diff --git a/compiler/rustc_mir_transform/src/const_prop.rs b/compiler/rustc_mir_transform/src/const_prop.rs index 54899fd4db49..2de8079a4dfb 100644 --- a/compiler/rustc_mir_transform/src/const_prop.rs +++ b/compiler/rustc_mir_transform/src/const_prop.rs @@ -917,84 +917,80 @@ impl<'tcx> MutVisitor<'tcx> for ConstPropagator<'_, 'tcx> { trace!("visit_statement: {:?}", statement); let source_info = statement.source_info; self.source_info = Some(source_info); - if let StatementKind::Assign(box (place, ref mut rval)) = statement.kind { - let can_const_prop = self.ecx.machine.can_const_prop[place.local]; - if let Some(()) = self.const_prop(rval, place) { - // This will return None if the above `const_prop` invocation only "wrote" a - // type whose creation requires no write. E.g. a generator whose initial state - // consists solely of uninitialized memory (so it doesn't capture any locals). - if let Some(ref value) = self.get_const(place) && self.should_const_prop(value) { - trace!("replacing {:?} with {:?}", rval, value); - self.replace_with_const(rval, value, source_info); - if can_const_prop == ConstPropMode::FullConstProp - || can_const_prop == ConstPropMode::OnlyInsideOwnBlock - { - trace!("propagated into {:?}", place); - } - } - match can_const_prop { - ConstPropMode::OnlyInsideOwnBlock => { - trace!( - "found local restricted to its block. \ - Will remove it from const-prop after block is finished. Local: {:?}", - place.local - ); - } - ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => { - trace!("can't propagate into {:?}", place); - if place.local != RETURN_PLACE { - Self::remove_const(&mut self.ecx, place.local); + match statement.kind { + StatementKind::Assign(box (place, ref mut rval)) => { + let can_const_prop = self.ecx.machine.can_const_prop[place.local]; + if let Some(()) = self.const_prop(rval, place) { + // This will return None if the above `const_prop` invocation only "wrote" a + // type whose creation requires no write. E.g. a generator whose initial state + // consists solely of uninitialized memory (so it doesn't capture any locals). + if let Some(ref value) = self.get_const(place) && self.should_const_prop(value) { + trace!("replacing {:?} with {:?}", rval, value); + self.replace_with_const(rval, value, source_info); + if can_const_prop == ConstPropMode::FullConstProp + || can_const_prop == ConstPropMode::OnlyInsideOwnBlock + { + trace!("propagated into {:?}", place); } } - ConstPropMode::FullConstProp => {} - } - } else { - // Const prop failed, so erase the destination, ensuring that whatever happens - // from here on, does not know about the previous value. - // This is important in case we have - // ```rust - // let mut x = 42; - // x = SOME_MUTABLE_STATIC; - // // x must now be uninit - // ``` - // FIXME: we overzealously erase the entire local, because that's easier to - // implement. - trace!( - "propagation into {:?} failed. - Nuking the entire site from orbit, it's the only way to be sure", - place, - ); - Self::remove_const(&mut self.ecx, place.local); - } - } else { - match statement.kind { - StatementKind::SetDiscriminant { ref place, .. } => { - match self.ecx.machine.can_const_prop[place.local] { - ConstPropMode::FullConstProp | ConstPropMode::OnlyInsideOwnBlock => { - if self.use_ecx(|this| this.ecx.statement(statement)).is_some() { - trace!("propped discriminant into {:?}", place); - } else { + match can_const_prop { + ConstPropMode::OnlyInsideOwnBlock => { + trace!( + "found local restricted to its block. \ + Will remove it from const-prop after block is finished. Local: {:?}", + place.local + ); + } + ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => { + trace!("can't propagate into {:?}", place); + if place.local != RETURN_PLACE { Self::remove_const(&mut self.ecx, place.local); } } - ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => { + ConstPropMode::FullConstProp => {} + } + } else { + // Const prop failed, so erase the destination, ensuring that whatever happens + // from here on, does not know about the previous value. + // This is important in case we have + // ```rust + // let mut x = 42; + // x = SOME_MUTABLE_STATIC; + // // x must now be uninit + // ``` + // FIXME: we overzealously erase the entire local, because that's easier to + // implement. + trace!( + "propagation into {:?} failed. + Nuking the entire site from orbit, it's the only way to be sure", + place, + ); + Self::remove_const(&mut self.ecx, place.local); + } + } + StatementKind::SetDiscriminant { ref place, .. } => { + match self.ecx.machine.can_const_prop[place.local] { + ConstPropMode::FullConstProp | ConstPropMode::OnlyInsideOwnBlock => { + if self.use_ecx(|this| this.ecx.statement(statement)).is_some() { + trace!("propped discriminant into {:?}", place); + } else { Self::remove_const(&mut self.ecx, place.local); } } + ConstPropMode::OnlyPropagateInto | ConstPropMode::NoPropagation => { + Self::remove_const(&mut self.ecx, place.local); + } } - StatementKind::StorageLive(local) | StatementKind::StorageDead(local) => { - let frame = self.ecx.frame_mut(); - frame.locals[local].value = - if let StatementKind::StorageLive(_) = statement.kind { - LocalValue::Live(interpret::Operand::Immediate( - interpret::Immediate::Uninit, - )) - } else { - LocalValue::Dead - }; - } - _ => {} } + StatementKind::StorageLive(local) | StatementKind::StorageDead(local) => { + let frame = self.ecx.frame_mut(); + frame.locals[local].value = if let StatementKind::StorageLive(_) = statement.kind { + LocalValue::Live(interpret::Operand::Immediate(interpret::Immediate::Uninit)) + } else { + LocalValue::Dead + }; + } + _ => {} } self.super_statement(statement, location);