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compute required_consts before promotion, and add promoteds that may fail

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This commit is contained in:
Ralf Jung 2024-03-12 18:15:58 +01:00
parent 7183fa09bb
commit b2b617a88e
4 changed files with 44 additions and 68 deletions
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17
compiler/rustc_mir_transform/src/lib.rs
View file

@ -333,6 +333,15 @@ fn mir_promoted(
body.tainted_by_errors = Some(error_reported);
}
// Collect `required_consts` *before* promotion, so if there are any consts being promoted
// we still add them to the list in the outer MIR body.
let mut required_consts = Vec::new();
let mut required_consts_visitor = RequiredConstsVisitor::new(&mut required_consts);
for (bb, bb_data) in traversal::reverse_postorder(&body) {
required_consts_visitor.visit_basic_block_data(bb, bb_data);
}
body.required_consts = required_consts;
// What we need to run borrowck etc.
let promote_pass = promote_consts::PromoteTemps::default();
pm::run_passes(
@ -342,14 +351,6 @@ fn mir_promoted(
Some(MirPhase::Analysis(AnalysisPhase::Initial)),
);
// Promotion generates new consts; we run this after promotion to ensure they are accounted for.
let mut required_consts = Vec::new();
let mut required_consts_visitor = RequiredConstsVisitor::new(&mut required_consts);
for (bb, bb_data) in traversal::reverse_postorder(&body) {
required_consts_visitor.visit_basic_block_data(bb, bb_data);
}
body.required_consts = required_consts;
let promoted = promote_pass.promoted_fragments.into_inner();
(tcx.alloc_steal_mir(body), tcx.alloc_steal_promoted(promoted))
}

49
compiler/rustc_mir_transform/src/promote_consts.rs
View file

@ -688,7 +688,6 @@ fn validate_call(
}
}
// FIXME(eddyb) remove the differences for promotability in `static`, `const`, `const fn`.
fn validate_candidates(
ccx: &ConstCx<'_, '_>,
temps: &mut IndexSlice<Local, TempState>,
@ -713,6 +712,10 @@ struct Promoter<'a, 'tcx> {
/// If true, all nested temps are also kept in the
/// source MIR, not moved to the promoted MIR.
keep_original: bool,
/// If true, add the new const (the promoted) to the required_consts of the parent MIR.
/// This is initially false and then set by the visitor when it encounters a `Call` terminator.
add_to_required: bool,
}
impl<'a, 'tcx> Promoter<'a, 'tcx> {
@ -815,6 +818,10 @@ fn promote_temp(&mut self, temp: Local) -> Local {
TerminatorKind::Call {
mut func, mut args, call_source: desugar, fn_span, ..
} => {
// This promoted involves a function call, so it may fail to evaluate.
// Let's make sure it is added to `required_consts` so that that failure cannot get lost.
self.add_to_required = true;
self.visit_operand(&mut func, loc);
for arg in &mut args {
self.visit_operand(&mut arg.node, loc);
@ -849,7 +856,7 @@ fn promote_temp(&mut self, temp: Local) -> Local {
fn promote_candidate(mut self, candidate: Candidate, next_promoted_id: usize) -> Body<'tcx> {
let def = self.source.source.def_id();
let mut rvalue = {
let (mut rvalue, promoted_op) = {
let promoted = &mut self.promoted;
let promoted_id = Promoted::new(next_promoted_id);
let tcx = self.tcx;
@ -859,11 +866,7 @@ fn promote_candidate(mut self, candidate: Candidate, next_promoted_id: usize) ->
let args = tcx.erase_regions(GenericArgs::identity_for_item(tcx, def));
let uneval = mir::UnevaluatedConst { def, args, promoted: Some(promoted_id) };
Operand::Constant(Box::new(ConstOperand {
span,
user_ty: None,
const_: Const::Unevaluated(uneval, ty),
}))
ConstOperand { span, user_ty: None, const_: Const::Unevaluated(uneval, ty) }
};
let blocks = self.source.basic_blocks.as_mut();
@ -896,22 +899,26 @@ fn promote_candidate(mut self, candidate: Candidate, next_promoted_id: usize) ->
let promoted_ref = local_decls.push(promoted_ref);
assert_eq!(self.temps.push(TempState::Unpromotable), promoted_ref);
let promoted_operand = promoted_operand(ref_ty, span);
let promoted_ref_statement = Statement {
source_info: statement.source_info,
kind: StatementKind::Assign(Box::new((
Place::from(promoted_ref),
Rvalue::Use(promoted_operand(ref_ty, span)),
Rvalue::Use(Operand::Constant(Box::new(promoted_operand))),
))),
};
self.extra_statements.push((loc, promoted_ref_statement));
Rvalue::Ref(
tcx.lifetimes.re_erased,
*borrow_kind,
Place {
local: mem::replace(&mut place.local, promoted_ref),
projection: List::empty(),
},
(
Rvalue::Ref(
tcx.lifetimes.re_erased,
*borrow_kind,
Place {
local: mem::replace(&mut place.local, promoted_ref),
projection: List::empty(),
},
),
promoted_operand,
)
};
@ -923,6 +930,12 @@ fn promote_candidate(mut self, candidate: Candidate, next_promoted_id: usize) ->
let span = self.promoted.span;
self.assign(RETURN_PLACE, rvalue, span);
// Now that we did promotion, we know whether we'll want to add this to `required_consts`.
if self.add_to_required {
self.source.required_consts.push(promoted_op);
}
self.promoted
}
}
@ -982,6 +995,11 @@ fn promote_candidates<'tcx>(
None,
body.tainted_by_errors,
);
// We keep `required_consts` of the new MIR body empty. All consts mentioned here have
// already been added to the parent MIR's `required_consts` (that is computed before
// promotion), and no matter where this promoted const ends up, our parent MIR must be
// somewhere in the reachable dependency chain so we can rely on its required consts being
// evaluated.
promoted.phase = MirPhase::Analysis(AnalysisPhase::Initial);
let promoter = Promoter {
@ -991,6 +1009,7 @@ fn promote_candidates<'tcx>(
temps: &mut temps,
extra_statements: &mut extra_statements,
keep_original: false,
add_to_required: false,
};
let mut promoted = promoter.promote_candidate(candidate, promotions.len());

4
tests/ui/rfcs/rfc-1623-static/rfc1623-2.rs
View file

@ -28,10 +28,6 @@ fn id<T>(t: T) -> T {
f: &id,
//~^ ERROR mismatched types
//~| ERROR mismatched types
//~| ERROR mismatched types
//~| ERROR mismatched types
//~| ERROR implementation of `Fn` is not general enough
//~| ERROR implementation of `Fn` is not general enough
//~| ERROR implementation of `Fn` is not general enough
//~| ERROR implementation of `Fn` is not general enough
};

42
tests/ui/rfcs/rfc-1623-static/rfc1623-2.stderr
View file

@ -34,45 +34,5 @@ LL | f: &id,
= note: `fn(&Foo<'2>) -> &Foo<'2> {id::<&Foo<'2>>}` must implement `FnOnce<(&'a Foo<'1>,)>`, for any lifetime `'1`...
= note: ...but it actually implements `FnOnce<(&Foo<'2>,)>`, for some specific lifetime `'2`
error[E0308]: mismatched types
--> $DIR/rfc1623-2.rs:28:8
|
LL | f: &id,
| ^^^ one type is more general than the other
|
= note: expected trait `for<'a, 'b> Fn(&'a Foo<'b>)`
found trait `Fn(&Foo<'_>)`
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
error[E0308]: mismatched types
--> $DIR/rfc1623-2.rs:28:8
|
LL | f: &id,
| ^^^ one type is more general than the other
|
= note: expected trait `for<'a, 'b> Fn(&'a Foo<'b>)`
found trait `Fn(&Foo<'_>)`
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
error: implementation of `FnOnce` is not general enough
--> $DIR/rfc1623-2.rs:28:8
|
LL | f: &id,
| ^^^ implementation of `FnOnce` is not general enough
|
= note: `fn(&'2 Foo<'_>) -> &'2 Foo<'_> {id::<&'2 Foo<'_>>}` must implement `FnOnce<(&'1 Foo<'b>,)>`, for any lifetime `'1`...
= note: ...but it actually implements `FnOnce<(&'2 Foo<'_>,)>`, for some specific lifetime `'2`
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
error: implementation of `FnOnce` is not general enough
--> $DIR/rfc1623-2.rs:28:8
|
LL | f: &id,
| ^^^ implementation of `FnOnce` is not general enough
|
= note: `fn(&Foo<'2>) -> &Foo<'2> {id::<&Foo<'2>>}` must implement `FnOnce<(&'a Foo<'1>,)>`, for any lifetime `'1`...
= note: ...but it actually implements `FnOnce<(&Foo<'2>,)>`, for some specific lifetime `'2`
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
error: aborting due to 8 previous errors
error: aborting due to 4 previous errors