mirror of
https://github.com/rust-lang/rust.git
synced 2025-04-28 02:57:37 +00:00
Remove const_prop.rs
and move its content to const_prop_lint.rs and dataflow_const_prop.rs where it is used
This commit is contained in:
Gurinder Singh
parent
23a3d777c8
commit
50e316bdc0
@ -1,161 +0,0 @@
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//! Propagates constants for early reporting of statically known
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//! assertion failures
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use rustc_index::bit_set::BitSet;
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use rustc_index::IndexVec;
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use rustc_middle::mir::visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor};
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use rustc_middle::mir::*;
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use rustc_middle::ty::{ParamEnv, TyCtxt};
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use rustc_target::abi::Size;
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/// The maximum number of bytes that we'll allocate space for a local or the return value.
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/// Needed for #66397, because otherwise we eval into large places and that can cause OOM or just
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/// Severely regress performance.
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const MAX_ALLOC_LIMIT: u64 = 1024;
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/// Macro for machine-specific `InterpError` without allocation.
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/// (These will never be shown to the user, but they help diagnose ICEs.)
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pub(crate) macro throw_machine_stop_str($($tt:tt)*) {{
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// We make a new local type for it. The type itself does not carry any information,
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// but its vtable (for the `MachineStopType` trait) does.
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#[derive(Debug)]
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struct Zst;
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// Printing this type shows the desired string.
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impl std::fmt::Display for Zst {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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write!(f, $($tt)*)
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}
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}
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impl rustc_middle::mir::interpret::MachineStopType for Zst {
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fn diagnostic_message(&self) -> rustc_errors::DiagnosticMessage {
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self.to_string().into()
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}
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fn add_args(
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self: Box<Self>,
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_: &mut dyn FnMut(rustc_errors::DiagnosticArgName, rustc_errors::DiagnosticArgValue),
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) {}
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}
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throw_machine_stop!(Zst)
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}}
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/// The mode that `ConstProp` is allowed to run in for a given `Local`.
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#[derive(Clone, Copy, Debug, PartialEq)]
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pub enum ConstPropMode {
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/// The `Local` can be propagated into and reads of this `Local` can also be propagated.
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FullConstProp,
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/// The `Local` can only be propagated into and from its own block.
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OnlyInsideOwnBlock,
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/// The `Local` cannot be part of propagation at all. Any statement
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/// referencing it either for reading or writing will not get propagated.
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NoPropagation,
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}
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pub struct CanConstProp {
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can_const_prop: IndexVec<Local, ConstPropMode>,
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// False at the beginning. Once set, no more assignments are allowed to that local.
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found_assignment: BitSet<Local>,
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}
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impl CanConstProp {
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/// Returns true if `local` can be propagated
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pub fn check<'tcx>(
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tcx: TyCtxt<'tcx>,
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param_env: ParamEnv<'tcx>,
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body: &Body<'tcx>,
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) -> IndexVec<Local, ConstPropMode> {
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let mut cpv = CanConstProp {
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can_const_prop: IndexVec::from_elem(ConstPropMode::FullConstProp, &body.local_decls),
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found_assignment: BitSet::new_empty(body.local_decls.len()),
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};
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for (local, val) in cpv.can_const_prop.iter_enumerated_mut() {
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let ty = body.local_decls[local].ty;
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match tcx.layout_of(param_env.and(ty)) {
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Ok(layout) if layout.size < Size::from_bytes(MAX_ALLOC_LIMIT) => {}
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// Either the layout fails to compute, then we can't use this local anyway
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// or the local is too large, then we don't want to.
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_ => {
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*val = ConstPropMode::NoPropagation;
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continue;
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}
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}
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}
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// Consider that arguments are assigned on entry.
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for arg in body.args_iter() {
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cpv.found_assignment.insert(arg);
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}
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cpv.visit_body(body);
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cpv.can_const_prop
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}
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}
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impl<'tcx> Visitor<'tcx> for CanConstProp {
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fn visit_place(&mut self, place: &Place<'tcx>, mut context: PlaceContext, loc: Location) {
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use rustc_middle::mir::visit::PlaceContext::*;
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// Dereferencing just read the addess of `place.local`.
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if place.projection.first() == Some(&PlaceElem::Deref) {
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context = NonMutatingUse(NonMutatingUseContext::Copy);
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}
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self.visit_local(place.local, context, loc);
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self.visit_projection(place.as_ref(), context, loc);
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}
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fn visit_local(&mut self, local: Local, context: PlaceContext, _: Location) {
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use rustc_middle::mir::visit::PlaceContext::*;
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match context {
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// These are just stores, where the storing is not propagatable, but there may be later
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// mutations of the same local via `Store`
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| MutatingUse(MutatingUseContext::Call)
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| MutatingUse(MutatingUseContext::AsmOutput)
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| MutatingUse(MutatingUseContext::Deinit)
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// Actual store that can possibly even propagate a value
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| MutatingUse(MutatingUseContext::Store)
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| MutatingUse(MutatingUseContext::SetDiscriminant) => {
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if !self.found_assignment.insert(local) {
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match &mut self.can_const_prop[local] {
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// If the local can only get propagated in its own block, then we don't have
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// to worry about multiple assignments, as we'll nuke the const state at the
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// end of the block anyway, and inside the block we overwrite previous
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// states as applicable.
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ConstPropMode::OnlyInsideOwnBlock => {}
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ConstPropMode::NoPropagation => {}
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other @ ConstPropMode::FullConstProp => {
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trace!(
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"local {:?} can't be propagated because of multiple assignments. Previous state: {:?}",
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local, other,
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);
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*other = ConstPropMode::OnlyInsideOwnBlock;
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}
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}
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}
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}
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// Reading constants is allowed an arbitrary number of times
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NonMutatingUse(NonMutatingUseContext::Copy)
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| NonMutatingUse(NonMutatingUseContext::Move)
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| NonMutatingUse(NonMutatingUseContext::Inspect)
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| NonMutatingUse(NonMutatingUseContext::PlaceMention)
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| NonUse(_) => {}
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// These could be propagated with a smarter analysis or just some careful thinking about
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// whether they'd be fine right now.
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MutatingUse(MutatingUseContext::Yield)
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| MutatingUse(MutatingUseContext::Drop)
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| MutatingUse(MutatingUseContext::Retag)
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// These can't ever be propagated under any scheme, as we can't reason about indirect
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// mutation.
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| NonMutatingUse(NonMutatingUseContext::SharedBorrow)
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| NonMutatingUse(NonMutatingUseContext::FakeBorrow)
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| NonMutatingUse(NonMutatingUseContext::AddressOf)
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| MutatingUse(MutatingUseContext::Borrow)
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| MutatingUse(MutatingUseContext::AddressOf) => {
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trace!("local {:?} can't be propagated because it's used: {:?}", local, context);
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self.can_const_prop[local] = ConstPropMode::NoPropagation;
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}
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MutatingUse(MutatingUseContext::Projection)
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| NonMutatingUse(NonMutatingUseContext::Projection) => bug!("visit_place should not pass {context:?} for {local:?}"),
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}
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}
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}
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@ -9,17 +9,14 @@ use rustc_const_eval::interpret::{
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use rustc_data_structures::fx::FxHashSet;
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use rustc_hir::def::DefKind;
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use rustc_hir::HirId;
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use rustc_index::bit_set::BitSet;
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use rustc_index::{Idx, IndexVec};
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use rustc_middle::mir::visit::Visitor;
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use rustc_index::{bit_set::BitSet, Idx, IndexVec};
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use rustc_middle::mir::visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor};
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use rustc_middle::mir::*;
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use rustc_middle::ty::layout::{LayoutError, LayoutOf, LayoutOfHelpers, TyAndLayout};
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use rustc_middle::ty::{self, ConstInt, ParamEnv, ScalarInt, Ty, TyCtxt, TypeVisitableExt};
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use rustc_span::Span;
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use rustc_target::abi::{Abi, FieldIdx, HasDataLayout, Size, TargetDataLayout, VariantIdx};
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use crate::const_prop::CanConstProp;
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use crate::const_prop::ConstPropMode;
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use crate::dataflow_const_prop::DummyMachine;
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use crate::errors::{AssertLint, AssertLintKind};
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use crate::MirLint;
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@ -849,3 +846,128 @@ impl<'tcx> Visitor<'tcx> for ConstPropagator<'_, 'tcx> {
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}
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}
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}
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/// The maximum number of bytes that we'll allocate space for a local or the return value.
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/// Needed for #66397, because otherwise we eval into large places and that can cause OOM or just
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/// Severely regress performance.
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const MAX_ALLOC_LIMIT: u64 = 1024;
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/// The mode that `ConstProp` is allowed to run in for a given `Local`.
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#[derive(Clone, Copy, Debug, PartialEq)]
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pub enum ConstPropMode {
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/// The `Local` can be propagated into and reads of this `Local` can also be propagated.
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FullConstProp,
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/// The `Local` can only be propagated into and from its own block.
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OnlyInsideOwnBlock,
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/// The `Local` cannot be part of propagation at all. Any statement
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/// referencing it either for reading or writing will not get propagated.
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NoPropagation,
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}
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pub struct CanConstProp {
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can_const_prop: IndexVec<Local, ConstPropMode>,
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// False at the beginning. Once set, no more assignments are allowed to that local.
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found_assignment: BitSet<Local>,
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}
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impl CanConstProp {
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/// Returns true if `local` can be propagated
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pub fn check<'tcx>(
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tcx: TyCtxt<'tcx>,
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param_env: ParamEnv<'tcx>,
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body: &Body<'tcx>,
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) -> IndexVec<Local, ConstPropMode> {
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let mut cpv = CanConstProp {
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can_const_prop: IndexVec::from_elem(ConstPropMode::FullConstProp, &body.local_decls),
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found_assignment: BitSet::new_empty(body.local_decls.len()),
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};
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for (local, val) in cpv.can_const_prop.iter_enumerated_mut() {
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let ty = body.local_decls[local].ty;
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match tcx.layout_of(param_env.and(ty)) {
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Ok(layout) if layout.size < Size::from_bytes(MAX_ALLOC_LIMIT) => {}
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// Either the layout fails to compute, then we can't use this local anyway
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// or the local is too large, then we don't want to.
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_ => {
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*val = ConstPropMode::NoPropagation;
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continue;
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}
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}
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}
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// Consider that arguments are assigned on entry.
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for arg in body.args_iter() {
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cpv.found_assignment.insert(arg);
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}
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cpv.visit_body(body);
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cpv.can_const_prop
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}
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}
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impl<'tcx> Visitor<'tcx> for CanConstProp {
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fn visit_place(&mut self, place: &Place<'tcx>, mut context: PlaceContext, loc: Location) {
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use rustc_middle::mir::visit::PlaceContext::*;
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// Dereferencing just read the addess of `place.local`.
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if place.projection.first() == Some(&PlaceElem::Deref) {
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context = NonMutatingUse(NonMutatingUseContext::Copy);
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}
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self.visit_local(place.local, context, loc);
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self.visit_projection(place.as_ref(), context, loc);
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}
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fn visit_local(&mut self, local: Local, context: PlaceContext, _: Location) {
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use rustc_middle::mir::visit::PlaceContext::*;
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match context {
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// These are just stores, where the storing is not propagatable, but there may be later
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// mutations of the same local via `Store`
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| MutatingUse(MutatingUseContext::Call)
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| MutatingUse(MutatingUseContext::AsmOutput)
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| MutatingUse(MutatingUseContext::Deinit)
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// Actual store that can possibly even propagate a value
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| MutatingUse(MutatingUseContext::Store)
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| MutatingUse(MutatingUseContext::SetDiscriminant) => {
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if !self.found_assignment.insert(local) {
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match &mut self.can_const_prop[local] {
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// If the local can only get propagated in its own block, then we don't have
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// to worry about multiple assignments, as we'll nuke the const state at the
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// end of the block anyway, and inside the block we overwrite previous
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// states as applicable.
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ConstPropMode::OnlyInsideOwnBlock => {}
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ConstPropMode::NoPropagation => {}
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other @ ConstPropMode::FullConstProp => {
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trace!(
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"local {:?} can't be propagated because of multiple assignments. Previous state: {:?}",
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local, other,
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);
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*other = ConstPropMode::OnlyInsideOwnBlock;
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}
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}
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}
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}
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// Reading constants is allowed an arbitrary number of times
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NonMutatingUse(NonMutatingUseContext::Copy)
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| NonMutatingUse(NonMutatingUseContext::Move)
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| NonMutatingUse(NonMutatingUseContext::Inspect)
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| NonMutatingUse(NonMutatingUseContext::PlaceMention)
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| NonUse(_) => {}
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// These could be propagated with a smarter analysis or just some careful thinking about
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// whether they'd be fine right now.
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MutatingUse(MutatingUseContext::Yield)
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| MutatingUse(MutatingUseContext::Drop)
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| MutatingUse(MutatingUseContext::Retag)
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// These can't ever be propagated under any scheme, as we can't reason about indirect
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// mutation.
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| NonMutatingUse(NonMutatingUseContext::SharedBorrow)
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| NonMutatingUse(NonMutatingUseContext::FakeBorrow)
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| NonMutatingUse(NonMutatingUseContext::AddressOf)
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| MutatingUse(MutatingUseContext::Borrow)
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| MutatingUse(MutatingUseContext::AddressOf) => {
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trace!("local {:?} can't be propagated because it's used: {:?}", local, context);
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self.can_const_prop[local] = ConstPropMode::NoPropagation;
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}
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MutatingUse(MutatingUseContext::Projection)
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| NonMutatingUse(NonMutatingUseContext::Projection) => bug!("visit_place should not pass {context:?} for {local:?}"),
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}
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}
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}
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@ -21,7 +21,32 @@ use rustc_span::def_id::DefId;
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use rustc_span::DUMMY_SP;
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use rustc_target::abi::{Abi, FieldIdx, Size, VariantIdx, FIRST_VARIANT};
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use crate::const_prop::throw_machine_stop_str;
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/// Macro for machine-specific `InterpError` without allocation.
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/// (These will never be shown to the user, but they help diagnose ICEs.)
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pub(crate) macro throw_machine_stop_str($($tt:tt)*) {{
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// We make a new local type for it. The type itself does not carry any information,
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// but its vtable (for the `MachineStopType` trait) does.
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#[derive(Debug)]
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struct Zst;
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// Printing this type shows the desired string.
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impl std::fmt::Display for Zst {
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fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
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write!(f, $($tt)*)
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}
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}
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impl rustc_middle::mir::interpret::MachineStopType for Zst {
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fn diagnostic_message(&self) -> rustc_errors::DiagnosticMessage {
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self.to_string().into()
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}
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fn add_args(
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self: Box<Self>,
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_: &mut dyn FnMut(rustc_errors::DiagnosticArgName, rustc_errors::DiagnosticArgValue),
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) {}
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}
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throw_machine_stop!(Zst)
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}}
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// These constants are somewhat random guesses and have not been optimized.
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// If `tcx.sess.mir_opt_level() >= 4`, we ignore the limits (this can become very expensive).
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@ -59,7 +59,6 @@ mod remove_place_mention;
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mod add_subtyping_projections;
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pub mod cleanup_post_borrowck;
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mod const_debuginfo;
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mod const_prop;
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mod const_prop_lint;
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mod copy_prop;
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mod coroutine;
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