Attempt to fix JIT instruction cache coherency on Arm64 #614
Conversation
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
![cubic-dev-ai[bot]](https://avatars.githubusercontent.com/in/1082092?s=60&v=4){kind=small}
This comment was marked as outdated.
This comment was marked as outdated.
Sorry, something went wrong.
jserv
commented
Sep 21, 2025
There was a problem hiding this comment.
Benchmarks
| Benchmark suite | Current: ef57d84 | Previous: 9ba5553 | Ratio |
|---|---|---|---|
Dhrystone |
1333 Average DMIPS over 10 runs |
1323 Average DMIPS over 10 runs |
0.99 |
Coremark |
957.852 Average iterations/sec over 10 runs |
906.292 Average iterations/sec over 10 runs |
0.95 |
This comment was automatically generated by workflow using github-action-benchmark.
jserv
force-pushed
the
fix-regressions
branch
from
c69de51 to
a3d4647
Compare
visitorckw
reviewed
Sep 21, 2025
jserv
force-pushed
the
fix-regressions
branch
10 times, most recently
from
879d4eb to
a568fcf
Compare
jserv
force-pushed
the
fix-regressions
branch
7 times, most recently
from
2852a99 to
77e4f83
Compare
jserv
changed the title
jserv
force-pushed
the
fix-regressions
branch
from
77e4f83 to
f738357
Compare
This comment was marked as outdated.
This comment was marked as outdated.
Sorry, something went wrong.
This comment was marked as outdated.
This comment was marked as outdated.
Sorry, something went wrong.
jserv
force-pushed
the
fix-regressions
branch
2 times, most recently
from
6df6884 to
3340a9b
Compare
jserv
force-pushed
the
fix-regressions
branch
19 times, most recently
from
84ab530 to
786e15e
Compare
This addresses critical issues in the JIT compiler that caused failures, particularly noticeable when ENABLE_EXT_F=0: 1. Check translation success before execution: The emulator now verifies that jit_translate() successfully marked a block as "hot" before attempting to execute the JIT-compiled code. This prevents execution of incomplete or failed translations. 2. Reset jump count on cache flush: The state->n_jumps counter was not being reset during code_cache_flush(), causing stale jump entries to persist and corrupt subsequent translations. 3. Mark incomplete translations properly: When a cache flush occurs mid-translation, the block is now correctly marked as not hot, ensuring it won't be mistakenly executed as valid JIT code. These fixes resolve the non-deterministic test failures observed in the pi calculation test and other compute-intensive benchmarks.
jserv
force-pushed
the
fix-regressions
branch
from
786e15e to
9ba5553
Compare
- Move pthread_jit_write_protect_np(false) before reading MAP_JIT memory in update_branch_imm since Apple Silicon requires write mode for both read and write operations on MAP_JIT memory - Add missing cache invalidation in resolve_jumps() for x86_64 after patching jump offsets
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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 JIT compiler was experiencing intermittent failures on Arm64 / Apple Silicon due to missing instruction cache invalidation after patching branch instructions. When update_branch_imm() modified branch targets in JIT-compiled code, the CPU's instruction cache was not being invalidated, causing it to execute stale cached instructions instead of the newly patched ones.