diff options
| -rw-r--r-- | compiler/rustc_abi/src/layout.rs | 11 | ||||
| -rw-r--r-- | compiler/rustc_abi/src/lib.rs | 15 | ||||
| -rw-r--r-- | compiler/rustc_middle/src/ty/mod.rs | 10 |
3 files changed, 27 insertions, 9 deletions
diff --git a/compiler/rustc_abi/src/layout.rs b/compiler/rustc_abi/src/layout.rs index 5160b4ed0a2..7432768be4a 100644 --- a/compiler/rustc_abi/src/layout.rs +++ b/compiler/rustc_abi/src/layout.rs @@ -968,8 +968,8 @@ fn univariant< let mut align = if pack.is_some() { dl.i8_align } else { dl.aggregate_align }; let mut max_repr_align = repr.align; let mut inverse_memory_index: IndexVec<u32, FieldIdx> = fields.indices().collect(); - let optimize = !repr.inhibit_struct_field_reordering(); - if optimize && fields.len() > 1 { + let optimize_field_order = !repr.inhibit_struct_field_reordering(); + if optimize_field_order && fields.len() > 1 { let end = if let StructKind::MaybeUnsized = kind { fields.len() - 1 } else { fields.len() }; let optimizing = &mut inverse_memory_index.raw[..end]; let fields_excluding_tail = &fields.raw[..end]; @@ -1176,7 +1176,7 @@ fn univariant< // If field 5 has offset 0, offsets[0] is 5, and memory_index[5] should be 0. // Field 5 would be the first element, so memory_index is i: // Note: if we didn't optimize, it's already right. - let memory_index = if optimize { + let memory_index = if optimize_field_order { inverse_memory_index.invert_bijective_mapping() } else { debug_assert!(inverse_memory_index.iter().copied().eq(fields.indices())); @@ -1189,6 +1189,9 @@ fn univariant< } let mut layout_of_single_non_zst_field = None; let mut abi = Abi::Aggregate { sized }; + + let optimize_abi = !repr.inhibit_newtype_abi_optimization(); + // Try to make this a Scalar/ScalarPair. if sized && size.bytes() > 0 { // We skip *all* ZST here and later check if we are good in terms of alignment. @@ -1205,7 +1208,7 @@ fn univariant< match field.abi { // For plain scalars, or vectors of them, we can't unpack // newtypes for `#[repr(C)]`, as that affects C ABIs. - Abi::Scalar(_) | Abi::Vector { .. } if optimize => { + Abi::Scalar(_) | Abi::Vector { .. } if optimize_abi => { abi = field.abi; } // But scalar pairs are Rust-specific and get diff --git a/compiler/rustc_abi/src/lib.rs b/compiler/rustc_abi/src/lib.rs index df29b3d54f0..be42bc84932 100644 --- a/compiler/rustc_abi/src/lib.rs +++ b/compiler/rustc_abi/src/lib.rs @@ -43,14 +43,17 @@ bitflags! { const IS_SIMD = 1 << 1; const IS_TRANSPARENT = 1 << 2; // Internal only for now. If true, don't reorder fields. + // On its own it does not prevent ABI optimizations. const IS_LINEAR = 1 << 3; - // If true, the type's layout can be randomized using - // the seed stored in `ReprOptions.field_shuffle_seed` + // If true, the type's crate has opted into layout randomization. + // Other flags can still inhibit reordering and thus randomization. + // The seed stored in `ReprOptions.field_shuffle_seed`. const RANDOMIZE_LAYOUT = 1 << 4; // Any of these flags being set prevent field reordering optimisation. - const IS_UNOPTIMISABLE = ReprFlags::IS_C.bits() + const FIELD_ORDER_UNOPTIMIZABLE = ReprFlags::IS_C.bits() | ReprFlags::IS_SIMD.bits() | ReprFlags::IS_LINEAR.bits(); + const ABI_UNOPTIMIZABLE = ReprFlags::IS_C.bits() | ReprFlags::IS_SIMD.bits(); } } @@ -139,10 +142,14 @@ impl ReprOptions { self.c() || self.int.is_some() } + pub fn inhibit_newtype_abi_optimization(&self) -> bool { + self.flags.intersects(ReprFlags::ABI_UNOPTIMIZABLE) + } + /// Returns `true` if this `#[repr()]` guarantees a fixed field order, /// e.g. `repr(C)` or `repr(<int>)`. pub fn inhibit_struct_field_reordering(&self) -> bool { - self.flags.intersects(ReprFlags::IS_UNOPTIMISABLE) || self.int.is_some() + self.flags.intersects(ReprFlags::FIELD_ORDER_UNOPTIMIZABLE) || self.int.is_some() } /// Returns `true` if this type is valid for reordering and `-Z randomize-layout` diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs index e41ea7507ef..874e75f7179 100644 --- a/compiler/rustc_middle/src/ty/mod.rs +++ b/compiler/rustc_middle/src/ty/mod.rs @@ -35,6 +35,7 @@ use rustc_data_structures::tagged_ptr::CopyTaggedPtr; use rustc_errors::{Diag, ErrorGuaranteed, StashKey}; use rustc_hir::def::{CtorKind, CtorOf, DefKind, DocLinkResMap, LifetimeRes, Res}; use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LocalDefId, LocalDefIdMap}; +use rustc_hir::LangItem; use rustc_index::IndexVec; use rustc_macros::{ extension, Decodable, Encodable, HashStable, TyDecodable, TyEncodable, TypeFoldable, @@ -1570,8 +1571,15 @@ impl<'tcx> TyCtxt<'tcx> { flags.insert(ReprFlags::RANDOMIZE_LAYOUT); } + // box is special, on the one hand the compiler assumes an ordered layout, with the pointer + // always at offset zero. On the other hand we want scalar abi optimizations. + let is_box = self.is_lang_item(did.to_def_id(), LangItem::OwnedBox); + // This is here instead of layout because the choice must make it into metadata. - if !self.consider_optimizing(|| format!("Reorder fields of {:?}", self.def_path_str(did))) { + if is_box + || !self + .consider_optimizing(|| format!("Reorder fields of {:?}", self.def_path_str(did))) + { flags.insert(ReprFlags::IS_LINEAR); } |