bjoernager/rust
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Simplify code flow.

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This commit is contained in:
Camille GILLOT 2023-05-20 08:54:16 +00:00
parent 8356802862
commit cae0dc2833
2 changed files with 157 additions and 222 deletions
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1
compiler/rustc_mir_transform/src/lib.rs
View file

@ -1,5 +1,6 @@
#![deny(rustc::untranslatable_diagnostic)] #![deny(rustc::untranslatable_diagnostic)]
#![deny(rustc::diagnostic_outside_of_impl)] #![deny(rustc::diagnostic_outside_of_impl)]
#![feature(assert_matches)]
#![feature(box_patterns)] #![feature(box_patterns)]
#![feature(cow_is_borrowed)] #![feature(cow_is_borrowed)]
#![feature(decl_macro)] #![feature(decl_macro)]

378
compiler/rustc_mir_transform/src/promote_consts.rs
View file

@ -12,6 +12,7 @@
//! initialization and can otherwise silence errors, if //! initialization and can otherwise silence errors, if
//! move analysis runs after promotion on broken MIR. //! move analysis runs after promotion on broken MIR.
use either::{Left, Right};
use rustc_hir as hir; use rustc_hir as hir;
use rustc_middle::mir; use rustc_middle::mir;
use rustc_middle::mir::visit::{MutVisitor, MutatingUseContext, PlaceContext, Visitor}; use rustc_middle::mir::visit::{MutVisitor, MutatingUseContext, PlaceContext, Visitor};
@ -22,6 +23,7 @@ use rustc_span::Span;
use rustc_index::{Idx, IndexSlice, IndexVec}; use rustc_index::{Idx, IndexSlice, IndexVec};
use std::assert_matches::assert_matches;
use std::cell::Cell; use std::cell::Cell;
use std::{cmp, iter, mem}; use std::{cmp, iter, mem};
@ -116,41 +118,38 @@ impl<'tcx> Visitor<'tcx> for Collector<'_, 'tcx> {
let temp = &mut self.temps[index]; let temp = &mut self.temps[index];
debug!("visit_local: temp={:?}", temp); debug!("visit_local: temp={:?}", temp);
if *temp == TempState::Undefined { *temp = match *temp {
match context { TempState::Undefined => match context {
PlaceContext::MutatingUse(MutatingUseContext::Store) PlaceContext::MutatingUse(MutatingUseContext::Store)
| PlaceContext::MutatingUse(MutatingUseContext::Call) => { | PlaceContext::MutatingUse(MutatingUseContext::Call) => {
*temp = TempState::Defined { location, uses: 0, valid: Err(()) }; TempState::Defined { location, uses: 0, valid: Err(()) }
}
_ => TempState::Unpromotable,
},
TempState::Defined { ref mut uses, .. } => {
// We always allow borrows, even mutable ones, as we need
// to promote mutable borrows of some ZSTs e.g., `&mut []`.
let allowed_use = match context {
PlaceContext::MutatingUse(MutatingUseContext::Borrow)
| PlaceContext::NonMutatingUse(_) => true,
PlaceContext::MutatingUse(_) | PlaceContext::NonUse(_) => false,
};
debug!("visit_local: allowed_use={:?}", allowed_use);
if allowed_use {
*uses += 1;
return; return;
} }
_ => { /* mark as unpromotable below */ } TempState::Unpromotable
} }
} else if let TempState::Defined { uses, .. } = temp { _ => TempState::Unpromotable,
// We always allow borrows, even mutable ones, as we need };
// to promote mutable borrows of some ZSTs e.g., `&mut []`.
let allowed_use = match context {
PlaceContext::MutatingUse(MutatingUseContext::Borrow)
| PlaceContext::NonMutatingUse(_) => true,
PlaceContext::MutatingUse(_) | PlaceContext::NonUse(_) => false,
};
debug!("visit_local: allowed_use={:?}", allowed_use);
if allowed_use {
*uses += 1;
return;
}
/* mark as unpromotable below */
}
*temp = TempState::Unpromotable;
} }
fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) { fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
self.super_rvalue(rvalue, location); self.super_rvalue(rvalue, location);
match *rvalue { if let Rvalue::Ref(..) = *rvalue {
Rvalue::Ref(..) => { self.candidates.push(Candidate { location });
self.candidates.push(Candidate { location });
}
_ => {}
} }
} }
} }
@ -189,230 +188,165 @@ struct Unpromotable;
impl<'tcx> Validator<'_, 'tcx> { impl<'tcx> Validator<'_, 'tcx> {
fn validate_candidate(&mut self, candidate: Candidate) -> Result<(), Unpromotable> { fn validate_candidate(&mut self, candidate: Candidate) -> Result<(), Unpromotable> {
let loc = candidate.location; let Left(statement) = self.body.stmt_at(candidate.location) else { bug!() };
let statement = &self.body[loc.block].statements[loc.statement_index]; let Some((_, Rvalue::Ref(_, kind, place))) = statement.kind.as_assign() else { bug!() };
match &statement.kind {
StatementKind::Assign(box (_, Rvalue::Ref(_, kind, place))) => {
// We can only promote interior borrows of promotable temps (non-temps
// don't get promoted anyway).
self.validate_local(place.local)?;
// The reference operation itself must be promotable. // We can only promote interior borrows of promotable temps (non-temps
// (Needs to come after `validate_local` to avoid ICEs.) // don't get promoted anyway).
self.validate_ref(*kind, place)?; self.validate_local(place.local)?;
// We do not check all the projections (they do not get promoted anyway), // The reference operation itself must be promotable.
// but we do stay away from promoting anything involving a dereference. // (Needs to come after `validate_local` to avoid ICEs.)
if place.projection.contains(&ProjectionElem::Deref) { self.validate_ref(*kind, place)?;
return Err(Unpromotable);
}
Ok(()) // We do not check all the projections (they do not get promoted anyway),
} // but we do stay away from promoting anything involving a dereference.
_ => bug!(), if place.projection.contains(&ProjectionElem::Deref) {
return Err(Unpromotable);
} }
Ok(())
} }
// FIXME(eddyb) maybe cache this? // FIXME(eddyb) maybe cache this?
fn qualif_local<Q: qualifs::Qualif>(&mut self, local: Local) -> bool { fn qualif_local<Q: qualifs::Qualif>(&mut self, local: Local) -> bool {
if let TempState::Defined { location: loc, .. } = self.temps[local] { let TempState::Defined { location: loc, .. } = self.temps[local] else {
let num_stmts = self.body[loc.block].statements.len(); return false;
};
if loc.statement_index < num_stmts { let stmt_or_term = self.body.stmt_at(loc);
let statement = &self.body[loc.block].statements[loc.statement_index]; match stmt_or_term {
match &statement.kind { Left(statement) => {
StatementKind::Assign(box (_, rhs)) => qualifs::in_rvalue::<Q, _>( let Some((_, rhs)) = statement.kind.as_assign() else {
self.ccx, span_bug!(statement.source_info.span, "{:?} is not an assignment", statement)
&mut |l| self.qualif_local::<Q>(l), };
rhs, qualifs::in_rvalue::<Q, _>(self.ccx, &mut |l| self.qualif_local::<Q>(l), rhs)
), }
_ => { Right(terminator) => {
span_bug!( assert_matches!(terminator.kind, TerminatorKind::Call { .. });
statement.source_info.span, let return_ty = self.body.local_decls[local].ty;
"{:?} is not an assignment", Q::in_any_value_of_ty(self.ccx, return_ty)
statement
);
}
}
} else {
let terminator = self.body[loc.block].terminator();
match &terminator.kind {
TerminatorKind::Call { .. } => {
let return_ty = self.body.local_decls[local].ty;
Q::in_any_value_of_ty(self.ccx, return_ty)
}
kind => {
span_bug!(terminator.source_info.span, "{:?} not promotable", kind);
}
}
} }
} else {
false
} }
} }
fn validate_local(&mut self, local: Local) -> Result<(), Unpromotable> { fn validate_local(&mut self, local: Local) -> Result<(), Unpromotable> {
if let TempState::Defined { location: loc, uses, valid } = self.temps[local] { let TempState::Defined { location: loc, uses, valid } = self.temps[local] else {
// We cannot promote things that need dropping, since the promoted value return Err(Unpromotable);
// would not get dropped. };
if self.qualif_local::<qualifs::NeedsDrop>(local) {
return Err(Unpromotable);
}
valid.or_else(|_| {
let ok = {
let block = &self.body[loc.block];
let num_stmts = block.statements.len();
if loc.statement_index < num_stmts { // We cannot promote things that need dropping, since the promoted value would not get
let statement = &block.statements[loc.statement_index]; // dropped.
match &statement.kind { if self.qualif_local::<qualifs::NeedsDrop>(local) {
StatementKind::Assign(box (_, rhs)) => self.validate_rvalue(rhs), return Err(Unpromotable);
_ => {
span_bug!(
statement.source_info.span,
"{:?} is not an assignment",
statement
);
}
}
} else {
let terminator = block.terminator();
match &terminator.kind {
TerminatorKind::Call { func, args, .. } => {
self.validate_call(func, args)
}
TerminatorKind::Yield { .. } => Err(Unpromotable),
kind => {
span_bug!(terminator.source_info.span, "{:?} not promotable", kind);
}
}
}
};
self.temps[local] = match ok {
Ok(()) => TempState::Defined { location: loc, uses, valid: Ok(()) },
Err(_) => TempState::Unpromotable,
};
ok
})
} else {
Err(Unpromotable)
} }
if valid.is_ok() {
return Ok(());
}
let ok = {
let stmt_or_term = self.body.stmt_at(loc);
match stmt_or_term {
Left(statement) => {
let Some((_, rhs)) = statement.kind.as_assign() else {
span_bug!(
statement.source_info.span,
"{:?} is not an assignment",
statement
)
};
self.validate_rvalue(rhs)
}
Right(terminator) => match &terminator.kind {
TerminatorKind::Call { func, args, .. } => self.validate_call(func, args),
TerminatorKind::Yield { .. } => Err(Unpromotable),
kind => {
span_bug!(terminator.source_info.span, "{:?} not promotable", kind);
}
},
}
};
self.temps[local] = match ok {
Ok(()) => TempState::Defined { location: loc, uses, valid: Ok(()) },
Err(_) => TempState::Unpromotable,
};
ok
} }
fn validate_place(&mut self, place: PlaceRef<'tcx>) -> Result<(), Unpromotable> { fn validate_place(&mut self, place: PlaceRef<'tcx>) -> Result<(), Unpromotable> {
match place.last_projection() { let Some((place_base, elem)) = place.last_projection() else {
None => self.validate_local(place.local), return self.validate_local(place.local);
Some((place_base, elem)) => { };
// Validate topmost projection, then recurse.
match elem {
ProjectionElem::Deref => {
let mut promotable = false;
// When a static is used by-value, that gets desugared to `*STATIC_ADDR`,
// and we need to be able to promote this. So check if this deref matches
// that specific pattern.
// We need to make sure this is a `Deref` of a local with no further projections. // Validate topmost projection, then recurse.
// Discussion can be found at match elem {
// https://github.com/rust-lang/rust/pull/74945#discussion_r463063247 // Recurse directly.
if let Some(local) = place_base.as_local() { ProjectionElem::ConstantIndex { .. }
if let TempState::Defined { location, .. } = self.temps[local] { | ProjectionElem::Subtype(_)
let def_stmt = self.body[location.block] | ProjectionElem::Subslice { .. } => {}
.statements
.get(location.statement_index);
if let Some(Statement {
kind:
StatementKind::Assign(box (
_,
Rvalue::Use(Operand::Constant(c)),
)),
..
}) = def_stmt
{
if let Some(did) = c.check_static_ptr(self.tcx) {
// Evaluating a promoted may not read statics except if it got
// promoted from a static (this is a CTFE check). So we
// can only promote static accesses inside statics.
if let Some(hir::ConstContext::Static(..)) = self.const_kind
{
if !self.tcx.is_thread_local_static(did) {
promotable = true;
}
}
}
}
}
}
if !promotable {
return Err(Unpromotable);
}
}
ProjectionElem::OpaqueCast(..) | ProjectionElem::Downcast(..) => {
return Err(Unpromotable);
}
ProjectionElem::ConstantIndex { .. } // Never recurse.
| ProjectionElem::Subtype(_) ProjectionElem::OpaqueCast(..) | ProjectionElem::Downcast(..) => {
| ProjectionElem::Subslice { .. } => {} return Err(Unpromotable);
}
ProjectionElem::Index(local) => { ProjectionElem::Deref => {
let mut promotable = false; // When a static is used by-value, that gets desugared to `*STATIC_ADDR`,
// Only accept if we can predict the index and are indexing an array. // and we need to be able to promote this. So check if this deref matches
let val = if let TempState::Defined { location: loc, .. } = // that specific pattern.
self.temps[local]
{
let block = &self.body[loc.block];
if loc.statement_index < block.statements.len() {
let statement = &block.statements[loc.statement_index];
match &statement.kind {
StatementKind::Assign(box (
_,
Rvalue::Use(Operand::Constant(c)),
)) => c.const_.try_eval_target_usize(self.tcx, self.param_env),
_ => None,
}
} else {
None
}
} else {
None
};
if let Some(idx) = val {
// Determine the type of the thing we are indexing.
let ty = place_base.ty(self.body, self.tcx).ty;
match ty.kind() {
ty::Array(_, len) => {
// It's an array; determine its length.
if let Some(len) =
len.try_eval_target_usize(self.tcx, self.param_env)
{
// If the index is in-bounds, go ahead.
if idx < len {
promotable = true;
}
}
}
_ => {}
}
}
if !promotable {
return Err(Unpromotable);
}
self.validate_local(local)?; // We need to make sure this is a `Deref` of a local with no further projections.
} // Discussion can be found at
// https://github.com/rust-lang/rust/pull/74945#discussion_r463063247
ProjectionElem::Field(..) => { if let Some(local) = place_base.as_local()
let base_ty = place_base.ty(self.body, self.tcx).ty; && let TempState::Defined { location, .. } = self.temps[local]
if base_ty.is_union() { && let Left(def_stmt) = self.body.stmt_at(location)
// No promotion of union field accesses. && let Some((_, Rvalue::Use(Operand::Constant(c)))) = def_stmt.kind.as_assign()
return Err(Unpromotable); && let Some(did) = c.check_static_ptr(self.tcx)
} // Evaluating a promoted may not read statics except if it got
} // promoted from a static (this is a CTFE check). So we
// can only promote static accesses inside statics.
&& let Some(hir::ConstContext::Static(..)) = self.const_kind
&& !self.tcx.is_thread_local_static(did)
{
// Recurse.
} else {
return Err(Unpromotable);
} }
}
ProjectionElem::Index(local) => {
// Only accept if we can predict the index and are indexing an array.
if let TempState::Defined { location: loc, .. } = self.temps[local]
&& let Left(statement) = self.body.stmt_at(loc)
&& let Some((_, Rvalue::Use(Operand::Constant(c)))) = statement.kind.as_assign()
&& let Some(idx) = c.const_.try_eval_target_usize(self.tcx, self.param_env)
// Determine the type of the thing we are indexing.
&& let ty::Array(_, len) = place_base.ty(self.body, self.tcx).ty.kind()
// It's an array; determine its length.
&& let Some(len) = len.try_eval_target_usize(self.tcx, self.param_env)
// If the index is in-bounds, go ahead.
&& idx < len
{
self.validate_local(local)?;
// Recurse.
} else {
return Err(Unpromotable);
}
}
self.validate_place(place_base) ProjectionElem::Field(..) => {
let base_ty = place_base.ty(self.body, self.tcx).ty;
if base_ty.is_union() {
// No promotion of union field accesses.
return Err(Unpromotable);
}
} }
} }
self.validate_place(place_base)
} }
fn validate_operand(&mut self, operand: &Operand<'tcx>) -> Result<(), Unpromotable> { fn validate_operand(&mut self, operand: &Operand<'tcx>) -> Result<(), Unpromotable> {