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Björn Steinbrink 92d1f155da Emit LLVM lifetime intrinsics to improve stack usage and codegen in general

Lifetime intrinsics help to reduce stack usage, because LLVM can apply
stack coloring to reuse the stack slots of dead allocas for new ones.

For example these functions now both use the same amount of stack, while
previous `bar()` used five times as much as `foo()`:

````rust
fn foo() {
  println("{}", 5);
}

fn bar() {
  println("{}", 5);
  println("{}", 5);
  println("{}", 5);
  println("{}", 5);
  println("{}", 5);
}
````

On top of that, LLVM can also optimize out certain operations when it
knows that memory is dead after a certain point. For example, it can
sometimes remove the zeroing used to cancel the drop glue. This is
possible when the glue drop itself was already removed because the
zeroing dominated the drop glue call. For example in:

````rust
pub fn bar(x: (Box<int>, int)) -> (Box<int>, int) {
    x
}
````

With optimizations, this currently results in:

````llvm
define void @_ZN3bar20h330fa42547df8179niaE({ i64*, i64 }* noalias nocapture nonnull sret, { i64*, i64 }* noalias nocapture nonnull) unnamed_addr #0 {
"_ZN29_$LP$Box$LT$int$GT$$C$int$RP$39glue_drop.$x22glue_drop$x22$LP$1347$RP$17h88cf42702e5a322aE.exit":
  %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)
  tail call void @llvm.memset.p0i8.i64(i8* %2, i8 0, i64 16, i32 8, i1 false)
  ret void
}
````

But with lifetime intrinsics we get:

````llvm
define void @_ZN3bar20h330fa42547df8179niaE({ i64*, i64 }* noalias nocapture nonnull sret, { i64*, i64 }* noalias nocapture nonnull) unnamed_addr #0 {
"_ZN29_$LP$Box$LT$int$GT$$C$int$RP$39glue_drop.$x22glue_drop$x22$LP$1347$RP$17h88cf42702e5a322aE.exit":
  %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)
  tail call void @llvm.lifetime.end(i64 16, i8* %2)
  ret void
}
````

Fixes #15665

2014-07-22 09:17:41 +02:00

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Emit LLVM lifetime intrinsics to improve stack usage and codegen in general

2014-07-22 09:17:41 +02:00

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README.md

The Rust Programming Language

This is a compiler for Rust, including standard libraries, tools and documentation.

Quick Start

Download a binary installer for your platform.
Read the tutorial.
Enjoy!

Note: Windows users can read the detailed getting started notes on the wiki.

Building from Source

Make sure you have installed the dependencies:
- g++ 4.7 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
- git
Download and build Rust:

You can either download a tarball or build directly from the repo.

To build from the tarball do:
```
 $ curl -O http://static.rust-lang.org/dist/rust-nightly.tar.gz
 $ tar -xzf rust-nightly.tar.gz
 $ cd rust-nightly
```
Or to build from the repo do:
```
 $ git clone https://github.com/rust-lang/rust.git
 $ cd rust
```
Now that you have Rust's source code, you can configure and build it:
```
 $ ./configure
 $ make && make install
```
Note: 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, and rustdoc, the API-documentation tool.
Read the tutorial.
Enjoy!

Building on Windows

To easily build on windows we can use MSYS2:

Grab the latest MSYS2 installer and go through the installer.
Now from the MSYS2 terminal we want to install the mingw64 toolchain and the other tools we need.
```
 $ pacman -S mingw-w64-i686-toolchain
 $ pacman -S base-devel
```
With that now start mingw32_shell.bat from where you installed MSYS2 (i.e. C:\msys).
From there just navigate to where you have Rust's source code, configure and build it:
```
 $ ./configure --build=i686-pc-mingw32
 $ make && make install
```

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:

Windows (7, 8, Server 2008 R2), x86 only
Linux (2.6.18 or later, various distributions), x86 and x86-64
OSX 10.7 (Lion) or greater, x86 and x86-64

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

Rust currently needs about 1.5 GiB of RAM to build without swapping; if it hits swap, it will take a very long time to build.

There is a lot more documentation in the wiki.

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See LICENSE-APACHE, LICENSE-MIT, and COPYRIGHT for details.

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