| use rustc_hir as hir; |
| use rustc_hir::lang_items::LangItem; |
| use rustc_middle::query::Providers; |
| use rustc_middle::ty::layout::{ |
| fn_can_unwind, FnAbiError, HasParamEnv, HasTyCtxt, LayoutCx, LayoutOf, TyAndLayout, |
| }; |
| use rustc_middle::ty::{self, InstanceDef, Ty, TyCtxt}; |
| use rustc_session::config::OptLevel; |
| use rustc_span::def_id::DefId; |
| use rustc_target::abi::call::{ |
| ArgAbi, ArgAttribute, ArgAttributes, ArgExtension, Conv, FnAbi, PassMode, Reg, RegKind, |
| RiscvInterruptKind, |
| }; |
| use rustc_target::abi::*; |
| use rustc_target::spec::abi::Abi as SpecAbi; |
| |
| use std::iter; |
| |
| pub fn provide(providers: &mut Providers) { |
| *providers = Providers { fn_abi_of_fn_ptr, fn_abi_of_instance, ..*providers }; |
| } |
| |
| // NOTE(eddyb) this is private to avoid using it from outside of |
| // `fn_abi_of_instance` - any other uses are either too high-level |
| // for `Instance` (e.g. typeck would use `Ty::fn_sig` instead), |
| // or should go through `FnAbi` instead, to avoid losing any |
| // adjustments `fn_abi_of_instance` might be performing. |
| #[tracing::instrument(level = "debug", skip(tcx, param_env))] |
| fn fn_sig_for_fn_abi<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| instance: ty::Instance<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| ) -> ty::PolyFnSig<'tcx> { |
| if let InstanceDef::ThreadLocalShim(..) = instance.def { |
| return ty::Binder::dummy(tcx.mk_fn_sig( |
| [], |
| tcx.thread_local_ptr_ty(instance.def_id()), |
| false, |
| hir::Unsafety::Normal, |
| rustc_target::spec::abi::Abi::Unadjusted, |
| )); |
| } |
| |
| let ty = instance.ty(tcx, param_env); |
| match *ty.kind() { |
| ty::FnDef(..) => { |
| // HACK(davidtwco,eddyb): This is a workaround for polymorphization considering |
| // parameters unused if they show up in the signature, but not in the `mir::Body` |
| // (i.e. due to being inside a projection that got normalized, see |
| // `tests/ui/polymorphization/normalized_sig_types.rs`), and codegen not keeping |
| // track of a polymorphization `ParamEnv` to allow normalizing later. |
| // |
| // We normalize the `fn_sig` again after substituting at a later point. |
| let mut sig = match *ty.kind() { |
| ty::FnDef(def_id, args) => tcx |
| .fn_sig(def_id) |
| .map_bound(|fn_sig| { |
| tcx.normalize_erasing_regions(tcx.param_env(def_id), fn_sig) |
| }) |
| .instantiate(tcx, args), |
| _ => unreachable!(), |
| }; |
| |
| if let ty::InstanceDef::VTableShim(..) = instance.def { |
| // Modify `fn(self, ...)` to `fn(self: *mut Self, ...)`. |
| sig = sig.map_bound(|mut sig| { |
| let mut inputs_and_output = sig.inputs_and_output.to_vec(); |
| inputs_and_output[0] = Ty::new_mut_ptr(tcx, inputs_and_output[0]); |
| sig.inputs_and_output = tcx.mk_type_list(&inputs_and_output); |
| sig |
| }); |
| } |
| sig |
| } |
| ty::Closure(def_id, args) => { |
| let sig = args.as_closure().sig(); |
| |
| let bound_vars = tcx.mk_bound_variable_kinds_from_iter( |
| sig.bound_vars().iter().chain(iter::once(ty::BoundVariableKind::Region(ty::BrEnv))), |
| ); |
| let br = ty::BoundRegion { |
| var: ty::BoundVar::from_usize(bound_vars.len() - 1), |
| kind: ty::BoundRegionKind::BrEnv, |
| }; |
| let env_region = ty::Region::new_late_bound(tcx, ty::INNERMOST, br); |
| let env_ty = tcx.closure_env_ty(def_id, args, env_region).unwrap(); |
| |
| let sig = sig.skip_binder(); |
| ty::Binder::bind_with_vars( |
| tcx.mk_fn_sig( |
| iter::once(env_ty).chain(sig.inputs().iter().cloned()), |
| sig.output(), |
| sig.c_variadic, |
| sig.unsafety, |
| sig.abi, |
| ), |
| bound_vars, |
| ) |
| } |
| ty::Coroutine(did, args, _) => { |
| let sig = args.as_coroutine().poly_sig(); |
| |
| let bound_vars = tcx.mk_bound_variable_kinds_from_iter( |
| sig.bound_vars().iter().chain(iter::once(ty::BoundVariableKind::Region(ty::BrEnv))), |
| ); |
| let br = ty::BoundRegion { |
| var: ty::BoundVar::from_usize(bound_vars.len() - 1), |
| kind: ty::BoundRegionKind::BrEnv, |
| }; |
| let env_ty = |
| Ty::new_mut_ref(tcx, ty::Region::new_late_bound(tcx, ty::INNERMOST, br), ty); |
| |
| let pin_did = tcx.require_lang_item(LangItem::Pin, None); |
| let pin_adt_ref = tcx.adt_def(pin_did); |
| let pin_args = tcx.mk_args(&[env_ty.into()]); |
| let env_ty = Ty::new_adt(tcx, pin_adt_ref, pin_args); |
| |
| let sig = sig.skip_binder(); |
| // The `FnSig` and the `ret_ty` here is for a coroutines main |
| // `Coroutine::resume(...) -> CoroutineState` function in case we |
| // have an ordinary coroutine, or the `Future::poll(...) -> Poll` |
| // function in case this is a special coroutine backing an async construct. |
| let (resume_ty, ret_ty) = if tcx.coroutine_is_async(did) { |
| // The signature should be `Future::poll(_, &mut Context<'_>) -> Poll<Output>` |
| let poll_did = tcx.require_lang_item(LangItem::Poll, None); |
| let poll_adt_ref = tcx.adt_def(poll_did); |
| let poll_args = tcx.mk_args(&[sig.return_ty.into()]); |
| let ret_ty = Ty::new_adt(tcx, poll_adt_ref, poll_args); |
| |
| // We have to replace the `ResumeTy` that is used for type and borrow checking |
| // with `&mut Context<'_>` which is used in codegen. |
| #[cfg(debug_assertions)] |
| { |
| if let ty::Adt(resume_ty_adt, _) = sig.resume_ty.kind() { |
| let expected_adt = |
| tcx.adt_def(tcx.require_lang_item(LangItem::ResumeTy, None)); |
| assert_eq!(*resume_ty_adt, expected_adt); |
| } else { |
| panic!("expected `ResumeTy`, found `{:?}`", sig.resume_ty); |
| }; |
| } |
| let context_mut_ref = Ty::new_task_context(tcx); |
| |
| (context_mut_ref, ret_ty) |
| } else { |
| // The signature should be `Coroutine::resume(_, Resume) -> CoroutineState<Yield, Return>` |
| let state_did = tcx.require_lang_item(LangItem::CoroutineState, None); |
| let state_adt_ref = tcx.adt_def(state_did); |
| let state_args = tcx.mk_args(&[sig.yield_ty.into(), sig.return_ty.into()]); |
| let ret_ty = Ty::new_adt(tcx, state_adt_ref, state_args); |
| |
| (sig.resume_ty, ret_ty) |
| }; |
| |
| ty::Binder::bind_with_vars( |
| tcx.mk_fn_sig( |
| [env_ty, resume_ty], |
| ret_ty, |
| false, |
| hir::Unsafety::Normal, |
| rustc_target::spec::abi::Abi::Rust, |
| ), |
| bound_vars, |
| ) |
| } |
| _ => bug!("unexpected type {:?} in Instance::fn_sig", ty), |
| } |
| } |
| |
| #[inline] |
| fn conv_from_spec_abi(tcx: TyCtxt<'_>, abi: SpecAbi) -> Conv { |
| use rustc_target::spec::abi::Abi::*; |
| match tcx.sess.target.adjust_abi(abi) { |
| RustIntrinsic | PlatformIntrinsic | Rust | RustCall => Conv::Rust, |
| |
| // This is intentionally not using `Conv::Cold`, as that has to preserve |
| // even SIMD registers, which is generally not a good trade-off. |
| RustCold => Conv::PreserveMost, |
| |
| // It's the ABI's job to select this, not ours. |
| System { .. } => bug!("system abi should be selected elsewhere"), |
| EfiApi => bug!("eficall abi should be selected elsewhere"), |
| |
| Stdcall { .. } => Conv::X86Stdcall, |
| Fastcall { .. } => Conv::X86Fastcall, |
| Vectorcall { .. } => Conv::X86VectorCall, |
| Thiscall { .. } => Conv::X86ThisCall, |
| C { .. } => Conv::C, |
| Unadjusted => Conv::C, |
| Win64 { .. } => Conv::X86_64Win64, |
| SysV64 { .. } => Conv::X86_64SysV, |
| Aapcs { .. } => Conv::ArmAapcs, |
| CCmseNonSecureCall => Conv::CCmseNonSecureCall, |
| PtxKernel => Conv::PtxKernel, |
| Msp430Interrupt => Conv::Msp430Intr, |
| X86Interrupt => Conv::X86Intr, |
| AmdGpuKernel => Conv::AmdGpuKernel, |
| AvrInterrupt => Conv::AvrInterrupt, |
| AvrNonBlockingInterrupt => Conv::AvrNonBlockingInterrupt, |
| RiscvInterruptM => Conv::RiscvInterrupt { kind: RiscvInterruptKind::Machine }, |
| RiscvInterruptS => Conv::RiscvInterrupt { kind: RiscvInterruptKind::Supervisor }, |
| Wasm => Conv::C, |
| |
| // These API constants ought to be more specific... |
| Cdecl { .. } => Conv::C, |
| } |
| } |
| |
| fn fn_abi_of_fn_ptr<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| query: ty::ParamEnvAnd<'tcx, (ty::PolyFnSig<'tcx>, &'tcx ty::List<Ty<'tcx>>)>, |
| ) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, &'tcx FnAbiError<'tcx>> { |
| let (param_env, (sig, extra_args)) = query.into_parts(); |
| |
| let cx = LayoutCx { tcx, param_env }; |
| fn_abi_new_uncached(&cx, sig, extra_args, None, None, false) |
| } |
| |
| fn fn_abi_of_instance<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| query: ty::ParamEnvAnd<'tcx, (ty::Instance<'tcx>, &'tcx ty::List<Ty<'tcx>>)>, |
| ) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, &'tcx FnAbiError<'tcx>> { |
| let (param_env, (instance, extra_args)) = query.into_parts(); |
| |
| let sig = fn_sig_for_fn_abi(tcx, instance, param_env); |
| |
| let caller_location = |
| instance.def.requires_caller_location(tcx).then(|| tcx.caller_location_ty()); |
| |
| fn_abi_new_uncached( |
| &LayoutCx { tcx, param_env }, |
| sig, |
| extra_args, |
| caller_location, |
| Some(instance.def_id()), |
| matches!(instance.def, ty::InstanceDef::Virtual(..)), |
| ) |
| } |
| |
| // Handle safe Rust thin and fat pointers. |
| fn adjust_for_rust_scalar<'tcx>( |
| cx: LayoutCx<'tcx, TyCtxt<'tcx>>, |
| attrs: &mut ArgAttributes, |
| scalar: Scalar, |
| layout: TyAndLayout<'tcx>, |
| offset: Size, |
| is_return: bool, |
| drop_target_pointee: Option<Ty<'tcx>>, |
| ) { |
| // Booleans are always a noundef i1 that needs to be zero-extended. |
| if scalar.is_bool() { |
| attrs.ext(ArgExtension::Zext); |
| attrs.set(ArgAttribute::NoUndef); |
| return; |
| } |
| |
| if !scalar.is_uninit_valid() { |
| attrs.set(ArgAttribute::NoUndef); |
| } |
| |
| // Only pointer types handled below. |
| let Scalar::Initialized { value: Pointer(_), valid_range } = scalar else { return }; |
| |
| // Set `nonnull` if the validity range excludes zero, or for the argument to `drop_in_place`, |
| // which must be nonnull per its documented safety requirements. |
| if !valid_range.contains(0) || drop_target_pointee.is_some() { |
| attrs.set(ArgAttribute::NonNull); |
| } |
| |
| if let Some(pointee) = layout.pointee_info_at(&cx, offset) { |
| let kind = if let Some(kind) = pointee.safe { |
| Some(kind) |
| } else if let Some(pointee) = drop_target_pointee { |
| // The argument to `drop_in_place` is semantically equivalent to a mutable reference. |
| Some(PointerKind::MutableRef { unpin: pointee.is_unpin(cx.tcx, cx.param_env()) }) |
| } else { |
| None |
| }; |
| if let Some(kind) = kind { |
| attrs.pointee_align = Some(pointee.align); |
| |
| // `Box` are not necessarily dereferenceable for the entire duration of the function as |
| // they can be deallocated at any time. Same for non-frozen shared references (see |
| // <https://github.com/rust-lang/rust/pull/98017>), and for mutable references to |
| // potentially self-referential types (see |
| // <https://github.com/rust-lang/unsafe-code-guidelines/issues/381>). If LLVM had a way |
| // to say "dereferenceable on entry" we could use it here. |
| attrs.pointee_size = match kind { |
| PointerKind::Box { .. } |
| | PointerKind::SharedRef { frozen: false } |
| | PointerKind::MutableRef { unpin: false } => Size::ZERO, |
| PointerKind::SharedRef { frozen: true } |
| | PointerKind::MutableRef { unpin: true } => pointee.size, |
| }; |
| |
| // The aliasing rules for `Box<T>` are still not decided, but currently we emit |
| // `noalias` for it. This can be turned off using an unstable flag. |
| // See https://github.com/rust-lang/unsafe-code-guidelines/issues/326 |
| let noalias_for_box = cx.tcx.sess.opts.unstable_opts.box_noalias; |
| |
| // LLVM prior to version 12 had known miscompiles in the presence of noalias attributes |
| // (see #54878), so it was conditionally disabled, but we don't support earlier |
| // versions at all anymore. We still support turning it off using -Zmutable-noalias. |
| let noalias_mut_ref = cx.tcx.sess.opts.unstable_opts.mutable_noalias; |
| |
| // `&T` where `T` contains no `UnsafeCell<U>` is immutable, and can be marked as both |
| // `readonly` and `noalias`, as LLVM's definition of `noalias` is based solely on memory |
| // dependencies rather than pointer equality. However this only applies to arguments, |
| // not return values. |
| // |
| // `&mut T` and `Box<T>` where `T: Unpin` are unique and hence `noalias`. |
| let no_alias = match kind { |
| PointerKind::SharedRef { frozen } => frozen, |
| PointerKind::MutableRef { unpin } => unpin && noalias_mut_ref, |
| PointerKind::Box { unpin } => unpin && noalias_for_box, |
| }; |
| // We can never add `noalias` in return position; that LLVM attribute has some very surprising semantics |
| // (see <https://github.com/rust-lang/unsafe-code-guidelines/issues/385#issuecomment-1368055745>). |
| if no_alias && !is_return { |
| attrs.set(ArgAttribute::NoAlias); |
| } |
| |
| if matches!(kind, PointerKind::SharedRef { frozen: true }) && !is_return { |
| attrs.set(ArgAttribute::ReadOnly); |
| } |
| } |
| } |
| } |
| |
| // FIXME(eddyb) perhaps group the signature/type-containing (or all of them?) |
| // arguments of this method, into a separate `struct`. |
| #[tracing::instrument(level = "debug", skip(cx, caller_location, fn_def_id, force_thin_self_ptr))] |
| fn fn_abi_new_uncached<'tcx>( |
| cx: &LayoutCx<'tcx, TyCtxt<'tcx>>, |
| sig: ty::PolyFnSig<'tcx>, |
| extra_args: &[Ty<'tcx>], |
| caller_location: Option<Ty<'tcx>>, |
| fn_def_id: Option<DefId>, |
| // FIXME(eddyb) replace this with something typed, like an `enum`. |
| force_thin_self_ptr: bool, |
| ) -> Result<&'tcx FnAbi<'tcx, Ty<'tcx>>, &'tcx FnAbiError<'tcx>> { |
| let sig = cx.tcx.normalize_erasing_late_bound_regions(cx.param_env, sig); |
| |
| let conv = conv_from_spec_abi(cx.tcx(), sig.abi); |
| |
| let mut inputs = sig.inputs(); |
| let extra_args = if sig.abi == RustCall { |
| assert!(!sig.c_variadic && extra_args.is_empty()); |
| |
| if let Some(input) = sig.inputs().last() { |
| if let ty::Tuple(tupled_arguments) = input.kind() { |
| inputs = &sig.inputs()[0..sig.inputs().len() - 1]; |
| tupled_arguments |
| } else { |
| bug!( |
| "argument to function with \"rust-call\" ABI \ |
| is not a tuple" |
| ); |
| } |
| } else { |
| bug!( |
| "argument to function with \"rust-call\" ABI \ |
| is not a tuple" |
| ); |
| } |
| } else { |
| assert!(sig.c_variadic || extra_args.is_empty()); |
| extra_args |
| }; |
| |
| let target = &cx.tcx.sess.target; |
| let target_env_gnu_like = matches!(&target.env[..], "gnu" | "musl" | "uclibc"); |
| let win_x64_gnu = target.os == "windows" && target.arch == "x86_64" && target.env == "gnu"; |
| let linux_s390x_gnu_like = |
| target.os == "linux" && target.arch == "s390x" && target_env_gnu_like; |
| let linux_sparc64_gnu_like = |
| target.os == "linux" && target.arch == "sparc64" && target_env_gnu_like; |
| let linux_powerpc_gnu_like = |
| target.os == "linux" && target.arch == "powerpc" && target_env_gnu_like; |
| use SpecAbi::*; |
| let rust_abi = matches!(sig.abi, RustIntrinsic | PlatformIntrinsic | Rust | RustCall); |
| |
| let is_drop_in_place = |
| fn_def_id.is_some() && fn_def_id == cx.tcx.lang_items().drop_in_place_fn(); |
| |
| let arg_of = |ty: Ty<'tcx>, arg_idx: Option<usize>| -> Result<_, &'tcx FnAbiError<'tcx>> { |
| let span = tracing::debug_span!("arg_of"); |
| let _entered = span.enter(); |
| let is_return = arg_idx.is_none(); |
| let is_drop_target = is_drop_in_place && arg_idx == Some(0); |
| let drop_target_pointee = is_drop_target.then(|| match ty.kind() { |
| ty::RawPtr(ty::TypeAndMut { ty, .. }) => *ty, |
| _ => bug!("argument to drop_in_place is not a raw ptr: {:?}", ty), |
| }); |
| |
| let layout = |
| cx.layout_of(ty).map_err(|err| &*cx.tcx.arena.alloc(FnAbiError::Layout(*err)))?; |
| let layout = if force_thin_self_ptr && arg_idx == Some(0) { |
| // Don't pass the vtable, it's not an argument of the virtual fn. |
| // Instead, pass just the data pointer, but give it the type `*const/mut dyn Trait` |
| // or `&/&mut dyn Trait` because this is special-cased elsewhere in codegen |
| make_thin_self_ptr(cx, layout) |
| } else { |
| layout |
| }; |
| |
| let mut arg = ArgAbi::new(cx, layout, |layout, scalar, offset| { |
| let mut attrs = ArgAttributes::new(); |
| adjust_for_rust_scalar( |
| *cx, |
| &mut attrs, |
| scalar, |
| *layout, |
| offset, |
| is_return, |
| drop_target_pointee, |
| ); |
| attrs |
| }); |
| |
| if arg.layout.is_zst() { |
| // For some forsaken reason, x86_64-pc-windows-gnu |
| // doesn't ignore zero-sized struct arguments. |
| // The same is true for {s390x,sparc64,powerpc}-unknown-linux-{gnu,musl,uclibc}. |
| if is_return |
| || rust_abi |
| || (!win_x64_gnu |
| && !linux_s390x_gnu_like |
| && !linux_sparc64_gnu_like |
| && !linux_powerpc_gnu_like) |
| { |
| arg.mode = PassMode::Ignore; |
| } |
| } |
| |
| Ok(arg) |
| }; |
| |
| let mut fn_abi = FnAbi { |
| ret: arg_of(sig.output(), None)?, |
| args: inputs |
| .iter() |
| .copied() |
| .chain(extra_args.iter().copied()) |
| .chain(caller_location) |
| .enumerate() |
| .map(|(i, ty)| arg_of(ty, Some(i))) |
| .collect::<Result<_, _>>()?, |
| c_variadic: sig.c_variadic, |
| fixed_count: inputs.len() as u32, |
| conv, |
| can_unwind: fn_can_unwind(cx.tcx(), fn_def_id, sig.abi), |
| }; |
| fn_abi_adjust_for_abi(cx, &mut fn_abi, sig.abi, fn_def_id)?; |
| debug!("fn_abi_new_uncached = {:?}", fn_abi); |
| Ok(cx.tcx.arena.alloc(fn_abi)) |
| } |
| |
| #[tracing::instrument(level = "trace", skip(cx))] |
| fn fn_abi_adjust_for_abi<'tcx>( |
| cx: &LayoutCx<'tcx, TyCtxt<'tcx>>, |
| fn_abi: &mut FnAbi<'tcx, Ty<'tcx>>, |
| abi: SpecAbi, |
| fn_def_id: Option<DefId>, |
| ) -> Result<(), &'tcx FnAbiError<'tcx>> { |
| if abi == SpecAbi::Unadjusted { |
| return Ok(()); |
| } |
| |
| if abi == SpecAbi::Rust |
| || abi == SpecAbi::RustCall |
| || abi == SpecAbi::RustIntrinsic |
| || abi == SpecAbi::PlatformIntrinsic |
| { |
| // Look up the deduced parameter attributes for this function, if we have its def ID and |
| // we're optimizing in non-incremental mode. We'll tag its parameters with those attributes |
| // as appropriate. |
| let deduced_param_attrs = if cx.tcx.sess.opts.optimize != OptLevel::No |
| && cx.tcx.sess.opts.incremental.is_none() |
| { |
| fn_def_id.map(|fn_def_id| cx.tcx.deduced_param_attrs(fn_def_id)).unwrap_or_default() |
| } else { |
| &[] |
| }; |
| |
| let fixup = |arg: &mut ArgAbi<'tcx, Ty<'tcx>>, arg_idx: Option<usize>| { |
| if arg.is_ignore() { |
| return; |
| } |
| |
| match arg.layout.abi { |
| Abi::Aggregate { .. } => {} |
| |
| // This is a fun case! The gist of what this is doing is |
| // that we want callers and callees to always agree on the |
| // ABI of how they pass SIMD arguments. If we were to *not* |
| // make these arguments indirect then they'd be immediates |
| // in LLVM, which means that they'd used whatever the |
| // appropriate ABI is for the callee and the caller. That |
| // means, for example, if the caller doesn't have AVX |
| // enabled but the callee does, then passing an AVX argument |
| // across this boundary would cause corrupt data to show up. |
| // |
| // This problem is fixed by unconditionally passing SIMD |
| // arguments through memory between callers and callees |
| // which should get them all to agree on ABI regardless of |
| // target feature sets. Some more information about this |
| // issue can be found in #44367. |
| // |
| // Note that the platform intrinsic ABI is exempt here as |
| // that's how we connect up to LLVM and it's unstable |
| // anyway, we control all calls to it in libstd. |
| Abi::Vector { .. } |
| if abi != SpecAbi::PlatformIntrinsic |
| && cx.tcx.sess.target.simd_types_indirect => |
| { |
| arg.make_indirect(); |
| return; |
| } |
| |
| _ => return, |
| } |
| // `Aggregate` ABI must be adjusted to ensure that ABI-compatible Rust types are passed |
| // the same way. |
| |
| let size = arg.layout.size; |
| if arg.layout.is_unsized() || size > Pointer(AddressSpace::DATA).size(cx) { |
| arg.make_indirect(); |
| } else { |
| // We want to pass small aggregates as immediates, but using |
| // an LLVM aggregate type for this leads to bad optimizations, |
| // so we pick an appropriately sized integer type instead. |
| arg.cast_to(Reg { kind: RegKind::Integer, size }); |
| } |
| |
| // If we deduced that this parameter was read-only, add that to the attribute list now. |
| // |
| // The `readonly` parameter only applies to pointers, so we can only do this if the |
| // argument was passed indirectly. (If the argument is passed directly, it's an SSA |
| // value, so it's implicitly immutable.) |
| if let (Some(arg_idx), &mut PassMode::Indirect { ref mut attrs, .. }) = |
| (arg_idx, &mut arg.mode) |
| { |
| // The `deduced_param_attrs` list could be empty if this is a type of function |
| // we can't deduce any parameters for, so make sure the argument index is in |
| // bounds. |
| if let Some(deduced_param_attrs) = deduced_param_attrs.get(arg_idx) { |
| if deduced_param_attrs.read_only { |
| attrs.regular.insert(ArgAttribute::ReadOnly); |
| debug!("added deduced read-only attribute"); |
| } |
| } |
| } |
| }; |
| |
| fixup(&mut fn_abi.ret, None); |
| for (arg_idx, arg) in fn_abi.args.iter_mut().enumerate() { |
| fixup(arg, Some(arg_idx)); |
| } |
| } else { |
| fn_abi |
| .adjust_for_foreign_abi(cx, abi) |
| .map_err(|err| &*cx.tcx.arena.alloc(FnAbiError::AdjustForForeignAbi(err)))?; |
| } |
| |
| Ok(()) |
| } |
| |
| #[tracing::instrument(level = "debug", skip(cx))] |
| fn make_thin_self_ptr<'tcx>( |
| cx: &(impl HasTyCtxt<'tcx> + HasParamEnv<'tcx>), |
| layout: TyAndLayout<'tcx>, |
| ) -> TyAndLayout<'tcx> { |
| let tcx = cx.tcx(); |
| let fat_pointer_ty = if layout.is_unsized() { |
| // unsized `self` is passed as a pointer to `self` |
| // FIXME (mikeyhew) change this to use &own if it is ever added to the language |
| Ty::new_mut_ptr(tcx, layout.ty) |
| } else { |
| match layout.abi { |
| Abi::ScalarPair(..) | Abi::Scalar(..) => (), |
| _ => bug!("receiver type has unsupported layout: {:?}", layout), |
| } |
| |
| // In the case of Rc<Self>, we need to explicitly pass a *mut RcBox<Self> |
| // with a Scalar (not ScalarPair) ABI. This is a hack that is understood |
| // elsewhere in the compiler as a method on a `dyn Trait`. |
| // To get the type `*mut RcBox<Self>`, we just keep unwrapping newtypes until we |
| // get a built-in pointer type |
| let mut fat_pointer_layout = layout; |
| while !fat_pointer_layout.ty.is_unsafe_ptr() && !fat_pointer_layout.ty.is_ref() { |
| fat_pointer_layout = fat_pointer_layout |
| .non_1zst_field(cx) |
| .expect("not exactly one non-1-ZST field in a `DispatchFromDyn` type") |
| .1 |
| } |
| |
| fat_pointer_layout.ty |
| }; |
| |
| // we now have a type like `*mut RcBox<dyn Trait>` |
| // change its layout to that of `*mut ()`, a thin pointer, but keep the same type |
| // this is understood as a special case elsewhere in the compiler |
| let unit_ptr_ty = Ty::new_mut_ptr(tcx, Ty::new_unit(tcx)); |
| |
| TyAndLayout { |
| ty: fat_pointer_ty, |
| |
| // NOTE(eddyb) using an empty `ParamEnv`, and `unwrap`-ing the `Result` |
| // should always work because the type is always `*mut ()`. |
| ..tcx.layout_of(ty::ParamEnv::reveal_all().and(unit_ptr_ty)).unwrap() |
| } |
| } |
