fix: prevent int16 overflow in NEON non-dotprod fallback path - #459
Open
LEE GANGMIN (Mindev27) wants to merge 1 commit into
Open
fix: prevent int16 overflow in NEON non-dotprod fallback path#459LEE GANGMIN (Mindev27) wants to merge 1 commit into
LEE GANGMIN (Mindev27) wants to merge 1 commit into
Conversation
Author
|
@microsoft-github-policy-service agree |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
The non-dotprod NEON fallback accumulates vmlal_s8 results into int16x8_t across 32 loop iterations (256 multiply-adds total), which overflows int16 range and produces garbage output on ARMv8.0 CPUs like Cortex-A53/A73.
Fix by widening to int32 each iteration instead of every 32. Applied to all three dot product variants (1x1, 1xN, Nx1).
Partially addresses #411 (items 5 and 6).
Tested on M4 Pro (dotprod path) inference runs fine. Don't have ARMv8.0 hardware to test the non-dotprod path directly.