+ {
+ int power;
+
+ /* First, we simplify the cases of op1 == 1, 0 or -1. */
+ if (mpz_cmp_si (op1->value.integer, 1) == 0)
+ {
+ /* 1**op2 == 1 */
+ mpz_set_si (result->value.integer, 1);
+ }
+ else if (mpz_cmp_si (op1->value.integer, 0) == 0)
+ {
+ /* 0**op2 == 0, if op2 > 0
+ 0**op2 overflow, if op2 < 0 ; in that case, we
+ set the result to 0 and return ARITH_DIV0. */
+ mpz_set_si (result->value.integer, 0);
+ if (mpz_cmp_si (op2->value.integer, 0) < 0)
+ rc = ARITH_DIV0;
+ }
+ else if (mpz_cmp_si (op1->value.integer, -1) == 0)
+ {
+ /* (-1)**op2 == (-1)**(mod(op2,2)) */
+ unsigned int odd = mpz_fdiv_ui (op2->value.integer, 2);
+ if (odd)
+ mpz_set_si (result->value.integer, -1);
+ else
+ mpz_set_si (result->value.integer, 1);
+ }
+ /* Then, we take care of op2 < 0. */
+ else if (mpz_cmp_si (op2->value.integer, 0) < 0)
+ {
+ /* if op2 < 0, op1**op2 == 0 because abs(op1) > 1. */
+ mpz_set_si (result->value.integer, 0);
+ }
+ else if (gfc_extract_int (op2, &power) != NULL)
+ {
+ /* If op2 doesn't fit in an int, the exponentiation will
+ overflow, because op2 > 0 and abs(op1) > 1. */
+ mpz_t max;
+ int i = gfc_validate_kind (BT_INTEGER, result->ts.kind, false);
+
+ if (gfc_option.flag_range_check)
+ rc = ARITH_OVERFLOW;
+
+ /* Still, we want to give the same value as the processor. */
+ mpz_init (max);
+ mpz_add_ui (max, gfc_integer_kinds[i].huge, 1);
+ mpz_mul_ui (max, max, 2);
+ mpz_powm (result->value.integer, op1->value.integer,
+ op2->value.integer, max);
+ mpz_clear (max);
+ }
+ else
+ mpz_pow_ui (result->value.integer, op1->value.integer, power);
+ }