c2d419a341
Currently, some ScopeInfo fields are defined as indexed fields with a length of either one or zero, because the field might be present or it might not. Based on comments in https://crrev.com/c/v8/v8/+/2601880 , this strategy is not sustainable and we need a better way to represent optional fields so that we don't have to pass zero when accessing their only element. This change is a proposal to fix that problem. Syntax: I'm proposing using a question mark because TypeScript does, and Torque syntax looks somewhat like TypeScript. I don't feel strongly about this though, and I'm open to other suggestions. field_name?[condition_expression]: FieldType; Internal Torque compiler representation: Internally, I've updated the Torque compiler to still treat these fields as indexed, but with an extra flag saying they're optional. When getting a LocationReference for a field access expression on an optional field, Torque produces a Slice like it would for any other indexed field and subsequently calls AtIndex(0) to get a Reference. AtIndex can crash the process if the index is out of bounds (which is good), so some other parts of the Torque compiler need minor adjustments so that it doesn't take references to optional fields unless it actually needs them. Initialization: This proposal doesn't include any changes to initialization logic, so an optional field can still be initialized using '...' and an iterator. Perhaps we could introduce an Optional<T> struct for prettier initialization in a future change. Bug: v8:7793 Change-Id: I37649495f4c259e685261f53e4cf2859da66a31f Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2706306 Commit-Queue: Seth Brenith <seth.brenith@microsoft.com> Reviewed-by: Nico Hartmann <nicohartmann@chromium.org> Reviewed-by: Leszek Swirski <leszeks@chromium.org> Cr-Commit-Position: refs/heads/master@{#73018} |
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V8 JavaScript Engine
V8 is Google's open source JavaScript engine.
V8 implements ECMAScript as specified in ECMA-262.
V8 is written in C++ and is used in Google Chrome, the open source browser from Google.
V8 can run standalone, or can be embedded into any C++ application.
V8 Project page: https://v8.dev/docs
Getting the Code
Checkout depot tools, and run
fetch v8
This will checkout V8 into the directory v8 and fetch all of its dependencies.
To stay up to date, run
git pull origin
gclient sync
For fetching all branches, add the following into your remote
configuration in .git/config:
fetch = +refs/branch-heads/*:refs/remotes/branch-heads/*
fetch = +refs/tags/*:refs/tags/*
Contributing
Please follow the instructions mentioned at v8.dev/docs/contribute.