33e1a6e944
Turbofan applies the following optimization to external reference loads on arm64 and x64: if the root-relative offset to an external reference's address is known to be constant (and the root register has been initialized), calculate the external reference as |kRootRegister + <offset>| instead of loading it from the external reference table. There are two main cases to consider: 1. External references to arbitrary addresses in the native address space, e.g. libc_memcpy. These kinds of external references have a fixed address within the same running process, but may (and likely will) change between processes (e.g.: mksnapshot and later chromium), and the root-relative offset is different for each Isolate within the same process. These kinds of external references can be optimized as above when *not* generating code which will later be serialized, and *not* generating isolate-independent code. 2. External references to addresses within the fixed-size region of the Isolate (essentially: within IsolateData). Since these move with the Isolate, their root-relative offset is guaranteed to be constant at all times. The optimization can always be applied to these cases as long as the root register has been initialized. Prior to this CL, we only recognized and optimized for case 1. This CL additionally adds support for 2. An example of improved code generated due to this CL: Before: // r13 is the kRootRegister on x64. // 0x3010 is the root-relative offset to Isolate::context_address. leaq rdx, [r13+0x3010] movq r8, [rdx] After: movq rdx, [r13+0x3010] Bug: v8:9534 Change-Id: Idfcca751e98a56c0e5ead2c701c12a677df75399 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1748727 Commit-Queue: Jakob Gruber <jgruber@chromium.org> Auto-Submit: Jakob Gruber <jgruber@chromium.org> Reviewed-by: Tobias Tebbi <tebbi@chromium.org> Cr-Commit-Position: refs/heads/master@{#63158} |
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| build_overrides | ||
| custom_deps | ||
| docs | ||
| gni | ||
| include | ||
| infra | ||
| samples | ||
| src | ||
| test | ||
| testing | ||
| third_party | ||
| tools | ||
| .clang-format | ||
| .clang-tidy | ||
| .editorconfig | ||
| .flake8 | ||
| .git-blame-ignore-revs | ||
| .gitattributes | ||
| .gitignore | ||
| .gn | ||
| .vpython | ||
| .ycm_extra_conf.py | ||
| AUTHORS | ||
| BUILD.gn | ||
| ChangeLog | ||
| CODE_OF_CONDUCT.md | ||
| codereview.settings | ||
| COMMON_OWNERS | ||
| DEPS | ||
| ENG_REVIEW_OWNERS | ||
| INFRA_OWNERS | ||
| INTL_OWNERS | ||
| LICENSE | ||
| LICENSE.fdlibm | ||
| LICENSE.strongtalk | ||
| LICENSE.v8 | ||
| LICENSE.valgrind | ||
| MIPS_OWNERS | ||
| OWNERS | ||
| PPC_OWNERS | ||
| PRESUBMIT.py | ||
| README.md | ||
| S390_OWNERS | ||
| WATCHLISTS | ||
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.