This repository has been archived by the owner on Aug 2, 2022. It is now read-only.
Remove unwinding frames from WAVM code generation #7047
Merged
Conversation
This file contains 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
WAVM, via LLVM, generates unwinding frames for each wasm that is instantiated. This allows exceptions to unwind through the JITed code. Unfortunately when hundreds or thousands of these unwinding frames are registered exception unwinding becomes exceptionally slow. This change removes generation of the unwinding frames. Because exceptions can no longer unwind through WAVM’s compiled code, all exceptions must be caught before unwinding reaches the compiled code. This means none of the intrinsics — either the ones we register or the ones wavm registers itself — can allow an exception to escape. Instead, the exception_ptr is stored and we longjmp through the compiled code.
heifner
suggested changes
Apr 9, 2019
heifner
approved these changes
Apr 15, 2019
Sign up for free
to subscribe to this conversation on GitHub.
Already have an account?
Sign in.
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Outdated suggestions cannot be applied.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.
Change Description
WAVM, via LLVM, generates unwinding frames for each wasm that is instantiated. This allows exceptions to unwind through the JITed code. Unfortunately when hundreds or thousands of these unwinding frames are registered exception unwinding becomes exceptionally slow.
This change removes generation of the unwinding frames. Because exceptions can no longer unwind through WAVM’s compiled code, all exceptions must be caught before unwinding reaches the compiled code. This means none of the intrinsics — either the ones we register or the ones wavm registers itself — can allow an exception to escape. Instead, the exception_ptr is stored and we longjmp through the compiled code.
This can provide substantial performance improvement when there are thousands of wasm instances active at once.
Consensus Changes
API Changes
Documentation Additions