Variable allocation internal error

[sarranz]

I have no clue what's going on here, so I don't know whether this is already covered by a different issue. The if (false) seems to be necessary.

fn f(reg ptr u64[1] a, reg u64 x) -> stack u64[1], reg u64 {
    stack ptr u64[1] s;
    s = a;
    a = s;
    return a, x;
}

export
fn main() {
    reg u64 x;
    x = 0;

    stack u64[1] a;
    a[0] = 0;

    if (false) {
        _, _ = f(a, x);
    }
}

gives

"ble.jazz", line 3 (4-10):
internal compilation error in function f:
  Variable allocation: a (defined at "ble.jazz", line 1 (20-21)) and RAX : variable already set

[vbgl]

Do you hit this issue in an actual program? Here, all of the code is dead: no effect, no return value. Unfortunately, the f function survives too long. Eliminating dead functions after constant propagation might help.

[sarranz]

Yes, in libjade. This is halfway through a merge, so maybe it doesn't make much sense. The export function
jade_kem_kyber_kyber512_amd64_ref_keypair_derand calls __crypto_kem_keypair_derand_jazz, which calls __indcpa_keypair_derand, which calls

fn _poly_getnoise_eta1 ... {
  stack u8[KYBER_ETA1*KYBER_N/4 + (3 - KYBER_ETA1)*64] buf;
  ...
  if (KYBER_ETA1 == 2) {  // <-- This is false
    buf[0:KYBER_ETA2*KYBER_N/4], ms = _shake256_128_33(buf[0:KYBER_ETA2*KYBER_N/4], extseed, ms);
  } else {
    buf = _shake256_192_33(buf, extseed);
  }
  ...
  rp = __poly_cbd_eta1(rp, buf[0:KYBER_ETA1*KYBER_N/4]);
  return rp, ms;
}

and

fn _shake256_128_33(reg ptr u8[128] out ... {
  stack ptr u8[128] s_out;
  ...
  s_out = out;
  ...
  out = s_out;
  for i = 0 to 128 {
    c = state[u8 i];
    out[i] = c;
  }
  return out, ms;
}