Cherry-pick to main: Fix use-of-uninitialized-value in SVE accumulator operations (#18)#25
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Cherry-pick to main: Fix use-of-uninitialized-value in SVE accumulator operations (#18)#25
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Use `_m` (merge) instead of `_x` (don't-care) for SVE multiply-accumulate operations on accumulator vectors. The `_x` variant leaves inactive lanes undefined, but the final `svaddv` with `svptrue` sums all lanes including those undefined ones, causing MemorySanitizer to report use-of-uninitialized-value when vector length is not a multiple of the SVE register width. The `_m` variant preserves the accumulator value for inactive lanes, keeping them at their initialized zero. Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com> (cherry picked from commit 5a0677a)
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This is a cherry-pick of #18 to branch main
Use
_m(merge) instead of_x(don't-care) for SVE multiply-accumulate operations on accumulator vectors. The_xvariant leaves inactive lanes undefined, but the finalsvaddvwithsvptruesums all lanes including those undefined ones, causing MemorySanitizer to report use-of-uninitialized-value when vector length is not a multiple of the SVE register width. The_mvariant preserves the accumulator value for inactive lanes, keeping them at their initialized zero.(cherry picked from commit 5a0677a)