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Fix flaky opt_priokey -strict and cover binary exclusive scan

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ASLR-dependent ConstEval seeding let E4 miss OOR counterexamples; use a
deterministic seed and force OOR key collisions. Add I9 (NB=12) for the
thermometer fallback path Greptile flagged.

Co-authored-by: Cursor <cursoragent@cursor.com>
This commit is contained in:
Akash Levy 2026-07-08 23:20:22 -07:00
parent 665bd1099a
commit a022ca524d
2 changed files with 78 additions and 12 deletions
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51
passes/opt/opt_priokey.cc
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@ -264,26 +264,21 @@ struct OptPrioKeyWorker {
range = 1ULL << cap;
}
ConstEval ce(module);
uint64_t lfsr = 0x9e3779b97f4a7c15ULL ^ (uintptr_t)read;
// Deterministic seed (not a Cell*): ASLR made uintptr_t seeding flake
// across runs, so -strict could miss the OOR counterexample.
uint64_t lfsr = 0x9e3779b97f4a7c15ULL ^ ((uint64_t)S << 1) ^
((uint64_t)kw << 17) ^ (uint64_t)GetSize(steps);
auto rnd = [&]() {
lfsr ^= lfsr << 13; lfsr ^= lfsr >> 7; lfsr ^= lfsr << 17;
return lfsr;
};
for (int t = 0; t < fp_trials; t++) {
auto trial = [&](int rk, const vector<int> &kv, const vector<int> &gv) -> bool {
ce.push();
int rk = (int)(rnd() % range);
ce.set(read_key, Const(rk, GetSize(read_key)));
vector<int> kv(GetSize(steps));
vector<int> gv(GetSize(steps));
for (int i = 0; i < GetSize(steps); i++) {
kv[i] = (int)(rnd() % range);
ce.set(steps[i].key, Const(kv[i], GetSize(steps[i].key)));
if (steps[i].guard == State::S1) {
gv[i] = 1;
} else {
gv[i] = (int)(rnd() & 1);
if (steps[i].guard != State::S1)
ce.set(SigSpec(steps[i].guard), Const(gv[i], 1));
}
}
SigSpec out(read->getPort(ID::Y));
SigSpec undef;
@ -293,7 +288,39 @@ struct OptPrioKeyWorker {
for (int i = 0; i < GetSize(steps); i++)
if (gv[i] && kv[i] == rk) { expect = 1; break; }
ce.pop();
if (!ok || actual != expect)
return ok && actual == expect;
};
// Strict + non-pow2 S: force OOR key collisions the rewrite would accept
// but the S-bit accumulator cannot store (taken[key>=S] is not a set bit).
if (strict && range > (uint64_t)S && !steps.empty()) {
int oor_n = (int)(range - (uint64_t)S);
int forced = oor_n < 16 ? oor_n : 16;
for (int f = 0; f < forced; f++) {
int rk = S + f;
vector<int> kv(GetSize(steps), 0);
vector<int> gv(GetSize(steps), 0);
kv[0] = rk;
gv[0] = 1;
for (int i = 1; i < GetSize(steps); i++) {
kv[i] = (int)(rnd() % range);
gv[i] = steps[i].guard == State::S1 ? 1 : (int)(rnd() & 1);
}
if (!trial(rk, kv, gv))
return false;
}
}
for (int t = 0; t < fp_trials; t++) {
int rk = (int)(rnd() % range);
vector<int> kv(GetSize(steps));
vector<int> gv(GetSize(steps));
for (int i = 0; i < GetSize(steps); i++) {
kv[i] = (int)(rnd() % range);
if (steps[i].guard == State::S1)
gv[i] = 1;
else
gv[i] = (int)(rnd() & 1);
}
if (!trial(rk, kv, gv))
return false;
}
return true;