FunC incorrectly optimizes expressions with operators: /, %, <

[jeshecdom]

Based on tact-lang/tact#3019

Code to reproduce

int calc(int x) {
    return (((x / -1) % 2) > -2);
}

() main() {
    throw_if(16, calc(-115792089237316195423570985008687907853269984665640564039457584007913129639936));
}

Output Fift

// automatically generated from `func_test.fc` 
DECLPROC calc
DECLPROC main
calc PROC:<{
  DROP
  TRUE
}>
main PROC:<{
  256 PUSHNEGPOW2
  calc CALLDICT
  16 THROWIF
}>

Actual behavior when executed

calc always returns true.

Expected behavior when executed

Exit code 4, since x / -1 should produce an overflow when x = -115792089237316195423570985008687907853269984665640564039457584007913129639936 (i.e., x = MIN_INT).

Side note: We can produce a related but different expression that also gets mapped into TRUE by replacing the subexpression x / -1 for other expression that also produces overflows. For example, the following expressions also get transformed into TRUE in Fift, but they should produce error code 4 on the provided value for x:

• ((-1 * x) % 2) > -2 for x = MIN_INT.
• ((- x) % 2) > -2 for x = MIN_INT.
• ((x * 2) % 2) > -2 for x = MAX_INT (i.e., x = 115792089237316195423570985008687907853269984665640564039457584007913129639935).
• ((x + 1) % 2) > -2 for x = MAX_INT.

[jeshecdom]

The same happens for operators: ~/, ^/, ^%, ~%. For example, all these expressions are mapped to TRUE:

(((x ~/ -1) ~% 2) > -2)
(((x ^/ -1) ~% 2) > -2)
(((x ~/ -1) ^% 2) > -2)
(((x ^/ -1) ^% 2) > -2)