runtime/jit: add user frame support for JIT compilers and VMs by carli2 · Pull Request #81237 · golang/go

carli2 · 2026-08-31T05:50:28Z

This implements proposal #78189 on the current master branch.

It adds an experimental runtime/jit API for cooperative dynamically
generated code. JIT compilers and VMs can register executable regions with
declarative unwind metadata, provide precise stack maps, preserve Go pointers
and caller frame pointers across stack growth, support panic and recover
across registered frames, participate in tracebacks, observe cooperative
preemption requests, and obtain the metadata needed to emit Go-compatible
split-stack checks. Consecutive generated frames are unwound, scanned, and
relocated as one chain.

The API also supports prepared, precisely typed allocations for objects with
repeated tails. MemCP uses this for variable-sized JIT closure environments.
It is included because raw byte allocations cannot describe their pointers to
the garbage collector. Reviewer feedback is welcome on whether this part
should remain here or move to a separate proposal and change.

The complete feature is gated behind GOEXPERIMENT=jit. The stack walker and
garbage collector consume copied declarative metadata and do not invoke
JIT-owned callbacks.

MemCP uses this implementation to JIT-compile Scheme and query-planner code.
A self-recursion microbenchmark improves by 30 to 33 times. Its complete
Scheme and SQL regression workload improved from approximately 11 to 13
minutes to 8 minutes 31 seconds when the integration was introduced. These
are consumer measurements, not Go project benchmarks.

The change covers registered return PCs, nested generated frames, precise GC
scanning, stack relocation, panic/recover, tracebacks, and forced stack
growth. Recoverable synchronous hardware faults whose interrupted PC itself
lies in generated code are not yet specified or tested; proposal discussion
should decide whether that belongs here or in a follow-up.

The implementation was rebased onto current master and built using the Go
1.27 JIT fork as bootstrap. On linux/amd64,
GOEXPERIMENT=jit go test runtime/jit, GOEXPERIMENT=jit go test runtime, and
GOEXPERIMENT=jit go test cmd/api pass. The default runtime test without the
experiment and the runtime/jit race test pass as well. The runtime/jit tests
cross-compile for every architecture covered by their Linux trampolines and
for 386, amd64, and arm64 on Windows.

The separate Go 1.27 branch in the organization fork remains a reproducible
downstream toolchain snapshot. This change intentionally targets master.

Updates #78189

google-cla · 2026-08-31T05:50:46Z

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

gopherbot · 2026-09-02T09:06:19Z

This PR (HEAD: fc9129b) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/826384.

Important tips:

Don't comment on this PR. All discussion takes place in Gerrit.
You need a Gmail or other Google account to log in to Gerrit.
To change your code in response to feedback:
- Push a new commit to the branch used by your GitHub PR.
- A new "patch set" will then appear in Gerrit.
- Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
- Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
- Multiple commits in the PR will be squashed by GerritBot.
The title and description of the GitHub PR are used to construct the final commit message.
- Edit these as needed via the GitHub web interface (not via Gerrit or git).
- You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

gopherbot · 2026-09-02T09:26:20Z

Message from Gopher Robot:

Patch Set 1:

(1 comment)

Please don’t reply on this GitHub thread. Visit golang.org/cl/826384.
After addressing review feedback, remember to publish your drafts!

gopherbot · 2026-09-03T18:00:43Z

This PR (HEAD: ee6687e) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/826384.

Important tips:

Don't comment on this PR. All discussion takes place in Gerrit.
You need a Gmail or other Google account to log in to Gerrit.
To change your code in response to feedback:
- Push a new commit to the branch used by your GitHub PR.
- A new "patch set" will then appear in Gerrit.
- Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
- Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
- Multiple commits in the PR will be squashed by GerritBot.
The title and description of the GitHub PR are used to construct the final commit message.
- Edit these as needed via the GitHub web interface (not via Gerrit or git).
- You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

gopherbot · 2026-09-03T18:20:52Z

This PR (HEAD: 724544f) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/826384.

Important tips:

Don't comment on this PR. All discussion takes place in Gerrit.
You need a Gmail or other Google account to log in to Gerrit.
To change your code in response to feedback:
- Push a new commit to the branch used by your GitHub PR.
- A new "patch set" will then appear in Gerrit.
- Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
- Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
- Multiple commits in the PR will be squashed by GerritBot.
The title and description of the GitHub PR are used to construct the final commit message.
- Edit these as needed via the GitHub web interface (not via Gerrit or git).
- You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

gopherbot · 2026-09-03T19:00:11Z

This PR (HEAD: 946caf2) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/826384.

Important tips:

Don't comment on this PR. All discussion takes place in Gerrit.
You need a Gmail or other Google account to log in to Gerrit.
To change your code in response to feedback:
- Push a new commit to the branch used by your GitHub PR.
- A new "patch set" will then appear in Gerrit.
- Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
- Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
- Multiple commits in the PR will be squashed by GerritBot.
The title and description of the GitHub PR are used to construct the final commit message.
- Edit these as needed via the GitHub web interface (not via Gerrit or git).
- You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

gopherbot · 2026-09-03T21:00:26Z

Message from Carl-Philip Hänsch:

Patch Set 4:

(2 comments)

Please don’t reply on this GitHub thread. Visit golang.org/cl/826384.
After addressing review feedback, remember to publish your drafts!

gopherbot · 2026-09-05T09:02:03Z

This PR (HEAD: c3e63e0) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/826384.

Important tips:

Don't comment on this PR. All discussion takes place in Gerrit.
You need a Gmail or other Google account to log in to Gerrit.
To change your code in response to feedback:
- Push a new commit to the branch used by your GitHub PR.
- A new "patch set" will then appear in Gerrit.
- Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
- Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
- Multiple commits in the PR will be squashed by GerritBot.
The title and description of the GitHub PR are used to construct the final commit message.
- Edit these as needed via the GitHub web interface (not via Gerrit or git).
- You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

Add a new package runtime/jit that allows programs to register regions of dynamically generated executable code with the Go runtime. This enables the stack unwinder, panic/recover, and GC to handle frames from JIT-compiled code, WASM engines, and embedded VMs gracefully instead of crashing with "unknown pc". The package provides: - Three unwind modes: UnwindStop (end traceback), UnwindSkip (skip user frames via Next callback), UnwindDeclare (skip + describe in tracebacks via Describe callback) - GC integration via ScanStack callback for marking Go pointers held in user code shadow stacks - Register/Unregister lifecycle with Handle type Runtime internals: - Copy-on-write region registry with atomic pointer swap for lock-free reads from the unwinder (runs on system stack) - Unwinder patches in initAt() and next() to resolve user frame PCs via the Next callback before throwing on unknown PCs - traceback2() patch to call Describe for UnwindDeclare regions - markroot() fixed root to call ScanStack during GC mark phase Gated behind GOEXPERIMENT=jit. Without the experiment, the runtime/jit package is excluded from builds. The runtime-internal code has negligible cost when no regions are registered (single atomic load returning nil). Tests cover registration, concurrency, panic/recover through user frames, runtime.Callers, runtime.Stack, GC, UnwindDeclare with Describe, and ScanStack. ISA-specific JIT trampolines for all 13 Linux architectures. Fixes golang#78189

Keep UnwindStop as a hard traceback boundary even when the region has an unwind recipe. Preserve trailing padding when a repeated tail has zero-sized elements. Add coverage for the stack-check metadata and both boundary cases. Updates golang#78189

gopherbot · 2026-09-06T20:54:01Z

This PR (HEAD: 1c0b2e3) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/826384.

Important tips:

Don't comment on this PR. All discussion takes place in Gerrit.
You need a Gmail or other Google account to log in to Gerrit.
To change your code in response to feedback:
- Push a new commit to the branch used by your GitHub PR.
- A new "patch set" will then appear in Gerrit.
- Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
- Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
- Multiple commits in the PR will be squashed by GerritBot.
The title and description of the GitHub PR are used to construct the final commit message.
- Edit these as needed via the GitHub web interface (not via Gerrit or git).
- You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

gopherbot · 2026-09-06T21:10:51Z

Message from Carl-Philip Hänsch:

Patch Set 6: Code-Review+1

(1 comment)

Please don’t reply on this GitHub thread. Visit golang.org/cl/826384.
After addressing review feedback, remember to publish your drafts!

carli2 mentioned this pull request Aug 31, 2026

proposal: runtime/jit: user frame support for JIT compilers and VMs #78189

Open

carli2 force-pushed the jit-foreign-frames-master branch from 7259e81 to fc9129b Compare September 2, 2026 08:53

carli2 mentioned this pull request Sep 3, 2026

runtime/jit: expose typed allocation for closure contexts launix-de/go#1

Closed

carli2 added 12 commits September 6, 2026 22:36

runtime/jit: expose cooperative preemption state

3e922c1

runtime/jit: scan precise user frame stack maps

3f1a769

runtime/jit: grow user frame registry dynamically

a07e9a6

runtime/jit: relocate caller frame pointers on stack growth

1811147

runtime/jit: allocate repeated-tail objects

b4be716

runtime/jit: harden repeated-tail layouts

70781d4

runtime/jit: unwind consecutive user frames

f7b38c2

runtime/jit: expose stack check metadata

1fd27d1

runtime/jit: stress stack map publication and frame relocation

0cda7ef

runtime/jit: document complete public API

1c0b2e3

carli2 force-pushed the jit-foreign-frames-master branch from c3e63e0 to 1c0b2e3 Compare September 6, 2026 20:43

Navigation Menu

Uh oh!

runtime/jit: add user frame support for JIT compilers and VMs - #81237

runtime/jit: add user frame support for JIT compilers and VMs#81237
carli2 wants to merge 12 commits into
golang:masterfrom
launix-de:jit-foreign-frames-master

carli2 commented Aug 31, 2026 •

edited

Loading

Uh oh!

google-cla Bot commented Aug 31, 2026

Uh oh!

gopherbot commented Sep 2, 2026

Uh oh!

gopherbot commented Sep 2, 2026

Uh oh!

gopherbot commented Sep 3, 2026

Uh oh!

gopherbot commented Sep 3, 2026

Uh oh!

gopherbot commented Sep 3, 2026

Uh oh!

gopherbot commented Sep 3, 2026

Uh oh!

gopherbot commented Sep 5, 2026

Uh oh!

gopherbot commented Sep 6, 2026

Uh oh!

gopherbot commented Sep 6, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Uh oh!

Conversation

carli2 commented Aug 31, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

google-cla Bot commented Aug 31, 2026

Uh oh!

gopherbot commented Sep 2, 2026

Uh oh!

gopherbot commented Sep 2, 2026

Uh oh!

gopherbot commented Sep 3, 2026

Uh oh!

gopherbot commented Sep 3, 2026

Uh oh!

gopherbot commented Sep 3, 2026

Uh oh!

gopherbot commented Sep 3, 2026

Uh oh!

gopherbot commented Sep 5, 2026

Uh oh!

gopherbot commented Sep 6, 2026

Uh oh!

gopherbot commented Sep 6, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

carli2 commented Aug 31, 2026 •

edited

Loading