1 files changed, 57 insertions, 0 deletions
diff --git a/vendor/portable-atomic/src/imp/interrupt/avr.rs b/vendor/portable-atomic/src/imp/interrupt/avr.rs
new file mode 100644
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--- /dev/null
+++ b/vendor/portable-atomic/src/imp/interrupt/avr.rs
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+// Adapted from https://github.com/Rahix/avr-device.
+//
+// Refs:
+// - AVR Instruction Set Manual https://ww1.microchip.com/downloads/en/DeviceDoc/AVR-InstructionSet-Manual-DS40002198.pdf
+
+#[cfg(not(portable_atomic_no_asm))]
+use core::arch::asm;
+
+pub(super) type State = u8;
+
+/// Disables interrupts and returns the previous interrupt state.
+#[inline]
+pub(super) fn disable() -> State {
+    let sreg: State;
+    // SAFETY: reading the status register (SREG) 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.
+        // Do not use `preserves_flags` because CLI modifies the I bit of the status register (SREG).
+        // Refs: https://ww1.microchip.com/downloads/en/DeviceDoc/AVR-InstructionSet-Manual-DS40002198.pdf#page=58
+        #[cfg(not(portable_atomic_no_asm))]
+        asm!(
+            "in {0}, 0x3F",
+            "cli",
+            out(reg) sreg,
+            options(nostack),
+        );
+        #[cfg(portable_atomic_no_asm)]
+        {
+            llvm_asm!("in $0, 0x3F" : "=r"(sreg) ::: "volatile");
+            llvm_asm!("cli" ::: "memory" : "volatile");
+        }
+    }
+    sreg
+}
+
+/// Restores the previous interrupt state.
+///
+/// # Safety
+///
+/// The state must be the one retrieved by the previous `disable`.
+#[inline]
+pub(super) unsafe fn restore(sreg: State) {
+    // SAFETY: the caller must guarantee that the state was retrieved by the previous `disable`,
+    unsafe {
+        // This clobbers the entire status register. See msp430.rs to safety on this.
+        //
+        // Do not use `nomem` and `readonly` because prevent preceding memory accesses from being reordered after interrupts are enabled.
+        // Do not use `preserves_flags` because OUT modifies the status register (SREG).
+        #[cfg(not(portable_atomic_no_asm))]
+        asm!("out 0x3F, {0}", in(reg) sreg, options(nostack));
+        #[cfg(portable_atomic_no_asm)]
+        llvm_asm!("out 0x3F, $0" :: "r"(sreg) : "memory" : "volatile");
+    }
+}