This is a documentation-only patch that standardizes the presentation of vector types like `u32x4` and mask types like `mask32x16`.
The reasoning behind the patch was as follows:
1. Standardized terminology should be preferred, so `element` instead of `value` and `SIMD vector` instead of `vector`. These terms appear in the rest of the documentation and tutorials.
2. Try to avoid situations where two numbers are next to each other. So `16 elements of 32 bits` instead of `16 32-bit elements`.
4. Try to anticipate what readers are looking for -- so state the full bit-width directly.
### Vector Types
- Before: Vector of 32 `i8` values
- After: A 256-bit SIMD vector with 32 elements of type `i8`.
### Mask Types
- Before: Vector of 16 16-bit masks
- After: A mask for SIMD vectors with 16 elements of 32 bits.
This updates the standard library's documentation to use the new syntax. The
documentation is worthwhile to update as it should be more idiomatic
(particularly for features like this, which are nice for users to get acquainted
with). The general codebase is likely more hassle than benefit to update: it'll
hurt git blame, and generally updates can be done by folks updating the code if
(and when) that makes things more readable with the new format.
A few places in the compiler and library code are updated (mostly just due to
already having been done when this commit was first authored).
Now that we are thoroughly embedded in libcore, we don't need these on by default.
Indeed, their presence may provide confusing results during integration attempts.
Sync portable-simd for bitmasks &c.
In the ideal case, where everything works easily and nothing has to be rearranged, it is as simple as:
- `git subtree pull -P library/portable-simd https://github.com/rust-lang/portable-simd - ${branch}`
- write the commit message
- `python x.py test --stage 1` to make sure it runs
- `git push` to your PR-to-rustc branch
If anything borks up this flow, you can fix it with sufficient git wizardry but you are usually better off going back to the source, fixing it, and starting over, before you open the PR.
r? `@calebzulawski`
Another approach that fixesrust-lang/portable-simd#223, as an alternative to rust-lang/portable-simd#238.
This adds the `ToBitMask` trait, which is implemented on a vector for each bitmask type it supports. This includes all unsigned integers with enough bits to contain it. The byte array variant has been separated out for now into rust-lang/portable-simd#246 and still requires `generic_const_exprs`, but the integer variants no longer require it and can make it to nightly.
* Explain unsafe contracts of core::simd
This permeates the module with remarks on safety for pub methods,
layout of the Simd type, correct use of intrinsics, et cetera.
This is mostly to help others curious about how core::simd works,
including other Rust contributors, `unsafe` library authors,
and eventually ourselves.
Remove overflow panic from divrem and add basic docs to Simd<T, N>
This finishes normalizing Simd<T, N> to being approximately equivalent to Simd<Wrapping<T>, N> for all implemented operations I can think of. It also documents this fact, allowing this to closerust-lang/portable-simd#56.
