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// SPDX-License-Identifier: Apache-2.0 OR MIT
// Adapted from https://github.com/rust-embedded/cortex-m.
//
// Generated asm:
// - armv6-m https://godbolt.org/z/YxME38xcM
#[cfg(not(portable_atomic_no_asm))]
use core::arch::asm;
pub(super) use core::sync::atomic;
pub(super) type State = u32;
/// Disables interrupts and returns the previous interrupt state.
#[inline]
pub(super) fn disable() -> State {
let r: State;
// SAFETY: reading the priority mask register and disabling interrupts are safe.
// (see module-level comments of interrupt/mod.rs on the safety of using privileged instructions)
unsafe {
// Do not use `nomem` and `readonly` because prevent subsequent memory accesses from being reordered before interrupts are disabled.
asm!(
"mrs {0}, PRIMASK",
"cpsid i",
out(reg) r,
options(nostack, preserves_flags),
);
}
r
}
/// Restores the previous interrupt state.
///
/// # Safety
///
/// The state must be the one retrieved by the previous `disable`.
#[inline]
pub(super) unsafe fn restore(r: State) {
if r & 0x1 == 0 {
// SAFETY: the caller must guarantee that the state was retrieved by the previous `disable`,
// and we've checked that interrupts were enabled before disabling interrupts.
unsafe {
// Do not use `nomem` and `readonly` because prevent preceding memory accesses from being reordered after interrupts are enabled.
asm!("cpsie i", options(nostack, preserves_flags));
}
}
}
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