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cjgillotcjgillot
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Merge if-let and match.
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‎compiler/rustc_mir_transform/src/const_prop.rs

Lines changed: 63 additions & 67 deletions
Original file line numberDiff line numberDiff line change
@@ -985,84 +985,80 @@ impl<'tcx> MutVisitor<'tcx> for ConstPropagator<'_, 'tcx> {
985985
trace!("visit_statement: {:?}", statement);
986986
let source_info = statement.source_info;
987987
self.source_info = Some(source_info);
988-
if let StatementKind::Assign(box (place, ref mut rval)) = statement.kind {
989-
let can_const_prop = self.ecx.machine.can_const_prop[place.local];
990-
if let Some(()) = self.const_prop(rval, place) {
991-
// This will return None if the above `const_prop` invocation only "wrote" a
992-
// type whose creation requires no write. E.g. a generator whose initial state
993-
// consists solely of uninitialized memory (so it doesn't capture any locals).
994-
if let Some(ref value) = self.get_const(place) && self.should_const_prop(value) {
995-
trace!("replacing {:?} with {:?}", rval, value);
996-
self.replace_with_const(rval, value, source_info);
997-
if can_const_prop == ConstPropMode::FullConstProp
998-
|| can_const_prop == ConstPropMode::OnlyInsideOwnBlock
999-
{
1000-
trace!("propagated into {:?}", place);
988+
match statement.kind {
989+
StatementKind::Assign(box (place, ref mut rval)) => {
990+
let can_const_prop = self.ecx.machine.can_const_prop[place.local];
991+
if let Some(()) = self.const_prop(rval, place) {
992+
// This will return None if the above `const_prop` invocation only "wrote" a
993+
// type whose creation requires no write. E.g. a generator whose initial state
994+
// consists solely of uninitialized memory (so it doesn't capture any locals).
995+
if let Some(ref value) = self.get_const(place) && self.should_const_prop(value) {
996+
trace!("replacing {:?} with {:?}", rval, value);
997+
self.replace_with_const(rval, value, source_info);
998+
if can_const_prop == ConstPropMode::FullConstProp
999+
|| can_const_prop == ConstPropMode::OnlyInsideOwnBlock
1000+
{
1001+
trace!("propagated into {:?}", place);
1002+
}
10011003
}
1002-
}
1003-
match can_const_prop {
1004-
ConstPropMode::OnlyInsideOwnBlock => {
1005-
trace!(
1006-
"found local restricted to its block. \
1004+
match can_const_prop {
1005+
ConstPropMode::OnlyInsideOwnBlock => {
1006+
trace!(
1007+
"found local restricted to its block. \
10071008
Will remove it from const-prop after block is finished. Local: {:?}",
1008-
place.local
1009-
);
1010-
}
1011-
ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => {
1012-
trace!("can't propagate into {:?}", place);
1013-
if place.local != RETURN_PLACE {
1014-
Self::remove_const(&mut self.ecx, place.local);
1009+
place.local
1010+
);
10151011
}
1016-
}
1017-
ConstPropMode::FullConstProp => {}
1018-
}
1019-
} else {
1020-
// Const prop failed, so erase the destination, ensuring that whatever happens
1021-
// from here on, does not know about the previous value.
1022-
// This is important in case we have
1023-
// ```rust
1024-
// let mut x = 42;
1025-
// x = SOME_MUTABLE_STATIC;
1026-
// // x must now be uninit
1027-
// ```
1028-
// FIXME: we overzealously erase the entire local, because that's easier to
1029-
// implement.
1030-
trace!(
1031-
"propagation into {:?} failed.
1032-
Nuking the entire site from orbit, it's the only way to be sure",
1033-
place,
1034-
);
1035-
Self::remove_const(&mut self.ecx, place.local);
1036-
}
1037-
} else {
1038-
match statement.kind {
1039-
StatementKind::SetDiscriminant { ref place, .. } => {
1040-
match self.ecx.machine.can_const_prop[place.local] {
1041-
ConstPropMode::FullConstProp | ConstPropMode::OnlyInsideOwnBlock => {
1042-
if self.use_ecx(|this| this.ecx.statement(statement)).is_some() {
1043-
trace!("propped discriminant into {:?}", place);
1044-
} else {
1012+
ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => {
1013+
trace!("can't propagate into {:?}", place);
1014+
if place.local != RETURN_PLACE {
10451015
Self::remove_const(&mut self.ecx, place.local);
10461016
}
10471017
}
1048-
ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => {
1049-
Self::remove_const(&mut self.ecx, place.local);
1050-
}
1018+
ConstPropMode::FullConstProp => {}
10511019
}
1020+
} else {
1021+
// Const prop failed, so erase the destination, ensuring that whatever happens
1022+
// from here on, does not know about the previous value.
1023+
// This is important in case we have
1024+
// ```rust
1025+
// let mut x = 42;
1026+
// x = SOME_MUTABLE_STATIC;
1027+
// // x must now be uninit
1028+
// ```
1029+
// FIXME: we overzealously erase the entire local, because that's easier to
1030+
// implement.
1031+
trace!(
1032+
"propagation into {:?} failed.
1033+
Nuking the entire site from orbit, it's the only way to be sure",
1034+
place,
1035+
);
1036+
Self::remove_const(&mut self.ecx, place.local);
10521037
}
1053-
StatementKind::StorageLive(local) | StatementKind::StorageDead(local) => {
1054-
let frame = self.ecx.frame_mut();
1055-
frame.locals[local].value =
1056-
if let StatementKind::StorageLive(_) = statement.kind {
1057-
LocalValue::Live(interpret::Operand::Immediate(
1058-
interpret::Immediate::Uninit,
1059-
))
1038+
}
1039+
StatementKind::SetDiscriminant { ref place, .. } => {
1040+
match self.ecx.machine.can_const_prop[place.local] {
1041+
ConstPropMode::FullConstProp | ConstPropMode::OnlyInsideOwnBlock => {
1042+
if self.use_ecx(|this| this.ecx.statement(statement)).is_some() {
1043+
trace!("propped discriminant into {:?}", place);
10601044
} else {
1061-
LocalValue::Dead
1062-
};
1045+
Self::remove_const(&mut self.ecx, place.local);
1046+
}
1047+
}
1048+
ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => {
1049+
Self::remove_const(&mut self.ecx, place.local);
1050+
}
10631051
}
1064-
_ => {}
10651052
}
1053+
StatementKind::StorageLive(local) | StatementKind::StorageDead(local) => {
1054+
let frame = self.ecx.frame_mut();
1055+
frame.locals[local].value = if let StatementKind::StorageLive(_) = statement.kind {
1056+
LocalValue::Live(interpret::Operand::Immediate(interpret::Immediate::Uninit))
1057+
} else {
1058+
LocalValue::Dead
1059+
};
1060+
}
1061+
_ => {}
10661062
}
10671063

10681064
self.super_statement(statement, location);

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