Bug 300780 – [JSC][IPInt] High peak-memory footprint during module compilation compared to other engines

• Component: WebAssembly
• Status: NEW

[Yuta Saito]

Created attachment 477082 [details]
minimum reproducible code

We've observed that JavaScriptCore uses more memory during Wasm module compilation compared to other engines in our testing, especially for large Wasm modules. This appears to be related to IPInt metadata generation, and I wanted to share our findings in case this is helpful for optimization efforts.

During the module compilation stage in our test case (63 MB Wasm module) on macOS
- WebKit: 516MB
- Chrome: 249MB
- Firefox: 379MB

WebKit's memory usage is higher than the other engines we tested, and it more frequently crashes in our testing.

Based on our quick profiling, it seems that IPInt metadata generation involves substantial memory allocations. Our application has many cold functions, so the current approach of eagerly creating metadata for all functions might be using more memory than necessary for such cases.

We are also working on reducing our application's module size on our end, but it would be very helpful if there were improvements on the JSC side to mitigate this kind of case.

## Reproduction

WebKit Revision: 9de90808501f5acc03eb550000f69af0d9f78093


  $ npx serve ./bugs-webkit-org-ipint-footprint
  $ ./Tools/Scripts/run-minibrowser --release -- "http://localhost:3000"
  $ xctrace record --template "Allocations" --attach <WebContent.Development PID>
  $ # Click "Compile it" button on the page
  $ # Terminate the recording process

[Yuta Saito]

Created attachment 477083 [details]
Attach_93360_2025-10-15_19.21.23_C5822548.trace.zip

[Yuta Saito]

Created attachment 477084 [details]
minimum reproducible scripts

Added another JS script so that we can reproduce it with a standalone JSC:

  $ cd /path/to/bugs-webkit-org-ipint-footprint
  $ env DYLD_FRAMEWORK_PATH=/path/to/WebKitBuild/Release /path/to/WebKitBuild/Release/jsc --footprint ./test.jsc.js

[Radar WebKit Bug Importer]

<rdar://problem/163177683>