fs: copy: use copy_file_range on Linux
Linux 4.5 introduced a new system call [copy_file_range](http://man7.org/linux/man-pages/man2/copy_file_range.2.html) to copy data from one file to another.
This PR uses the new system call (if available). This has several advantages:
1. No need to constantly copy data from userspace to kernel space, if the buffer is small or the file is large
2. On some filesystems, like BTRFS, the kernel can leverage internal fs mechanisms for huge performance gains
3. Filesystems on the network dont need to copy data between the host and the client machine (they have to in the current read/write implementation)
I have created a small library that also implements the new system call for some huge performance gains here: https://github.com/nicokoch/fastcopy
Benchmark results are in the README
extend from_raw_parts docs for slices and strs to mention alignment requirement
The documentation for `str::from_raw_parts_mut` seems to not be visible because that method is private, bit I figured it could still be fixed. I also removed the reference to the no-longer-existing `str::from_raw_parts` while I was at it.
Alternatively, should I remove `str::from_raw_parts_mut` completely? it is only used in `str::split_at_mut`, where it might as well be inlined.
Add missing Wrapping methods, use doc_comment!
Re-opened version of #49393 . Finishing touches for #32463.
Note that this adds `Shl` and `Shr` implementations for `Wrapping<i128>` and `Wrapping<u128>`, which were previously missed. This is technically insta-stable, but I don't know why this would be a problem.
str::from_raw_parts has been removed long ago because it can be obtained via
str::from_utf8_unchecked and slice::from_raw_parts. The same goes for
str::from_raw_parts_mut.
operate on `HirId` instead of `NodeId` in `hir::Pat::each_binding`, and consequences of that
See #50928 for motivation.
Questions—
* Is #50928 actually a good idea as a plan of record, or is there some reason to keep `NodeId`s?
* Are the uses of `find_node_for_hir_id` in this initial submission OK (see the FIXME comments)?
* Can we bikeshed a better method names `struct_span_lint_hir` _&c._? (Coined in analogy to the `struct_span_lint_node` and `NodeId`, but it feels kind of semantically clunky.)
r? @michaelwoerister
Add simd math intrinsics and gather/scatter
This PR adds simd math intrinsics for floating-point vectors (sqrt, sin, cos, pow, exp, log, fma, abs, etc.) and the generic simd gather/scatter intrinsics.
Michael Woerister pointed out that `hir_to_node_id` (introduced in
August 2017's 28ddd7a4e) supersedes the functionality of
`find_node_for_hir_id` (just a hash lookup compared to that linear
search).
Changing the `each_binding` utility method to take the `HirId` of a
binding pattern rather than its `NodeId` seems like a modest first step
in support of the `HirId`ification initiative #50928. (The inspiration
for choosing this in particular came from the present author's previous
work on diagnostics issued during liveness analysis, which is the most
greatly affected module in this change.)
add suggestion applicabilities to librustc and libsyntax
A down payment on #50723. Interested in feedback on whether my `MaybeIncorrect` vs. `MachineApplicable` judgement calls are well-calibrated (and that we have a consensus on what this means).
r? @Manishearth
cc @killercup @estebank
