dbc57584bd
Passing higher alignment values gives the optimization passes more freedom since it can copy in larger chunks. This change results in rustc outputting the same post-optimization IR as clang for swaps and most copies excluding the lack of information about padding.
Code snippet:
```rust
#[inline(never)]
fn swap<T>(x: &mut T, y: &mut T) {
util::swap(x, y);
}
```
Original IR (for `int`):
```llvm
define internal fastcc void @_ZN9swap_283417_a71830ca3ed2d65d3_00E(i64*, i64*) #1 {
static_allocas:
%2 = icmp eq i64* %0, %1
br i1 %2, label %_ZN4util9swap_283717_a71830ca3ed2d65d3_00E.exit, label %3
; <label>:3 ; preds = %static_allocas
%4 = load i64* %0, align 1
%5 = load i64* %1, align 1
store i64 %5, i64* %0, align 1
store i64 %4, i64* %1, align 1
br label %_ZN4util9swap_283717_a71830ca3ed2d65d3_00E.exit
_ZN4util9swap_283717_a71830ca3ed2d65d3_00E.exit: ; preds = %3, %static_allocas
ret void
}
```
After #6710:
```llvm
define internal fastcc void @_ZN9swap_283017_a71830ca3ed2d65d3_00E(i64* nocapture, i64* nocapture) #1 {
static_allocas:
%2 = load i64* %0, align 1
%3 = load i64* %1, align 1
store i64 %3, i64* %0, align 1
store i64 %2, i64* %1, align 1
ret void
}
```
After this change:
```llvm
define internal fastcc void @_ZN9swap_283017_a71830ca3ed2d65d3_00E(i64* nocapture, i64* nocapture) #1 {
static_allocas:
%2 = load i64* %0, align 8
%3 = load i64* %1, align 8
store i64 %3, i64* %0, align 8
store i64 %2, i64* %1, align 8
ret void
}
```
Another example:
```rust
#[inline(never)]
fn set<T>(x: &mut T, y: T) {
*x = y;
}
```
Before, with `(int, int)` (align 1):
```llvm
define internal fastcc void @_ZN8set_282517_8fa972e3f9e451983_00E({ i64, i64 }* nocapture, { i64, i64 }* nocapture) #1 {
static_allocas:
%2 = bitcast { i64, i64 }* %1 to i8*
%3 = bitcast { i64, i64 }* %0 to i8*
tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %3, i8* %2, i64 16, i32 1, i1 false)
ret void
}
```
After, with `(int, int)` (align 8):
```llvm
define internal fastcc void @_ZN8set_282617_8fa972e3f9e451983_00E({ i64, i64 }* nocapture, { i64, i64 }* nocapture) #1 {
static_allocas:
%2 = bitcast { i64, i64 }* %1 to i8*
%3 = bitcast { i64, i64 }* %0 to i8*
tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %3, i8* %2, i64 16, i32 8, i1 false)
ret void
}
```
|
||
|---|---|---|
| doc | ||
| man | ||
| mk | ||
| src | ||
| .gitattributes | ||
| .gitignore | ||
| .gitmodules | ||
| AUTHORS.txt | ||
| configure | ||
| CONTRIBUTING.md | ||
| COPYRIGHT | ||
| LICENSE-APACHE | ||
| LICENSE-MIT | ||
| Makefile.in | ||
| README.md | ||
| RELEASES.txt | ||
The Rust Programming Language
This is a compiler for Rust, including standard libraries, tools and documentation.
Installation
The Rust compiler currently must be built from a tarball, unless you are on Windows, in which case using the installer is recommended.
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:
- Windows (7, Server 2008 R2), x86 only
- Linux (various distributions), x86 and x86-64
- OSX 10.6 ("Snow Leopard") or greater, x86 and x86-64
You may find that other platforms work, but these are our "tier 1" supported build environments that are most likely to work.
Note: Windows users should read the detailed getting started notes on the wiki. Even when using the binary installer the Windows build requires a MinGW installation, the precise details of which are not discussed here.
To build from source you will also need the following prerequisite packages:
- g++ 4.4 or clang++ 3.x
- python 2.6 or later (but not 3.x)
- perl 5.0 or later
- gnu make 3.81 or later
- curl
Assuming you're on a relatively modern *nix system and have met the prerequisites, something along these lines should work.
$ curl -O http://static.rust-lang.org/dist/rust-0.6.tar.gz
$ tar -xzf rust-0.6.tar.gz
$ cd rust-0.6
$ ./configure
$ make && make install
You may need to use sudo make install if you do not normally have
permission to modify the destination directory. The install locations
can be adjusted by passing a --prefix argument to
configure. Various other options are also supported, pass --help
for more information on them.
When complete, make install will place several programs into
/usr/local/bin: rustc, the Rust compiler; rustdoc, the
API-documentation tool, and rustpkg, the Rust package manager and build system.
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.
More help
The tutorial is a good starting point.