e5630ea97b
This addresses one of the major remaining slowdowns with embedded builtins on x64. When generating code for a call to a builtin callee from a builtin caller, we'd look up the Code target object from the builtins constant list, calculate the location of the first instruction, and jump to it. Note that for embedded builtin callees, the Code object is itself only a trampoline to the off-heap code and thus an additional indirection. An example of the call sequence in pseudo-asm: // Load from the constants list. mov reg, [kRootPointer, kBuiltinsConstantListOffset] mov reg, [reg, offset_of_the_code_constant] // Calculate first instruction and call it. add reg, Code::kHeaderOffset call reg // The trampoline forwards to the off-heap area. mov kOffHeapTrampolineRegister, <off-heap instruction_start> jmp kOffHeapTrampolineRegister This CL changes calls to embedded builtin targets to use pc-relative addressing. This reduces the above instruction sequence to: call <pc-relative offset to target instruction_start> Embedded-to-embedded calls jump directly to the embedded instruction stream, bypassing the trampoline. Heap-to-embedded calls (and all calls to heap-builtins) use pc-relative addressing targeting the on-heap Code object. Other relevant platforms (arm,arm64,mips,mips64) do not use pc-relative calls. For these, we'll need a different solution, e.g. a table of embedded builtin addresses reachable from the root pointer, similar to the external reference table. Bug: v8:6666 Change-Id: Ic0317d454e2da37d74eaecebcdfcbc0d5f5041ad Reviewed-on: https://chromium-review.googlesource.com/1068732 Commit-Queue: Jakob Gruber <jgruber@chromium.org> Reviewed-by: Michael Starzinger <mstarzinger@chromium.org> Cr-Commit-Position: refs/heads/master@{#53349} |
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| benchmarks | ||
| build_overrides | ||
| docs | ||
| gni | ||
| include | ||
| infra | ||
| samples | ||
| src | ||
| test | ||
| testing | ||
| third_party | ||
| tools | ||
| .clang-format | ||
| .editorconfig | ||
| .git-blame-ignore-revs | ||
| .gitattributes | ||
| .gitignore | ||
| .gn | ||
| .vpython | ||
| .ycm_extra_conf.py | ||
| AUTHORS | ||
| BUILD.gn | ||
| ChangeLog | ||
| CODE_OF_CONDUCT.md | ||
| codereview.settings | ||
| DEPS | ||
| LICENSE | ||
| LICENSE.fdlibm | ||
| LICENSE.strongtalk | ||
| LICENSE.v8 | ||
| LICENSE.valgrind | ||
| OWNERS | ||
| PRESUBMIT.py | ||
| README.md | ||
| snapshot_toolchain.gni | ||
| 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://github.com/v8/v8/wiki
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 on the V8 wiki.