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Simplify verify_candidate_branch.

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Let chains are perfect for this kind of function.
This commit is contained in:
Nicholas Nethercote 2024-08-29 15:36:24 +10:00
parent ec6fe4e198
commit cc09ab3c75
1 changed files with 23 additions and 37 deletions
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60
compiler/rustc_mir_transform/src/early_otherwise_branch.rs
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@ -310,42 +310,28 @@ fn verify_candidate_branch<'tcx>(
) -> bool {
// In order for the optimization to be correct, the branch must...
// ...have exactly one statement
let [statement] = branch.statements.as_slice() else {
return false;
};
// ...assign the discriminant of `place` in that statement
let StatementKind::Assign(boxed) = &statement.kind else { return false };
let (discr_place, Rvalue::Discriminant(from_place)) = &**boxed else { return false };
if *from_place != place {
return false;
if let [statement] = branch.statements.as_slice()
// ...assign the discriminant of `place` in that statement
&& let StatementKind::Assign(boxed) = &statement.kind
&& let (discr_place, Rvalue::Discriminant(from_place)) = &**boxed
&& *from_place == place
// ...make that assignment to a local
&& discr_place.projection.is_empty()
// ...terminate on a `SwitchInt` that invalidates that local
&& let TerminatorKind::SwitchInt { discr: switch_op, targets, .. } =
&branch.terminator().kind
&& *switch_op == Operand::Move(*discr_place)
// ...fall through to `destination` if the switch misses
&& destination == targets.otherwise()
// ...have a branch for value `value`
&& let mut iter = targets.iter()
&& let Some((target_value, _)) = iter.next()
&& target_value == value
// ...and have no more branches
&& iter.next().is_none()
{
true
} else {
false
}
// ...make that assignment to a local
if discr_place.projection.len() != 0 {
return false;
}
// ...terminate on a `SwitchInt` that invalidates that local
let TerminatorKind::SwitchInt { discr: switch_op, targets, .. } = &branch.terminator().kind
else {
return false;
};
if *switch_op != Operand::Move(*discr_place) {
return false;
}
// ...fall through to `destination` if the switch misses
if destination != targets.otherwise() {
return false;
}
// ...have a branch for value `value`
let mut iter = targets.iter();
let Some((target_value, _)) = iter.next() else {
return false;
};
if target_value != value {
return false;
}
// ...and have no more branches
if let Some(_) = iter.next() {
return false;
}
true
}