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bors 932c736479 Auto merge of #48057 - scottmcm:less-match-more-compare, r=dtolnay Simplify RangeInclusive::next[_back] `match`ing on an `Option<Ordering>` seems cause some confusion for LLVM; switching to just using comparison operators removes a few jumps from the simple `for` loops I was trying. cc https://github.com/rust-lang/rust/issues/45222 https://github.com/rust-lang/rust/issues/28237#issuecomment-363706510 Example: ```rust #[no_mangle] pub fn coresum(x: std::ops::RangeInclusive<u64>) -> u64 { let mut sum = 0; for i in x { sum += i ^ (i-1); } sum } ``` Today: ```asm coresum: xor r8d, r8d mov r9, -1 xor eax, eax jmp .LBB0_1 .LBB0_4: lea rcx, [rdi - 1] xor rcx, rdi add rax, rcx mov rsi, rdx mov rdi, r10 .LBB0_1: cmp rdi, rsi mov ecx, 1 cmovb rcx, r9 cmove rcx, r8 test rcx, rcx mov edx, 0 mov r10d, 1 je .LBB0_4 // 1 cmp rcx, -1 jne .LBB0_5 // 2 lea r10, [rdi + 1] mov rdx, rsi jmp .LBB0_4 // 3 .LBB0_5: ret ``` With this PR: ```asm coresum: cmp rcx, rdx jbe .LBB0_2 xor eax, eax ret .LBB0_2: xor r8d, r8d mov r9d, 1 xor eax, eax .p2align 4, 0x90 .LBB0_3: lea r10, [rcx + 1] cmp rcx, rdx cmovae rdx, r8 cmovae r10, r9 lea r11, [rcx - 1] xor r11, rcx add rax, r11 mov rcx, r10 cmp r10, rdx jbe .LBB0_3 // Just this ret ``` <details><summary>Though using internal iteration (`.map(\|i\| i ^ (i-1)).sum()`) is still shorter to type, and lets the compiler unroll it</summary> ```asm coresum_inner: .Lcfi0: .seh_proc coresum_inner sub rsp, 168 .Lcfi1: .seh_stackalloc 168 vmovdqa xmmword ptr [rsp + 144], xmm15 .Lcfi2: .seh_savexmm 15, 144 vmovdqa xmmword ptr [rsp + 128], xmm14 .Lcfi3: .seh_savexmm 14, 128 vmovdqa xmmword ptr [rsp + 112], xmm13 .Lcfi4: .seh_savexmm 13, 112 vmovdqa xmmword ptr [rsp + 96], xmm12 .Lcfi5: .seh_savexmm 12, 96 vmovdqa xmmword ptr [rsp + 80], xmm11 .Lcfi6: .seh_savexmm 11, 80 vmovdqa xmmword ptr [rsp + 64], xmm10 .Lcfi7: .seh_savexmm 10, 64 vmovdqa xmmword ptr [rsp + 48], xmm9 .Lcfi8: .seh_savexmm 9, 48 vmovdqa xmmword ptr [rsp + 32], xmm8 .Lcfi9: .seh_savexmm 8, 32 vmovdqa xmmword ptr [rsp + 16], xmm7 .Lcfi10: .seh_savexmm 7, 16 vmovdqa xmmword ptr [rsp], xmm6 .Lcfi11: .seh_savexmm 6, 0 .Lcfi12: .seh_endprologue cmp rdx, rcx jae .LBB1_2 xor eax, eax jmp .LBB1_13 .LBB1_2: mov r8, rdx sub r8, rcx jbe .LBB1_3 cmp r8, 7 jbe .LBB1_5 mov rax, r8 and rax, -8 mov r9, r8 and r9, -8 je .LBB1_5 add rax, rcx vmovq xmm0, rcx vpshufd xmm0, xmm0, 68 mov ecx, 1 vmovq xmm1, rcx vpslldq xmm1, xmm1, 8 vpaddq xmm1, xmm0, xmm1 vpxor xmm0, xmm0, xmm0 vpcmpeqd xmm11, xmm11, xmm11 vmovdqa xmm12, xmmword ptr [rip + __xmm@00000000000000010000000000000001] vmovdqa xmm13, xmmword ptr [rip + __xmm@00000000000000030000000000000003] vmovdqa xmm14, xmmword ptr [rip + __xmm@00000000000000050000000000000005] vmovdqa xmm15, xmmword ptr [rip + __xmm@00000000000000080000000000000008] mov rcx, r9 vpxor xmm4, xmm4, xmm4 vpxor xmm5, xmm5, xmm5 vpxor xmm6, xmm6, xmm6 .p2align 4, 0x90 .LBB1_9: vpaddq xmm7, xmm1, xmmword ptr [rip + __xmm@00000000000000020000000000000002] vpaddq xmm9, xmm1, xmmword ptr [rip + __xmm@00000000000000040000000000000004] vpaddq xmm10, xmm1, xmmword ptr [rip + __xmm@00000000000000060000000000000006] vpaddq xmm8, xmm1, xmm12 vpxor xmm7, xmm8, xmm7 vpaddq xmm2, xmm1, xmm13 vpxor xmm8, xmm2, xmm9 vpaddq xmm3, xmm1, xmm14 vpxor xmm3, xmm3, xmm10 vpaddq xmm2, xmm1, xmm11 vpxor xmm2, xmm2, xmm1 vpaddq xmm0, xmm2, xmm0 vpaddq xmm4, xmm7, xmm4 vpaddq xmm5, xmm8, xmm5 vpaddq xmm6, xmm3, xmm6 vpaddq xmm1, xmm1, xmm15 add rcx, -8 jne .LBB1_9 vpaddq xmm0, xmm4, xmm0 vpaddq xmm0, xmm5, xmm0 vpaddq xmm0, xmm6, xmm0 vpshufd xmm1, xmm0, 78 vpaddq xmm0, xmm0, xmm1 vmovq r10, xmm0 cmp r8, r9 jne .LBB1_6 jmp .LBB1_11 .LBB1_3: xor r10d, r10d jmp .LBB1_12 .LBB1_5: xor r10d, r10d mov rax, rcx .p2align 4, 0x90 .LBB1_6: lea rcx, [rax - 1] xor rcx, rax inc rax add r10, rcx cmp rdx, rax jne .LBB1_6 .LBB1_11: mov rcx, rdx .LBB1_12: lea rax, [rcx - 1] xor rax, rcx add rax, r10 .LBB1_13: vmovaps xmm6, xmmword ptr [rsp] vmovaps xmm7, xmmword ptr [rsp + 16] vmovaps xmm8, xmmword ptr [rsp + 32] vmovaps xmm9, xmmword ptr [rsp + 48] vmovaps xmm10, xmmword ptr [rsp + 64] vmovaps xmm11, xmmword ptr [rsp + 80] vmovaps xmm12, xmmword ptr [rsp + 96] vmovaps xmm13, xmmword ptr [rsp + 112] vmovaps xmm14, xmmword ptr [rsp + 128] vmovaps xmm15, xmmword ptr [rsp + 144] add rsp, 168 ret .seh_handlerdata .section .text,"xr",one_only,coresum_inner .Lcfi13: .seh_endproc ``` </details>		2018-02-08 06:38:30 +00:00
src	Auto merge of #48057 - scottmcm:less-match-more-compare, r=dtolnay	2018-02-08 06:38:30 +00:00
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README.md

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 or clang++ 3.x or later
- python 2.7 (but not 3.x)
- GNU make 3.81 or later
- cmake 3.4.3 or later
- curl
- git

Clone the source with git:

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

Build and install:
```
$ ./x.py build && sudo ./x.py install
```
Note: Install locations can be adjusted by copying the config file from ./config.toml.example to ./config.toml, and adjusting the prefix option 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 install will place several programs into /usr/local/bin: rustc, the Rust compiler, and rustdoc, 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.bat or mingw64_shell.bat from 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 run msys2_shell.cmd -mingw32 or msys2_shell.cmd -mingw64 from 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-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 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.

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