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// `SetDiscriminant` does not actually write anything if the chosen variant is the untagged variant
// of a niche encoding. However, it is UB to call `SetDiscriminant` with the untagged variant if the
// value currently encodes a different variant. Verify that we do correctly thread in this case.
//@ test-mir-pass: JumpThreading
#![feature(custom_mir)]
#![feature(core_intrinsics)]
use std::intrinsics::mir::*;
enum E<T> {
A,
B(T),
}
// EMIT_MIR set_no_discriminant.f.JumpThreading.diff
#[custom_mir(dialect = "runtime")]
pub fn f() -> usize {
// CHECK-LABEL: fn f(
// CHECK-NOT: switchInt
// CHECK: goto
// CHECK-NOT: switchInt
mir! {
let a: isize;
let e: E<char>;
{
e = E::A;
SetDiscriminant(e, 1); // UB!
a = Discriminant(e);
match a {
0 => bb0,
_ => bb1,
}
}
bb0 = {
RET = 0;
Return()
}
bb1 = {
RET = 1;
Return()
}
}
}
// EMIT_MIR set_no_discriminant.generic.JumpThreading.diff
#[custom_mir(dialect = "runtime")]
pub fn generic<T>() -> usize {
// CHECK-LABEL: fn generic(
// CHECK-NOT: switchInt
// CHECK: goto
// CHECK-NOT: switchInt
mir! {
let a: isize;
let e: E<T>;
{
e = E::A;
SetDiscriminant(e, 1); // UB!
a = Discriminant(e);
match a {
0 => bb0,
_ => bb1,
}
}
bb0 = {
RET = 0;
Return()
}
bb1 = {
RET = 1;
Return()
}
}
}
// CHECK-LABEL: fn main(
fn main() {
assert_eq!(f(), 0);
assert_eq!(generic::<char>(), 0);
}
|
