Restructure stdarch-gen-arm to use `Group`s with `Delimiter`s rather
than ad-hoc `Punct`s.
`Punct` should only be used to represent specific characters, and never
for bracket-like characters. Recent versions of `Punct::new` check this
with an assertion.
Note that there doesn't appear to be a way to emit a line break for
formatting reasons — `Punct::new('\n', ...)` no longer works — so this
also removes all blank lines between functions in the generated files.
This reflects the currently available set of sysctl values as of macOS 15, on 2024-12-21. Features not (yet) exposed by `is_aarch64_feature_detected` have been left in comments to document their existence for the future.
This is a resubmission of #1609 which was ruled optional but not
necessary at the time but it's now necessary. These weren't originally
applied as they weren't allowed in a `const` context but that's no
longer applicable. At the same time though be sure to add some small
tests to ensure that these intrinsics can be used in a `const` context.
Simiarly to other functions for `mm` and `mm256` register widths, the
first argument should be a pointer to the pointer type. See e.g.
`_mm256_store_si256` function.
The first rule of the `features` macro looks like this:
```
macro_rules! features {
(
@TARGET: $target:ident;
@CFG: $cfg:meta;
@MACRO_NAME: $macro_name:ident;
@MACRO_ATTRS: $(#[$macro_attrs:meta])*
$(@BIND_FEATURE_NAME: $bind_feature:tt; $feature_impl:tt; $(#[$deprecate_attr:meta];)?)*
$(@NO_RUNTIME_DETECTION: $nort_feature:tt; )*
$(@FEATURE: #[$stability_attr:meta] $feature:ident: $feature_lit:tt;
$(without cfg check: $feature_cfg_check:literal;)?
$(implied by target_features: [$($target_feature_lit:tt),*];)?
$(#[$feature_comment:meta])*)*
) => {
```
Notice all the `tt` specifiers. They are used because they are forwarded
to another macro. Only `ident`, `lifetime`, and `tt` specifiers can be
forwarded this way.
But there is an exception: `$feature_lit:tt`, which was added recently.
In theory it should cause an error like this:
```
error: no rules expected `literal` metavariable
--> /home/njn/dev/rust3/library/stdarch/crates/std_detect/src/detect/macros.rs:54:91
|
51 | / macro_rules! $macro_name {
52 | | $(
53 | | ($feature_lit) => {
54 | | $crate::detect_feature!($feature, $feature_lit $(, without cfg check: $feature_cfg_check)? ...
| | ^^^^^^^^^^^^^^^^^^ no rules expected this token in macro call
... |
88 | | };
89 | | }
| |_________- in this expansion of `is_x86_feature_detected!`
|
::: std/tests/run-time-detect.rs:145:27
|
145 | println!("tsc: {:?}", is_x86_feature_detected!("tsc"));
| ------------------------------- in this macro invocation
|
note: while trying to match keyword `true`
--> /home/njn/dev/rust3/library/stdarch/crates/std_detect/src/detect/macros.rs:12:55
|
12 | ($feature:tt, $feature_lit:tt, without cfg check: true) => {
| ^^^^
= note: captured metavariables except for `:tt`, `:ident` and `:lifetime` cannot be compared to other tokens
= note: see <https://doc.rust-lang.org/nightly/reference/macros-by-example.html#forwarding-a-matched-fragment> for more information
```
(The URL at the end of the error has more details about this forwarding
limitation.)
In practice it doesn't cause this error. I'm not sure why, but the
existing macro implementation in rustc is far from perfect, so it's
believable that it does the wrong thing here.
Why does this matter? Because https://github.com/rust-lang/rust/pull/124141
is modifying the macro implementation, and when that PR is applied the
error *does* occur. (It's one of several cases I have found where the
existing compiler accepts code it shouldn't, but #124141 causes that
code to be rejected.)
Fortunately the fix is simple: replace the `literal` specifier with `tt`.
