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Add asm goto support to asm! #119365

Merged
merged 13 commits into from
Mar 8, 2024
Merged

Add asm goto support to asm! #119365

merged 13 commits into from
Mar 8, 2024

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nbdd0121
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Tracking issue: #119364

This PR implements asm-goto support, using the syntax described in "future possibilities" section of RFC2873.

Currently I have only implemented the label part, not the fallthrough part (i.e. fallthrough is implicit). This doesn't reduce the expressive though, since you can use label-break to get arbitrary control flow or simply set a value and rely on jump threading optimisation to get the desired control flow. I can add that later if deemed necessary.

r? @Amanieu
cc @ojeda

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Dec 27, 2023
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rustbot commented Dec 27, 2023

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

Some changes occurred to the CTFE / Miri engine

cc @rust-lang/miri

This PR changes MIR

cc @oli-obk, @RalfJung, @JakobDegen, @davidtwco, @celinval, @vakaras

@nbdd0121 nbdd0121 mentioned this pull request Dec 27, 2023
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rustbot commented Dec 27, 2023

Some changes occurred in compiler/rustc_codegen_cranelift

cc @bjorn3

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rustbot commented Dec 28, 2023

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

Some changes occurred in compiler/rustc_codegen_gcc

cc @antoyo, @GuillaumeGomez

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This needs a page in the unstable book. It should contain everything that needs to be added to the inline asm page in the reference when this is eventually stabilized.

compiler/rustc_hir_typeck/src/expr.rs Outdated Show resolved Hide resolved
compiler/rustc_middle/src/mir/syntax.rs Show resolved Hide resolved
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compiler/rustc_codegen_llvm/src/asm.rs Show resolved Hide resolved
compiler/rustc_codegen_ssa/src/mir/block.rs Show resolved Hide resolved
}
```

The block must have unit type.
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This should be updated to clarify the behavior of diverging blocks, and how this interacts with noreturn.


// asm goto with outputs cause miscompilation in LLVM. UB can be triggered
// when outputs are used inside the label block when optimisation is enabled.
// See: https://github.com/llvm/llvm-project/issues/74483
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This is a blocker for stabilizing this feature.

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bors commented Jan 5, 2024

☔ The latest upstream changes (presumably #119621) made this pull request unmergeable. Please resolve the merge conflicts.

@Dylan-DPC Dylan-DPC added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Feb 20, 2024
@Amanieu Amanieu removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Feb 29, 2024
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RalfJung commented Mar 4, 2024

@bors r- (PR requeued by sync)

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Amanieu commented Mar 7, 2024

@bors r+

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bors commented Mar 7, 2024

📌 Commit 05a549b has been approved by Amanieu

It is now in the queue for this repository.

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Mar 7, 2024
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nbdd0121 commented Mar 7, 2024

Sorry, mistakenly committed library/stdarch..

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Amanieu commented Mar 7, 2024

@bors r+

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bors commented Mar 7, 2024

📌 Commit 0ee0f29 has been approved by Amanieu

It is now in the queue for this repository.

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Mar 8, 2024
Add asm goto support to `asm!`

Tracking issue: rust-lang#119364

This PR implements asm-goto support, using the syntax described in "future possibilities" section of [RFC2873](https://rust-lang.github.io/rfcs/2873-inline-asm.html#asm-goto).

Currently I have only implemented the `label` part, not the `fallthrough` part (i.e. fallthrough is implicit). This doesn't reduce the expressive though, since you can use label-break to get arbitrary control flow or simply set a value and rely on jump threading optimisation to get the desired control flow. I can add that later if deemed necessary.

r? `@Amanieu`
cc `@ojeda`
bors added a commit to rust-lang-ci/rust that referenced this pull request Mar 8, 2024
…iaskrgr

Rollup of 7 pull requests

Successful merges:

 - rust-lang#118623 (Improve std::fs::read_to_string example)
 - rust-lang#119365 (Add asm goto support to `asm!`)
 - rust-lang#120608 (Docs for std::ptr::slice_from_raw_parts)
 - rust-lang#121885 (Move generic `NonZero` `rustc_layout_scalar_valid_range_start` attribute to inner type.)
 - rust-lang#121938 (Fix quadratic behavior of repeated vectored writes)
 - rust-lang#122099 (Add  `#[inline]` to `BTreeMap::new` constructor)
 - rust-lang#122143 (PassWrapper: update for llvm/llvm-project@a3319371970b)

Failed merges:

 - rust-lang#122076 (Tweak the way we protect in-place function arguments in interpreters)

r? `@ghost`
`@rustbot` modify labels: rollup
bors added a commit to rust-lang-ci/rust that referenced this pull request Mar 8, 2024
…iaskrgr

Rollup of 8 pull requests

Successful merges:

 - rust-lang#118623 (Improve std::fs::read_to_string example)
 - rust-lang#119365 (Add asm goto support to `asm!`)
 - rust-lang#120608 (Docs for std::ptr::slice_from_raw_parts)
 - rust-lang#121832 (Add new Tier-3 target: `loongarch64-unknown-linux-musl`)
 - rust-lang#121938 (Fix quadratic behavior of repeated vectored writes)
 - rust-lang#122099 (Add  `#[inline]` to `BTreeMap::new` constructor)
 - rust-lang#122103 (Make TAITs and ATPITs capture late-bound lifetimes in scope)
 - rust-lang#122143 (PassWrapper: update for llvm/llvm-project@a3319371970b)

Failed merges:

 - rust-lang#122076 (Tweak the way we protect in-place function arguments in interpreters)

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit d774fbe into rust-lang:master Mar 8, 2024
11 checks passed
@rustbot rustbot added this to the 1.78.0 milestone Mar 8, 2024
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Mar 8, 2024
Rollup merge of rust-lang#119365 - nbdd0121:asm-goto, r=Amanieu

Add asm goto support to `asm!`

Tracking issue: rust-lang#119364

This PR implements asm-goto support, using the syntax described in "future possibilities" section of [RFC2873](https://rust-lang.github.io/rfcs/2873-inline-asm.html#asm-goto).

Currently I have only implemented the `label` part, not the `fallthrough` part (i.e. fallthrough is implicit). This doesn't reduce the expressive though, since you can use label-break to get arbitrary control flow or simply set a value and rely on jump threading optimisation to get the desired control flow. I can add that later if deemed necessary.

r? ``@Amanieu``
cc ``@ojeda``
bjorn3 pushed a commit to bjorn3/rust that referenced this pull request Mar 16, 2024
Add asm goto support to `asm!`

Tracking issue: rust-lang#119364

This PR implements asm-goto support, using the syntax described in "future possibilities" section of [RFC2873](https://rust-lang.github.io/rfcs/2873-inline-asm.html#asm-goto).

Currently I have only implemented the `label` part, not the `fallthrough` part (i.e. fallthrough is implicit). This doesn't reduce the expressive though, since you can use label-break to get arbitrary control flow or simply set a value and rely on jump threading optimisation to get the desired control flow. I can add that later if deemed necessary.

r? ``@Amanieu``
cc ``@ojeda``
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Mar 21, 2024
Add asm goto support to `asm!`

Tracking issue: rust-lang#119364

This PR implements asm-goto support, using the syntax described in "future possibilities" section of [RFC2873](https://rust-lang.github.io/rfcs/2873-inline-asm.html#asm-goto).

Currently I have only implemented the `label` part, not the `fallthrough` part (i.e. fallthrough is implicit). This doesn't reduce the expressive though, since you can use label-break to get arbitrary control flow or simply set a value and rely on jump threading optimisation to get the desired control flow. I can add that later if deemed necessary.

r? ``@Amanieu``
cc ``@ojeda``
ojeda added a commit to ojeda/linux that referenced this pull request Apr 1, 2024
This is the next upgrade to the Rust toolchain, from 1.77.1 to 1.78.0
(i.e. the latest) [1].

See the upgrade policy [2] and the comments on the first upgrade in
commit 3ed03f4 ("rust: upgrade to Rust 1.68.2").

# Unstable features

There have been no changes to the set of unstable features used in
our own code. Therefore, the only unstable features allowed to be used
outside the `kernel` crate is still `new_uninit`.

However, since we are finally dropping our `alloc` fork [3], all the
unstable features used by `alloc` (~30 language ones, ~60 library ones)
are not a concern anymore. This reduces the maintanance burden, increases
the chances of new compiler versions working without changes and gets
us closer to the goal of supporting several compiler versions.

It also means that, ignoring non-language/library features, we are
currently left with just the few language features needed to implement the
kernel `Arc`, the `new_uninit` library feature, the `compiler_builtins`
marker and the few `no_*` `cfg`s we pass when compiling `core`/`alloc`.

Please see [4] for details.

# Required changes

## LLVM's data layout

Rust 1.77.0 (i.e. the previous upgrade) introduced a check for matching
LLVM data layouts [5]. Then, Rust 1.78.0 upgraded LLVM's bundled major
version from 17 to 18 [6], which changed the data layout in x86 [7]. Thus
update the data layout in our custom target specification for x86 so
that the compiler does not complain about the mismatch:

    error: data-layout for target `target-5559158138856098584`,
    `e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128`,
    differs from LLVM target's `x86_64-linux-gnu` default layout,
    `e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128`

In the future, the goal is to drop the custom target specification
files. Meanwhile, if we want to support other LLVM versions used
in `rustc` (e.g. for LTO), we will need to add some extra logic
(e.g. conditional on LLVM's version, or extracting the data layout from
an existing built-in target specification).

## `unused_imports`

Rust's `unused_imports` lint covers both unused and redudant imports.
Now, in 1.78.0, the lint detects more cases of redundant imports [8].
Thus the previous commit cleaned them up.

## Clippy's `new_without_default`

Clippy now suggests to implement `Default` even when `new()` is `const`,
since `Default::default()` may call `const` functions even if it is not
`const` itself [9]. Thus the previous commit added the implementation.

# Other changes in Rust

Rust 1.78.0 introduces `feature(asm_goto)` [10] [11]. This feature was
discussed in the past [12].

Rust 1.78.0 introduced support for mutable pointers to Rust statics,
including a test case for the Linux kernel's `VTABLE` use case [13].

Rust 1.78.0 with debug assertions enabled (i.e. `-Cdebug-assertions=y`,
kernel's `CONFIG_RUST_DEBUG_ASSERTIONS=y`) will now always check all
unsafe preconditions, without a way to opt-out for particular cases [14].

Rust 1.78.0 also improved a couple issues we reported when giving feedback
for the new `--check-cfg` feature [15] [16].

# `alloc` upgrade and reviewing

As mentioned above, compiler upgrades will not update `alloc` anymore,
since we are dropping our `alloc` fork [3].

As a bonus, even if that series is not applied, the new compiler release
happens to build cleanly the existing `alloc` too (i.e. the previous
version's).

Link: https://github.com/rust-lang/rust/blob/stable/RELEASES.md#version-1770-2024-03-21 [1]
Link: https://rust-for-linux.com/rust-version-policy [2]
Link: https://lore.kernel.org/rust-for-linux/20240328013603.206764-1-wedsonaf@gmail.com/ [3]
Link: Rust-for-Linux#2 [4]
Link: rust-lang/rust#120062 [5]
Link: rust-lang/rust#120055 [6]
Link: https://reviews.llvm.org/D86310 [7]
Link: rust-lang/rust#117772 [8]
Link: rust-lang/rust-clippy#10903 [9]
Link: rust-lang/rust#119365 [10]
Link: rust-lang/rust#119364 [11]
Link: https://lore.kernel.org/rust-for-linux/ZWipTZysC2YL7qsq@Boquns-Mac-mini.home/ [12]
Link: rust-lang/rust#120932 [13]
Link: rust-lang/rust#120969 [14]
Link: rust-lang/rust#121202 [15]
Link: rust-lang/rust#121237 [16]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
ojeda added a commit to ojeda/linux that referenced this pull request Apr 1, 2024
This is the next upgrade to the Rust toolchain, from 1.77.1 to 1.78.0
(i.e. the latest) [1].

See the upgrade policy [2] and the comments on the first upgrade in
commit 3ed03f4 ("rust: upgrade to Rust 1.68.2").

# Unstable features

There have been no changes to the set of unstable features used in
our own code. Therefore, the only unstable features allowed to be used
outside the `kernel` crate is still `new_uninit`.

However, since we are finally dropping our `alloc` fork [3], all the
unstable features used by `alloc` (~30 language ones, ~60 library ones)
are not a concern anymore. This reduces the maintenance burden, increases
the chances of new compiler versions working without changes and gets
us closer to the goal of supporting several compiler versions.

It also means that, ignoring non-language/library features, we are
currently left with just the few language features needed to implement the
kernel `Arc`, the `new_uninit` library feature, the `compiler_builtins`
marker and the few `no_*` `cfg`s we pass when compiling `core`/`alloc`.

Please see [4] for details.

# Required changes

## LLVM's data layout

Rust 1.77.0 (i.e. the previous upgrade) introduced a check for matching
LLVM data layouts [5]. Then, Rust 1.78.0 upgraded LLVM's bundled major
version from 17 to 18 [6], which changed the data layout in x86 [7]. Thus
update the data layout in our custom target specification for x86 so
that the compiler does not complain about the mismatch:

    error: data-layout for target `target-5559158138856098584`,
    `e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128`,
    differs from LLVM target's `x86_64-linux-gnu` default layout,
    `e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128`

In the future, the goal is to drop the custom target specification
files. Meanwhile, if we want to support other LLVM versions used
in `rustc` (e.g. for LTO), we will need to add some extra logic
(e.g. conditional on LLVM's version, or extracting the data layout from
an existing built-in target specification).

## `unused_imports`

Rust's `unused_imports` lint covers both unused and redundant imports.
Now, in 1.78.0, the lint detects more cases of redundant imports [8].
Thus one of the previous patches cleaned them up.

## Clippy's `new_without_default`

Clippy now suggests to implement `Default` even when `new()` is `const`,
since `Default::default()` may call `const` functions even if it is not
`const` itself [9]. Thus one of the previous patches implemented it.

# Other changes in Rust

Rust 1.78.0 introduced `feature(asm_goto)` [10] [11]. This feature was
discussed in the past [12].

Rust 1.78.0 introduced support for mutable pointers to Rust statics,
including a test case for the Linux kernel's `VTABLE` use case [13].

Rust 1.78.0 with debug assertions enabled (i.e. `-Cdebug-assertions=y`,
kernel's `CONFIG_RUST_DEBUG_ASSERTIONS=y`) now always checks all unsafe
preconditions, without a way to opt-out for particular cases [14].

Rust 1.78.0 also improved a couple issues we reported when giving feedback
for the new `--check-cfg` feature [15] [16].

# `alloc` upgrade and reviewing

As mentioned above, compiler upgrades will not update `alloc` anymore,
since we are dropping our `alloc` fork [3].

Link: https://github.com/rust-lang/rust/blob/stable/RELEASES.md#version-1780-2024-05-02 [1]
Link: https://rust-for-linux.com/rust-version-policy [2]
Link: https://lore.kernel.org/rust-for-linux/20240328013603.206764-1-wedsonaf@gmail.com/ [3]
Link: Rust-for-Linux#2 [4]
Link: rust-lang/rust#120062 [5]
Link: rust-lang/rust#120055 [6]
Link: https://reviews.llvm.org/D86310 [7]
Link: rust-lang/rust#117772 [8]
Link: rust-lang/rust-clippy#10903 [9]
Link: rust-lang/rust#119365 [10]
Link: rust-lang/rust#119364 [11]
Link: https://lore.kernel.org/rust-for-linux/ZWipTZysC2YL7qsq@Boquns-Mac-mini.home/ [12]
Link: rust-lang/rust#120932 [13]
Link: rust-lang/rust#120969 [14]
Link: rust-lang/rust#121202 [15]
Link: rust-lang/rust#121237 [16]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
ojeda added a commit to ojeda/linux that referenced this pull request Apr 1, 2024
This is the next upgrade to the Rust toolchain, from 1.77.1 to 1.78.0
(i.e. the latest) [1].

See the upgrade policy [2] and the comments on the first upgrade in
commit 3ed03f4 ("rust: upgrade to Rust 1.68.2").

# Unstable features

There have been no changes to the set of unstable features used in
our own code. Therefore, the only unstable features allowed to be used
outside the `kernel` crate is still `new_uninit`.

However, since we are finally dropping our `alloc` fork [3], all the
unstable features used by `alloc` (~30 language ones, ~60 library ones)
are not a concern anymore. This reduces the maintenance burden, increases
the chances of new compiler versions working without changes and gets
us closer to the goal of supporting several compiler versions.

It also means that, ignoring non-language/library features, we are
currently left with just the few language features needed to implement the
kernel `Arc`, the `new_uninit` library feature, the `compiler_builtins`
marker and the few `no_*` `cfg`s we pass when compiling `core`/`alloc`.

Please see [4] for details.

# Required changes

## LLVM's data layout

Rust 1.77.0 (i.e. the previous upgrade) introduced a check for matching
LLVM data layouts [5]. Then, Rust 1.78.0 upgraded LLVM's bundled major
version from 17 to 18 [6], which changed the data layout in x86 [7]. Thus
update the data layout in our custom target specification for x86 so
that the compiler does not complain about the mismatch:

    error: data-layout for target `target-5559158138856098584`,
    `e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128`,
    differs from LLVM target's `x86_64-linux-gnu` default layout,
    `e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128`

In the future, the goal is to drop the custom target specifications.
Meanwhile, if we want to support other LLVM versions used in `rustc`
(e.g. for LTO), we will need to add some extra logic (e.g. conditional on
LLVM's version, or extracting the data layout from an existing built-in
target specification).

## `unused_imports`

Rust's `unused_imports` lint covers both unused and redundant imports.
Now, in 1.78.0, the lint detects more cases of redundant imports [8].
Thus one of the previous patches cleaned them up.

## Clippy's `new_without_default`

Clippy now suggests to implement `Default` even when `new()` is `const`,
since `Default::default()` may call `const` functions even if it is not
`const` itself [9]. Thus one of the previous patches implemented it.

# Other changes in Rust

Rust 1.78.0 introduced `feature(asm_goto)` [10] [11]. This feature was
discussed in the past [12].

Rust 1.78.0 introduced support for mutable pointers to Rust statics,
including a test case for the Linux kernel's `VTABLE` use case [13].

Rust 1.78.0 with debug assertions enabled (i.e. `-Cdebug-assertions=y`,
kernel's `CONFIG_RUST_DEBUG_ASSERTIONS=y`) now always checks all unsafe
preconditions, without a way to opt-out for particular cases [14].

Rust 1.78.0 also improved a couple issues we reported when giving feedback
for the new `--check-cfg` feature [15] [16].

# `alloc` upgrade and reviewing

As mentioned above, compiler upgrades will not update `alloc` anymore,
since we are dropping our `alloc` fork [3].

Link: https://github.com/rust-lang/rust/blob/stable/RELEASES.md#version-1780-2024-05-02 [1]
Link: https://rust-for-linux.com/rust-version-policy [2]
Link: https://lore.kernel.org/rust-for-linux/20240328013603.206764-1-wedsonaf@gmail.com/ [3]
Link: Rust-for-Linux#2 [4]
Link: rust-lang/rust#120062 [5]
Link: rust-lang/rust#120055 [6]
Link: https://reviews.llvm.org/D86310 [7]
Link: rust-lang/rust#117772 [8]
Link: rust-lang/rust-clippy#10903 [9]
Link: rust-lang/rust#119365 [10]
Link: rust-lang/rust#119364 [11]
Link: https://lore.kernel.org/rust-for-linux/ZWipTZysC2YL7qsq@Boquns-Mac-mini.home/ [12]
Link: rust-lang/rust#120932 [13]
Link: rust-lang/rust#120969 [14]
Link: rust-lang/rust#121202 [15]
Link: rust-lang/rust#121237 [16]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
ojeda added a commit to ojeda/linux that referenced this pull request May 5, 2024
This is the next upgrade to the Rust toolchain, from 1.77.1 to 1.78.0
(i.e. the latest) [1].

See the upgrade policy [2] and the comments on the first upgrade in
commit 3ed03f4 ("rust: upgrade to Rust 1.68.2").

It is much smaller than previous upgrades, since the `alloc` fork was
dropped in commit 9d0441b ("rust: alloc: remove our fork of the
`alloc` crate") [3].

# Unstable features

There have been no changes to the set of unstable features used in
our own code. Therefore, the only unstable features allowed to be used
outside the `kernel` crate is still `new_uninit`.

However, since we finally dropped our `alloc` fork [3], all the unstable
features used by `alloc` (~30 language ones, ~60 library ones) are not
a concern anymore. This reduces the maintenance burden, increases the
chances of new compiler versions working without changes and gets us
closer to the goal of supporting several compiler versions.

It also means that, ignoring non-language/library features, we are
currently left with just the few language features needed to implement the
kernel `Arc`, the `new_uninit` library feature, the `compiler_builtins`
marker and the few `no_*` `cfg`s we pass when compiling `core`/`alloc`.

Please see [4] for details.

# Required changes

## LLVM's data layout

Rust 1.77.0 (i.e. the previous upgrade) introduced a check for matching
LLVM data layouts [5]. Then, Rust 1.78.0 upgraded LLVM's bundled major
version from 17 to 18 [6], which changed the data layout in x86 [7]. Thus
update the data layout in our custom target specification for x86 so
that the compiler does not complain about the mismatch:

    error: data-layout for target `target-5559158138856098584`,
    `e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128`,
    differs from LLVM target's `x86_64-linux-gnu` default layout,
    `e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128`

In the future, the goal is to drop the custom target specifications.
Meanwhile, if we want to support other LLVM versions used in `rustc`
(e.g. for LTO), we will need to add some extra logic (e.g. conditional on
LLVM's version, or extracting the data layout from an existing built-in
target specification).

## `unused_imports`

Rust's `unused_imports` lint covers both unused and redundant imports.
Now, in 1.78.0, the lint detects more cases of redundant imports [8].
Thus one of the previous patches cleaned them up.

## Clippy's `new_without_default`

Clippy now suggests to implement `Default` even when `new()` is `const`,
since `Default::default()` may call `const` functions even if it is not
`const` itself [9]. Thus one of the previous patches implemented it.

# Other changes in Rust

Rust 1.78.0 introduced `feature(asm_goto)` [10] [11]. This feature was
discussed in the past [12].

Rust 1.78.0 introduced `feature(const_refs_to_static)` [13] to allow
referencing statics in constants and extended `feature(const_mut_refs)`
to allow raw mutable pointers in constants. Together, this should cover
the kernel's `VTABLE` use case. In fact, the implementation [14] in
upstream Rust added a test case for it [15].

Rust 1.78.0 with debug assertions enabled (i.e. `-Cdebug-assertions=y`,
kernel's `CONFIG_RUST_DEBUG_ASSERTIONS=y`) now always checks all unsafe
preconditions, though without a way to opt-out for particular cases [16].
It would be ideal to have a way to selectively disable certain checks
per-call site for this one (i.e. not just per check but for particular
instances of a check), even if the vast majority of the checks remain
in place [17].

Rust 1.78.0 also improved a couple issues we reported when giving feedback
for the new `--check-cfg` feature [18] [19].

# `alloc` upgrade and reviewing

As mentioned above, compiler upgrades will not update `alloc` anymore,
since we dropped our `alloc` fork [3].

Link: https://github.com/rust-lang/rust/blob/stable/RELEASES.md#version-1780-2024-05-02 [1]
Link: https://rust-for-linux.com/rust-version-policy [2]
Link: https://lore.kernel.org/rust-for-linux/20240328013603.206764-1-wedsonaf@gmail.com/ [3]
Link: Rust-for-Linux#2 [4]
Link: rust-lang/rust#120062 [5]
Link: rust-lang/rust#120055 [6]
Link: https://reviews.llvm.org/D86310 [7]
Link: rust-lang/rust#117772 [8]
Link: rust-lang/rust-clippy#10903 [9]
Link: rust-lang/rust#119365 [10]
Link: rust-lang/rust#119364 [11]
Link: https://lore.kernel.org/rust-for-linux/ZWipTZysC2YL7qsq@Boquns-Mac-mini.home/ [12]
Link: rust-lang/rust#119618 [13]
Link: rust-lang/rust#120932 [14]
Link: https://github.com/rust-lang/rust/pull/120932/files#diff-e6fc1622c46054cd46b1d225c5386c5554564b3b0fa8a03c2dc2d8627a1079d9 [15]
Link: rust-lang/rust#120969 [16]
Link: Rust-for-Linux#354 [17]
Link: rust-lang/rust#121202 [18]
Link: rust-lang/rust#121237 [19]
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20240401212303.537355-4-ojeda@kernel.org
[ Added a few more details and links I mentioned in the list. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
GuillaumeGomez pushed a commit to GuillaumeGomez/rust that referenced this pull request Jul 10, 2024
Add asm goto support to `asm!`

Tracking issue: rust-lang#119364

This PR implements asm-goto support, using the syntax described in "future possibilities" section of [RFC2873](https://rust-lang.github.io/rfcs/2873-inline-asm.html#asm-goto).

Currently I have only implemented the `label` part, not the `fallthrough` part (i.e. fallthrough is implicit). This doesn't reduce the expressive though, since you can use label-break to get arbitrary control flow or simply set a value and rely on jump threading optimisation to get the desired control flow. I can add that later if deemed necessary.

r? ``@Amanieu``
cc ``@ojeda``
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