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// unit-test: DataflowConstProp
#![feature(custom_mir, core_intrinsics, rustc_attrs)]
use std::intrinsics::mir::*;
enum E {
V1(i32),
V2(i32)
}
// EMIT_MIR enum.simple.DataflowConstProp.diff
fn simple() {
let e = E::V1(0);
let x = match e { E::V1(x) => x, E::V2(x) => x };
}
#[rustc_layout_scalar_valid_range_start(1)]
#[rustc_nonnull_optimization_guaranteed]
struct NonZeroUsize(usize);
// EMIT_MIR enum.mutate_discriminant.DataflowConstProp.diff
#[custom_mir(dialect = "runtime", phase = "post-cleanup")]
fn mutate_discriminant() -> u8 {
mir!(
let x: Option<NonZeroUsize>;
{
SetDiscriminant(x, 1);
// This assignment overwrites the niche in which the discriminant is stored.
place!(Field(Field(Variant(x, 1), 0), 0)) = 0_usize;
// So we cannot know the value of this discriminant.
let a = Discriminant(x);
match a {
0 => bb1,
_ => bad,
}
}
bb1 = {
RET = 1;
Return()
}
bad = {
RET = 2;
Unreachable()
}
)
}
// EMIT_MIR enum.multiple.DataflowConstProp.diff
fn multiple(x: bool, i: u8) {
let e = if x {
Some(i)
} else {
None
};
// The dataflow state must have:
// discriminant(e) => Top
// (e as Some).0 => Top
let x = match e { Some(i) => i, None => 0 };
// Therefore, `x` should be `Top` here, and no replacement shall happen.
let y = x;
}
fn main() {
simple();
mutate_discriminant();
multiple(false, 5);
}
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