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Still need to make it so that it maps discriminants to variant indexes. Maybe instead I can map the variant indexes to discriminants?
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kadmin
parent
18144b66e1
commit
96db5e9c7b
@ -4,7 +4,7 @@ use rustc_data_structures::stable_map::FxHashMap;
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use rustc_middle::mir::*;
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use rustc_middle::ty::{self, Const, List, Ty, TyCtxt};
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use rustc_span::def_id::DefId;
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use rustc_target::abi::{Size, Variants};
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use rustc_target::abi::{Size, TagEncoding, Variants};
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/// A pass that seeks to optimize unnecessary moves of large enum types, if there is a large
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/// enough discrepanc between them
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@ -31,17 +31,25 @@ impl<const D: u64> EnumSizeOpt<D> {
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match variants {
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Variants::Single { .. } => None,
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Variants::Multiple { variants, .. } if variants.len() <= 1 => None,
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Variants::Multiple { tag_encoding, .. }
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if matches!(tag_encoding, TagEncoding::Niche { .. }) =>
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{
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None
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}
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Variants::Multiple { variants, .. } => {
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let min = variants.iter().map(|v| v.size).min().unwrap();
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let max = variants.iter().map(|v| v.size).max().unwrap();
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if max.bytes() - min.bytes() < D {
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return None;
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}
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Some((
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layout.size,
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variants.len() as u64,
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variants.iter().map(|v| v.size).collect(),
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))
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let mut discr_sizes = vec![Size::ZERO; adt_def.discriminants(tcx).count()];
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for (var_idx, layout) in variants.iter_enumerated() {
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let disc_idx =
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adt_def.discriminant_for_variant(tcx, var_idx).val as usize;
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assert_eq!(discr_sizes[disc_idx], Size::ZERO);
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discr_sizes[disc_idx] = layout.size;
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}
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Some((layout.size, variants.len() as u64, discr_sizes))
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}
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}
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}
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@ -49,7 +57,7 @@ impl<const D: u64> EnumSizeOpt<D> {
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}
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}
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fn optim(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
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let mut match_cache = FxHashMap::default();
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let mut alloc_cache = FxHashMap::default();
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let body_did = body.source.def_id();
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let mut patch = MirPatch::new(body);
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let (bbs, local_decls) = body.basic_blocks_and_local_decls_mut();
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@ -61,39 +69,45 @@ impl<const D: u64> EnumSizeOpt<D> {
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Rvalue::Use(Operand::Copy(rhs) | Operand::Move(rhs)),
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)) => {
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let ty = lhs.ty(local_decls, tcx).ty;
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let source_info = st.source_info;
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let span = source_info.span;
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let (total_size, num_variants, sizes) =
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if let Some((ts, nv, s)) = match_cache.get(ty) {
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(*ts, *nv, s)
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} else if let Some((ts, nv, s)) = Self::candidate(tcx, ty, body_did) {
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// FIXME(jknodt) use entry API.
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match_cache.insert(ty, (ts, nv, s));
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let (ts, nv, s) = match_cache.get(ty).unwrap();
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(*ts, *nv, s)
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if let Some((ts, nv, s)) = Self::candidate(tcx, ty, body_did) {
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(ts, nv, s)
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} else {
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return None;
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};
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let source_info = st.source_info;
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let span = source_info.span;
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let alloc = if let Some(alloc) = alloc_cache.get(ty) {
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alloc
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} else {
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let mut data =
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vec![0; std::mem::size_of::<usize>() * num_variants as usize];
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data.copy_from_slice(unsafe { std::mem::transmute(&sizes[..]) });
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let alloc = interpret::Allocation::from_bytes(
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data,
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tcx.data_layout.ptr_sized_integer().align(&tcx.data_layout).abi,
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Mutability::Not,
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);
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let alloc = tcx.intern_const_alloc(alloc);
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alloc_cache.insert(ty, alloc);
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// FIXME(jknodt) use entry API
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alloc_cache.get(ty).unwrap()
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};
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let tmp_ty = tcx.mk_ty(ty::Array(
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tcx.types.usize,
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Const::from_usize(tcx, num_variants),
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));
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let new_local = patch.new_temp(tmp_ty, span);
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let store_live =
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Statement { source_info, kind: StatementKind::StorageLive(new_local) };
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let size_array_local = patch.new_temp(tmp_ty, span);
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let store_live = Statement {
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source_info,
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kind: StatementKind::StorageLive(size_array_local),
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};
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let place = Place { local: new_local, projection: List::empty() };
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let mut data =
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vec![0; std::mem::size_of::<usize>() * num_variants as usize];
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data.copy_from_slice(unsafe { std::mem::transmute(&sizes[..]) });
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let alloc = interpret::Allocation::from_bytes(
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data,
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tcx.data_layout.ptr_sized_integer().align(&tcx.data_layout).abi,
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);
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let alloc = tcx.intern_const_alloc(alloc);
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let place = Place { local: size_array_local, projection: List::empty() };
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let constant_vals = Constant {
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span,
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user_ty: None,
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@ -134,9 +148,9 @@ impl<const D: u64> EnumSizeOpt<D> {
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kind: StatementKind::Assign(box (
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size_place,
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Rvalue::Use(Operand::Copy(Place {
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local: discr_place.local,
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local: size_array_local,
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projection: tcx
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.intern_place_elems(&[PlaceElem::Index(size_place.local)]),
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.intern_place_elems(&[PlaceElem::Index(discr_place.local)]),
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})),
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)),
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};
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@ -187,8 +201,10 @@ impl<const D: u64> EnumSizeOpt<D> {
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}),
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};
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let store_dead =
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Statement { source_info, kind: StatementKind::StorageDead(new_local) };
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let store_dead = Statement {
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source_info,
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kind: StatementKind::StorageDead(size_array_local),
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};
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let iter = std::array::IntoIter::new([
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store_live,
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const_assign,
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