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bors 2d91939bb7 Auto merge of - scottmcm:array-drain, r=thomcc 
Improve the `array::map` codegen

The `map` method on arrays [is documented as sometimes performing poorly](https://doc.rust-lang.org/std/primitive.array.html#note-on-performance-and-stack-usage), and after [a question on URLO](https://users.rust-lang.org/t/try-trait-residual-o-trait-and-try-collect-into-array/88510?u=scottmcm) prompted me to take another look at the core [`try_collect_into_array`](7c46fb2111/library/core/src/array/mod.rs (L865-L912)) function, I had some ideas that ended up working better than I'd expected.

There's three main ideas in here, split over three commits:
1. Don't use `array::IntoIter` when we can avoid it, since that seems to not get SRoA'd, meaning that every step writes things like loop counters into the stack unnecessarily
2. Don't return arrays in `Result`s unnecessarily, as that doesn't seem to optimize away even with `unwrap_unchecked` (perhaps because it needs to get moved into a new LLVM type to account for the discriminant)
3. Don't distract LLVM with all the `Option` dances when we know for sure we have enough items (like in `map` and `zip`).  This one's a larger commit as to do it I ended up adding a new `pub(crate)` trait, but hopefully those changes are still straight-forward.

(No libs-api changes; everything should be completely implementation-detail-internal.)

It's still not completely fixed -- I think it needs pcwalton's `memcpy` optimizations still () to get further -- but this seems to go much better than before.  And the remaining `memcpy`s are just `transmute`-equivalent (`[T; N] -> ManuallyDrop<[T; N]>` and `[MaybeUninit<T>; N] -> [T; N]`), so hopefully those will be easier to remove with LLVM16 than the previous subobject copies 🤞

r? `@thomcc`

As a simple example, this test
```rust
pub fn long_integer_map(x: [u32; 64]) -> [u32; 64] {
    x.map(|x| 13 * x + 7)
}
```
On nightly <https://rust.godbolt.org/z/xK7548TGj> takes `sub rsp, 808`
```llvm
start:
  %array.i.i.i.i = alloca [64 x i32], align 4
  %_3.sroa.5.i.i.i = alloca [65 x i32], align 4
  %_5.i = alloca %"core::iter::adapters::map::Map<core::array::iter::IntoIter<u32, 64>, [closure@/app/example.rs:2:11: 2:14]>", align 8
```
(and yes, that's a 6**5**-element array `alloca` despite 6**4**-element input and output)

But with this PR it's only `sub rsp, 520`
```llvm
start:
  %array.i.i.i.i.i.i = alloca [64 x i32], align 4
  %array1.i.i.i = alloca %"core::mem::manually_drop::ManuallyDrop<[u32; 64]>", align 4
```

Similarly, the loop it emits on nightly is scalar-only and horrifying
```nasm
.LBB0_1:
        mov     esi, 64
        mov     edi, 0
        cmp     rdx, 64
        je      .LBB0_3
        lea     rsi, [rdx + 1]
        mov     qword ptr [rsp + 784], rsi
        mov     r8d, dword ptr [rsp + 4*rdx + 528]
        mov     edi, 1
        lea     edx, [r8 + 2*r8]
        lea     r8d, [r8 + 4*rdx]
        add     r8d, 7
.LBB0_3:
        test    edi, edi
        je      .LBB0_11
        mov     dword ptr [rsp + 4*rcx + 272], r8d
        cmp     rsi, 64
        jne     .LBB0_6
        xor     r8d, r8d
        mov     edx, 64
        test    r8d, r8d
        jne     .LBB0_8
        jmp     .LBB0_11
.LBB0_6:
        lea     rdx, [rsi + 1]
        mov     qword ptr [rsp + 784], rdx
        mov     edi, dword ptr [rsp + 4*rsi + 528]
        mov     r8d, 1
        lea     esi, [rdi + 2*rdi]
        lea     edi, [rdi + 4*rsi]
        add     edi, 7
        test    r8d, r8d
        je      .LBB0_11
.LBB0_8:
        mov     dword ptr [rsp + 4*rcx + 276], edi
        add     rcx, 2
        cmp     rcx, 64
        jne     .LBB0_1
```

whereas with this PR it's unrolled and vectorized
```nasm
	vpmulld	ymm1, ymm0, ymmword ptr [rsp + 64]
	vpaddd	ymm1, ymm1, ymm2
	vmovdqu	ymmword ptr [rsp + 328], ymm1
	vpmulld	ymm1, ymm0, ymmword ptr [rsp + 96]
	vpaddd	ymm1, ymm1, ymm2
	vmovdqu	ymmword ptr [rsp + 360], ymm1
```
(though sadly still stack-to-stack)
2023-02-13 10:18:48 +00:00
.github Rollup merge of - Mark-Simulacrum:rename-auto-template, r=estebank 2023-02-08 07:13:28 +01:00
.reuse remove old REUSE entry 2022-11-09 23:20:02 -05:00
compiler Auto merge of - nnethercote:reduce-interning, r=compiler-errors 2023-02-13 00:35:26 +00:00
library Auto merge of - scottmcm:array-drain, r=thomcc 2023-02-13 10:18:48 +00:00
LICENSES Rewrite LLVM's archive writer in Rust 2022-11-26 19:35:32 +00:00
src Rollup merge of - GuillaumeGomez:update-browser-ui-test, r=notriddle 2023-02-13 11:12:51 +05:30
tests Auto merge of - scottmcm:array-drain, r=thomcc 2023-02-13 10:18:48 +00:00
.editorconfig Add .editorconfig 2021-02-02 18:13:18 +01:00
.git-blame-ignore-revs Ignore tests move in git blame 2023-01-13 06:54:30 +00:00
.gitattributes Remove rustfmt tests from top-level .gitattributes 2021-06-04 09:04:54 -04:00
.gitignore Change src/test to tests in source files, fix tidy and tests 2023-01-11 09:32:13 +00:00
.gitmodules Update LLVM submodule 2022-12-07 08:40:49 +01:00
.mailmap Add mailmap for commits made by xes@meta.com 2023-02-06 10:35:40 -08:00
Cargo.lock Rollup merge of - chenyukang:yukang/add-only-modified, r=albertlarsan68 2023-02-11 17:18:42 +01:00
Cargo.toml update some dependencies 2023-01-31 23:31:12 +01:00
CODE_OF_CONDUCT.md Remove the code of conduct; instead link https://www.rust-lang.org/conduct.html 2019-10-05 22:55:19 +02:00
config.toml.example Auto merge of - clubby789:bootstrap-lto-off, r=simulacrum 2023-02-03 01:19:04 +00:00
configure Enforce Python 3 as much as possible 2020-04-10 09:09:58 -04:00
CONTRIBUTING.md Link to other resources instead of inlining their information 2022-12-23 19:03:50 -06:00
COPYRIGHT Update COPYRIGHT file 2022-10-30 10:23:14 -04:00
LICENSE-APACHE Remove appendix from LICENCE-APACHE 2019-12-30 14:25:53 +00:00
LICENSE-MIT LICENSE-MIT: Remove inaccurate (misattributed) copyright notice 2017-07-26 16:51:58 -07:00
README.md Add extra_unused_type_parameters lint 2023-02-02 19:37:34 -05:00
RELEASES.md Release 1.67.1 2023-02-09 15:22:35 -08:00
rustfmt.toml Change src/test to tests in source files, fix tidy and tests 2023-01-11 09:32:13 +00:00
triagebot.toml Remove Esteban from review queues for a while 2023-02-04 11:48:50 +00:00
x Add better python discovery 2022-10-31 08:33:24 +01:00
x.ps1 Powershell: Create a Start-Process wrapper 2022-12-28 19:41:42 +00:00
x.py assert that should_fix_bins_and_dylibs has been run 2023-01-31 18:22:01 +01:00

README.md

The Rust Programming Language

This is the main source code repository for Rust. It contains the compiler, standard library, and documentation.

Note: this README is for users rather than contributors. If you wish to contribute to the compiler, you should read CONTRIBUTING.md instead.

Quick Start

Read "Installation" from The Book.

Installing from Source

The Rust build system uses a Python script called x.py to build the compiler, which manages the bootstrapping process. It lives at the root of the project.

The x.py command can be run directly on most Unix systems in the following format:

./x.py <subcommand> [flags]

This is how the documentation and examples assume you are running x.py. Some alternative ways are:

# On a Unix shell if you don't have the necessary `python3` command
./x <subcommand> [flags]

# On the Windows Command Prompt (if .py files are configured to run Python)
x.py <subcommand> [flags]

# You can also run Python yourself, e.g.:
python x.py <subcommand> [flags]

More information about x.py can be found by running it with the --help flag or reading the rustc dev guide.

Dependencies

Make sure you have installed the dependencies:

  • python 3 or 2.7
  • git
  • A C compiler (when building for the host, cc is enough; cross-compiling may need additional compilers)
  • curl (not needed on Windows)
  • pkg-config if you are compiling on Linux and targeting Linux
  • libiconv (already included with glibc on Debian-based distros)

To build Cargo, you'll also need OpenSSL (libssl-dev or openssl-devel on most Unix distros).

If building LLVM from source, you'll need additional tools:

  • g++, clang++, or MSVC with versions listed on LLVM's documentation
  • ninja, or GNU make 3.81 or later (Ninja is recommended, especially on Windows)
  • cmake 3.13.4 or later
  • libstdc++-static may be required on some Linux distributions such as Fedora and Ubuntu

On tier 1 or tier 2 with host tools platforms, you can also choose to download LLVM by setting llvm.download-ci-llvm = true. Otherwise, you'll need LLVM installed and llvm-config in your path. See the rustc-dev-guide for more info.

Building on a Unix-like system

  1. Clone the source with git:

    git clone https://github.com/rust-lang/rust.git
cd rust

  1. Configure the build settings:

    The Rust build system uses a file named config.toml in the root of the source tree to determine various configuration settings for the build. Set up the defaults intended for distros to get started. You can see a full list of options in config.toml.example.

    printf 'profile = "user" \nchangelog-seen = 2 \n' > config.toml

    If you plan to use x.py install to create an installation, it is recommended that you set the prefix value in the [install] section to a directory.

  2. Build and install:

    ./x.py build && ./x.py install

    When complete, ./x.py install will place several programs into $PREFIX/bin: rustc, the Rust compiler, and rustdoc, the API-documentation tool. If you've set profile = "user" or build.extended = true, it will also include Cargo, Rust's package manager.

Building on Windows

On Windows, we suggest using winget to install dependencies by running the following in a terminal:

winget install -e Python.Python.3
winget install -e Kitware.CMake
winget install -e Git.Git

Then edit your system's PATH variable and add: C:\Program Files\CMake\bin. See this guide on editing the system PATH from the Java documentation.

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. Use the MSVC build of Rust to interop with software produced by Visual Studio and the GNU build to interop with GNU software built using the MinGW/MSYS2 toolchain.

MinGW

MSYS2 can be used to easily build Rust on Windows:

  1. Download the latest MSYS2 installer and go through the installer.

  2. Run mingw32_shell.bat or mingw64_shell.bat from the MSYS2 installation directory (e.g. C:\msys64), depending on whether you want 32-bit or 64-bit Rust. (As of the latest version of MSYS2 you have to run msys2_shell.cmd -mingw32 or msys2_shell.cmd -mingw64 from the command line instead.)

  3. 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', 'cmake',
# and 'ninja' 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-python \
            mingw-w64-x86_64-cmake \
            mingw-w64-x86_64-gcc \
            mingw-w64-x86_64-ninja

  4. 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 2017 (or later) so rustc can use its linker. The simplest way is to get Visual Studio, check the "C++ build tools" and "Windows 10 SDK" workload.

(If you're installing CMake yourself, be careful that "C++ CMake tools for Windows" doesn't get included under "Individual components".)

With these dependencies installed, you can build the compiler in a cmd.exe shell with:

python x.py build

Right now, building Rust only works with some known versions of Visual Studio. If you have a more recent version installed and the build system doesn't understand, 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\2019\Community\VC\Auxiliary\Build\vcvars64.bat"
python x.py build

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-gnu
    • x86_64-pc-windows-gnu
  • The MSVC ABI
    • i686-pc-windows-msvc
    • x86_64-pc-windows-msvc

The build triple can be specified by either specifying --build=<triple> when invoking x.py commands, or by creating a config.toml file (as described in Installing 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

configure generates a config.toml which can also be used with normal x.py invocations.

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. That is, 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 stage of development). As such, source builds require an Internet connection to fetch snapshots, and an OS that can execute the available snapshot binaries.

See https://doc.rust-lang.org/nightly/rustc/platform-support.html for a list of supported platforms. Only "host tools" platforms have a pre-compiled snapshot binary available; to compile for a platform without host tools you must cross-compile.

You may find that other platforms work, but these are our officially supported build environments that are most likely to work.

Getting Help

See https://www.rust-lang.org/community for a list of chat platforms and forums.

Contributing

See CONTRIBUTING.md.

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.

Trademark

The Rust Foundation owns and protects the Rust and Cargo trademarks and logos (the "Rust Trademarks").

If you want to use these names or brands, please read the media guide.

Third-party logos may be subject to third-party copyrights and trademarks. See Licenses for details.