Function libdivide_s32_recover

numpy/core/include/numpy/libdivide/libdivide.h:1008–1042

}

int32_t libdivide_s32_recover(const struct libdivide_s32_t *denom) {
    uint8_t more = denom->more;
    uint8_t shift = more & LIBDIVIDE_32_SHIFT_MASK;
    if (!denom->magic) {
        uint32_t absD = 1U << shift;
        if (more & LIBDIVIDE_NEGATIVE_DIVISOR) {
            absD = -absD;
        }
        return (int32_t)absD;
    } else {
        // Unsigned math is much easier
        // We negate the magic number only in the branchfull case, and we don't
        // know which case we're in. However we have enough information to
        // determine the correct sign of the magic number. The divisor was
        // negative if LIBDIVIDE_NEGATIVE_DIVISOR is set. If ADD_MARKER is set,
        // the magic number's sign is opposite that of the divisor.
        // We want to compute the positive magic number.
        int negative_divisor = (more & LIBDIVIDE_NEGATIVE_DIVISOR);
        int magic_was_negated = (more & LIBDIVIDE_ADD_MARKER)
            ? denom->magic > 0 : denom->magic < 0;

        // Handle the power of 2 case (including branchfree)
        if (denom->magic == 0) {
            int32_t result = 1U << shift;
            return negative_divisor ? -result : result;
        }

        uint32_t d = (uint32_t)(magic_was_negated ? -denom->magic : denom->magic);
        uint64_t n = 1ULL << (32 + shift); // this shift cannot exceed 30
        uint32_t q = (uint32_t)(n / d);
        int32_t result = (int32_t)q;
        result += 1;
        return negative_divisor ? -result : result;
    }
}

int32_t libdivide_s32_branchfree_recover(const struct libdivide_s32_branchfree_t *denom) {
    return libdivide_s32_recover((const struct libdivide_s32_t *)denom);