bjoernager/rust
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Clarify which kinds of MIR are allowed during which phases.

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This enhances documentation with these details and extends the validator to check these requirements
more thoroughly. As a part of this, we add a new `Deaggregated` phase, and rename other phases so
that their names more naturally correspond to what they represent.
This commit is contained in:
Jakob Degen 2022-03-05 20:37:04 -05:00
parent 547369d3d8
commit fe40240e4d
8 changed files with 98 additions and 52 deletions
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2
compiler/rustc_const_eval/src/transform/promote_consts.rs
View file

@ -42,7 +42,7 @@ pub struct PromoteTemps<'tcx> {
impl<'tcx> MirPass<'tcx> for PromoteTemps<'tcx> {
fn phase_change(&self) -> Option<MirPhase> {
Some(MirPhase::ConstPromotion)
Some(MirPhase::ConstsPromoted)
}
fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {

74
compiler/rustc_const_eval/src/transform/validate.rs
View file

@ -266,22 +266,15 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
);
}
}
// The deaggregator currently does not deaggreagate arrays.
// So for now, we ignore them here.
Rvalue::Aggregate(box AggregateKind::Array { .. }, _) => {}
// All other aggregates must be gone after some phases.
Rvalue::Aggregate(box kind, _) => {
if self.mir_phase > MirPhase::DropLowering
&& !matches!(kind, AggregateKind::Generator(..))
{
// Generators persist until the state machine transformation, but all
// other aggregates must have been lowered.
self.fail(
location,
format!("{:?} have been lowered to field assignments", rvalue),
)
} else if self.mir_phase > MirPhase::GeneratorLowering {
// No more aggregates after drop and generator lowering.
Rvalue::Aggregate(agg_kind, _) => {
let disallowed = match **agg_kind {
AggregateKind::Array(..) => false,
AggregateKind::Generator(..) => {
self.mir_phase >= MirPhase::GeneratorsLowered
}
_ => self.mir_phase >= MirPhase::Deaggregated,
};
if disallowed {
self.fail(
location,
format!("{:?} have been lowered to field assignments", rvalue),
@ -289,7 +282,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
}
}
Rvalue::Ref(_, BorrowKind::Shallow, _) => {
if self.mir_phase > MirPhase::DropLowering {
if self.mir_phase >= MirPhase::DropsLowered {
self.fail(
location,
"`Assign` statement with a `Shallow` borrow should have been removed after drop lowering phase",
@ -300,7 +293,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
}
}
StatementKind::AscribeUserType(..) => {
if self.mir_phase > MirPhase::DropLowering {
if self.mir_phase >= MirPhase::DropsLowered {
self.fail(
location,
"`AscribeUserType` should have been removed after drop lowering phase",
@ -308,7 +301,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
}
}
StatementKind::FakeRead(..) => {
if self.mir_phase > MirPhase::DropLowering {
if self.mir_phase >= MirPhase::DropsLowered {
self.fail(
location,
"`FakeRead` should have been removed after drop lowering phase",
@ -351,10 +344,18 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
self.fail(location, format!("bad arg ({:?} != usize)", op_cnt_ty))
}
}
StatementKind::SetDiscriminant { .. }
| StatementKind::StorageLive(..)
StatementKind::SetDiscriminant { .. } => {
if self.mir_phase < MirPhase::DropsLowered {
self.fail(location, "`SetDiscriminant` is not allowed until drop elaboration");
}
}
StatementKind::Retag(_, _) => {
// FIXME(JakobDegen) The validator should check that `self.mir_phase <
// DropsLowered`. However, this causes ICEs with generation of drop shims, which
// seem to fail to set their `MirPhase` correctly.
}
StatementKind::StorageLive(..)
| StatementKind::StorageDead(..)
| StatementKind::Retag(_, _)
| StatementKind::Coverage(_)
| StatementKind::Nop => {}
}
@ -424,10 +425,10 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
}
}
TerminatorKind::DropAndReplace { target, unwind, .. } => {
if self.mir_phase > MirPhase::DropLowering {
if self.mir_phase >= MirPhase::DropsLowered {
self.fail(
location,
"`DropAndReplace` is not permitted to exist after drop elaboration",
"`DropAndReplace` should have been removed during drop elaboration",
);
}
self.check_edge(location, *target, EdgeKind::Normal);
@ -494,7 +495,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
}
}
TerminatorKind::Yield { resume, drop, .. } => {
if self.mir_phase > MirPhase::GeneratorLowering {
if self.mir_phase >= MirPhase::GeneratorsLowered {
self.fail(location, "`Yield` should have been replaced by generator lowering");
}
self.check_edge(location, *resume, EdgeKind::Normal);
@ -503,10 +504,22 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
}
}
TerminatorKind::FalseEdge { real_target, imaginary_target } => {
if self.mir_phase >= MirPhase::DropsLowered {
self.fail(
location,
"`FalseEdge` should have been removed after drop elaboration",
);
}
self.check_edge(location, *real_target, EdgeKind::Normal);
self.check_edge(location, *imaginary_target, EdgeKind::Normal);
}
TerminatorKind::FalseUnwind { real_target, unwind } => {
if self.mir_phase >= MirPhase::DropsLowered {
self.fail(
location,
"`FalseUnwind` should have been removed after drop elaboration",
);
}
self.check_edge(location, *real_target, EdgeKind::Normal);
if let Some(unwind) = unwind {
self.check_edge(location, *unwind, EdgeKind::Unwind);
@ -520,12 +533,19 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
self.check_edge(location, *cleanup, EdgeKind::Unwind);
}
}
TerminatorKind::GeneratorDrop => {
if self.mir_phase >= MirPhase::GeneratorsLowered {
self.fail(
location,
"`GeneratorDrop` should have been replaced by generator lowering",
);
}
}
// Nothing to validate for these.
TerminatorKind::Resume
| TerminatorKind::Abort
| TerminatorKind::Return
| TerminatorKind::Unreachable
| TerminatorKind::GeneratorDrop => {}
| TerminatorKind::Unreachable => {}
}
self.super_terminator(terminator, location);