Since #24783, the style guidelines recommend that unit tests should live in a submodule `tests` rather than `test` to not clash with the possible use of libtest. This is especially important for benchmark tests as they require libtest. Fixes#24923.
`call_once` guarantees that there is a happens-before relationship between its closure and code following it via the sequentially consistent atomic store/loads of `self.cnt`.
This error indicates that a constant references itself.
All constants need to resolve to a value in an acyclic manner.
For example, neither of the following can be sensibly compiled:
```
const X: u32 = X;
```
```
const X: u32 = Y;
const Y: u32 = X;
```
These are useful when you want to catch the signals, like when you're making a kernel, or if you just don't want the overhead. (I don't know if there are any of the second kind of people, I don't think it's a good idea, but hey, choice is good).
Currently, LLVM lowers a cttz8 on x86_64 to these instructions:
```asm
movzbl %dil, %eax
bsfl %eax, %eax
movl $32, %ecx
cmovnel %eax, %ecx
cmpl $32, %ecx
movl $8, %eax
cmovnel %ecx, %eax
```
To improve the codegen, we can zero extend the 8 bit integer, then set
bit 8 and perform a cttz operation on the extended value. That way
there's no conditional operation involved at all.
This was discovered by this benchmark: https://github.com/Kimundi/long_strings_without_repeats
Timings on my box with the current nightly:
```
running 4 tests
test bench_cpp_naive_big ... bench: 5479222 ns/iter (+/- 254222)
test bench_noop_big ... bench: 571405 ns/iter (+/- 111950)
test bench_rust_naive_big ... bench: 7798102 ns/iter (+/- 148841)
test bench_rust_unsafe_big ... bench: 6606488 ns/iter (+/- 67529)
```
Timings with the patch applied:
```
running 4 tests
test bench_cpp_naive_big ... bench: 5470944 ns/iter (+/- 7109)
test bench_noop_big ... bench: 568944 ns/iter (+/- 6895)
test bench_rust_naive_big ... bench: 6795901 ns/iter (+/- 43806)
test bench_rust_unsafe_big ... bench: 5584879 ns/iter (+/- 5291)
```
This commit is an implementation of [RFC 1044][rfc] which adds additional
surface area to the `std::fs` module. All new APIs are `#[unstable]` behind
assorted feature names for each one.
[rfc]: https://github.com/rust-lang/rfcs/pull/1044
The new APIs added are:
* `fs::canonicalize` - bindings to `realpath` on unix and
`GetFinalPathNameByHandle` on windows.
* `fs::symlink_metadata` - similar to `lstat` on unix
* `fs::FileType` and accessor methods as `is_{file,dir,symlink}`
* `fs::Metadata::file_type` - accessor for the raw file type
* `fs::DirEntry::metadata` - acquisition of metadata which is free on Windows
but requires a syscall on unix.
* `fs::DirEntry::file_type` - access the file type which may not require a
syscall on most platforms.
* `fs::DirEntry::file_name` - access just the file name without leading
components.
* `fs::PathExt::symlink_metadata` - convenience method for the top-level
function.
* `fs::PathExt::canonicalize` - convenience method for the top-level
function.
* `fs::PathExt::read_link` - convenience method for the top-level
function.
* `fs::PathExt::read_dir` - convenience method for the top-level
function.
* `std::os::raw` - type definitions for raw OS/C types available on all
platforms.
* `std::os::$platform` - new modules have been added for all currently supported
platforms (e.g. those more specific than just `unix`).
* `std::os::$platform::raw` - platform-specific type definitions. These modules
are populated with the bare essentials necessary for lowing I/O types into
their raw representations, and currently largely consist of the `stat`
definition for unix platforms.
This commit also deprecates `Metadata::{modified, accessed}` in favor of
inspecting the raw representations via the lowering methods of `Metadata`.
Closes https://github.com/rust-lang/rust/issues/24796
```asm
movzbl %dil, %eax
bsfl %eax, %eax
movl $32, %ecx
cmovnel %eax, %ecx
cmpl $32, %ecx
movl $8, %eax
cmovnel %ecx, %eax
```
which has some unnecessary overhead, having two conditional moves.
To improve the codegen, we can zero extend the 8 bit integer, then set
bit 8 and perform a cttz operation on the extended value. That way
there's no conditional operation involved at all.
metdata: Fix zero-normalization of the pos of a `MultiByteChar`
Fix#24687
The source byte/character mappings for every crate track the collection of multi-characters from its source files specially. When we import the source information for another file into the current compilation unit, we assign its byte-positions unique values by shifting them all by a fixed adjustment, tracked in the `start_pos` field. But when we pull out the source span information for one function from one crate and into our own crate, we need to re-normalize the byte positions: subtracting the old `start_pos` and adding the new `start_pos`. The `new_imported_filemap(..)` method handles adding the new `start_pos`, so all `creader` needs to do is re-normalize each `pos` to zero.
It seems like it was indeed trying to do this, but it mistakenly added the old `start_pos` instead of subtracting it.
Since #24783, the style guidelines recommend that unit tests should live in a submodule `tests` rather than `test` to not clash with the possible use of libtest. This is especially important for benchmark tests as they require libtest. Fixes#24923.
There are still quite a few ignored Android tests kicking around, most of which were added in 445faca844, which has a pretty unfortunate commit message.
r? @alexcrichton
