sve2 HISTSEG support for fast ondemand parsing on ARM #108
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emcastillo
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emcastillo
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Codecov ReportAll modified and coverable lines are covered by tests ✅
Additional details and impacted files@@ Coverage Diff @@
## master #108 +/- ##
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- Coverage 74.79% 73.40% -1.40%
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Files 21 22 +1
Lines 2436 2741 +305
Branches 667 749 +82
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+ Hits 1822 2012 +190
- Misses 297 430 +133
+ Partials 317 299 -18 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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#110 The CI bugs have been fixed，please rebase master |
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@xiegx94 |
xiegx94
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Aug 12, 2025
| #include "../common/arm_common/skip.inc.h" | ||
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| // Requires clang vx or GCC>=14 | ||
| #if (defined(__clang__) && (__clang_major__ >= 14)) || \ |
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__has_include would be better
| #if (defined(__clang__) && (__clang_major__ >= 14)) || \ | ||
| (defined(__GNUC__) && !defined(__clang__) && (__GNUC__ >= 14)) | ||
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| #define USE_SVE_HIST 1 |
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check USE_SVE_HIST is not defined.
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@xiegx94 |
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Hi @xiegx94 :) any chance you can look at it soon? |
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This PR uses the SVE2 HISTSEG instruction to improve performance of ondemand parsing in ARM cpus
https://developer.arm.com/documentation/ddi0602/latest/SVE-Instructions/HISTSEG--Count-matching-elements-in-vector-segments-
Creating the bitmasks for each structural character is very expensive in ARM due to the lack of pmovmskb similar instructions. Histseg gives us the number of characters of interest in a single instruction with low latency and high throughput in neoverse v2 cpus.
This allows us to skip mask creation of characters that are not present and even to implement some fast path codes when we have only quotes for example. It is worth noting that x86 doesn't have an equivalent instruction and the avx2 VP2INTERSECT instruction doesn't support int8 datatypes.
Performance:
Master branch
This PR
This is faster than even the most recent x86 cpus which shows result around 24Gi/s for twitter.
Thanks to @supermartian !
This PR is contributed by nvidia.