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