69b71e4410
From `#[align]` -> `#[rustc_align]`. Attributes starting with `rustc`
are always perma-unstable and feature-gated by `feature(rustc_attrs)`.
See regression RUST-143834.
For the underlying problem where even introducing new feature-gated
unstable built-in attributes can break user code such as
```rs
macro_rules! align {
() => {
/* .. */
};
}
pub(crate) use align; // `use` here becomes ambiguous
```
refer to RUST-134963.
Since the `#[align]` attribute is still feature-gated by
`feature(fn_align)`, we can rename it as a mitigation. Note that
`#[rustc_align]` will obviously mean that current unstable user code
using `feature(fn_aling)` will need additionally `feature(rustc_attrs)`,
but this is a short-term mitigation to buy time, and is expected to be
changed to a better name with less collision potential.
See
<https://rust-lang.zulipchat.com/#narrow/channel/238009-t-compiler.2Fmeetings/topic/.5Bweekly.5D.202025-07-17/near/529290371>
where mitigation options were considered.
47 lines
1.2 KiB
Rust
47 lines
1.2 KiB
Rust
//@ compile-flags: -C no-prepopulate-passes -Copt-level=0 -Zmin-function-alignment=16
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//@ needs-asm-support
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//@ ignore-arm no "ret" mnemonic
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//@ ignore-wasm32 aligning functions is not currently supported on wasm (#143368)
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// FIXME(#82232, #143834): temporarily renamed to mitigate `#[align]` nameres ambiguity
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#![feature(rustc_attrs)]
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#![feature(fn_align)]
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#![crate_type = "lib"]
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// functions without explicit alignment use the global minimum
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//
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// CHECK: .balign 16
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#[no_mangle]
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#[unsafe(naked)]
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pub extern "C" fn naked_no_explicit_align() {
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core::arch::naked_asm!("ret")
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}
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// CHECK: .balign 16
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#[no_mangle]
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#[rustc_align(8)]
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#[unsafe(naked)]
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pub extern "C" fn naked_lower_align() {
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core::arch::naked_asm!("ret")
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}
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// CHECK: .balign 32
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#[no_mangle]
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#[rustc_align(32)]
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#[unsafe(naked)]
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pub extern "C" fn naked_higher_align() {
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core::arch::naked_asm!("ret")
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}
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// cold functions follow the same rules as other functions
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//
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// in GCC, the `-falign-functions` does not apply to cold functions, but
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// `-Zmin-function-alignment` applies to all functions.
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//
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// CHECK: .balign 16
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#[no_mangle]
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#[cold]
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#[unsafe(naked)]
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pub extern "C" fn no_explicit_align_cold() {
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core::arch::naked_asm!("ret")
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}
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