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Store a ConstantKind in CollectAndPatch.

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This commit is contained in:
Camille GILLOT 2023-09-12 15:45:19 +00:00
parent 054ed8e7eb
commit 8a3a0dd64e
1 changed files with 28 additions and 23 deletions
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51
compiler/rustc_mir_transform/src/dataflow_const_prop.rs
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@ -10,7 +10,7 @@ use rustc_middle::mir::interpret::{AllocId, ConstAllocation, ConstValue, InterpR
use rustc_middle::mir::visit::{MutVisitor, NonMutatingUseContext, PlaceContext, Visitor};
use rustc_middle::mir::*;
use rustc_middle::ty::layout::TyAndLayout;
use rustc_middle::ty::{self, ScalarInt, Ty, TyCtxt};
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_mir_dataflow::value_analysis::{
Map, PlaceIndex, State, TrackElem, ValueAnalysis, ValueAnalysisWrapper, ValueOrPlace,
};
@ -524,10 +524,10 @@ struct CollectAndPatch<'tcx, 'locals> {
/// For a given MIR location, this stores the values of the operands used by that location. In
/// particular, this is before the effect, such that the operands of `_1 = _1 + _2` are
/// properly captured. (This may become UB soon, but it is currently emitted even by safe code.)
before_effect: FxHashMap<(Location, Place<'tcx>), ScalarInt>,
before_effect: FxHashMap<(Location, Place<'tcx>), ConstantKind<'tcx>>,
/// Stores the assigned values for assignments where the Rvalue is constant.
assignments: FxHashMap<Location, ScalarInt>,
assignments: FxHashMap<Location, ConstantKind<'tcx>>,
}
impl<'tcx, 'locals> CollectAndPatch<'tcx, 'locals> {
@ -540,12 +540,21 @@ impl<'tcx, 'locals> CollectAndPatch<'tcx, 'locals> {
}
}
fn make_operand(&self, scalar: ScalarInt, ty: Ty<'tcx>) -> Operand<'tcx> {
Operand::Constant(Box::new(Constant {
span: DUMMY_SP,
user_ty: None,
literal: ConstantKind::Val(ConstValue::Scalar(scalar.into()), ty),
}))
fn try_make_constant(
&self,
place: Place<'tcx>,
state: &State<FlatSet<Scalar>>,
map: &Map,
) -> Option<ConstantKind<'tcx>> {
let FlatSet::Elem(Scalar::Int(value)) = state.get(place.as_ref(), &map) else {
return None;
};
let ty = place.ty(self.local_decls, self.tcx).ty;
Some(ConstantKind::Val(ConstValue::Scalar(value.into()), ty))
}
fn make_operand(&self, literal: ConstantKind<'tcx>) -> Operand<'tcx> {
Operand::Constant(Box::new(Constant { span: DUMMY_SP, user_ty: None, literal }))
}
}
@ -583,9 +592,7 @@ impl<'mir, 'tcx>
// Don't overwrite the assignment if it already uses a constant (to keep the span).
}
StatementKind::Assign(box (place, _)) => {
if let FlatSet::Elem(Scalar::Int(value)) =
state.get(place.as_ref(), &results.analysis.0.map)
{
if let Some(value) = self.try_make_constant(place, state, &results.analysis.0.map) {
self.assignments.insert(location, value);
}
}
@ -614,8 +621,7 @@ impl<'tcx> MutVisitor<'tcx> for CollectAndPatch<'tcx, '_> {
if let Some(value) = self.assignments.get(&location) {
match &mut statement.kind {
StatementKind::Assign(box (_, rvalue)) => {
let ty = rvalue.ty(self.local_decls, self.tcx);
*rvalue = Rvalue::Use(self.make_operand(*value, ty));
*rvalue = Rvalue::Use(self.make_operand(*value));
}
_ => bug!("found assignment info for non-assign statement"),
}
@ -628,8 +634,7 @@ impl<'tcx> MutVisitor<'tcx> for CollectAndPatch<'tcx, '_> {
match operand {
Operand::Copy(place) | Operand::Move(place) => {
if let Some(value) = self.before_effect.get(&(location, *place)) {
let ty = place.ty(self.local_decls, self.tcx).ty;
*operand = self.make_operand(*value, ty);
*operand = self.make_operand(*value);
} else if !place.projection.is_empty() {
self.super_operand(operand, location)
}
@ -643,11 +648,11 @@ impl<'tcx> MutVisitor<'tcx> for CollectAndPatch<'tcx, '_> {
elem: PlaceElem<'tcx>,
location: Location,
) -> Option<PlaceElem<'tcx>> {
if let PlaceElem::Index(local) = elem
&& let Some(value) = self.before_effect.get(&(location, local.into()))
&& let Ok(offset) = value.try_to_target_usize(self.tcx)
&& let Some(min_length) = offset.checked_add(1)
{
if let PlaceElem::Index(local) = elem {
let offset = self.before_effect.get(&(location, local.into()))?;
let offset = offset.try_to_scalar()?;
let offset = offset.to_target_usize(&self.tcx).ok()?;
let min_length = offset.checked_add(1)?;
Some(PlaceElem::ConstantIndex { offset, min_length, from_end: false })
} else {
None
@ -664,7 +669,7 @@ struct OperandCollector<'tcx, 'map, 'locals, 'a> {
impl<'tcx> Visitor<'tcx> for OperandCollector<'tcx, '_, '_, '_> {
fn visit_operand(&mut self, operand: &Operand<'tcx>, location: Location) {
if let Some(place) = operand.place() {
if let FlatSet::Elem(Scalar::Int(value)) = self.state.get(place.as_ref(), self.map) {
if let Some(value) = self.visitor.try_make_constant(place, self.state, self.map) {
self.visitor.before_effect.insert((location, place), value);
} else if !place.projection.is_empty() {
// Try to propagate into `Index` projections.
@ -675,7 +680,7 @@ impl<'tcx> Visitor<'tcx> for OperandCollector<'tcx, '_, '_, '_> {
fn visit_local(&mut self, local: Local, ctxt: PlaceContext, location: Location) {
if let PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy | NonMutatingUseContext::Move) = ctxt
&& let FlatSet::Elem(Scalar::Int(value)) = self.state.get(local.into(), self.map)
&& let Some(value) = self.visitor.try_make_constant(local.into(), self.state, self.map)
{
self.visitor.before_effect.insert((location, local.into()), value);
}