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Recognize discriminant reads as no-ops in RemoveNoopLandingPads #77793

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Oct 11, 2020
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Recognize discriminant reads as no-ops in RemoveNoopLandingPads #77793

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2 changes: 1 addition & 1 deletion compiler/rustc_mir/src/transform/remove_noop_landing_pads.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -43,7 +43,7 @@ impl RemoveNoopLandingPads {
// These are all nops in a landing pad
}

StatementKind::Assign(box (place, Rvalue::Use(_))) => {
StatementKind::Assign(box (place, Rvalue::Use(_) | Rvalue::Discriminant(_))) => {
if place.as_local().is_some() {
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I wonder how common it is to have writes to unprojected locals that are not drop flags along the cleanup path? Seems like we could ignore these as well.

// Writing to a local (e.g., a drop flag) does not
// turn a landing pad to a non-nop
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