LGTM2
On 3/26/25 9:37 PM, Domenic Denicola wrote:
Thanks for the answers! LGTM1.
On Wed, Mar 26, 2025 at 7:25 PM Emanuel Ziegler
<ecmzieg...@chromium.org> wrote:
Ah, I looked in the wrong "binary" rendering of the spec. This is
the correct link:
https://webassembly.github.io/branch-hinting/metadata/code/binary.html
(yes, it's extremely simple)
I updated the link in the feature. Sorry for the confusion!
On Wed, Mar 26, 2025 at 10:31 AM Emanuel Ziegler
<ecmzieg...@chromium.org> wrote:
See answers below. Thanks!
On Wed, Mar 26, 2025 at 2:26 AM Domenic Denicola
<dome...@chromium.org> wrote:
On Tue, Mar 25, 2025 at 9:49 PM Emanuel Ziegler
<ecmzieg...@chromium.org> wrote:
Hi all,
We are preparing to ship the WebAssembly Branch Hints
proposal in M136 which has been voted to phase 4 in
the Wasm Community Group last July. Chrome is now
catching up with shipping it after requests from
partners. The feature is already implemented in Firefox.
The proposal was championed by Yuri Iozzelli from
Leaning Technologies and the V8 team was not involved
in its standardization process. The implementation has
no effect on existing code by design which is why a
Finch trial would not yield any insights. We have a
Chromium feature available for a Finch kill-switch if
necessary.
Thank you,
Emanuel
Contact emails
ecmzieg...@chromium.org, jkumme...@chromium.org
Explainer
None
Specification
https://github.com/WebAssembly/branch-hinting/blob/main/proposals/branch-hinting/Overview.md
It seems like you put the explainer in the specification
field, and didn't link to the specification. I guess the
spec is at
https://github.com/WebAssembly/branch-hinting/blob/main/document/core/appendix/custom.rst
? Although I'm not sure the rendering there is quite
right... is there a better URL?
Unfortunately, the rendered content has not been updated in a
while and this is the only source of truth until the spec is
fully merged into the Wasm spec.
Summary
Improves the performance of compiled WebAssembly code
by informing the engine that a particular branch
instruction is very likely to take a specific path.
This allows the engine to make better decisions for
code layout (improving instruction cache hits) and
register allocation.
https://github.com/WebAssembly/branch-hinting/blob/main/proposals/branch-hinting/Overview.md
Blink component
Blink>JavaScript>WebAssembly
<https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3EJavaScript%3EWebAssembly%22>
TAG review
None
TAG review status
Not applicable
Risks
Interoperability and Compatibility
None
Can you expand on why you believe there are no interop and
compat risks?
This is a fully optional proposal without any difference in
functionality. If an engine does not support it, it will
simply run the code a little slower.
/Gecko/: No signal
/WebKit/: No signal
/Web developers/: No signals
/Other signals/:
WebView application risks
Does this intent deprecate or change behavior of
existing APIs, such that it has potentially high risk
for Android WebView-based applications?
None
Debuggability
None
Will this feature be supported on all six
Blink platforms (Windows, Mac, Linux,
ChromeOS, Android, and Android WebView)?
No
Why not?
Sorry, that was a mistake and has been fixed. We are planning
on shipping it everywhere since the changes are not
architecture dependent.
Is this feature fully tested by
web-platform-tests
<https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?
No
Why not?
Because there is no observable behavior change that could be
tested against.
Flag name on about://flags
None
Finch feature name
V8Flag_experimental_wasm_branch_hinting
Requires code in //chrome?
False
Estimated milestones
Shipping on desktop 136
Shipping on Android 136
Shipping on WebView 136
Anticipated spec changes
Open questions about a feature may be a source of
future web compat or interop issues. Please list open
issues (e.g. links to known github issues in the
project for the feature specification) whose
resolution may introduce web compat/interop risk
(e.g., changing to naming or structure of the API in a
non-backward-compatible way).
None
Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/5165273114738688?gate=5186994509185024
This intent message was generated by Chrome Platform
Status <https://chromestatus.com/>.
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