latest->patchNo))
!= this->done.end())
continue;
} else {
if (this->done.find(std::make_pair(latest->patchNo, rev.first))
!= this->done.end())
continue;
}
for (const auto& state : rev.second) {
ConstraintSet cmbnSet;
{
std::set<ref<Expr>> combination;
for (auto const& constraint : state->constraints)
combination.insert(this->visitorA.visit(constraint));
for (auto const& constraint : latest->constraints)
combination.insert(this->visitorB.visit(constraint));
for (auto const& constraint : combination)
cmbnSet.push_back(constraint);
}
std::vector<const Array*> objects;
ref<Expr> distinction;
for (const auto& sym : state->symbolics) {
if (isSymArg(sym.second->name)) {
objects.push_back(sym.second);
continue;
}
if (!isSymOut(sym.second->name))
continue;
unsigned char i = sym.second->name.size() - 1;
while (sym.second->name[i] != '!' && sym.second->name[i] != '_')
--i;
const auto& name = sym.second->name[i] == '_'
? sym.second->name.substr(0, i) : sym.second->name;
objects.push_back(arrayCache.CreateArray(name + "!a",
sym.second->size));
objects.push_back(arrayCache.CreateArray(name + "!b",
sym.second->size));
// FIXME: impossible to use visitor hash
for (const auto& a : this->visitorA.outVars[name]) {
const auto ne = NotExpr::create(EqExpr::create(a.second,
this->visitorB.outVars[name][a.first]));
if (distinction.get() == nullptr)
distinction = ne;
else
distinction = OrExpr::create(ne, distinction);
}
}
if (distinction.get() == nullptr)
continue; // no common symbolic
cmbnSet.push_back(distinction);
std::vector<Bytes> values;
std::unique_ptr<TimingSolver>& solver = *this->solver; // do judge!
solver->setTimeout(solverTimeout);
bool success = solver->getInitialValues(cmbnSet, objects, values,
state->queryMetaData);
solver->setTimeout(time::Span());
if (!success)
continue;
this->extract(latest, state, objects, values);
assert(!this->tests.empty());
break; // one diff test per termination for now
}
}
}
void
Differentiator::log()
{
for (const auto& t : this->tests) {
std::map<Bytes, std::set<std::uint64_t>> stdoutClusters;
std::map<std::pair<std::string, Bytes>,
std::set<std::uint64_t>> varClusters;
for (const auto& rev : t.second) {
for (const auto& var : rev.second.first)
varClusters[var].insert(rev.first);
stdoutClusters[rev.second.second].insert(rev.first);
if (stdoutClusters.size() > 1) {
llvm::errs() << "Args:";
for (const auto& s : t.first) {
llvm::errs() << ' ';
for (const auto c : s)
llvm::errs() << (int) c << '.';
}
llvm::errs() << '\n';
for (const auto& so : stdoutClusters) {
llvm::errs() << "Revisions:";
for (const auto& r : so.second)
llvm::errs() << ' ' << r;
llvm::errs() << '\n' << std::string((const char*) so.first.data());
}
llvm::errs() << '\n';
}
}
}
}
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