Disable SVE targets under MemorySanitizer#17
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groeneai wants to merge 1 commit intoClickHouse:ClickHouse/v6.5.15from
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Disable SVE targets under MemorySanitizer#17groeneai wants to merge 1 commit intoClickHouse:ClickHouse/v6.5.15from
groeneai wants to merge 1 commit intoClickHouse:ClickHouse/v6.5.15from
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MSAN cannot instrument ARM SVE intrinsics (predicated loads, vector arithmetic, reductions). Even `svdupq_n_f32(0.f, ...)` — a literal constant — is flagged as uninitialized because MSAN has no SVE-specific shadow propagation. The existing mitigations (zero-initialized probe buffer and SIMSIMD_UNPOISON on results) are insufficient because MSAN reports the error *inside* the SVE kernel, before the dispatch wrapper can unpoison anything. Disable all SVE compilation targets when building with MSAN so SimSIMD falls back to NEON/scalar implementations that MSAN can track correctly. CIDB confirms zero NEON-related MSAN false positives in 90 days. Co-Authored-By: Claude Opus 4.6 <[email protected]>
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cc @rschu1ze — could you review this? Disables SVE compilation targets under MSAN to fix false-positive |
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Summary
MSAN cannot instrument ARM SVE intrinsics (predicated loads, vector arithmetic,
reductions). Even
svdupq_n_f32(0.f, ...)— a literal constant — is flagged asuninitialized because MSAN has no SVE-specific shadow propagation.
The existing mitigations from PRs #14 (zero-initialized probe buffer +
SIMSIMD_UNPOISONon results) are insufficient: MSAN reports the error insidethe SVE kernel during
svld1_f32,svmla_f32_x,svaddv_f32, before controlreturns to the dispatch wrapper where unpoisoning happens.
Fix
Disable all SVE compilation targets (
SIMSIMD_TARGET_SVE,SVE2,SVE_F16,SVE_BF16,SVE_I8) when building with MSAN. SimSIMD automatically falls backto NEON/scalar implementations that MSAN can track correctly.
Placed immediately after the SVE/SVE2 default definitions (line 43) so the
#undef+#define 0overrides take effect before any downstream#if.Evidence
arm_msanfailures on ClickHouse PR #98677, all with identicalsimsimd_cos_f32_svestack trace atspatial.h:818update) were merged, confirming the previous fixes are insufficient for SVE
🤖 Generated with Claude Code