f853cf79b5
Optimize `Once::doit`: perform optimistic check that initializtion is
already completed. `load` is much cheaper than `fetch_add` at least
on x86_64.
Verified with this test:
```
static mut o: one::Once = one::ONCE_INIT;
unsafe {
loop {
let start = time::precise_time_ns();
let iters = 50000000u64;
for _ in range(0, iters) {
o.doit(|| { println!("once!"); });
}
let end = time::precise_time_ns();
let ps_per_iter = 1000 * (end - start) / iters;
println!("{} ps per iter", ps_per_iter);
// confuse the optimizer
o.doit(|| { println!("once!"); });
}
}
```
Test executed on Mac, Intel Core i7 2GHz. Result is:
* 20ns per iteration without patch
* 4ns per iteration with this patch applied
Once.doit could be even faster (800ps per iteration), if `doit` function
was split into a pair of `doit`/`doit_slow`, and `doit` marked as
`#[inline]` like this:
```
#[inline(always)]
pub fn doit(&self, f: ||) {
if self.cnt.load(atomics::SeqCst) < 0 {
return
}
self.doit_slow(f);
}
fn doit_slow(&self, f: ||) { ... }
```
|
||
|---|---|---|
| .. | ||
| compiler-rt@ed112ca1e4 | ||
| compiletest | ||
| doc | ||
| driver | ||
| etc | ||
| gyp@1e46da1000 | ||
| jemalloc@6a96910f2e | ||
| libarena | ||
| libbacktrace | ||
| libcollections | ||
| libcore | ||
| libflate | ||
| libfmt_macros | ||
| libfourcc | ||
| libgetopts | ||
| libglob | ||
| libgraphviz | ||
| libgreen | ||
| libhexfloat | ||
| liblibc | ||
| liblog | ||
| libnative | ||
| libnum | ||
| librand | ||
| libregex | ||
| libregex_macros | ||
| librustc | ||
| librustdoc | ||
| librustuv | ||
| libsemver | ||
| libserialize | ||
| libstd | ||
| libsync | ||
| libsyntax | ||
| libterm | ||
| libtest | ||
| libtime | ||
| liburl | ||
| libuuid | ||
| libuv@43495892de | ||
| libworkcache | ||
| llvm@4b4d0533b4 | ||
| rt | ||
| rustllvm | ||
| test | ||
| README.md | ||
| snapshots.txt | ||
This is a preliminary version of the Rust compiler, libraries and tools.
Source layout:
| Path | Description |
|---|---|
librustc/ |
The self-hosted compiler |
libstd/ |
The standard library (imported and linked by default) |
libextra/ |
The "extras" library (slightly more peripheral code) |
libgreen/ |
The M:N runtime library |
libnative/ |
The 1:1 runtime library |
libsyntax/ |
The Rust parser and pretty-printer |
libcollections/ |
A collection of useful data structures and containers |
libnum/ |
Extended number support library (complex, rational, etc) |
libtest/ |
Rust's test-runner code |
| ------------------- | --------------------------------------------------------- |
libarena/ |
The arena (a fast but limited) memory allocator |
libflate/ |
Simple compression library |
libfourcc/ |
Data format identifier library |
libgetopts/ |
Get command-line-options library |
libglob/ |
Unix glob patterns library |
libregex/ |
Regular expressions |
libsemver/ |
Rust's semantic versioning library |
libserialize/ |
Encode-Decode types library |
libsync/ |
Concurrency mechanisms and primitives |
libterm/ |
ANSI color library for terminals |
libtime/ |
Time operations library |
libuuid/ |
UUID's handling code |
| ------------------- | --------------------------------------------------------- |
rt/ |
The runtime system |
rt/rust_*.c |
- Some of the runtime services |
rt/vg |
- Valgrind headers |
rt/msvc |
- MSVC support |
rt/sundown |
- The Markdown library used by rustdoc |
| ------------------- | --------------------------------------------------------- |
compiletest/ |
The test runner |
test/ |
Testsuite |
test/codegen |
- Tests for the LLVM IR infrastructure |
test/compile-fail |
- Tests that should fail to compile |
test/debug-info |
- Tests for the debuginfo tool |
test/run-fail |
- Tests that should compile, run and fail |
test/run-make |
- Tests that depend on a Makefile infrastructure |
test/run-pass |
- Tests that should compile, run and succeed |
test/bench |
- Benchmarks and miscellaneous |
test/pretty |
- Pretty-printer tests |
test/auxiliary |
- Dependencies of tests |
| ------------------- | --------------------------------------------------------- |
librustdoc/ |
The Rust API documentation tool |
libuv/ |
The libuv submodule |
librustuv/ |
Rust libuv support code |
| ------------------- | --------------------------------------------------------- |
llvm/ |
The LLVM submodule |
rustllvm/ |
LLVM support code |
| ------------------- | --------------------------------------------------------- |
etc/ |
Scripts, editors support, misc |
NOTE: This list (especially the second part of the table which contains modules and libraries) is highly volatile and subject to change.