diff options
Diffstat (limited to 'compiler/rustc_middle/src/mir/interpret/mod.rs')
| -rw-r--r-- | compiler/rustc_middle/src/mir/interpret/mod.rs | 73 |
1 files changed, 50 insertions, 23 deletions
diff --git a/compiler/rustc_middle/src/mir/interpret/mod.rs b/compiler/rustc_middle/src/mir/interpret/mod.rs index 16093cfca6a..4e95e600b5a 100644 --- a/compiler/rustc_middle/src/mir/interpret/mod.rs +++ b/compiler/rustc_middle/src/mir/interpret/mod.rs @@ -18,6 +18,7 @@ use smallvec::{smallvec, SmallVec}; use tracing::{debug, trace}; use rustc_ast::LitKind; +use rustc_attr::InlineAttr; use rustc_data_structures::fx::FxHashMap; use rustc_data_structures::sync::{HashMapExt, Lock}; use rustc_errors::ErrorGuaranteed; @@ -134,10 +135,11 @@ pub fn specialized_encode_alloc_id<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>>( AllocDiscriminant::Alloc.encode(encoder); alloc.encode(encoder); } - GlobalAlloc::Function(fn_instance) => { - trace!("encoding {:?} with {:#?}", alloc_id, fn_instance); + GlobalAlloc::Function { instance, unique } => { + trace!("encoding {:?} with {:#?}", alloc_id, instance); AllocDiscriminant::Fn.encode(encoder); - fn_instance.encode(encoder); + instance.encode(encoder); + unique.encode(encoder); } GlobalAlloc::VTable(ty, poly_trait_ref) => { trace!("encoding {:?} with {ty:#?}, {poly_trait_ref:#?}", alloc_id); @@ -285,7 +287,12 @@ impl<'s> AllocDecodingSession<'s> { trace!("creating fn alloc ID"); let instance = ty::Instance::decode(decoder); trace!("decoded fn alloc instance: {:?}", instance); - let alloc_id = decoder.interner().reserve_and_set_fn_alloc(instance); + let unique = bool::decode(decoder); + // Here we cannot call `reserve_and_set_fn_alloc` as that would use a query, which + // is not possible in this context. That's why the allocation stores + // whether it is unique or not. + let alloc_id = + decoder.interner().reserve_and_set_fn_alloc_internal(instance, unique); alloc_id } AllocDiscriminant::VTable => { @@ -323,7 +330,12 @@ impl<'s> AllocDecodingSession<'s> { #[derive(Debug, Clone, Eq, PartialEq, Hash, TyDecodable, TyEncodable, HashStable)] pub enum GlobalAlloc<'tcx> { /// The alloc ID is used as a function pointer. - Function(Instance<'tcx>), + Function { + instance: Instance<'tcx>, + /// Stores whether this instance is unique, i.e. all pointers to this function use the same + /// alloc ID. + unique: bool, + }, /// This alloc ID points to a symbolic (not-reified) vtable. VTable(Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>), /// The alloc ID points to a "lazy" static variable that did not get computed (yet). @@ -349,7 +361,7 @@ impl<'tcx> GlobalAlloc<'tcx> { #[inline] pub fn unwrap_fn(&self) -> Instance<'tcx> { match *self { - GlobalAlloc::Function(instance) => instance, + GlobalAlloc::Function { instance, .. } => instance, _ => bug!("expected function, got {:?}", self), } } @@ -368,7 +380,7 @@ impl<'tcx> GlobalAlloc<'tcx> { #[inline] pub fn address_space(&self, cx: &impl HasDataLayout) -> AddressSpace { match self { - GlobalAlloc::Function(..) => cx.data_layout().instruction_address_space, + GlobalAlloc::Function { .. } => cx.data_layout().instruction_address_space, GlobalAlloc::Static(..) | GlobalAlloc::Memory(..) | GlobalAlloc::VTable(..) => { AddressSpace::DATA } @@ -426,7 +438,7 @@ impl<'tcx> TyCtxt<'tcx> { fn reserve_and_set_dedup(self, alloc: GlobalAlloc<'tcx>) -> AllocId { let mut alloc_map = self.alloc_map.lock(); match alloc { - GlobalAlloc::Function(..) | GlobalAlloc::Static(..) | GlobalAlloc::VTable(..) => {} + GlobalAlloc::Function { .. } | GlobalAlloc::Static(..) | GlobalAlloc::VTable(..) => {} GlobalAlloc::Memory(..) => bug!("Trying to dedup-reserve memory with real data!"), } if let Some(&alloc_id) = alloc_map.dedup.get(&alloc) { @@ -445,30 +457,45 @@ impl<'tcx> TyCtxt<'tcx> { self.reserve_and_set_dedup(GlobalAlloc::Static(static_id)) } + /// Generates an `AllocId` for a function. The caller must already have decided whether this + /// function obtains a unique AllocId or gets de-duplicated via the cache. + fn reserve_and_set_fn_alloc_internal(self, instance: Instance<'tcx>, unique: bool) -> AllocId { + let alloc = GlobalAlloc::Function { instance, unique }; + if unique { + // Deduplicate. + self.reserve_and_set_dedup(alloc) + } else { + // Get a fresh ID. + let mut alloc_map = self.alloc_map.lock(); + let id = alloc_map.reserve(); + alloc_map.alloc_map.insert(id, alloc); + id + } + } + /// Generates an `AllocId` for a function. Depending on the function type, /// this might get deduplicated or assigned a new ID each time. pub fn reserve_and_set_fn_alloc(self, instance: Instance<'tcx>) -> AllocId { // Functions cannot be identified by pointers, as asm-equal functions can get deduplicated // by the linker (we set the "unnamed_addr" attribute for LLVM) and functions can be - // duplicated across crates. - // We thus generate a new `AllocId` for every mention of a function. This means that - // `main as fn() == main as fn()` is false, while `let x = main as fn(); x == x` is true. - // However, formatting code relies on function identity (see #58320), so we only do - // this for generic functions. Lifetime parameters are ignored. + // duplicated across crates. We thus generate a new `AllocId` for every mention of a + // function. This means that `main as fn() == main as fn()` is false, while `let x = main as + // fn(); x == x` is true. However, as a quality-of-life feature it can be useful to identify + // certain functions uniquely, e.g. for backtraces. So we identify whether codegen will + // actually emit duplicate functions. It does that when they have non-lifetime generics, or + // when they can be inlined. All other functions are given a unique address. + // This is not a stable guarantee! The `inline` attribute is a hint and cannot be relied + // upon for anything. But if we don't do this, backtraces look terrible. let is_generic = instance .args .into_iter() .any(|kind| !matches!(kind.unpack(), GenericArgKind::Lifetime(_))); - if is_generic { - // Get a fresh ID. - let mut alloc_map = self.alloc_map.lock(); - let id = alloc_map.reserve(); - alloc_map.alloc_map.insert(id, GlobalAlloc::Function(instance)); - id - } else { - // Deduplicate. - self.reserve_and_set_dedup(GlobalAlloc::Function(instance)) - } + let can_be_inlined = match self.codegen_fn_attrs(instance.def_id()).inline { + InlineAttr::Never => false, + _ => true, + }; + let unique = !is_generic && !can_be_inlined; + self.reserve_and_set_fn_alloc_internal(instance, unique) } /// Generates an `AllocId` for a (symbolic, not-reified) vtable. Will get deduplicated. |