memx 0.2.0

memory functions like libc memcmp(), memchr(), memmem(), memcpy(), memset()
Documentation 
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use crate::mem as basic;
use crate::utils::*;
use core::cmp::Ordering;

#[cfg(target_arch = "x86")]
use core::arch::x86 as mmx;
#[cfg(target_arch = "x86_64")]
use core::arch::x86_64 as mmx;

use mmx::__m128i;
use mmx::_mm_cmpeq_epi8;
use mmx::_mm_load_si128;
use mmx::_mm_loadu_si128;
use mmx::_mm_movemask_epi8;
/*
use mmx::__m256i;
use mmx::_mm256_cmpeq_epi8;
use mmx::_mm256_load_si256;
use mmx::_mm256_loadu_si256;
use mmx::_mm256_movemask_epi8;
*/
#[cfg(any(target_arch = "x86_64", target_arch = "x86"))]
use super::cpuid;

use core::sync::atomic::AtomicPtr;
use core::sync::atomic::Ordering as AtomicOrdering;
type _FuncType = fn(&[u8], &[u8]) -> Ordering;

const _FUNC: _FuncType = _fnptr_setup_func;
static _FUNC_PTR_ATOM: AtomicPtr<_FuncType> = AtomicPtr::new(_FUNC as *mut _FuncType);

#[inline(never)]
fn _fnptr_setup_func(a: &[u8], b: &[u8]) -> Ordering {
    #[cfg(target_arch = "x86_64")]
    let func = if cpuid::has_avx2() {
        _memcmp_avx2
    } else {
        _memcmp_sse2
    };
    #[cfg(target_arch = "x86")]
    let func = if cpuid::has_avx2() {
        _memcmp_avx2
    } else if cpuid::has_sse2() {
        _memcmp_sse2
    } else {
        _memcmp_basic
    };
    //
    _FUNC_PTR_ATOM.store(func as *mut _FuncType, AtomicOrdering::Relaxed);
    unsafe { func(a, b) }
}

#[inline(always)]
pub(crate) fn _memcmp_impl(a: &[u8], b: &[u8]) -> Ordering {
    let func_u = _FUNC_PTR_ATOM.load(AtomicOrdering::Relaxed);
    #[allow(clippy::crosspointer_transmute)]
    let func: _FuncType = unsafe { core::mem::transmute(func_u) };
    func(a, b)
}

unsafe fn _memcmp_basic(a: &[u8], b: &[u8]) -> Ordering {
    basic::_memcmp_impl(a, b)
}

#[cfg(any(target_arch = "x86_64", target_arch = "x86"))]
#[target_feature(enable = "sse2")]
#[allow(clippy::missing_safety_doc)]
pub unsafe fn _memcmp_sse2(a: &[u8], b: &[u8]) -> Ordering {
    _memcmp_sse2_impl(a, b)
}

#[cfg(any(target_arch = "x86_64", target_arch = "x86"))]
#[target_feature(enable = "avx2")]
#[allow(clippy::missing_safety_doc)]
pub unsafe fn _memcmp_avx2(a: &[u8], b: &[u8]) -> Ordering {
    _memcmp_sse2_impl(a, b)
    //_memcmp_avx2_impl(a, b)
}

#[inline(always)]
fn _memcmp_sse2_impl(a: &[u8], b: &[u8]) -> Ordering {
    let a_len = a.len();
    let b_len = b.len();
    let min_len = a_len.min(b_len);
    if min_len < 16 {
        basic::_start_cmp_64(a, b)
    } else {
        let mut a_ptr = a.as_ptr();
        let mut b_ptr = b.as_ptr();
        let end_ptr = unsafe { a_ptr.add(min_len) };
        a_ptr.prefetch_read_data();
        b_ptr.prefetch_read_data();
        // to a aligned pointer
        {
            if !a_ptr.is_aligned_u128() {
                #[cfg(not(feature = "test_alignment_check"))]
                {
                    let r = unsafe { _cmp_b16_uu_x1(a_ptr, b_ptr) };
                    if !r.is_eq() {
                        return r;
                    }
                    let remaining_align = 0x10_usize - ((a_ptr as usize) & 0x0F_usize);
                    a_ptr = unsafe { a_ptr.add(remaining_align) };
                    b_ptr = unsafe { b_ptr.add(remaining_align) };
                }
                #[cfg(feature = "test_alignment_check")]
                {
                    let r = basic::_cmp_to_aligned_u128(a_ptr, b_ptr);
                    if let Some((ap, bp)) = r.0 {
                        a_ptr = ap;
                        b_ptr = bp;
                    } else if let Some(v) = r.1 {
                        return v;
                    }
                }
            }
        }
        // the loop
        if b_ptr.is_aligned_u128() {
            {
                let unroll = 4;
                let loop_size = 16;
                while a_ptr.is_not_over(end_ptr, loop_size * unroll) {
                    a_ptr.prefetch_read_data();
                    b_ptr.prefetch_read_data();
                    let r = _cmp_b16_aa_x4(a_ptr, b_ptr);
                    if !r.is_eq() {
                        return r;
                    }
                    a_ptr = unsafe { a_ptr.add(loop_size * unroll) };
                    b_ptr = unsafe { b_ptr.add(loop_size * unroll) };
                }
            }
            {
                let unroll = 1;
                let loop_size = 16;
                while a_ptr.is_not_over(end_ptr, loop_size * unroll) {
                    let r = unsafe { _cmp_b16_aa_x1(a_ptr, b_ptr) };
                    if !r.is_eq() {
                        return r;
                    }
                    a_ptr = unsafe { a_ptr.add(loop_size * unroll) };
                    b_ptr = unsafe { b_ptr.add(loop_size * unroll) };
                }
            }
        } else {
            {
                let unroll = 4;
                let loop_size = 16;
                while a_ptr.is_not_over(end_ptr, loop_size * unroll) {
                    a_ptr.prefetch_read_data();
                    b_ptr.prefetch_read_data();
                    let r = _cmp_b16_au_x4(a_ptr, b_ptr);
                    if !r.is_eq() {
                        return r;
                    }
                    a_ptr = unsafe { a_ptr.add(loop_size * unroll) };
                    b_ptr = unsafe { b_ptr.add(loop_size * unroll) };
                }
            }
            {
                let unroll = 1;
                let loop_size = 16;
                while a_ptr.is_not_over(end_ptr, loop_size * unroll) {
                    let r = unsafe { _cmp_b16_au_x1(a_ptr, b_ptr) };
                    if !r.is_eq() {
                        return r;
                    }
                    a_ptr = unsafe { a_ptr.add(loop_size * unroll) };
                    b_ptr = unsafe { b_ptr.add(loop_size * unroll) };
                }
            }
        }
        // the remaining data is the max: 15 bytes.
        basic::_memcmp_remaining_15_bytes_impl(a_ptr, b_ptr, a_len, b_len, end_ptr)
    }
}

#[inline(always)]
unsafe fn _cmp_b16_uu_x1(a_ptr: *const u8, b_ptr: *const u8) -> Ordering {
    let mask_0 = unsafe {
        let mm_0_a = _mm_loadu_si128(a_ptr as *const __m128i);
        let mm_0_b = _mm_loadu_si128(b_ptr as *const __m128i);
        let mm_0_eq = _mm_cmpeq_epi8(mm_0_a, mm_0_b);
        _mm_movemask_epi8(mm_0_eq) as u64
    };
    //
    if mask_0 == 0xffff {
        Ordering::Equal
    } else {
        let bits = !mask_0;
        let pos = bits.trailing_zeros() as usize;
        let aa_ptr = unsafe { a_ptr.add(pos) };
        let bb_ptr = unsafe { b_ptr.add(pos) };
        let aac = unsafe { *aa_ptr };
        let bbc = unsafe { *bb_ptr };
        aac.cmp(&bbc)
    }
}

#[inline(always)]
unsafe fn _cmp_b16_au_x1(a_ptr: *const u8, b_ptr: *const u8) -> Ordering {
    let mask_0 = unsafe {
        let mm_0_a = _mm_load_si128(a_ptr as *const __m128i);
        let mm_0_b = _mm_loadu_si128(b_ptr as *const __m128i);
        let mm_0_eq = _mm_cmpeq_epi8(mm_0_a, mm_0_b);
        _mm_movemask_epi8(mm_0_eq) as u64
    };
    //
    if mask_0 == 0xffff {
        Ordering::Equal
    } else {
        let bits = !mask_0;
        let pos = bits.trailing_zeros() as usize;
        let aa_ptr = unsafe { a_ptr.add(pos) };
        let bb_ptr = unsafe { b_ptr.add(pos) };
        let aac = unsafe { *aa_ptr };
        let bbc = unsafe { *bb_ptr };
        aac.cmp(&bbc)
    }
}

#[inline(always)]
fn _cmp_b16_au_x2(a_ptr: *const u8, b_ptr: *const u8) -> Ordering {
    let r = unsafe { _cmp_b16_au_x1(a_ptr, b_ptr) };
    if !r.is_eq() {
        return r;
    }
    unsafe { _cmp_b16_au_x1(a_ptr.add(16), b_ptr.add(16)) }
}

#[inline(always)]
fn _cmp_b16_au_x4(a_ptr: *const u8, b_ptr: *const u8) -> Ordering {
    let r = _cmp_b16_au_x2(a_ptr, b_ptr);
    if !r.is_eq() {
        return r;
    }
    _cmp_b16_au_x2(unsafe { a_ptr.add(16 * 2) }, unsafe { b_ptr.add(16 * 2) })
}

#[inline(always)]
fn _cmp_b16_au_x8(a_ptr: *const u8, b_ptr: *const u8) -> Ordering {
    let r = _cmp_b16_au_x4(a_ptr, b_ptr);
    if !r.is_eq() {
        return r;
    }
    _cmp_b16_au_x4(unsafe { a_ptr.add(16 * 4) }, unsafe { b_ptr.add(16 * 4) })
}

#[inline(always)]
fn _cmp_b16_au_x16(a_ptr: *const u8, b_ptr: *const u8) -> Ordering {
    let r = _cmp_b16_au_x8(a_ptr, b_ptr);
    if !r.is_eq() {
        return r;
    }
    _cmp_b16_au_x8(unsafe { a_ptr.add(16 * 8) }, unsafe { b_ptr.add(16 * 8) })
}

#[inline(always)]
unsafe fn _cmp_b16_aa_x1(a_ptr: *const u8, b_ptr: *const u8) -> Ordering {
    let mask_0 = unsafe {
        let mm_0_a = _mm_load_si128(a_ptr as *const __m128i);
        let mm_0_b = _mm_load_si128(b_ptr as *const __m128i);
        let mm_0_eq = _mm_cmpeq_epi8(mm_0_a, mm_0_b);
        _mm_movemask_epi8(mm_0_eq) as u64
    };
    //
    if mask_0 == 0xffff {
        Ordering::Equal
    } else {
        let bits = !mask_0;
        let pos = bits.trailing_zeros() as usize;
        let aa_ptr = unsafe { a_ptr.add(pos) };
        let bb_ptr = unsafe { b_ptr.add(pos) };
        let aac = unsafe { *aa_ptr };
        let bbc = unsafe { *bb_ptr };
        aac.cmp(&bbc)
    }
}

#[inline(always)]
fn _cmp_b16_aa_x2(a_ptr: *const u8, b_ptr: *const u8) -> Ordering {
    let r = unsafe { _cmp_b16_aa_x1(a_ptr, b_ptr) };
    if !r.is_eq() {
        return r;
    }
    unsafe { _cmp_b16_aa_x1(a_ptr.add(16), b_ptr.add(16)) }
}

#[inline(always)]
fn _cmp_b16_aa_x4(a_ptr: *const u8, b_ptr: *const u8) -> Ordering {
    let r = _cmp_b16_aa_x2(a_ptr, b_ptr);
    if !r.is_eq() {
        return r;
    }
    _cmp_b16_aa_x2(unsafe { a_ptr.add(16 * 2) }, unsafe { b_ptr.add(16 * 2) })
}

#[inline(always)]
fn _cmp_b16_aa_x8(a_ptr: *const u8, b_ptr: *const u8) -> Ordering {
    let r = _cmp_b16_aa_x4(a_ptr, b_ptr);
    if !r.is_eq() {
        return r;
    }
    _cmp_b16_aa_x4(unsafe { a_ptr.add(16 * 4) }, unsafe { b_ptr.add(16 * 4) })
}

#[inline(always)]
fn _cmp_b16_aa_x16(a_ptr: *const u8, b_ptr: *const u8) -> Ordering {
    let r = _cmp_b16_aa_x8(a_ptr, b_ptr);
    if !r.is_eq() {
        return r;
    }
    _cmp_b16_aa_x8(unsafe { a_ptr.add(16 * 8) }, unsafe { b_ptr.add(16 * 8) })
}

#[cfg(test)]
mod disasm {
    use super::*;
    use core::cmp::Ordering;
    //
    #[test]
    fn do_procs() {
        let a = b"abcdefg".to_vec();
        let b = b"abcdefg".to_vec();
        let a = a.as_slice();
        let b = b.as_slice();
        assert_eq!(do_proc_basic(a, b), Ordering::Equal);
        assert_eq!(do_proc_sse2(a, b), Ordering::Equal);
        assert_eq!(do_proc_avx2(a, b), Ordering::Equal);
    }
    fn do_proc_basic(a: &[u8], b: &[u8]) -> Ordering {
        unsafe { _memcmp_basic(a, b) }
    }
    fn do_proc_sse2(a: &[u8], b: &[u8]) -> Ordering {
        unsafe { _memcmp_sse2(a, b) }
    }
    fn do_proc_avx2(a: &[u8], b: &[u8]) -> Ordering {
        unsafe { _memcmp_avx2(a, b) }
    }
}