Tracking issue: https://github.com/rust-lang/rust/issues/40180
This calling convention can be used for definining interrupt handlers on
32-bit and 64-bit x86 targets. The compiler then uses `iret` instead of
`ret` for returning and ensures that all registers are restored to their
original values.
Usage:
```
extern "x86-interrupt" fn handler(stack_frame: &ExceptionStackFrame) {…}
```
for interrupts and exceptions without error code and
```
extern "x86-interrupt" fn page_fault_handler(stack_frame: &ExceptionStackFrame,
error_code: u64) {…}
```
for exceptions that push an error code (e.g., page faults or general
protection faults). The programmer must ensure that the correct version
is used for each interrupt.
For more details see the [LLVM PR][1] and the corresponding [proposal][2].
[1]: https://reviews.llvm.org/D15567
[2]: http://lists.llvm.org/pipermail/cfe-dev/2015-September/045171.html
