Specialize some methods of `io::Chain`
This PR specializes the implementation of some methods of `io::Chain`, which could bring performance improvements when using it.
Portable SIMD subtree update
Syncs nightly to the latest changes from rust-lang/portable-simd
r? `@rust-lang/libs`
Also, fixes#119904 which is now fixed upstream.
Reduce monomorphisation bloat in small_c_string
This is a code path usually next to an FFI call, so taking the `dyn` slowdown for the 1159 llvm-line (fat lto, codegen-units 1, release build) drop in my testing program [t2fanrd](https://github.com/GnomedDev/t2fanrd) is worth it imo.
Remove unnecessary unit binding
It appears that the unit binding is not necessary at this time. However, I am unsure of its importance in the past. Please let me know if it is unsafe to remove.
Move `OsStr::slice_encoded_bytes` validation to platform modules
This delegates OS string slicing (`OsStr::slice_encoded_bytes`) validation to the underlying platform implementation. For now that results in increased performance and better error messages on Windows without any changes to semantics. In the future we may want to provide different semantics for different platforms.
The existing implementation is still used on Unix and most other platforms and is now optimized a little better.
Tracking issue: https://github.com/rust-lang/rust/issues/118485
cc `@epage,` `@BurntSushi`
Tracking import use types for more accurate redundant import checking
fixes#117448
By tracking import use types to check whether it is scope uses or the other situations like module-relative uses, we can do more accurate redundant import checking.
For example unnecessary imports in std::prelude that can be eliminated:
```rust
use std::option::Option::Some;//~ WARNING the item `Some` is imported redundantly
use std::option::Option::None; //~ WARNING the item `None` is imported redundantly
```
fixes#117448
For example unnecessary imports in std::prelude that can be eliminated:
```rust
use std::option::Option::Some;//~ WARNING the item `Some` is imported redundantly
use std::option::Option::None; //~ WARNING the item `None` is imported redundantly
```
Fix typo in VecDeque::handle_capacity_increase() doc comment.
Strategies B and C both show a full buffer before the capacity increase, while strategy A had one empty element left. Filled the last element in.
Don't use mem::zeroed in vec::IntoIter
`mem::zeroed` is not a trivial function. Maybe it was once, but now it involves multiple locals, copies, and an intrinsic that gets monomorphized into a call to `panic_nounwind` for iterators of types like `Vec<&T>`. Of course all that complexity is trivially optimized out, but generating a bunch of IR where we don't need to just so we can optimize it away later is silly.
Add examples to document the return type of quickselect functions
Currently, `select_nth_unstable`, `select_nth_unstable_by`, and `select_nth_unstable_by_key`'s examples do not show how to use the return values of the functions in an example, so this PR adds that in.
Note: I didn't know what to call the parameters, so I settled on lesser, median, greater because the example is used for median finding so I retained that naming for the pivot, but lesser and greater are poor names for the example that sorts in descending order, because lesser and greater are then flipped.
I think it's common to say "lo" and "hi" for low and high respectively, but that's also not great when the comparator flips the elements. Otherwise, "left" and "right" are also commonly used but I think that's poor naming because some languages read right to left so those names are also unintuitive.
Lesser and greater are also not that great but I found a test that used `less`, `equal`, `greater` so I took that: dfa88b328f/library/core/tests/slice.rs (L1962)
Use a hardcoded constant instead of calling OpenProcessToken.
Now that Win 7 support is dropped, we can resurrect #90144.
GetCurrentProcessToken is defined in processthreadsapi.h as:
FORCEINLINE
HANDLE
GetCurrentProcessToken (
VOID
)
{
return (HANDLE)(LONG_PTR) -4;
}
Since it's very unlikely that this constant will ever change, let's just use it instead of making calls to get the same information.
Make `io::BorrowedCursor::advance` safe
This also keeps the old `advance` method under `advance_unchecked` name.
This makes pattern like `std::io::default_read_buf` safe to write.
Now that Win 7 support is dropped, we can resurrect #90144.
GetCurrentProcessToken is defined in processthreadsapi.h as:
FORCEINLINE
HANDLE
GetCurrentProcessToken (
VOID
)
{
return (HANDLE)(LONG_PTR) -4;
}
Since it's very unlikely that this constant will ever change, let's just use it instead of making calls to get the same information.
Rename MaybeUninit::write_slice
A step to push #79995 forward.
https://github.com/rust-lang/libs-team/issues/122 also suggested to make them inherent methods, but they can't be — they'd conflict with slice's regular methods.
Implement intrinsics with fallback bodies
fixes#93145 (though we can port many more intrinsics)
cc #63585
The way this works is that the backend logic for generating custom code for intrinsics has been made fallible. The only failure path is "this intrinsic is unknown". The `Instance` (that was `InstanceDef::Intrinsic`) then gets converted to `InstanceDef::Item`, which represents the fallback body. A regular function call to that body is then codegenned. This is currently implemented for
* codegen_ssa (so llvm and gcc)
* codegen_cranelift
other backends will need to adjust, but they can just keep doing what they were doing if they prefer (though adding new intrinsics to the compiler will then require them to implement them, instead of getting the fallback body).
cc `@scottmcm` `@WaffleLapkin`
### todo
* [ ] miri support
* [x] default intrinsic name to name of function instead of requiring it to be specified in attribute
* [x] make sure that the bodies are always available (must be collected for metadata)
doc: add note about panicking examples for strict_overflow_ops
The first commit adds a note before the panicking examples for strict_overflow_ops to make it clearer that the following examples should panic and why, without needing the reader to hover the mouse over the information icon.
The second commit adds panicking examples for division by zero operations for strict division operations on unsigned numbers. The signed numbers already have two panicking examples each: one for division by zero and one for overflowing division (`MIN/-1`); this commit includes the division by zero examples for the unsigned numbers.
