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Sep 23, 2025
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perf: reduce allocation on x86 #13

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358f778
perf: reduce allocation on x86
Brooooooklyn Sep 23, 2025
277863a
docs: update benchmark result
Brooooooklyn Sep 23, 2025
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20 changes: 10 additions & 10 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -27,21 +27,21 @@ Numbers below come from `cargo bench` runs on GitHub Actions hardware. Criterion

| Implementation | Median time | vs fastest |
| --------------------- | ------------- | ---------- |
| **`escape simd`** | **345.06 µs** | **1.00×** |
| `escape v_jsonescape` | 576.25 µs | 1.67× |
| `escape generic` | 657.94 µs | 1.91× |
| `serde_json` | 766.72 µs | 2.22× |
| `json-escape` | 782.65 µs | 2.27× |
| **`escape simd`** | **341.18 µs** | **1.00×** |
| `escape v_jsonescape` | 555.47 µs | 1.63× |
| `escape generic` | 656.85 µs | 1.93× |
| `serde_json` | 744.75 µs | 2.18× |
| `json-escape` | 777.15 µs | 2.28× |

**Fixtures payload (~300 iterations)**

| Implementation | Median time | vs fastest |
| --------------------- | ------------ | ---------- |
| **`escape simd`** | **12.84 ms** | **1.00×** |
| `escape v_jsonescape` | 19.66 ms | 1.53× |
| `escape generic` | 22.53 ms | 1.75× |
| `serde_json` | 24.65 ms | 1.92× |
| `json-escape` | 26.64 ms | 2.07× |
| **`escape simd`** | **12.67 ms** | **1.00×** |
| `escape v_jsonescape` | 20.58 ms | 1.62× |
| `escape generic` | 22.57 ms | 1.78× |
| `serde_json` | 24.52 ms | 1.94× |
| `json-escape` | 26.97 ms | 2.13× |

### GitHub Actions aarch64 (`ubuntu-24.04-arm`)

Expand Down
22 changes: 11 additions & 11 deletions src/generic.rs
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Original file line number Diff line number Diff line change
@@ -1,19 +1,24 @@
#[inline]
// Slightly modified version of
// <https://github.com/serde-rs/json/blob/d12e943590208da738c092db92c34b39796a2538/src/ser.rs#L2079>
// Borrowed from:
// <https://github.com/oxc-project/oxc-sourcemap/blob/e533e6ca4d08c538d8d4df74eacd29437851591f/src/encode.rs#L331>
pub fn escape_generic<S: AsRef<str>>(s: S) -> String {
let s = s.as_ref();
let bytes = s.as_bytes();

// Estimate capacity - most strings don't need much escaping
// Add some padding for potential escapes
let estimated_capacity = bytes.len() + bytes.len() / 2 + 2;
let mut result = Vec::with_capacity(estimated_capacity);

result.push(b'"');
escape_inner(bytes, &mut result);
result.push(b'"');
// SAFETY: We only pushed valid UTF-8 bytes (original string bytes and ASCII escape sequences)
unsafe { String::from_utf8_unchecked(result) }
}

#[inline]
// Slightly modified version of
// <https://github.com/serde-rs/json/blob/d12e943590208da738c092db92c34b39796a2538/src/ser.rs#L2079>
// Borrowed from:
// <https://github.com/oxc-project/oxc-sourcemap/blob/e533e6ca4d08c538d8d4df74eacd29437851591f/src/encode.rs#L331>
pub(crate) fn escape_inner(bytes: &[u8], result: &mut Vec<u8>) {
let mut start = 0;
let mut i = 0;

Expand Down Expand Up @@ -55,11 +60,6 @@ pub fn escape_generic<S: AsRef<str>>(s: S) -> String {
if start < bytes.len() {
result.extend_from_slice(&bytes[start..]);
}

result.push(b'"');

// SAFETY: We only pushed valid UTF-8 bytes (original string bytes and ASCII escape sequences)
unsafe { String::from_utf8_unchecked(result) }
}

const BB: u8 = b'b'; // \x08
Expand Down
37 changes: 23 additions & 14 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -22,21 +22,21 @@
//!
//! | Implementation | Median time | vs fastest |
//! | --------------------- | ------------- | ---------- |
//! | **`escape simd`** | **345.06 µs** | **1.00×** |
//! | `escape v_jsonescape` | 576.25 µs | 1.67× |
//! | `escape generic` | 657.94 µs | 1.91× |
//! | `serde_json` | 766.72 µs | 2.22× |
//! | `json-escape` | 782.65 µs | 2.27× |
//! | **`escape simd`** | **341.18 µs** | **1.00×** |
//! | `escape v_jsonescape` | 555.47 µs | 1.63× |
//! | `escape generic` | 656.85 µs | 1.93× |
//! | `serde_json` | 744.75 µs | 2.18× |
//! | `json-escape` | 777.15 µs | 2.28× |
//!
//! **Fixtures payload (~300 iterations)**
//!
//! | Implementation | Median time | vs fastest |
//! | --------------------- | ------------ | ---------- |
//! | **`escape simd`** | **12.84 ms** | **1.00×** |
//! | `escape v_jsonescape` | 19.66 ms | 1.53× |
//! | `escape generic` | 22.53 ms | 1.75× |
//! | `serde_json` | 24.65 ms | 1.92× |
//! | `json-escape` | 26.64 ms | 2.07× |
//! | **`escape simd`** | **12.67 ms** | **1.00×** |
//! | `escape v_jsonescape` | 20.58 ms | 1.62× |
//! | `escape generic` | 22.57 ms | 1.78× |
//! | `serde_json` | 24.52 ms | 1.94× |
//! | `json-escape` | 26.97 ms | 2.13× |
//!
//! ### GitHub Actions aarch64 (`ubuntu-24.04-arm`)
//!
Expand Down Expand Up @@ -121,16 +121,25 @@ pub use generic::escape_generic;
pub fn escape<S: AsRef<str>>(input: S) -> String {
#[cfg(target_arch = "x86_64")]
{
use generic::escape_inner;

let mut result = Vec::with_capacity(input.as_ref().len() + input.as_ref().len() / 2 + 2);
result.push(b'"');
let s = input.as_ref();
let bytes = s.as_bytes();
// Runtime CPU feature detection for x86_64
if is_x86_feature_detected!("avx512f") && is_x86_feature_detected!("avx512bw") {
unsafe { return x86::escape_avx512(input) }
unsafe { x86::escape_avx512(bytes, &mut result) }
} else if is_x86_feature_detected!("avx2") {
unsafe { return x86::escape_avx2(input) }
unsafe { x86::escape_avx2(bytes, &mut result) }
} else if is_x86_feature_detected!("sse2") {
unsafe { return x86::escape_sse2(input) }
unsafe { x86::escape_sse2(bytes, &mut result) }
} else {
return escape_generic(input);
escape_inner(bytes, &mut result);
}
result.push(b'"');
// SAFETY: We only pushed valid UTF-8 bytes (original string bytes and ASCII escape sequences)
unsafe { String::from_utf8_unchecked(result) }
}

#[cfg(target_arch = "aarch64")]
Expand Down
78 changes: 23 additions & 55 deletions src/x86.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -31,17 +31,9 @@ fn sub(a: *const u8, b: *const u8) -> usize {

#[target_feature(enable = "avx512f", enable = "avx512bw")]
#[inline]
pub unsafe fn escape_avx512<S: AsRef<str>>(input: S) -> String {
let s = input.as_ref();
let bytes = s.as_bytes();
pub unsafe fn escape_avx512(bytes: &[u8], result: &mut Vec<u8>) {
let len = bytes.len();

// Pre-allocate with estimated capacity
let estimated_capacity = len + len / 2 + 2;
let mut result = Vec::with_capacity(estimated_capacity);

result.push(b'"');

let start_ptr = bytes.as_ptr();
let end_ptr = bytes[len..].as_ptr();
let mut ptr = start_ptr;
Expand Down Expand Up @@ -80,7 +72,7 @@ pub unsafe fn escape_avx512<S: AsRef<str>>(input: S) -> String {
if start < i {
result.extend_from_slice(&bytes[start..i]);
}
write_escape(&mut result, escape_byte, c);
write_escape(result, escape_byte, c);
start = i + 1;
mask &= mask - 1;
}
Expand Down Expand Up @@ -143,11 +135,11 @@ pub unsafe fn escape_avx512<S: AsRef<str>>(input: S) -> String {
start = sub(ptr, start_ptr) + LOOP_SIZE_AVX512;
} else {
// Process each 64-byte chunk that has escapes
process_mask_avx512(ptr, start_ptr, &mut result, &mut start, bytes, mask_a, 0);
process_mask_avx512(ptr, start_ptr, result, &mut start, bytes, mask_a, 0);
process_mask_avx512(
ptr,
start_ptr,
&mut result,
result,
&mut start,
bytes,
mask_b,
Expand All @@ -156,7 +148,7 @@ pub unsafe fn escape_avx512<S: AsRef<str>>(input: S) -> String {
process_mask_avx512(
ptr,
start_ptr,
&mut result,
result,
&mut start,
bytes,
mask_c,
Expand All @@ -165,7 +157,7 @@ pub unsafe fn escape_avx512<S: AsRef<str>>(input: S) -> String {
process_mask_avx512(
ptr,
start_ptr,
&mut result,
result,
&mut start,
bytes,
mask_d,
Expand Down Expand Up @@ -199,7 +191,7 @@ pub unsafe fn escape_avx512<S: AsRef<str>>(input: S) -> String {
if start < i {
result.extend_from_slice(&bytes[start..i]);
}
write_escape(&mut result, escape_byte, c);
write_escape(result, escape_byte, c);
start = i + 1;
mask &= mask - 1;
}
Expand Down Expand Up @@ -229,39 +221,28 @@ pub unsafe fn escape_avx512<S: AsRef<str>>(input: S) -> String {
if start < i {
result.extend_from_slice(&bytes[start..i]);
}
write_escape(&mut result, escape_byte, c);
write_escape(result, escape_byte, c);
start = i + 1;
mask &= mask - 1;
}
}
}
} else {
// Fall back to AVX2 for small strings
return escape_avx2(input);
return escape_avx2(bytes, result);
}

// Copy any remaining bytes
if start < len {
result.extend_from_slice(&bytes[start..]);
}

result.push(b'"');
unsafe { String::from_utf8_unchecked(result) }
}

#[target_feature(enable = "avx2")]
#[inline]
pub unsafe fn escape_avx2<S: AsRef<str>>(input: S) -> String {
let s = input.as_ref();
let bytes = s.as_bytes();
pub unsafe fn escape_avx2(bytes: &[u8], result: &mut Vec<u8>) {
let len = bytes.len();

// Pre-allocate with estimated capacity
let estimated_capacity = len + len / 2 + 2;
let mut result = Vec::with_capacity(estimated_capacity);

result.push(b'"');

let start_ptr = bytes.as_ptr();
let end_ptr = bytes[len..].as_ptr();
let mut ptr = start_ptr;
Expand Down Expand Up @@ -297,7 +278,7 @@ pub unsafe fn escape_avx2<S: AsRef<str>>(input: S) -> String {
if start < i {
result.extend_from_slice(&bytes[start..i]);
}
write_escape(&mut result, escape_byte, c);
write_escape(result, escape_byte, c);
start = i + 1;
}
mask ^= 1 << cur;
Expand Down Expand Up @@ -372,11 +353,11 @@ pub unsafe fn escape_avx2<S: AsRef<str>>(input: S) -> String {
let mask_d = _mm256_movemask_epi8(cmp_d);

// Process each 32-byte chunk that has escapes
process_mask_avx(ptr, start_ptr, &mut result, &mut start, bytes, mask_a, 0);
process_mask_avx(ptr, start_ptr, result, &mut start, bytes, mask_a, 0);
process_mask_avx(
ptr,
start_ptr,
&mut result,
result,
&mut start,
bytes,
mask_b,
Expand All @@ -385,7 +366,7 @@ pub unsafe fn escape_avx2<S: AsRef<str>>(input: S) -> String {
process_mask_avx(
ptr,
start_ptr,
&mut result,
result,
&mut start,
bytes,
mask_c,
Expand All @@ -394,7 +375,7 @@ pub unsafe fn escape_avx2<S: AsRef<str>>(input: S) -> String {
process_mask_avx(
ptr,
start_ptr,
&mut result,
result,
&mut start,
bytes,
mask_d,
Expand Down Expand Up @@ -428,7 +409,7 @@ pub unsafe fn escape_avx2<S: AsRef<str>>(input: S) -> String {
if start < i {
result.extend_from_slice(&bytes[start..i]);
}
write_escape(&mut result, escape_byte, c);
write_escape(result, escape_byte, c);
start = i + 1;
}
mask ^= 1 << cur;
Expand Down Expand Up @@ -464,7 +445,7 @@ pub unsafe fn escape_avx2<S: AsRef<str>>(input: S) -> String {
if start < i {
result.extend_from_slice(&bytes[start..i]);
}
write_escape(&mut result, escape_byte, c);
write_escape(result, escape_byte, c);
start = i + 1;
}
mask ^= 1 << cur;
Expand All @@ -477,30 +458,20 @@ pub unsafe fn escape_avx2<S: AsRef<str>>(input: S) -> String {
}
} else {
// Fall back to SSE2 for small strings
return escape_sse2(input);
return escape_sse2(bytes, result);
}

// Copy any remaining bytes
if start < len {
result.extend_from_slice(&bytes[start..]);
}

result.push(b'"');
unsafe { String::from_utf8_unchecked(result) }
}

#[target_feature(enable = "sse2")]
#[inline]
pub unsafe fn escape_sse2<S: AsRef<str>>(input: S) -> String {
let s = input.as_ref();
let bytes = s.as_bytes();
pub unsafe fn escape_sse2(bytes: &[u8], result: &mut Vec<u8>) {
let len = bytes.len();

let estimated_capacity = len + len / 2 + 2;
let mut result = Vec::with_capacity(estimated_capacity);

result.push(b'"');

let start_ptr = bytes.as_ptr();
let end_ptr = bytes[len..].as_ptr();
let mut ptr = start_ptr;
Expand All @@ -518,7 +489,7 @@ pub unsafe fn escape_sse2<S: AsRef<str>>(input: S) -> String {
if start < i {
result.extend_from_slice(&bytes[start..i]);
}
write_escape(&mut result, escape_byte, c);
write_escape(result, escape_byte, c);
start = i + 1;
}
ptr = ptr.offset(1);
Expand Down Expand Up @@ -552,7 +523,7 @@ pub unsafe fn escape_sse2<S: AsRef<str>>(input: S) -> String {
if start < i {
result.extend_from_slice(&bytes[start..i]);
}
write_escape(&mut result, escape_byte, c);
write_escape(result, escape_byte, c);
start = i + 1;
}
mask ^= 1 << cur;
Expand Down Expand Up @@ -587,7 +558,7 @@ pub unsafe fn escape_sse2<S: AsRef<str>>(input: S) -> String {
if start < i {
result.extend_from_slice(&bytes[start..i]);
}
write_escape(&mut result, escape_byte, c);
write_escape(result, escape_byte, c);
start = i + 1;
}
mask ^= 1 << cur;
Expand Down Expand Up @@ -623,7 +594,7 @@ pub unsafe fn escape_sse2<S: AsRef<str>>(input: S) -> String {
if start < i {
result.extend_from_slice(&bytes[start..i]);
}
write_escape(&mut result, escape_byte, c);
write_escape(result, escape_byte, c);
start = i + 1;
}
mask ^= 1 << cur;
Expand All @@ -640,9 +611,6 @@ pub unsafe fn escape_sse2<S: AsRef<str>>(input: S) -> String {
if start < len {
result.extend_from_slice(&bytes[start..]);
}

result.push(b'"');
unsafe { String::from_utf8_unchecked(result) }
}

#[inline(always)]
Expand Down
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