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Elaborate ShallowInitBox too.

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This commit is contained in:
Camille Gillot
2025-10-12 22:01:08 +00:00
parent 4ddbb60512
commit 51275e82c9
11 changed files with 260 additions and 148 deletions
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2
compiler/rustc_mir_transform/src/dataflow_const_prop.rs
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@@ -480,6 +480,7 @@ impl<'a, 'tcx> ConstAnalysis<'a, 'tcx> {
Rvalue::Discriminant(place) => state.get_discr(place.as_ref(), &self.map),
Rvalue::Use(operand) => return self.handle_operand(operand, state),
Rvalue::CopyForDeref(_) => bug!("`CopyForDeref` in runtime MIR"),
Rvalue::ShallowInitBox(..) => bug!("`ShallowInitBox` in runtime MIR"),
Rvalue::Ref(..) | Rvalue::RawPtr(..) => {
// We don't track such places.
return ValueOrPlace::TOP;
@@ -489,7 +490,6 @@ impl<'a, 'tcx> ConstAnalysis<'a, 'tcx> {
| Rvalue::Cast(..)
| Rvalue::BinaryOp(..)
| Rvalue::Aggregate(..)
| Rvalue::ShallowInitBox(..)
| Rvalue::WrapUnsafeBinder(..) => {
// No modification is possible through these r-values.
return ValueOrPlace::TOP;

97
compiler/rustc_mir_transform/src/elaborate_box_derefs.rs
View File

@@ -1,13 +1,16 @@
//! This pass transforms derefs of Box into a deref of the pointer inside Box.
//!
//! Box is not actually a pointer so it is incorrect to dereference it directly.
//!
//! `ShallowInitBox` being a device for drop elaboration to understand deferred assignment to box
//! contents, we do not need this any more on runtime MIR.
use rustc_abi::FieldIdx;
use rustc_hir::def_id::DefId;
use rustc_abi::{FieldIdx, VariantIdx};
use rustc_index::IndexVec;
use rustc_middle::mir::visit::MutVisitor;
use rustc_middle::mir::*;
use rustc_middle::span_bug;
use rustc_middle::ty::{Ty, TyCtxt};
use rustc_middle::ty::{self, Ty, TyCtxt};
use crate::patch::MirPatch;
@@ -15,12 +18,12 @@ use crate::patch::MirPatch;
fn build_ptr_tys<'tcx>(
tcx: TyCtxt<'tcx>,
pointee: Ty<'tcx>,
unique_did: DefId,
nonnull_did: DefId,
unique_def: ty::AdtDef<'tcx>,
nonnull_def: ty::AdtDef<'tcx>,
) -> (Ty<'tcx>, Ty<'tcx>, Ty<'tcx>) {
let args = tcx.mk_args(&[pointee.into()]);
let unique_ty = tcx.type_of(unique_did).instantiate(tcx, args);
let nonnull_ty = tcx.type_of(nonnull_did).instantiate(tcx, args);
let unique_ty = Ty::new_adt(tcx, unique_def, args);
let nonnull_ty = Ty::new_adt(tcx, nonnull_def, args);
let ptr_ty = Ty::new_imm_ptr(tcx, pointee);
(unique_ty, nonnull_ty, ptr_ty)
@@ -36,8 +39,8 @@ pub(super) fn build_projection<'tcx>(
struct ElaborateBoxDerefVisitor<'a, 'tcx> {
tcx: TyCtxt<'tcx>,
unique_did: DefId,
nonnull_did: DefId,
unique_def: ty::AdtDef<'tcx>,
nonnull_def: ty::AdtDef<'tcx>,
local_decls: &'a mut LocalDecls<'tcx>,
patch: MirPatch<'tcx>,
}
@@ -64,7 +67,7 @@ impl<'a, 'tcx> MutVisitor<'tcx> for ElaborateBoxDerefVisitor<'a, 'tcx> {
let source_info = self.local_decls[place.local].source_info;
let (unique_ty, nonnull_ty, ptr_ty) =
build_ptr_tys(tcx, boxed_ty, self.unique_did, self.nonnull_did);
build_ptr_tys(tcx, boxed_ty, self.unique_def, self.nonnull_def);
let ptr_local = self.patch.new_temp(ptr_ty, source_info.span);
@@ -86,6 +89,68 @@ impl<'a, 'tcx> MutVisitor<'tcx> for ElaborateBoxDerefVisitor<'a, 'tcx> {
self.super_place(place, context, location);
}
fn visit_statement(&mut self, stmt: &mut Statement<'tcx>, location: Location) {
self.super_statement(stmt, location);
let tcx = self.tcx;
let source_info = stmt.source_info;
if let StatementKind::Assign(box (_, ref mut rvalue)) = stmt.kind
&& let Rvalue::ShallowInitBox(ref mut mutptr_to_u8, pointee) = *rvalue
&& let ty::Adt(box_adt, box_args) = Ty::new_box(tcx, pointee).kind()
{
let args = tcx.mk_args(&[pointee.into()]);
let (unique_ty, nonnull_ty, ptr_ty) =
build_ptr_tys(tcx, pointee, self.unique_def, self.nonnull_def);
let adt_kind = |def: ty::AdtDef<'tcx>, args| {
Box::new(AggregateKind::Adt(def.did(), VariantIdx::ZERO, args, None, None))
};
let zst = |ty| {
Operand::Constant(Box::new(ConstOperand {
span: source_info.span,
user_ty: None,
const_: Const::zero_sized(ty),
}))
};
let constptr = self.patch.new_temp(ptr_ty, source_info.span);
self.patch.add_assign(
location,
constptr.into(),
Rvalue::Cast(CastKind::Transmute, mutptr_to_u8.clone(), ptr_ty),
);
let nonnull = self.patch.new_temp(nonnull_ty, source_info.span);
self.patch.add_assign(
location,
nonnull.into(),
Rvalue::Aggregate(
adt_kind(self.nonnull_def, args),
IndexVec::from_raw(vec![Operand::Move(constptr.into())]),
),
);
let unique = self.patch.new_temp(unique_ty, source_info.span);
let phantomdata_ty =
self.unique_def.non_enum_variant().fields[FieldIdx::ONE].ty(tcx, args);
self.patch.add_assign(
location,
unique.into(),
Rvalue::Aggregate(
adt_kind(self.unique_def, args),
IndexVec::from_raw(vec![Operand::Move(nonnull.into()), zst(phantomdata_ty)]),
),
);
let global_alloc_ty =
box_adt.non_enum_variant().fields[FieldIdx::ONE].ty(tcx, box_args);
*rvalue = Rvalue::Aggregate(
adt_kind(*box_adt, box_args),
IndexVec::from_raw(vec![Operand::Move(unique.into()), zst(global_alloc_ty)]),
);
}
}
}
pub(super) struct ElaborateBoxDerefs;
@@ -97,18 +162,22 @@ impl<'tcx> crate::MirPass<'tcx> for ElaborateBoxDerefs {
let unique_did = tcx.adt_def(def_id).non_enum_variant().fields[FieldIdx::ZERO].did;
let Some(nonnull_def) = tcx.type_of(unique_did).instantiate_identity().ty_adt_def() else {
let Some(unique_def) = tcx.type_of(unique_did).instantiate_identity().ty_adt_def() else {
span_bug!(tcx.def_span(unique_did), "expected Box to contain Unique")
};
let nonnull_did = nonnull_def.non_enum_variant().fields[FieldIdx::ZERO].did;
let nonnull_did = unique_def.non_enum_variant().fields[FieldIdx::ZERO].did;
let Some(nonnull_def) = tcx.type_of(nonnull_did).instantiate_identity().ty_adt_def() else {
span_bug!(tcx.def_span(nonnull_did), "expected Unique to contain Nonnull")
};
let patch = MirPatch::new(body);
let local_decls = &mut body.local_decls;
let mut visitor =
ElaborateBoxDerefVisitor { tcx, unique_did, nonnull_did, local_decls, patch };
ElaborateBoxDerefVisitor { tcx, unique_def, nonnull_def, local_decls, patch };
for (block, data) in body.basic_blocks.as_mut_preserves_cfg().iter_enumerated_mut() {
visitor.visit_basic_block_data(block, data);
@@ -131,7 +200,7 @@ impl<'tcx> crate::MirPass<'tcx> for ElaborateBoxDerefs {
new_projections.get_or_insert_with(|| base.projection.to_vec());
let (unique_ty, nonnull_ty, ptr_ty) =
build_ptr_tys(tcx, boxed_ty, unique_did, nonnull_did);
build_ptr_tys(tcx, boxed_ty, unique_def, nonnull_def);
new_projections.extend_from_slice(&build_projection(unique_ty, nonnull_ty));
// While we can't project into `NonNull<_>` in a basic block

6
compiler/rustc_mir_transform/src/gvn.rs
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@@ -1073,8 +1073,10 @@ impl<'body, 'a, 'tcx> VnState<'body, 'a, 'tcx> {
}
// Unsupported values.
Rvalue::ThreadLocalRef(..) | Rvalue::ShallowInitBox(..) => return None,
Rvalue::CopyForDeref(_) => bug!("`CopyForDeref` in runtime MIR"),
Rvalue::ThreadLocalRef(..) => return None,
Rvalue::CopyForDeref(_) | Rvalue::ShallowInitBox(..) => {
bug!("forbidden in runtime MIR: {rvalue:?}")
}
};
let ty = rvalue.ty(self.local_decls, self.tcx);
Some(self.insert(ty, value))

12
compiler/rustc_mir_transform/src/validate.rs
View File

@@ -656,7 +656,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
) {
match elem {
ProjectionElem::Deref
if self.body.phase >= MirPhase::Runtime(RuntimePhase::PostCleanup) =>
if self.body.phase >= MirPhase::Runtime(RuntimePhase::Initial) =>
{
let base_ty = place_ref.ty(&self.body.local_decls, self.tcx).ty;
@@ -1047,7 +1047,11 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
assert!(!adt_def.is_union());
let variant = &adt_def.variants()[idx];
if variant.fields.len() != fields.len() {
self.fail(location, "adt has the wrong number of initialized fields");
self.fail(location, format!(
"adt {def_id:?} has the wrong number of initialized fields, expected {}, found {}",
fields.len(),
variant.fields.len(),
));
}
for (src, dest) in std::iter::zip(fields, &variant.fields) {
let dest_ty = self
@@ -1250,6 +1254,10 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
}
}
Rvalue::ShallowInitBox(operand, _) => {
if self.body.phase >= MirPhase::Runtime(RuntimePhase::Initial) {
self.fail(location, format!("ShallowInitBox after ElaborateBoxDerefs"))
}
let a = operand.ty(&self.body.local_decls, self.tcx);
check_kinds!(a, "Cannot shallow init type {:?}", ty::RawPtr(..));
}