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cac431ba75
The `AggregateKind` enum ends up in the final mir `Body`. Currently, any changes to `AdtDef` (regardless of how significant they are) will legitimately cause the overall result of `optimized_mir` to change, invalidating any codegen re-use involving that mir. This will get worse once we start hashing the `Span` inside `FieldDef` (which is itself contained in `AdtDef`). To try to reduce these kinds of invalidations, this commit changes `AggregateKind::Adt` to store just the `DefId`, instead of the full `AdtDef`. This allows the result of `optimized_mir` to be unchanged if the `AdtDef` changes in a way that doesn't actually affect any of the MIR we build.
77 lines
2.7 KiB
Rust
77 lines
2.7 KiB
Rust
use rustc_index::vec::Idx;
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use rustc_middle::mir::*;
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use rustc_middle::ty::{Ty, TyCtxt};
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use rustc_target::abi::VariantIdx;
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use std::convert::TryFrom;
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use std::iter::TrustedLen;
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/// Expand `lhs = Rvalue::Aggregate(kind, operands)` into assignments to the fields.
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///
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/// Produces something like
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///
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/// (lhs as Variant).field0 = arg0; // We only have a downcast if this is an enum
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/// (lhs as Variant).field1 = arg1;
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/// discriminant(lhs) = variant_index; // If lhs is an enum or generator.
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pub fn expand_aggregate<'tcx>(
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mut lhs: Place<'tcx>,
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operands: impl Iterator<Item = (Operand<'tcx>, Ty<'tcx>)> + TrustedLen,
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kind: AggregateKind<'tcx>,
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source_info: SourceInfo,
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tcx: TyCtxt<'tcx>,
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) -> impl Iterator<Item = Statement<'tcx>> + TrustedLen {
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let mut set_discriminant = None;
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let active_field_index = match kind {
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AggregateKind::Adt(adt_did, variant_index, _, _, active_field_index) => {
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let adt_def = tcx.adt_def(adt_did);
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if adt_def.is_enum() {
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set_discriminant = Some(Statement {
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kind: StatementKind::SetDiscriminant { place: Box::new(lhs), variant_index },
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source_info,
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});
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lhs = tcx.mk_place_downcast(lhs, adt_def, variant_index);
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}
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active_field_index
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}
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AggregateKind::Generator(..) => {
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// Right now we only support initializing generators to
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// variant 0 (Unresumed).
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let variant_index = VariantIdx::new(0);
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set_discriminant = Some(Statement {
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kind: StatementKind::SetDiscriminant { place: Box::new(lhs), variant_index },
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source_info,
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});
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// Operands are upvars stored on the base place, so no
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// downcast is necessary.
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None
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}
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_ => None,
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};
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operands
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.enumerate()
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.map(move |(i, (op, ty))| {
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let lhs_field = if let AggregateKind::Array(_) = kind {
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let offset = u64::try_from(i).unwrap();
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tcx.mk_place_elem(
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lhs,
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ProjectionElem::ConstantIndex {
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offset,
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min_length: offset + 1,
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from_end: false,
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},
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)
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} else {
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let field = Field::new(active_field_index.unwrap_or(i));
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tcx.mk_place_field(lhs, field, ty)
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};
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Statement {
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source_info,
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kind: StatementKind::Assign(Box::new((lhs_field, Rvalue::Use(op)))),
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}
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})
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.chain(set_discriminant)
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}
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