/* hardware integer division program, by Manna returns q==A//B */ void abort() { }; extern void abort(); extern int __VERIFIER_nondet_int(); /*@ requires (1); ensures ((cond != 0)); @*/ void assume_abort_if_not(int cond) { if(!cond) {abort();} } /*@ requires ((cond != 0)) && (cond != 0); ensures ((cond != 0)) && (1); @*/ void __VERIFIER_assert(int cond) { if (!(cond)) { ERROR: {/*@ assert(0); */;} } return; } int main() { int A, B; int r, d, p, q; A = __VERIFIER_nondet_int(); assume_abort_if_not(A>=0 && A<=1); B = 1; r = A; d = B; p = 1; q = 0; /*@ loop invariant (((((((((0 <= A) && (A == r)) && (p == 2)) && (A <= 1)) && (d == 2)) && (q == 0)) && (B == 1)) || (((((((0 <= A) && (A == r)) && (A <= 1)) && (d == 1)) && (q == 0)) && (B == 1)) && (p == 1)))); @*/ while (1) { __VERIFIER_assert(q == 0); __VERIFIER_assert(r == A); __VERIFIER_assert(d == B * p); if (!(r >= d)) break; d = 2 * d; p = 2 * p; } /*@ loop invariant ((((((((A == r) && (p == 2)) && (d == 2)) && (q == 0)) && (B == 1)) || (((((A == ((long long) r + 1)) && (d == 1)) && (B == 1)) && (q == 1)) && (p == 1))) || (((((A == r) && (d == 1)) && (q == 0)) && (B == 1)) && (p == 1)))); @*/ while (1) { __VERIFIER_assert(A == q*B + r); __VERIFIER_assert(d == B*p); if (!(p != 1)) break; d = d / 2; p = p / 2; if (r >= d) { r = r - d; q = q + p; } } __VERIFIER_assert(A == d*q + r); __VERIFIER_assert(B == d); return 0; }