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use safe chunking in wasm32/aarch64 compare256 #312

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Merged
folkertdev merged 2 commits into from
Mar 3, 2025
Merged

use safe chunking in wasm32/aarch64 compare256 #312

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261b304
remove unsafe cast from wasm compare256
folkertdev Mar 3, 2025
7c20fc5
use safe chunking for aarch64 too
folkertdev Mar 3, 2025
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14 changes: 7 additions & 7 deletions zlib-rs/src/deflate/compare256.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -119,12 +119,12 @@ mod neon {
/// Behavior is undefined if the `neon` target feature is not enabled
#[target_feature(enable = "neon")]
pub unsafe fn compare256(src0: &[u8; 256], src1: &[u8; 256]) -> usize {
let src0: &[[u8; 16]; 16] = unsafe { core::mem::transmute(src0) };
let src1: &[[u8; 16]; 16] = unsafe { core::mem::transmute(src1) };
let src0 = src0.chunks_exact(16);
let src1 = src1.chunks_exact(16);

let mut len = 0;

for (a, b) in src0.iter().zip(src1) {
for (a, b) in src0.zip(src1) {
unsafe {
let a: uint8x16_t = vld1q_u8(a.as_ptr());
let b: uint8x16_t = vld1q_u8(b.as_ptr());
Expand Down Expand Up @@ -234,12 +234,12 @@ mod wasm32 {

#[target_feature(enable = "simd128")]
pub fn compare256(src0: &[u8; 256], src1: &[u8; 256]) -> usize {
let src0: &[[u8; 16]; 16] = unsafe { core::mem::transmute(src0) };
let src1: &[[u8; 16]; 16] = unsafe { core::mem::transmute(src1) };
let src0 = src0.chunks_exact(16);
let src1 = src1.chunks_exact(16);

let mut len = 0;

for (chunk0, chunk1) in src0.iter().zip(src1) {
for (chunk0, chunk1) in src0.zip(src1) {
// SAFETY: these are valid pointers to slice data.
let v128_src0 = unsafe { v128_load(chunk0.as_ptr() as *const v128) };
let v128_src1 = unsafe { v128_load(chunk1.as_ptr() as *const v128) };
Expand All @@ -248,7 +248,7 @@ mod wasm32 {
let mask = u8x16_bitmask(v128_cmp);

if mask != 0xFFFF {
let match_byte = (!mask).trailing_zeros(); /* Invert bits so identical = 0 */
let match_byte = mask.trailing_ones();
return len + match_byte as usize;
}

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