502de01ff4
This commit changes the ABI of SIMD types in the "Rust" ABI to unconditionally be passed via pointers instead of being passed as immediates. This should fix a longstanding issue, #44367, where SIMD-using programs ended up showing very odd behavior at runtime because the ABI between functions was mismatched. As a bit of a recap, this is sort of an LLVM bug and sort of an LLVM feature (today's behavior). LLVM will generate code for a function solely looking at the function it's generating, including calls to other functions. Let's then say you've got something that looks like: ```llvm define void @foo() { ; no target features enabled call void @bar(<i64 x 4> zeroinitializer) ret void } define void @bar(<i64 x 4>) #0 { ; enables the AVX feature ... } ``` LLVM will codegen the call to `bar` *without* using AVX registers becauase `foo` doesn't have access to these registers. Instead it's generated with emulation that uses two 128-bit registers. The `bar` function, on the other hand, will expect its argument in an AVX register (as it has AVX enabled). This means we've got a codegen problem! Comments on #44367 have some more contexutal information but the crux of the issue is that if we want SIMD to work in general we'll need to ensure that whenever a function calls another they ABI of the arguments being passed is in agreement. One possible solution to this would be to insert "shim functions" where whenever a `target_feature` mismatch is detected the compiler inserts a shim function where you pass arguments via memory to the shim and then the shim loads the values and calls the target function (where the shim and the target have the same target features enabled). This unfortunately is quite nontrivial to implement in rustc today (especially when accounting for function pointers and such). This commit takes a different solution, *always* passing SIMD arguments through memory instead of passing as immediates. This strategy solves the problem at the LLVM layer because the ABI between two functions never uses SIMD registers. This also shouldn't be a hit to performance because SIMD performance is thought to often rely on inlining anyway, where a `call` instruction, even if using SIMD registers, would be disastrous to performance regardless. LLVM should then be more than capable of fixing all our memory usage to use registers instead after enough inlining has been performed. Note that there's a few caveats to this commit though: * The "platform intrinsic" ABI is omitted from "always pass via memory". This ABI is used to define intrinsics like `simd_shuffle4` where LLVM and rustc need to have the arguments as an immediate. * Additionally this commit does *not* fix the `extern` ("C") ABI. This means that the bug in #44367 can still happen when using non-Rust-ABI functions. My hope is that before stabilization we can ban and/or warn about SIMD types in these functions (as AFAIK there's not much motivation to belong there anyway), but I'll leave that for a later commit and if this is merged I'll file a follow-up issue. All in all this... Closes #44367
The Rust Programming Language
This is the main source code repository for Rust. It contains the compiler, standard library, and documentation.
Quick Start
Read "Installation" from The Book.
Building from Source
Building on *nix
-
Make sure you have installed the dependencies:
g++4.7 or later orclang++3.x or laterpython2.7 (but not 3.x)- GNU
make3.81 or later cmake3.4.3 or latercurlgit
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Clone the source with
git:$ git clone https://github.com/rust-lang/rust.git $ cd rust
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Build and install:
$ ./x.py build && sudo ./x.py installNote: Install locations can be adjusted by copying the config file from
./config.toml.exampleto./config.toml, and adjusting theprefixoption under[install]. Various other options, such as enabling debug information, are also supported, and are documented in the config file.When complete,
sudo ./x.py installwill place several programs into/usr/local/bin:rustc, the Rust compiler, andrustdoc, the API-documentation tool. This install does not include Cargo, Rust's package manager, which you may also want to build.
Building on Windows
There are two prominent ABIs in use on Windows: the native (MSVC) ABI used by Visual Studio, and the GNU ABI used by the GCC toolchain. Which version of Rust you need depends largely on what C/C++ libraries you want to interoperate with: for interop with software produced by Visual Studio use the MSVC build of Rust; for interop with GNU software built using the MinGW/MSYS2 toolchain use the GNU build.
MinGW
MSYS2 can be used to easily build Rust on Windows:
-
Grab the latest MSYS2 installer and go through the installer.
-
Run
mingw32_shell.batormingw64_shell.batfrom wherever you installed MSYS2 (i.e.C:\msys64), depending on whether you want 32-bit or 64-bit Rust. (As of the latest version of MSYS2 you have to runmsys2_shell.cmd -mingw32ormsys2_shell.cmd -mingw64from the command line instead) -
From this terminal, install the required tools:
# Update package mirrors (may be needed if you have a fresh install of MSYS2) $ pacman -Sy pacman-mirrors # Install build tools needed for Rust. If you're building a 32-bit compiler, # then replace "x86_64" below with "i686". If you've already got git, python, # or CMake installed and in PATH you can remove them from this list. Note # that it is important that you do **not** use the 'python2' and 'cmake' # packages from the 'msys2' subsystem. The build has historically been known # to fail with these packages. $ pacman -S git \ make \ diffutils \ tar \ mingw-w64-x86_64-python2 \ mingw-w64-x86_64-cmake \ mingw-w64-x86_64-gcc -
Navigate to Rust's source code (or clone it), then build it:
$ ./x.py build && ./x.py install
MSVC
MSVC builds of Rust additionally require an installation of Visual Studio 2013
(or later) so rustc can use its linker. Make sure to check the “C++ tools”
option.
With these dependencies installed, you can build the compiler in a cmd.exe
shell with:
> python x.py build
Currently building Rust only works with some known versions of Visual Studio. If you have a more recent version installed the build system doesn't understand then you may need to force rustbuild to use an older version. This can be done by manually calling the appropriate vcvars file before running the bootstrap.
CALL "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\amd64\vcvars64.bat"
python x.py build
If you are seeing build failure when compiling rustc_binaryen, make sure the path
length of the rust folder is not longer than 22 characters.
Specifying an ABI
Each specific ABI can also be used from either environment (for example, using the GNU ABI in powershell) by using an explicit build triple. The available Windows build triples are:
- GNU ABI (using GCC)
i686-pc-windows-gnux86_64-pc-windows-gnu
- The MSVC ABI
i686-pc-windows-msvcx86_64-pc-windows-msvc
The build triple can be specified by either specifying --build=<triple> when
invoking x.py commands, or by copying the config.toml file (as described
in Building From Source), and modifying the build option under the [build]
section.
Configure and Make
While it's not the recommended build system, this project also provides a
configure script and makefile (the latter of which just invokes x.py).
$ ./configure
$ make && sudo make install
When using the configure script, the generated config.mk file may override the
config.toml file. To go back to the config.toml file, delete the generated
config.mk file.
Building Documentation
If you’d like to build the documentation, it’s almost the same:
$ ./x.py doc
The generated documentation will appear under doc in the build directory for
the ABI used. I.e., if the ABI was x86_64-pc-windows-msvc, the directory will be
build\x86_64-pc-windows-msvc\doc.
Notes
Since the Rust compiler is written in Rust, it must be built by a precompiled "snapshot" version of itself (made in an earlier state of development). As such, source builds require a connection to the Internet, to fetch snapshots, and an OS that can execute the available snapshot binaries.
Snapshot binaries are currently built and tested on several platforms:
| Platform / Architecture | x86 | x86_64 |
|---|---|---|
| Windows (7, 8, Server 2008 R2) | ✓ | ✓ |
| Linux (2.6.18 or later) | ✓ | ✓ |
| OSX (10.7 Lion or later) | ✓ | ✓ |
You may find that other platforms work, but these are our officially supported build environments that are most likely to work.
Rust currently needs between 600MiB and 1.5GiB of RAM to build, depending on platform. If it hits swap, it will take a very long time to build.
There is more advice about hacking on Rust in CONTRIBUTING.md.
Getting Help
The Rust community congregates in a few places:
- Stack Overflow - Direct questions about using the language.
- users.rust-lang.org - General discussion and broader questions.
- /r/rust - News and general discussion.
Contributing
To contribute to Rust, please see CONTRIBUTING.
Rust has an IRC culture and most real-time collaboration happens in a variety of channels on Mozilla's IRC network, irc.mozilla.org. The most popular channel is #rust, a venue for general discussion about Rust. And a good place to ask for help would be #rust-beginners.
License
Rust is primarily distributed under the terms of both the MIT license and the Apache License (Version 2.0), with portions covered by various BSD-like licenses.
See LICENSE-APACHE, LICENSE-MIT, and COPYRIGHT for details.