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goto.rs
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goto.rs
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//@ only-x86_64
//@ run-pass
//@ needs-asm-support
#![deny(unreachable_code)]
#![feature(asm_goto)]
use std::arch::asm;
fn goto_fallthough() {
unsafe {
asm!(
"/* {} */",
label {
unreachable!();
}
)
}
}
fn goto_jump() {
unsafe {
let mut value = false;
asm!(
"jmp {}",
label {
value = true;
}
);
assert!(value);
}
}
// 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
/*
fn goto_out_fallthrough() {
unsafe {
let mut out: usize;
asm!(
"lea {}, [{} + 1]",
"/* {} */",
out(reg) out,
in(reg) 0x12345678usize,
label {
unreachable!();
}
);
assert_eq!(out, 0x12345679);
}
}
fn goto_out_jump() {
unsafe {
let mut value = false;
let mut out: usize;
asm!(
"lea {}, [{} + 1]",
"jmp {}",
out(reg) out,
in(reg) 0x12345678usize,
label {
value = true;
assert_eq!(out, 0x12345679);
}
);
assert!(value);
}
}
*/
fn goto_noreturn() {
unsafe {
let a;
asm!(
"jmp {}",
label {
a = 1;
},
options(noreturn)
);
assert_eq!(a, 1);
}
}
#[warn(unreachable_code)]
fn goto_noreturn_diverge() {
unsafe {
asm!(
"jmp {}",
label {
return;
},
options(noreturn)
);
unreachable!();
//~^ WARN unreachable statement
}
}
fn main() {
goto_fallthough();
goto_jump();
// goto_out_fallthrough();
// goto_out_jump();
goto_noreturn();
goto_noreturn_diverge();
}