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rawpatchinlineside by side (parent: b7d1e33)
| author | Jean Boussier <[email protected]> | |
| Mon, 28 Apr 2025 13:23:48 +0000 (28 15:23 +0200) | ||
| committer | Jean Boussier <[email protected]> | |
| Wed, 30 Apr 2025 06:12:41 +0000 (30 08:12 +0200) |
`c < 32 || c == 34` is equivalent to `c ^ 2 < 33`.
Found in: https://lemire.me/blog/2025/04/13/detect-control-characters-quotes-and-backslashes-efficiently-using-swar/
The gain seem mostly present on micro-benchmark, and even there aren't
very consistent, but it's never slower.
```
== Encoding long string (124001 bytes)
ruby 3.4.2 (2025-02-15 revision https://github.com/ruby/json/commit/d2930f8e7a) +YJIT +PRISM [arm64-darwin24]
Warming up --------------------------------------
after 5.295k i/100ms
Calculating -------------------------------------
after 55.796k (± 3.4%) i/s (17.92 μs/i) - 280.635k in 5.035690s
Comparison:
before: 49840.7 i/s
after: 55795.8 i/s - 1.12x faster
```
https://github.com/ruby/json/commit/034c5debd8
Found in: https://lemire.me/blog/2025/04/13/detect-control-characters-quotes-and-backslashes-efficiently-using-swar/
The gain seem mostly present on micro-benchmark, and even there aren't
very consistent, but it's never slower.
```
== Encoding long string (124001 bytes)
ruby 3.4.2 (2025-02-15 revision https://github.com/ruby/json/commit/d2930f8e7a) +YJIT +PRISM [arm64-darwin24]
Warming up --------------------------------------
after 5.295k i/100ms
Calculating -------------------------------------
after 55.796k (± 3.4%) i/s (17.92 μs/i) - 280.635k in 5.035690s
Comparison:
before: 49840.7 i/s
after: 55795.8 i/s - 1.12x faster
```
https://github.com/ruby/json/commit/034c5debd8
| ext/json/generator/generator.c | patchblobblamehistory |
{
uint8x16_t chunk = vld1q_u8((const unsigned char *)ptr);
- const uint8x16_t lower_bound = vdupq_n_u8(' ');
- const uint8x16_t backslash = vdupq_n_u8('\\');
- const uint8x16_t dblquote = vdupq_n_u8('\"');
+ // Trick: c < 32 || c == 34 can be factored as c ^ 2 < 33
+ // https://lemire.me/blog/2025/04/13/detect-control-characters-quotes-and-backslashes-efficiently-using-swar/
+ const uint8x16_t too_low_or_dbl_quote = vcltq_u8(veorq_u8(chunk, vdupq_n_u8(2)), vdupq_n_u8(33));
- uint8x16_t too_low = vcltq_u8(chunk, lower_bound);
- uint8x16_t has_backslash = vceqq_u8(chunk, backslash);
- uint8x16_t has_dblquote = vceqq_u8(chunk, dblquote);
- uint8x16_t needs_escape = vorrq_u8(too_low, vorrq_u8(has_backslash, has_dblquote));
+ uint8x16_t has_backslash = vceqq_u8(chunk, vdupq_n_u8('\\'));
+ uint8x16_t needs_escape = vorrq_u8(too_low_or_dbl_quote, has_backslash);
return neon_match_mask(needs_escape);
}
{
__m128i chunk = _mm_loadu_si128((__m128i const*)ptr);
- const __m128i lower_bound = _mm_set1_epi8(' ');
- const __m128i backslash = _mm_set1_epi8('\\');
- const __m128i dblquote = _mm_set1_epi8('\"');
-
- __m128i too_low = _mm_cmplt_epu8(chunk, lower_bound);
- __m128i has_backslash = _mm_cmpeq_epi8(chunk, backslash);
- __m128i has_dblquote = _mm_cmpeq_epi8(chunk, dblquote);
- __m128i needs_escape = _mm_or_si128(too_low, _mm_or_si128(has_backslash, has_dblquote));
+ // Trick: c < 32 || c == 34 can be factored as c ^ 2 < 33
+ // https://lemire.me/blog/2025/04/13/detect-control-characters-quotes-and-backslashes-efficiently-using-swar/
+ __m128i too_low_or_dbl_quote = _mm_cmplt_epu8(_mm_xor_si128(chunk, _mm_set1_epi8(2)), _mm_set1_epi8(33));
+ __m128i has_backslash = _mm_cmpeq_epi8(chunk, _mm_set1_epi8('\\'));
+ __m128i needs_escape = _mm_or_si128(too_low_or_dbl_quote, has_backslash);
return _mm_movemask_epi8(needs_escape);
}