Update dataflow impls to reflect new interface
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@ -6,7 +6,6 @@ use rustc_index::bit_set::BitSet;
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use rustc_index::vec::Idx;
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use rustc_middle::mir::{self, Body, Location};
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use rustc_middle::ty::{self, TyCtxt};
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use rustc_target::abi::VariantIdx;
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use super::MoveDataParamEnv;
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@ -19,6 +18,7 @@ use super::drop_flag_effects_for_function_entry;
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use super::drop_flag_effects_for_location;
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use super::on_lookup_result_bits;
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use crate::dataflow::drop_flag_effects;
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use crate::dataflow::framework::SwitchIntEdgeEffects;
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mod borrowed_locals;
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pub(super) mod borrows;
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@ -352,24 +352,46 @@ impl<'tcx> GenKillAnalysis<'tcx> for MaybeInitializedPlaces<'_, 'tcx> {
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);
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}
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fn discriminant_switch_effect(
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fn switch_int_edge_effects<G: GenKill<Self::Idx>>(
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&self,
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trans: &mut impl GenKill<Self::Idx>,
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_block: mir::BasicBlock,
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enum_place: mir::Place<'tcx>,
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_adt: &ty::AdtDef,
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variant: VariantIdx,
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block: mir::BasicBlock,
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discr: &mir::Operand<'tcx>,
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edge_effects: &mut impl SwitchIntEdgeEffects<G>,
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) {
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// Kill all move paths that correspond to variants we know to be inactive along this
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// particular outgoing edge of a `SwitchInt`.
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drop_flag_effects::on_all_inactive_variants(
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self.tcx,
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self.body,
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self.move_data(),
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enum_place,
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variant,
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|mpi| trans.kill(mpi),
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);
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let enum_ = discr.place().and_then(|discr| {
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switch_on_enum_discriminant(self.tcx, &self.body, &self.body[block], discr)
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});
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let (enum_place, enum_def) = match enum_ {
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Some(x) => x,
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None => return,
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};
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let mut discriminants = enum_def.discriminants(self.tcx);
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edge_effects.apply(|trans, edge| {
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let value = match edge.value {
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Some(x) => x,
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None => return,
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};
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// MIR building adds discriminants to the `values` array in the same order as they
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// are yielded by `AdtDef::discriminants`. We rely on this to match each
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// discriminant in `values` to its corresponding variant in linear time.
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let (variant, _) = discriminants
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.find(|&(_, discr)| discr.val == value)
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.expect("Order of `AdtDef::discriminants` differed from `SwitchInt::values`");
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// Kill all move paths that correspond to variants we know to be inactive along this
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// particular outgoing edge of a `SwitchInt`.
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drop_flag_effects::on_all_inactive_variants(
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self.tcx,
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self.body,
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self.move_data(),
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enum_place,
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variant,
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|mpi| trans.kill(mpi),
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);
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});
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}
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}
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@ -441,28 +463,50 @@ impl<'tcx> GenKillAnalysis<'tcx> for MaybeUninitializedPlaces<'_, 'tcx> {
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);
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}
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fn discriminant_switch_effect(
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fn switch_int_edge_effects<G: GenKill<Self::Idx>>(
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&self,
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trans: &mut impl GenKill<Self::Idx>,
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_block: mir::BasicBlock,
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enum_place: mir::Place<'tcx>,
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_adt: &ty::AdtDef,
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variant: VariantIdx,
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block: mir::BasicBlock,
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discr: &mir::Operand<'tcx>,
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edge_effects: &mut impl SwitchIntEdgeEffects<G>,
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) {
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if !self.mark_inactive_variants_as_uninit {
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return;
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}
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// Mark all move paths that correspond to variants other than this one as maybe
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// uninitialized (in reality, they are *definitely* uninitialized).
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drop_flag_effects::on_all_inactive_variants(
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self.tcx,
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self.body,
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self.move_data(),
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enum_place,
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variant,
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|mpi| trans.gen(mpi),
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);
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let enum_ = discr.place().and_then(|discr| {
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switch_on_enum_discriminant(self.tcx, &self.body, &self.body[block], discr)
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});
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let (enum_place, enum_def) = match enum_ {
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Some(x) => x,
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None => return,
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};
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let mut discriminants = enum_def.discriminants(self.tcx);
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edge_effects.apply(|trans, edge| {
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let value = match edge.value {
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Some(x) => x,
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None => return,
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};
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// MIR building adds discriminants to the `values` array in the same order as they
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// are yielded by `AdtDef::discriminants`. We rely on this to match each
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// discriminant in `values` to its corresponding variant in linear time.
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let (variant, _) = discriminants
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.find(|&(_, discr)| discr.val == value)
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.expect("Order of `AdtDef::discriminants` differed from `SwitchInt::values`");
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// Mark all move paths that correspond to variants other than this one as maybe
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// uninitialized (in reality, they are *definitely* uninitialized).
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drop_flag_effects::on_all_inactive_variants(
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self.tcx,
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self.body,
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self.move_data(),
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enum_place,
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variant,
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|mpi| trans.gen(mpi),
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);
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});
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}
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}
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@ -624,3 +668,42 @@ impl<'tcx> GenKillAnalysis<'tcx> for EverInitializedPlaces<'_, 'tcx> {
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}
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}
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}
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/// Inspect a `SwitchInt`-terminated basic block to see if the condition of that `SwitchInt` is
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/// an enum discriminant.
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///
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/// We expect such blocks to have a call to `discriminant` as their last statement like so:
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///
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/// ```text
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/// ...
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/// _42 = discriminant(_1)
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/// SwitchInt(_42, ..)
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/// ```
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///
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/// If the basic block matches this pattern, this function returns the place corresponding to the
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/// enum (`_1` in the example above) as well as the `AdtDef` of that enum.
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fn switch_on_enum_discriminant(
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tcx: TyCtxt<'tcx>,
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body: &'mir mir::Body<'tcx>,
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block: &'mir mir::BasicBlockData<'tcx>,
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switch_on: mir::Place<'tcx>,
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) -> Option<(mir::Place<'tcx>, &'tcx ty::AdtDef)> {
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match block.statements.last().map(|stmt| &stmt.kind) {
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Some(mir::StatementKind::Assign(box (lhs, mir::Rvalue::Discriminant(discriminated))))
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if *lhs == switch_on =>
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{
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match &discriminated.ty(body, tcx).ty.kind() {
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ty::Adt(def, _) => Some((*discriminated, def)),
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// `Rvalue::Discriminant` is also used to get the active yield point for a
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// generator, but we do not need edge-specific effects in that case. This may
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// change in the future.
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ty::Generator(..) => None,
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t => bug!("`discriminant` called on unexpected type {:?}", t),
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}
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}
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_ => None,
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}
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}
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