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//@ compile-flags: -Copt-level=3
#![crate_type = "lib"]
// The bug here was that it was loading and storing the whole value.
// It's ok for it to load the discriminant,
// to preserve the UB from `unreachable_unchecked`,
// but it better only store the constant discriminant of `B`.
pub enum State {
A([u8; 753]),
B([u8; 753]),
}
// CHECK-LABEL: @update
#[no_mangle]
pub unsafe fn update(s: *mut State) {
// CHECK-NOT: alloca
// CHECK-NOT: load
// CHECK-NOT: store
// CHECK-NOT: memcpy
// CHECK-NOT: 75{{3|4}}
// CHECK: %[[TAG:.+]] = load i8, ptr %s, align 1
// CHECK-NEXT: trunc nuw i8 %[[TAG]] to i1
// CHECK-NOT: load
// CHECK-NOT: store
// CHECK-NOT: memcpy
// CHECK-NOT: 75{{3|4}}
// CHECK: store i8 1, ptr %s, align 1
// CHECK-NOT: load
// CHECK-NOT: store
// CHECK-NOT: memcpy
// CHECK-NOT: 75{{3|4}}
// CHECK: ret
let State::A(v) = s.read() else { std::hint::unreachable_unchecked() };
s.write(State::B(v));
}
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