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use core::{arch::x86_64::*, cmp, mem::size_of};
use super::sse2;
const VECTOR_SIZE: usize = size_of::<__m256i>();
const VECTOR_ALIGN: usize = VECTOR_SIZE - 1;
// The number of bytes to loop at in one iteration of memchr/memrchr.
const LOOP_SIZE: usize = 4 * VECTOR_SIZE;
// The number of bytes to loop at in one iteration of memchr2/memrchr2 and
// memchr3/memrchr3. There was no observable difference between 128 and 64
// bytes in benchmarks. memchr3 in particular only gets a very slight speed up
// from the loop unrolling.
const LOOP_SIZE2: usize = 2 * VECTOR_SIZE;
#[target_feature(enable = "avx2")]
pub unsafe fn memchr(n1: u8, haystack: &[u8]) -> Option<usize> {
// For a high level explanation for how this algorithm works, see the
// sse2 implementation. The avx implementation here is the same, but with
// 256-bit vectors instead of 128-bit vectors.
// This routine is called whenever a match is detected. It is specifically
// marked as unlineable because it improves the codegen of the unrolled
// loop below. Inlining this seems to cause codegen with some extra adds
// and a load that aren't necessary. This seems to result in about a 10%
// improvement for the memchr1/crate/huge/never benchmark.
//
// Interestingly, I couldn't observe a similar improvement for memrchr.
#[cold]
#[inline(never)]
#[target_feature(enable = "avx2")]
unsafe fn matched(
start_ptr: *const u8,
ptr: *const u8,
eqa: __m256i,
eqb: __m256i,
eqc: __m256i,
eqd: __m256i,
) -> usize {
let mut at = sub(ptr, start_ptr);
let mask = _mm256_movemask_epi8(eqa);
if mask != 0 {
return at + forward_pos(mask);
}
at += VECTOR_SIZE;
let mask = _mm256_movemask_epi8(eqb);
if mask != 0 {
return at + forward_pos(mask);
}
at += VECTOR_SIZE;
let mask = _mm256_movemask_epi8(eqc);
if mask != 0 {
return at + forward_pos(mask);
}
at += VECTOR_SIZE;
let mask = _mm256_movemask_epi8(eqd);
debug_assert!(mask != 0);
at + forward_pos(mask)
}
let start_ptr = haystack.as_ptr();
let end_ptr = start_ptr.add(haystack.len());
let mut ptr = start_ptr;
if haystack.len() < VECTOR_SIZE {
// For small haystacks, defer to the SSE2 implementation. Codegen
// suggests this completely avoids touching the AVX vectors.
return sse2::memchr(n1, haystack);
}
let vn1 = _mm256_set1_epi8(n1 as i8);
let loop_size = cmp::min(LOOP_SIZE, haystack.len());
if let Some(i) = forward_search1(start_ptr, end_ptr, ptr, vn1) {
return Some(i);
}
ptr = ptr.add(VECTOR_SIZE - (start_ptr as usize & VECTOR_ALIGN));
debug_assert!(ptr > start_ptr && end_ptr.sub(VECTOR_SIZE) >= start_ptr);
while loop_size == LOOP_SIZE && ptr <= end_ptr.sub(loop_size) {
debug_assert_eq!(0, (ptr as usize) % VECTOR_SIZE);
let a = _mm256_load_si256(ptr as *const __m256i);
let b = _mm256_load_si256(ptr.add(VECTOR_SIZE) as *const __m256i);
let c = _mm256_load_si256(ptr.add(2 * VECTOR_SIZE) as *const __m256i);
let d = _mm256_load_si256(ptr.add(3 * VECTOR_SIZE) as *const __m256i);
let eqa = _mm256_cmpeq_epi8(vn1, a);
let eqb = _mm256_cmpeq_epi8(vn1, b);
let eqc = _mm256_cmpeq_epi8(vn1, c);
let eqd = _mm256_cmpeq_epi8(vn1, d);
let or1 = _mm256_or_si256(eqa, eqb);
let or2 = _mm256_or_si256(eqc, eqd);
let or3 = _mm256_or_si256(or1, or2);
if _mm256_movemask_epi8(or3) != 0 {
return Some(matched(start_ptr, ptr, eqa, eqb, eqc, eqd));
}
ptr = ptr.add(loop_size);
}
while ptr <= end_ptr.sub(VECTOR_SIZE) {
debug_assert!(sub(end_ptr, ptr) >= VECTOR_SIZE);
if let Some(i) = forward_search1(start_ptr, end_ptr, ptr, vn1) {
return Some(i);
}
ptr = ptr.add(VECTOR_SIZE);
}
if ptr < end_ptr {
debug_assert!(sub(end_ptr, ptr) < VECTOR_SIZE);
ptr = ptr.sub(VECTOR_SIZE - sub(end_ptr, ptr));
debug_assert_eq!(sub(end_ptr, ptr), VECTOR_SIZE);
return forward_search1(start_ptr, end_ptr, ptr, vn1);
}
None
}
#[target_feature(enable = "avx2")]
pub unsafe fn memchr2(n1: u8, n2: u8, haystack: &[u8]) -> Option<usize> {
#[cold]
#[inline(never)]
#[target_feature(enable = "avx2")]
unsafe fn matched(
start_ptr: *const u8,
ptr: *const u8,
eqa1: __m256i,
eqa2: __m256i,
eqb1: __m256i,
eqb2: __m256i,
) -> usize {
let mut at = sub(ptr, start_ptr);
let mask1 = _mm256_movemask_epi8(eqa1);
let mask2 = _mm256_movemask_epi8(eqa2);
if mask1 != 0 || mask2 != 0 {
return at + forward_pos2(mask1, mask2);
}
at += VECTOR_SIZE;
let mask1 = _mm256_movemask_epi8(eqb1);
let mask2 = _mm256_movemask_epi8(eqb2);
at + forward_pos2(mask1, mask2)
}
let vn1 = _mm256_set1_epi8(n1 as i8);
let vn2 = _mm256_set1_epi8(n2 as i8);
let len = haystack.len();
let loop_size = cmp::min(LOOP_SIZE2, len);
let start_ptr = haystack.as_ptr();
let end_ptr = start_ptr.add(haystack.len());
let mut ptr = start_ptr;
if haystack.len() < VECTOR_SIZE {
while ptr < end_ptr {
if *ptr == n1 || *ptr == n2 {
return Some(sub(ptr, start_ptr));
}
ptr = ptr.offset(1);
}
return None;
}
if let Some(i) = forward_search2(start_ptr, end_ptr, ptr, vn1, vn2) {
return Some(i);
}
ptr = ptr.add(VECTOR_SIZE - (start_ptr as usize & VECTOR_ALIGN));
debug_assert!(ptr > start_ptr && end_ptr.sub(VECTOR_SIZE) >= start_ptr);
while loop_size == LOOP_SIZE2 && ptr <= end_ptr.sub(loop_size) {
debug_assert_eq!(0, (ptr as usize) % VECTOR_SIZE);
let a = _mm256_load_si256(ptr as *const __m256i);
let b = _mm256_load_si256(ptr.add(VECTOR_SIZE) as *const __m256i);
let eqa1 = _mm256_cmpeq_epi8(vn1, a);
let eqb1 = _mm256_cmpeq_epi8(vn1, b);
let eqa2 = _mm256_cmpeq_epi8(vn2, a);
let eqb2 = _mm256_cmpeq_epi8(vn2, b);
let or1 = _mm256_or_si256(eqa1, eqb1);
let or2 = _mm256_or_si256(eqa2, eqb2);
let or3 = _mm256_or_si256(or1, or2);
if _mm256_movemask_epi8(or3) != 0 {
return Some(matched(start_ptr, ptr, eqa1, eqa2, eqb1, eqb2));
}
ptr = ptr.add(loop_size);
}
while ptr <= end_ptr.sub(VECTOR_SIZE) {
if let Some(i) = forward_search2(start_ptr, end_ptr, ptr, vn1, vn2) {
return Some(i);
}
ptr = ptr.add(VECTOR_SIZE);
}
if ptr < end_ptr {
debug_assert!(sub(end_ptr, ptr) < VECTOR_SIZE);
ptr = ptr.sub(VECTOR_SIZE - sub(end_ptr, ptr));
debug_assert_eq!(sub(end_ptr, ptr), VECTOR_SIZE);
return forward_search2(start_ptr, end_ptr, ptr, vn1, vn2);
}
None
}
#[target_feature(enable = "avx2")]
pub unsafe fn memchr3(
n1: u8,
n2: u8,
n3: u8,
haystack: &[u8],
) -> Option<usize> {
#[cold]
#[inline(never)]
#[target_feature(enable = "avx2")]
unsafe fn matched(
start_ptr: *const u8,
ptr: *const u8,
eqa1: __m256i,
eqa2: __m256i,
eqa3: __m256i,
eqb1: __m256i,
eqb2: __m256i,
eqb3: __m256i,
) -> usize {
let mut at = sub(ptr, start_ptr);
let mask1 = _mm256_movemask_epi8(eqa1);
let mask2 = _mm256_movemask_epi8(eqa2);
let mask3 = _mm256_movemask_epi8(eqa3);
if mask1 != 0 || mask2 != 0 || mask3 != 0 {
return at + forward_pos3(mask1, mask2, mask3);
}
at += VECTOR_SIZE;
let mask1 = _mm256_movemask_epi8(eqb1);
let mask2 = _mm256_movemask_epi8(eqb2);
let mask3 = _mm256_movemask_epi8(eqb3);
at + forward_pos3(mask1, mask2, mask3)
}
let vn1 = _mm256_set1_epi8(n1 as i8);
let vn2 = _mm256_set1_epi8(n2 as i8);
let vn3 = _mm256_set1_epi8(n3 as i8);
let len = haystack.len();
let loop_size = cmp::min(LOOP_SIZE2, len);
let start_ptr = haystack.as_ptr();
let end_ptr = start_ptr.add(haystack.len());
let mut ptr = start_ptr;
if haystack.len() < VECTOR_SIZE {
while ptr < end_ptr {
if *ptr == n1 || *ptr == n2 || *ptr == n3 {
return Some(sub(ptr, start_ptr));
}
ptr = ptr.offset(1);
}
return None;
}
if let Some(i) = forward_search3(start_ptr, end_ptr, ptr, vn1, vn2, vn3) {
return Some(i);
}
ptr = ptr.add(VECTOR_SIZE - (start_ptr as usize & VECTOR_ALIGN));
debug_assert!(ptr > start_ptr && end_ptr.sub(VECTOR_SIZE) >= start_ptr);
while loop_size == LOOP_SIZE2 && ptr <= end_ptr.sub(loop_size) {
debug_assert_eq!(0, (ptr as usize) % VECTOR_SIZE);
let a = _mm256_load_si256(ptr as *const __m256i);
let b = _mm256_load_si256(ptr.add(VECTOR_SIZE) as *const __m256i);
let eqa1 = _mm256_cmpeq_epi8(vn1, a);
let eqb1 = _mm256_cmpeq_epi8(vn1, b);
let eqa2 = _mm256_cmpeq_epi8(vn2, a);
let eqb2 = _mm256_cmpeq_epi8(vn2, b);
let eqa3 = _mm256_cmpeq_epi8(vn3, a);
let eqb3 = _mm256_cmpeq_epi8(vn3, b);
let or1 = _mm256_or_si256(eqa1, eqb1);
let or2 = _mm256_or_si256(eqa2, eqb2);
let or3 = _mm256_or_si256(eqa3, eqb3);
let or4 = _mm256_or_si256(or1, or2);
let or5 = _mm256_or_si256(or3, or4);
if _mm256_movemask_epi8(or5) != 0 {
return Some(matched(
start_ptr, ptr, eqa1, eqa2, eqa3, eqb1, eqb2, eqb3,
));
}
ptr = ptr.add(loop_size);
}
while ptr <= end_ptr.sub(VECTOR_SIZE) {
if let Some(i) =
forward_search3(start_ptr, end_ptr, ptr, vn1, vn2, vn3)
{
return Some(i);
}
ptr = ptr.add(VECTOR_SIZE);
}
if ptr < end_ptr {
debug_assert!(sub(end_ptr, ptr) < VECTOR_SIZE);
ptr = ptr.sub(VECTOR_SIZE - sub(end_ptr, ptr));
debug_assert_eq!(sub(end_ptr, ptr), VECTOR_SIZE);
return forward_search3(start_ptr, end_ptr, ptr, vn1, vn2, vn3);
}
None
}
#[target_feature(enable = "avx2")]
pub unsafe fn memrchr(n1: u8, haystack: &[u8]) -> Option<usize> {
let vn1 = _mm256_set1_epi8(n1 as i8);
let len = haystack.len();
let loop_size = cmp::min(LOOP_SIZE, len);
let start_ptr = haystack.as_ptr();
let end_ptr = start_ptr.add(haystack.len());
let mut ptr = end_ptr;
if haystack.len() < VECTOR_SIZE {
while ptr > start_ptr {
ptr = ptr.offset(-1);
if *ptr == n1 {
return Some(sub(ptr, start_ptr));
}
}
return None;
}
ptr = ptr.sub(VECTOR_SIZE);
if let Some(i) = reverse_search1(start_ptr, end_ptr, ptr, vn1) {
return Some(i);
}
ptr = (end_ptr as usize & !VECTOR_ALIGN) as *const u8;
debug_assert!(start_ptr <= ptr && ptr <= end_ptr);
while loop_size == LOOP_SIZE && ptr >= start_ptr.add(loop_size) {
debug_assert_eq!(0, (ptr as usize) % VECTOR_SIZE);
ptr = ptr.sub(loop_size);
let a = _mm256_load_si256(ptr as *const __m256i);
let b = _mm256_load_si256(ptr.add(VECTOR_SIZE) as *const __m256i);
let c = _mm256_load_si256(ptr.add(2 * VECTOR_SIZE) as *const __m256i);
let d = _mm256_load_si256(ptr.add(3 * VECTOR_SIZE) as *const __m256i);
let eqa = _mm256_cmpeq_epi8(vn1, a);
let eqb = _mm256_cmpeq_epi8(vn1, b);
let eqc = _mm256_cmpeq_epi8(vn1, c);
let eqd = _mm256_cmpeq_epi8(vn1, d);
let or1 = _mm256_or_si256(eqa, eqb);
let or2 = _mm256_or_si256(eqc, eqd);
let or3 = _mm256_or_si256(or1, or2);
if _mm256_movemask_epi8(or3) != 0 {
let mut at = sub(ptr.add(3 * VECTOR_SIZE), start_ptr);
let mask = _mm256_movemask_epi8(eqd);
if mask != 0 {
return Some(at + reverse_pos(mask));
}
at -= VECTOR_SIZE;
let mask = _mm256_movemask_epi8(eqc);
if mask != 0 {
return Some(at + reverse_pos(mask));
}
at -= VECTOR_SIZE;
let mask = _mm256_movemask_epi8(eqb);
if mask != 0 {
return Some(at + reverse_pos(mask));
}
at -= VECTOR_SIZE;
let mask = _mm256_movemask_epi8(eqa);
debug_assert!(mask != 0);
return Some(at + reverse_pos(mask));
}
}
while ptr >= start_ptr.add(VECTOR_SIZE) {
ptr = ptr.sub(VECTOR_SIZE);
if let Some(i) = reverse_search1(start_ptr, end_ptr, ptr, vn1) {
return Some(i);
}
}
if ptr > start_ptr {
debug_assert!(sub(ptr, start_ptr) < VECTOR_SIZE);
return reverse_search1(start_ptr, end_ptr, start_ptr, vn1);
}
None
}
#[target_feature(enable = "avx2")]
pub unsafe fn memrchr2(n1: u8, n2: u8, haystack: &[u8]) -> Option<usize> {
let vn1 = _mm256_set1_epi8(n1 as i8);
let vn2 = _mm256_set1_epi8(n2 as i8);
let len = haystack.len();
let loop_size = cmp::min(LOOP_SIZE2, len);
let start_ptr = haystack.as_ptr();
let end_ptr = start_ptr.add(haystack.len());
let mut ptr = end_ptr;
if haystack.len() < VECTOR_SIZE {
while ptr > start_ptr {
ptr = ptr.offset(-1);
if *ptr == n1 || *ptr == n2 {
return Some(sub(ptr, start_ptr));
}
}
return None;
}
ptr = ptr.sub(VECTOR_SIZE);
if let Some(i) = reverse_search2(start_ptr, end_ptr, ptr, vn1, vn2) {
return Some(i);
}
ptr = (end_ptr as usize & !VECTOR_ALIGN) as *const u8;
debug_assert!(start_ptr <= ptr && ptr <= end_ptr);
while loop_size == LOOP_SIZE2 && ptr >= start_ptr.add(loop_size) {
debug_assert_eq!(0, (ptr as usize) % VECTOR_SIZE);
ptr = ptr.sub(loop_size);
let a = _mm256_load_si256(ptr as *const __m256i);
let b = _mm256_load_si256(ptr.add(VECTOR_SIZE) as *const __m256i);
let eqa1 = _mm256_cmpeq_epi8(vn1, a);
let eqb1 = _mm256_cmpeq_epi8(vn1, b);
let eqa2 = _mm256_cmpeq_epi8(vn2, a);
let eqb2 = _mm256_cmpeq_epi8(vn2, b);
let or1 = _mm256_or_si256(eqa1, eqb1);
let or2 = _mm256_or_si256(eqa2, eqb2);
let or3 = _mm256_or_si256(or1, or2);
if _mm256_movemask_epi8(or3) != 0 {
let mut at = sub(ptr.add(VECTOR_SIZE), start_ptr);
let mask1 = _mm256_movemask_epi8(eqb1);
let mask2 = _mm256_movemask_epi8(eqb2);
if mask1 != 0 || mask2 != 0 {
return Some(at + reverse_pos2(mask1, mask2));
}
at -= VECTOR_SIZE;
let mask1 = _mm256_movemask_epi8(eqa1);
let mask2 = _mm256_movemask_epi8(eqa2);
return Some(at + reverse_pos2(mask1, mask2));
}
}
while ptr >= start_ptr.add(VECTOR_SIZE) {
ptr = ptr.sub(VECTOR_SIZE);
if let Some(i) = reverse_search2(start_ptr, end_ptr, ptr, vn1, vn2) {
return Some(i);
}
}
if ptr > start_ptr {
debug_assert!(sub(ptr, start_ptr) < VECTOR_SIZE);
return reverse_search2(start_ptr, end_ptr, start_ptr, vn1, vn2);
}
None
}
#[target_feature(enable = "avx2")]
pub unsafe fn memrchr3(
n1: u8,
n2: u8,
n3: u8,
haystack: &[u8],
) -> Option<usize> {
let vn1 = _mm256_set1_epi8(n1 as i8);
let vn2 = _mm256_set1_epi8(n2 as i8);
let vn3 = _mm256_set1_epi8(n3 as i8);
let len = haystack.len();
let loop_size = cmp::min(LOOP_SIZE2, len);
let start_ptr = haystack.as_ptr();
let end_ptr = start_ptr.add(haystack.len());
let mut ptr = end_ptr;
if haystack.len() < VECTOR_SIZE {
while ptr > start_ptr {
ptr = ptr.offset(-1);
if *ptr == n1 || *ptr == n2 || *ptr == n3 {
return Some(sub(ptr, start_ptr));
}
}
return None;
}
ptr = ptr.sub(VECTOR_SIZE);
if let Some(i) = reverse_search3(start_ptr, end_ptr, ptr, vn1, vn2, vn3) {
return Some(i);
}
ptr = (end_ptr as usize & !VECTOR_ALIGN) as *const u8;
debug_assert!(start_ptr <= ptr && ptr <= end_ptr);
while loop_size == LOOP_SIZE2 && ptr >= start_ptr.add(loop_size) {
debug_assert_eq!(0, (ptr as usize) % VECTOR_SIZE);
ptr = ptr.sub(loop_size);
let a = _mm256_load_si256(ptr as *const __m256i);
let b = _mm256_load_si256(ptr.add(VECTOR_SIZE) as *const __m256i);
let eqa1 = _mm256_cmpeq_epi8(vn1, a);
let eqb1 = _mm256_cmpeq_epi8(vn1, b);
let eqa2 = _mm256_cmpeq_epi8(vn2, a);
let eqb2 = _mm256_cmpeq_epi8(vn2, b);
let eqa3 = _mm256_cmpeq_epi8(vn3, a);
let eqb3 = _mm256_cmpeq_epi8(vn3, b);
let or1 = _mm256_or_si256(eqa1, eqb1);
let or2 = _mm256_or_si256(eqa2, eqb2);
let or3 = _mm256_or_si256(eqa3, eqb3);
let or4 = _mm256_or_si256(or1, or2);
let or5 = _mm256_or_si256(or3, or4);
if _mm256_movemask_epi8(or5) != 0 {
let mut at = sub(ptr.add(VECTOR_SIZE), start_ptr);
let mask1 = _mm256_movemask_epi8(eqb1);
let mask2 = _mm256_movemask_epi8(eqb2);
let mask3 = _mm256_movemask_epi8(eqb3);
if mask1 != 0 || mask2 != 0 || mask3 != 0 {
return Some(at + reverse_pos3(mask1, mask2, mask3));
}
at -= VECTOR_SIZE;
let mask1 = _mm256_movemask_epi8(eqa1);
let mask2 = _mm256_movemask_epi8(eqa2);
let mask3 = _mm256_movemask_epi8(eqa3);
return Some(at + reverse_pos3(mask1, mask2, mask3));
}
}
while ptr >= start_ptr.add(VECTOR_SIZE) {
ptr = ptr.sub(VECTOR_SIZE);
if let Some(i) =
reverse_search3(start_ptr, end_ptr, ptr, vn1, vn2, vn3)
{
return Some(i);
}
}
if ptr > start_ptr {
debug_assert!(sub(ptr, start_ptr) < VECTOR_SIZE);
return reverse_search3(start_ptr, end_ptr, start_ptr, vn1, vn2, vn3);
}
None
}
#[target_feature(enable = "avx2")]
unsafe fn forward_search1(
start_ptr: *const u8,
end_ptr: *const u8,
ptr: *const u8,
vn1: __m256i,
) -> Option<usize> {
debug_assert!(sub(end_ptr, start_ptr) >= VECTOR_SIZE);
debug_assert!(start_ptr <= ptr);
debug_assert!(ptr <= end_ptr.sub(VECTOR_SIZE));
let chunk = _mm256_loadu_si256(ptr as *const __m256i);
let mask = _mm256_movemask_epi8(_mm256_cmpeq_epi8(chunk, vn1));
if mask != 0 {
Some(sub(ptr, start_ptr) + forward_pos(mask))
} else {
None
}
}
#[target_feature(enable = "avx2")]
unsafe fn forward_search2(
start_ptr: *const u8,
end_ptr: *const u8,
ptr: *const u8,
vn1: __m256i,
vn2: __m256i,
) -> Option<usize> {
debug_assert!(sub(end_ptr, start_ptr) >= VECTOR_SIZE);
debug_assert!(start_ptr <= ptr);
debug_assert!(ptr <= end_ptr.sub(VECTOR_SIZE));
let chunk = _mm256_loadu_si256(ptr as *const __m256i);
let eq1 = _mm256_cmpeq_epi8(chunk, vn1);
let eq2 = _mm256_cmpeq_epi8(chunk, vn2);
if _mm256_movemask_epi8(_mm256_or_si256(eq1, eq2)) != 0 {
let mask1 = _mm256_movemask_epi8(eq1);
let mask2 = _mm256_movemask_epi8(eq2);
Some(sub(ptr, start_ptr) + forward_pos2(mask1, mask2))
} else {
None
}
}
#[target_feature(enable = "avx2")]
unsafe fn forward_search3(
start_ptr: *const u8,
end_ptr: *const u8,
ptr: *const u8,
vn1: __m256i,
vn2: __m256i,
vn3: __m256i,
) -> Option<usize> {
debug_assert!(sub(end_ptr, start_ptr) >= VECTOR_SIZE);
debug_assert!(start_ptr <= ptr);
debug_assert!(ptr <= end_ptr.sub(VECTOR_SIZE));
let chunk = _mm256_loadu_si256(ptr as *const __m256i);
let eq1 = _mm256_cmpeq_epi8(chunk, vn1);
let eq2 = _mm256_cmpeq_epi8(chunk, vn2);
let eq3 = _mm256_cmpeq_epi8(chunk, vn3);
let or = _mm256_or_si256(eq1, eq2);
if _mm256_movemask_epi8(_mm256_or_si256(or, eq3)) != 0 {
let mask1 = _mm256_movemask_epi8(eq1);
let mask2 = _mm256_movemask_epi8(eq2);
let mask3 = _mm256_movemask_epi8(eq3);
Some(sub(ptr, start_ptr) + forward_pos3(mask1, mask2, mask3))
} else {
None
}
}
#[target_feature(enable = "avx2")]
unsafe fn reverse_search1(
start_ptr: *const u8,
end_ptr: *const u8,
ptr: *const u8,
vn1: __m256i,
) -> Option<usize> {
debug_assert!(sub(end_ptr, start_ptr) >= VECTOR_SIZE);
debug_assert!(start_ptr <= ptr);
debug_assert!(ptr <= end_ptr.sub(VECTOR_SIZE));
let chunk = _mm256_loadu_si256(ptr as *const __m256i);
let mask = _mm256_movemask_epi8(_mm256_cmpeq_epi8(vn1, chunk));
if mask != 0 {
Some(sub(ptr, start_ptr) + reverse_pos(mask))
} else {
None
}
}
#[target_feature(enable = "avx2")]
unsafe fn reverse_search2(
start_ptr: *const u8,
end_ptr: *const u8,
ptr: *const u8,
vn1: __m256i,
vn2: __m256i,
) -> Option<usize> {
debug_assert!(sub(end_ptr, start_ptr) >= VECTOR_SIZE);
debug_assert!(start_ptr <= ptr);
debug_assert!(ptr <= end_ptr.sub(VECTOR_SIZE));
let chunk = _mm256_loadu_si256(ptr as *const __m256i);
let eq1 = _mm256_cmpeq_epi8(chunk, vn1);
let eq2 = _mm256_cmpeq_epi8(chunk, vn2);
if _mm256_movemask_epi8(_mm256_or_si256(eq1, eq2)) != 0 {
let mask1 = _mm256_movemask_epi8(eq1);
let mask2 = _mm256_movemask_epi8(eq2);
Some(sub(ptr, start_ptr) + reverse_pos2(mask1, mask2))
} else {
None
}
}
#[target_feature(enable = "avx2")]
unsafe fn reverse_search3(
start_ptr: *const u8,
end_ptr: *const u8,
ptr: *const u8,
vn1: __m256i,
vn2: __m256i,
vn3: __m256i,
) -> Option<usize> {
debug_assert!(sub(end_ptr, start_ptr) >= VECTOR_SIZE);
debug_assert!(start_ptr <= ptr);
debug_assert!(ptr <= end_ptr.sub(VECTOR_SIZE));
let chunk = _mm256_loadu_si256(ptr as *const __m256i);
let eq1 = _mm256_cmpeq_epi8(chunk, vn1);
let eq2 = _mm256_cmpeq_epi8(chunk, vn2);
let eq3 = _mm256_cmpeq_epi8(chunk, vn3);
let or = _mm256_or_si256(eq1, eq2);
if _mm256_movemask_epi8(_mm256_or_si256(or, eq3)) != 0 {
let mask1 = _mm256_movemask_epi8(eq1);
let mask2 = _mm256_movemask_epi8(eq2);
let mask3 = _mm256_movemask_epi8(eq3);
Some(sub(ptr, start_ptr) + reverse_pos3(mask1, mask2, mask3))
} else {
None
}
}
/// Compute the position of the first matching byte from the given mask. The
/// position returned is always in the range [0, 31].
///
/// The mask given is expected to be the result of _mm256_movemask_epi8.
fn forward_pos(mask: i32) -> usize {
// We are dealing with little endian here, where the most significant byte
// is at a higher address. That means the least significant bit that is set
// corresponds to the position of our first matching byte. That position
// corresponds to the number of zeros after the least significant bit.
mask.trailing_zeros() as usize
}
/// Compute the position of the first matching byte from the given masks. The
/// position returned is always in the range [0, 31]. Each mask corresponds to
/// the equality comparison of a single byte.
///
/// The masks given are expected to be the result of _mm256_movemask_epi8,
/// where at least one of the masks is non-zero (i.e., indicates a match).
fn forward_pos2(mask1: i32, mask2: i32) -> usize {
debug_assert!(mask1 != 0 || mask2 != 0);
forward_pos(mask1 | mask2)
}
/// Compute the position of the first matching byte from the given masks. The
/// position returned is always in the range [0, 31]. Each mask corresponds to
/// the equality comparison of a single byte.
///
/// The masks given are expected to be the result of _mm256_movemask_epi8,
/// where at least one of the masks is non-zero (i.e., indicates a match).
fn forward_pos3(mask1: i32, mask2: i32, mask3: i32) -> usize {
debug_assert!(mask1 != 0 || mask2 != 0 || mask3 != 0);
forward_pos(mask1 | mask2 | mask3)
}
/// Compute the position of the last matching byte from the given mask. The
/// position returned is always in the range [0, 31].
///
/// The mask given is expected to be the result of _mm256_movemask_epi8.
fn reverse_pos(mask: i32) -> usize {
// We are dealing with little endian here, where the most significant byte
// is at a higher address. That means the most significant bit that is set
// corresponds to the position of our last matching byte. The position from
// the end of the mask is therefore the number of leading zeros in a 32
// bit integer, and the position from the start of the mask is therefore
// 32 - (leading zeros) - 1.
VECTOR_SIZE - (mask as u32).leading_zeros() as usize - 1
}
/// Compute the position of the last matching byte from the given masks. The
/// position returned is always in the range [0, 31]. Each mask corresponds to
/// the equality comparison of a single byte.
///
/// The masks given are expected to be the result of _mm256_movemask_epi8,
/// where at least one of the masks is non-zero (i.e., indicates a match).
fn reverse_pos2(mask1: i32, mask2: i32) -> usize {
debug_assert!(mask1 != 0 || mask2 != 0);
reverse_pos(mask1 | mask2)
}
/// Compute the position of the last matching byte from the given masks. The
/// position returned is always in the range [0, 31]. Each mask corresponds to
/// the equality comparison of a single byte.
///
/// The masks given are expected to be the result of _mm256_movemask_epi8,
/// where at least one of the masks is non-zero (i.e., indicates a match).
fn reverse_pos3(mask1: i32, mask2: i32, mask3: i32) -> usize {
debug_assert!(mask1 != 0 || mask2 != 0 || mask3 != 0);
reverse_pos(mask1 | mask2 | mask3)
}
/// Subtract `b` from `a` and return the difference. `a` should be greater than
/// or equal to `b`.
fn sub(a: *const u8, b: *const u8) -> usize {
debug_assert!(a >= b);
(a as usize) - (b as usize)
}