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Milad Farazmand c314cf7466 PPC/s390: [Liftoff] Improve initialization for many locals Port `a8cdda9947` Original Commit Message: WebAssembly locals are specified to be zero on function entry. Liftoff implements this by just storing the constant 0 in the virtual stack for integer types, and using one floating point register initialized to zero for all floating point types. For big counts of locals this leads to problems (manifesting as huge blocks of code being generated) once we hit a merge point: All those constants (for int) and all duplicate register uses (for floats) need to be fixed up, by using separate registers for the locals or spilling to the stack if no more registers are available. All this spilling generates a lot of code, and can even happen multiple times within a function. This CL optimizes for such cases by spilling all locals to the stack initially. All merges within the function body get much smaller then. The spilled values rarely have to be loaded anyway, because the initial zero value is usually overwritten before the first use. To optimize the code size for initializing big numbers of locals on the stack, this CL also introduces the platform-specific {FillStackSlotsWithZero} method which uses a loop for bigger local counts. This often saves dozens of kilobytes for very big functions, and shows an overall code size reduction of 4-5 percent for big modules. R=clemensb@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com BUG= LOG=N Change-Id: I2459080a1f6acfdd212e9a93a868d028980c5554 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1863370 Reviewed-by: Junliang Yan <jyan@ca.ibm.com> Reviewed-by: Milad Farazmand <miladfar@ca.ibm.com> Commit-Queue: Milad Farazmand <miladfar@ca.ibm.com> Cr-Commit-Position: refs/heads/master@{#64301}		2019-10-15 17:50:29 +00:00
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README.md

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.