mmtk/util/metadata/side_metadata/

helpers.rs

use super::ranges::BitOffset;
use super::SideMetadataSpec;
use crate::util::constants::LOG_BYTES_IN_PAGE;
use crate::util::constants::{BITS_IN_WORD, BYTES_IN_PAGE, LOG_BITS_IN_BYTE};
use crate::util::conversions::rshift_align_up;
use crate::util::heap::layout::vm_layout::VMLayout;
#[cfg(target_pointer_width = "32")]
use crate::util::metadata::side_metadata::address_to_chunked_meta_address;
use crate::util::os::*;
use crate::util::Address;
use crate::MMAPPER;

/// Performs address translation in contiguous metadata spaces (e.g. global and policy-specific in 64-bits, and global in 32-bits)
pub(super) fn address_to_contiguous_meta_address(
    metadata_spec: &SideMetadataSpec,
    data_addr: Address,
) -> Address {
    let log_bits_num = metadata_spec.log_num_of_bits as i32;
    let log_bytes_in_region = metadata_spec.log_bytes_in_region;

    let shift = (LOG_BITS_IN_BYTE as i32) - log_bits_num;

    if shift >= 0 {
        metadata_spec.get_starting_address() + ((data_addr >> log_bytes_in_region) >> shift)
    } else {
        metadata_spec.get_starting_address() + ((data_addr >> log_bytes_in_region) << (-shift))
    }
}

/// Performs reverse address translation from contiguous metadata bits to data addresses.
/// The input address and bit shift should be aligned.
///
/// Arguments:
/// * `metadata_spec`: The side metadata spec. It should be contiguous side metadata.
/// * `metadata_addr`; The metadata address. Returned by [`address_to_contiguous_meta_address`].
/// * `bit`: The bit shift for the metadata. Returned by [`meta_byte_lshift`].
pub(super) fn contiguous_meta_address_to_address(
    metadata_spec: &SideMetadataSpec,
    metadata_addr: Address,
    bit: u8,
) -> Address {
    debug_assert_eq!(
        align_metadata_address(metadata_spec, metadata_addr, bit),
        (metadata_addr, bit)
    );
    let shift = (LOG_BITS_IN_BYTE as i32) - metadata_spec.log_num_of_bits as i32;
    let relative_meta_addr = metadata_addr - metadata_spec.get_starting_address();

    let data_addr_intermediate = if shift >= 0 {
        relative_meta_addr << shift
    } else {
        relative_meta_addr >> (-shift)
    };
    let data_addr_bit_shift = if shift >= 0 {
        metadata_spec.log_bytes_in_region - metadata_spec.log_num_of_bits
    } else {
        metadata_spec.log_bytes_in_region
    };

    let data_addr = (data_addr_intermediate << metadata_spec.log_bytes_in_region)
        + ((bit as usize) << data_addr_bit_shift);

    unsafe { Address::from_usize(data_addr) }
}

/// Align an pair of a metadata address and a metadata bit offset to the start of this metadata value.
/// For example, when the metadata is 4 bits, it should only start at bit 0 or bit 4.
/// When the metadata is 16 bits, it should only start at bit 0, and its metadata address should be aligned to 2 bytes.
/// This is important, as [`contiguous_meta_address_to_address`] can only convert the start address of metadata to
/// the data address.
pub(super) fn align_metadata_address(
    spec: &SideMetadataSpec,
    metadata_addr: Address,
    bit: u8,
) -> (Address, u8) {
    if spec.log_num_of_bits >= LOG_BITS_IN_BYTE as usize {
        (
            metadata_addr.align_down(1 << (spec.log_num_of_bits - LOG_BITS_IN_BYTE as usize)),
            0,
        )
    } else {
        (
            metadata_addr,
            crate::util::conversions::raw_align_down(
                bit as usize,
                (1 << spec.log_num_of_bits) as usize,
            ) as u8,
        )
    }
}

/// Unmaps the specified metadata range, or panics.
#[cfg(test)]
pub(crate) fn ensure_munmap_metadata(start: Address, size: usize) {
    trace!("ensure_munmap_metadata({}, 0x{:x})", start, size);

    assert!(OS::munmap(start, size).is_ok())
}

/// Unmaps a metadata space (`spec`) for the specified data address range (`start` and `size`)
/// Returns the size in bytes that get munmapped.
#[cfg(test)]
pub(crate) fn ensure_munmap_contiguous_metadata_space(
    start: Address,
    size: usize,
    spec: &SideMetadataSpec,
) -> usize {
    // nearest page-aligned starting address
    let metadata_start = address_to_meta_address(spec, start);
    let mmap_start = metadata_start.align_down(BYTES_IN_PAGE);
    // nearest page-aligned ending address
    let metadata_size = data_to_meta_size_round_up(spec, size);
    let mmap_size = (metadata_start + metadata_size).align_up(BYTES_IN_PAGE) - mmap_start;
    if mmap_size > 0 {
        ensure_munmap_metadata(mmap_start, mmap_size);
    }
    mmap_size
}

/// Tries to mmap the metadata space (`spec`) for the specified data address range (`start` and `size`).
/// Setting `no_reserve` to true means the function will only map address range, without reserving swap-space/physical memory.
/// Returns the size in bytes that gets mmapped in the function if success.
pub(super) fn try_mmap_contiguous_metadata_space(
    start: Address,
    size: usize,
    spec: &SideMetadataSpec,
    no_reserve: bool,
    anno: &MmapAnnotation,
) -> MmapResult<usize> {
    debug_assert!(start.is_aligned_to(BYTES_IN_PAGE));
    debug_assert!(size % BYTES_IN_PAGE == 0);

    // nearest page-aligned starting address
    let metadata_start = address_to_meta_address(spec, start);
    let mmap_start = metadata_start.align_down(BYTES_IN_PAGE);
    // nearest page-aligned ending address
    let metadata_size = data_to_meta_size_round_up(spec, size);
    let mmap_size = (metadata_start + metadata_size).align_up(BYTES_IN_PAGE) - mmap_start;
    if mmap_size > 0 {
        if !no_reserve {
            MMAPPER.ensure_mapped(
                mmap_start,
                mmap_size >> LOG_BYTES_IN_PAGE,
                HugePageSupport::No,
                MmapProtection::ReadWrite,
                anno,
            )
        } else {
            MMAPPER.quarantine_address_range(
                mmap_start,
                mmap_size >> LOG_BYTES_IN_PAGE,
                HugePageSupport::No,
                anno,
            )
        }
        .map(|_| mmap_size)
    } else {
        Ok(0)
    }
}

/// Performs the translation of data address (`data_addr`) to metadata address for the specified metadata (`metadata_spec`).
pub(crate) fn address_to_meta_address(
    metadata_spec: &SideMetadataSpec,
    data_addr: Address,
) -> Address {
    #[cfg(target_pointer_width = "32")]
    let res = {
        if metadata_spec.is_global {
            address_to_contiguous_meta_address(metadata_spec, data_addr)
        } else {
            address_to_chunked_meta_address(metadata_spec, data_addr)
        }
    };
    #[cfg(target_pointer_width = "64")]
    let res = { address_to_contiguous_meta_address(metadata_spec, data_addr) };

    trace!(
        "address_to_meta_address({:?}, addr: {}) -> 0x{:x}",
        metadata_spec,
        data_addr,
        res
    );

    res
}

/// Return the base-2 logarithm of the ratio of data bits and metadata bits per region.
///
/// Suppose a memory region has `data_bits` bits of data, and `meta_bits` bits of metadata for
/// `metadata_spec`, and the result of `log_data_meta_ratio(metadata_spec)` is `shift`, then
///
/// -   `data_bits >> shift == meta_bits`
/// -   `meta_bits << shift == data_bits`
pub(super) const fn log_data_meta_ratio(metadata_spec: &SideMetadataSpec) -> usize {
    let log_data_bits_in_region = (LOG_BITS_IN_BYTE as usize) + metadata_spec.log_bytes_in_region;
    let log_meta_bits_in_region = metadata_spec.log_num_of_bits;

    // TODO: In theory, it is possible to construct a side metadata that has more metadata bits than
    // data bits per region.  But such pathological side metadata consumes way too much memory, and
    // should never be used in any useful applications.  It should be forbidden.
    log_data_bits_in_region - log_meta_bits_in_region
}

/// Calculate the amount of metadata needed for the give amount of data memory, round up to nearest
/// integer. `data_size` can be in any unit, e.g. bits, bytes, pages, blocks, chunks, etc., and the
/// result has the same unit.
pub(super) const fn data_to_meta_size_round_up(
    metadata_spec: &SideMetadataSpec,
    data_size: usize,
) -> usize {
    rshift_align_up(data_size, log_data_meta_ratio(metadata_spec))
}

/// Calculate the amount of data governed by the give amount of metadata.  `meta_size` can be in any
/// unit, e.g. bits, bytes, pages, blocks, chunks, etc., and the result has the same unit.
pub(super) const fn meta_to_data_size(metadata_spec: &SideMetadataSpec, meta_size: usize) -> usize {
    meta_size << log_data_meta_ratio(metadata_spec)
}

#[allow(dead_code)]
pub(super) const fn metadata_address_range_size(metadata_spec: &SideMetadataSpec) -> usize {
    1usize << (VMLayout::LOG_ARCH_ADDRESS_SPACE - log_data_meta_ratio(metadata_spec))
}

pub(super) fn meta_byte_lshift(metadata_spec: &SideMetadataSpec, data_addr: Address) -> u8 {
    let bits_num_log = metadata_spec.log_num_of_bits as i32;
    if bits_num_log >= 3 {
        return 0;
    }
    let rem_shift = BITS_IN_WORD as i32 - ((LOG_BITS_IN_BYTE as i32) - bits_num_log);
    ((((data_addr >> metadata_spec.log_bytes_in_region) << rem_shift) >> rem_shift) << bits_num_log)
        as u8
}

pub(super) fn meta_byte_mask(metadata_spec: &SideMetadataSpec) -> u8 {
    let bits_num_log = metadata_spec.log_num_of_bits;
    ((1usize << (1usize << bits_num_log)) - 1) as u8
}

/// The result type for find meta bits functions.
pub enum FindMetaBitResult {
    Found { addr: Address, bit: u8 },
    NotFound,
    UnmappedMetadata,
}

// Check and find the last bit that is set. We try load words where possible, and fall back to load bytes.
pub fn find_last_non_zero_bit_in_metadata_bytes(
    meta_start: Address,
    meta_end: Address,
) -> FindMetaBitResult {
    use crate::util::constants::BYTES_IN_ADDRESS;

    let mmap_granularity = MMAPPER.granularity();

    let mut cur = meta_end;
    // We need to check if metadata address is mapped or not.  But we make use of the granularity of
    // the `Mmapper` to reduce the number of checks.  This records the start of a grain that is
    // tested to be mapped.
    let mut mapped_grain = Address::MAX;
    while cur > meta_start {
        // If we can check the whole word, set step to word size. Otherwise, the step is 1 (byte) and we check byte.
        let step = if cur.is_aligned_to(BYTES_IN_ADDRESS) && cur - BYTES_IN_ADDRESS >= meta_start {
            BYTES_IN_ADDRESS
        } else {
            1
        };
        // Move to the address so we can load from it
        cur -= step;
        // The value we check has to be in the range.
        debug_assert!(
            cur >= meta_start && cur < meta_end,
            "Check metadata value at meta address {}, which is not in the range of [{}, {})",
            cur,
            meta_start,
            meta_end
        );

        // If we are looking at an address that is not in a mapped chunk, we need to check if the chunk if mapped.
        if cur < mapped_grain {
            if cur.is_mapped() {
                // This is mapped. No need to check for this chunk.
                mapped_grain = cur.align_down(mmap_granularity);
            } else {
                return FindMetaBitResult::UnmappedMetadata;
            }
        }

        if step == BYTES_IN_ADDRESS {
            // Load and check a usize word
            let value = unsafe { cur.load::<usize>() };
            if value != 0 {
                let bit = find_last_non_zero_bit::<usize>(value, 0, usize::BITS as u8).unwrap();
                let byte_offset = bit >> LOG_BITS_IN_BYTE;
                let bit_offset = bit - ((byte_offset) << LOG_BITS_IN_BYTE);
                return FindMetaBitResult::Found {
                    addr: cur + byte_offset as usize,
                    bit: bit_offset,
                };
            }
        } else {
            // Load and check a byte
            let value = unsafe { cur.load::<u8>() };
            if let Some(bit) = find_last_non_zero_bit::<u8>(value, 0, 8) {
                return FindMetaBitResult::Found { addr: cur, bit };
            }
        }
    }
    FindMetaBitResult::NotFound
}

// Check and find the last non-zero bit in the same byte.
pub fn find_last_non_zero_bit_in_metadata_bits(
    addr: Address,
    start_bit: u8,
    end_bit: u8,
) -> FindMetaBitResult {
    if !addr.is_mapped() {
        return FindMetaBitResult::UnmappedMetadata;
    }
    let byte = unsafe { addr.load::<u8>() };
    if let Some(bit) = find_last_non_zero_bit::<u8>(byte, start_bit, end_bit) {
        return FindMetaBitResult::Found { addr, bit };
    }
    FindMetaBitResult::NotFound
}

use num_traits::{CheckedShl, PrimInt};
fn find_last_non_zero_bit<T>(value: T, start: u8, end: u8) -> Option<u8>
where
    T: PrimInt + CheckedShl,
{
    let mask = match T::one().checked_shl((end - start) as u32) {
        Some(shl) => (shl - T::one()) << (start as u32),
        None => T::max_value() << (start as u32),
    };
    let masked = value & mask;
    if masked.is_zero() {
        None
    } else {
        let leading_zeroes = masked.leading_zeros();
        let total_bits = std::mem::size_of::<T>() * u8::BITS as usize;
        Some(total_bits as u8 - leading_zeroes as u8 - 1)
    }
}

pub fn scan_non_zero_bits_in_metadata_bytes(
    meta_start: Address,
    meta_end: Address,
    visit_bit: &mut impl FnMut(Address, BitOffset),
) {
    use crate::util::constants::BYTES_IN_ADDRESS;

    let mut cursor = meta_start;
    while cursor < meta_end && !cursor.is_aligned_to(BYTES_IN_ADDRESS) {
        let byte = unsafe { cursor.load::<u8>() };
        scan_non_zero_bits_in_metadata_word(cursor, byte as usize, visit_bit);
        cursor += 1usize;
    }

    while cursor + BYTES_IN_ADDRESS < meta_end {
        let word = unsafe { cursor.load::<usize>() };
        scan_non_zero_bits_in_metadata_word(cursor, word, visit_bit);
        cursor += BYTES_IN_ADDRESS;
    }

    while cursor < meta_end {
        let byte = unsafe { cursor.load::<u8>() };
        scan_non_zero_bits_in_metadata_word(cursor, byte as usize, visit_bit);
        cursor += 1usize;
    }
}

fn scan_non_zero_bits_in_metadata_word(
    meta_addr: Address,
    mut word: usize,
    visit_bit: &mut impl FnMut(Address, BitOffset),
) {
    while word != 0 {
        let bit = word.trailing_zeros();
        visit_bit(meta_addr, bit as u8);
        word = word & (word - 1);
    }
}

pub fn scan_non_zero_bits_in_metadata_bits(
    meta_addr: Address,
    bit_start: BitOffset,
    bit_end: BitOffset,
    visit_bit: &mut impl FnMut(Address, BitOffset),
) {
    let byte = unsafe { meta_addr.load::<u8>() };
    for bit in bit_start..bit_end {
        if byte & (1 << bit) != 0 {
            visit_bit(meta_addr, bit);
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::util::metadata::side_metadata::*;

    fn should_skip_spec_on_this_target(spec: &SideMetadataSpec) -> bool {
        use layout::LOG_GLOBAL_SIDE_METADATA_WORST_CASE_RATIO;
        log_data_meta_ratio(spec) < LOG_GLOBAL_SIDE_METADATA_WORST_CASE_RATIO
    }

    fn test_round_trip_conversion(spec: &SideMetadataSpec, test_data: &[Address]) {
        if should_skip_spec_on_this_target(spec) {
            eprintln!(
                "Skipping {} on this target: spec ratio is outside global side metadata worst-case bound",
                spec.name
            );
            return;
        }

        core_test_initialize_side_metadata();

        for ref_addr in test_data {
            let addr = *ref_addr;

            // This is an aligned address. When we do roundtrip conversion, we will get back the original address.
            {
                assert!(addr.is_aligned_to(1 << spec.log_bytes_in_region));
                let meta_addr = address_to_contiguous_meta_address(spec, addr);
                let shift = meta_byte_lshift(spec, addr);
                assert_eq!(
                    contiguous_meta_address_to_address(spec, meta_addr, shift),
                    addr
                );
            }

            // This is an unaligned address. When we do roundtrip conversion, we will get the aligned address.
            {
                let next_addr = addr + 1usize;
                let meta_addr = address_to_contiguous_meta_address(spec, next_addr);
                let shift = meta_byte_lshift(spec, next_addr);
                assert_eq!(
                    contiguous_meta_address_to_address(spec, meta_addr, shift),
                    addr
                ); // we get back addr (which is the aligned address)
            }
        }
    }

    const TEST_ADDRESS_8B_REGION: [Address; 8] = [
        unsafe { Address::from_usize(0x8000_0000) },
        unsafe { Address::from_usize(0x8000_0008) },
        unsafe { Address::from_usize(0x8000_0010) },
        unsafe { Address::from_usize(0x8000_0018) },
        unsafe { Address::from_usize(0x8000_0020) },
        unsafe { Address::from_usize(0x8001_0000) },
        unsafe { Address::from_usize(0x8001_0008) },
        unsafe { Address::from_usize(0xd000_0000) },
    ];

    #[test]
    fn test_contiguous_metadata_conversion_0_3() {
        let spec = SideMetadataSpec {
            name: "ContiguousMetadataTestSpec",
            is_global: true,
            offset: 0,
            log_num_of_bits: 0,
            log_bytes_in_region: 3,
        };

        test_round_trip_conversion(&spec, &TEST_ADDRESS_8B_REGION);
    }

    #[test]
    fn test_contiguous_metadata_conversion_1_3() {
        let spec = SideMetadataSpec {
            name: "ContiguousMetadataTestSpec",
            is_global: true,
            offset: 0,
            log_num_of_bits: 1,
            log_bytes_in_region: 3,
        };

        test_round_trip_conversion(&spec, &TEST_ADDRESS_8B_REGION);
    }

    #[test]
    fn test_contiguous_metadata_conversion_4_3() {
        let spec = SideMetadataSpec {
            name: "ContiguousMetadataTestSpec",
            is_global: true,
            offset: 0,
            log_num_of_bits: 4,
            log_bytes_in_region: 3,
        };

        test_round_trip_conversion(&spec, &TEST_ADDRESS_8B_REGION);
    }

    #[test]
    fn test_contiguous_metadata_conversion_5_3() {
        let spec = SideMetadataSpec {
            name: "ContiguousMetadataTestSpec",
            is_global: true,
            offset: 0,
            log_num_of_bits: 5,
            log_bytes_in_region: 3,
        };

        test_round_trip_conversion(&spec, &TEST_ADDRESS_8B_REGION);
    }

    const TEST_ADDRESS_4KB_REGION: [Address; 8] = [
        unsafe { Address::from_usize(0x8000_0000) },
        unsafe { Address::from_usize(0x8000_1000) },
        unsafe { Address::from_usize(0x8000_2000) },
        unsafe { Address::from_usize(0x8000_3000) },
        unsafe { Address::from_usize(0x8000_4000) },
        unsafe { Address::from_usize(0x8001_0000) },
        unsafe { Address::from_usize(0x8001_1000) },
        unsafe { Address::from_usize(0xd000_0000) },
    ];

    #[test]
    fn test_contiguous_metadata_conversion_0_12() {
        let spec = SideMetadataSpec {
            name: "ContiguousMetadataTestSpec",
            is_global: true,
            offset: 0,
            log_num_of_bits: 0,
            log_bytes_in_region: 12, // 4K
        };

        test_round_trip_conversion(&spec, &TEST_ADDRESS_4KB_REGION);
    }

    #[test]
    fn test_find_last_non_zero_bit_in_u8() {
        use super::find_last_non_zero_bit;
        let bit = find_last_non_zero_bit::<u8>(0b100101, 0, 1);
        assert_eq!(bit, Some(0));

        let bit = find_last_non_zero_bit::<u8>(0b100101, 0, 3);
        assert_eq!(bit, Some(2));

        let bit = find_last_non_zero_bit::<u8>(0b100101, 0, 8);
        assert_eq!(bit, Some(5));

        let bit = find_last_non_zero_bit::<u8>(0b0, 0, 1);
        assert_eq!(bit, None);
    }

    #[test]
    fn test_align_metadata_address() {
        let create_spec = |log_num_of_bits: usize| SideMetadataSpec {
            name: "AlignMetadataBitTestSpec",
            is_global: true,
            offset: 0,
            log_num_of_bits,
            log_bytes_in_region: 3,
        };

        const ADDR_1000: Address = unsafe { Address::from_usize(0x1000) };
        const ADDR_1001: Address = unsafe { Address::from_usize(0x1001) };
        const ADDR_1002: Address = unsafe { Address::from_usize(0x1002) };
        const ADDR_1003: Address = unsafe { Address::from_usize(0x1003) };
        const ADDR_1004: Address = unsafe { Address::from_usize(0x1004) };
        const ADDR_1005: Address = unsafe { Address::from_usize(0x1005) };
        const ADDR_1006: Address = unsafe { Address::from_usize(0x1006) };
        const ADDR_1007: Address = unsafe { Address::from_usize(0x1007) };
        const ADDR_1008: Address = unsafe { Address::from_usize(0x1008) };
        const ADDR_1009: Address = unsafe { Address::from_usize(0x1009) };

        let metadata_2bits = create_spec(1);
        assert_eq!(
            align_metadata_address(&metadata_2bits, ADDR_1000, 0),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_2bits, ADDR_1000, 1),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_2bits, ADDR_1000, 2),
            (ADDR_1000, 2)
        );
        assert_eq!(
            align_metadata_address(&metadata_2bits, ADDR_1000, 3),
            (ADDR_1000, 2)
        );
        assert_eq!(
            align_metadata_address(&metadata_2bits, ADDR_1000, 4),
            (ADDR_1000, 4)
        );
        assert_eq!(
            align_metadata_address(&metadata_2bits, ADDR_1000, 5),
            (ADDR_1000, 4)
        );
        assert_eq!(
            align_metadata_address(&metadata_2bits, ADDR_1000, 6),
            (ADDR_1000, 6)
        );
        assert_eq!(
            align_metadata_address(&metadata_2bits, ADDR_1000, 7),
            (ADDR_1000, 6)
        );

        let metadata_4bits = create_spec(2);
        assert_eq!(
            align_metadata_address(&metadata_4bits, ADDR_1000, 0),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_4bits, ADDR_1000, 1),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_4bits, ADDR_1000, 2),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_4bits, ADDR_1000, 3),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_4bits, ADDR_1000, 4),
            (ADDR_1000, 4)
        );
        assert_eq!(
            align_metadata_address(&metadata_4bits, ADDR_1000, 5),
            (ADDR_1000, 4)
        );
        assert_eq!(
            align_metadata_address(&metadata_4bits, ADDR_1000, 6),
            (ADDR_1000, 4)
        );
        assert_eq!(
            align_metadata_address(&metadata_4bits, ADDR_1000, 7),
            (ADDR_1000, 4)
        );

        let metadata_8bits = create_spec(3);
        assert_eq!(
            align_metadata_address(&metadata_8bits, ADDR_1000, 0),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_8bits, ADDR_1000, 1),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_8bits, ADDR_1000, 2),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_8bits, ADDR_1000, 3),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_8bits, ADDR_1000, 4),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_8bits, ADDR_1000, 5),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_8bits, ADDR_1000, 6),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_8bits, ADDR_1000, 7),
            (ADDR_1000, 0)
        );

        let metadata_16bits = create_spec(4);
        assert_eq!(
            align_metadata_address(&metadata_16bits, ADDR_1000, 0),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_16bits, ADDR_1000, 1),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_16bits, ADDR_1000, 2),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_16bits, ADDR_1000, 3),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_16bits, ADDR_1000, 4),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_16bits, ADDR_1000, 5),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_16bits, ADDR_1000, 6),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_16bits, ADDR_1000, 7),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_16bits, ADDR_1001, 0),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_16bits, ADDR_1001, 1),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_16bits, ADDR_1001, 2),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_16bits, ADDR_1001, 3),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_16bits, ADDR_1001, 4),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_16bits, ADDR_1001, 5),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_16bits, ADDR_1001, 6),
            (ADDR_1000, 0)
        );
        assert_eq!(
            align_metadata_address(&metadata_16bits, ADDR_1001, 7),
            (ADDR_1000, 0)
        );
    }
}