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(crate) 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_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 coroutine_kind = tcx.coroutine_kind(did).unwrap(); let sig = args.as_coroutine().sig(); let bound_vars = tcx.mk_bound_variable_kinds_from_iter(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_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 = match coroutine_kind { hir::CoroutineKind::Gen(_) => { // Iterator::next doesn't accept a pinned argument, // unlike for all other coroutine kinds. env_ty } hir::CoroutineKind::Async(_) | hir::CoroutineKind::AsyncGen(_) | hir::CoroutineKind::Coroutine => Ty::new_adt(tcx, pin_adt_ref, pin_args), }; // The `FnSig` and the `ret_ty` here is for a coroutines main // `Coroutine::resume(...) -> CoroutineState` function in case we // have an ordinary coroutine, the `Future::poll(...) -> Poll` // function in case this is a special coroutine backing an async construct // or the `Iterator::next(...) -> Option` function in case this is a // special coroutine backing a gen construct. let (resume_ty, ret_ty) = match coroutine_kind { hir::CoroutineKind::Async(_) => { // The signature should be `Future::poll(_, &mut Context<'_>) -> Poll` assert_eq!(sig.yield_ty, tcx.types.unit); 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); (Some(context_mut_ref), ret_ty) } hir::CoroutineKind::Gen(_) => { // The signature should be `Iterator::next(_) -> Option` let option_did = tcx.require_lang_item(LangItem::Option, None); let option_adt_ref = tcx.adt_def(option_did); let option_args = tcx.mk_args(&[sig.yield_ty.into()]); let ret_ty = Ty::new_adt(tcx, option_adt_ref, option_args); assert_eq!(sig.return_ty, tcx.types.unit); assert_eq!(sig.resume_ty, tcx.types.unit); (None, ret_ty) } hir::CoroutineKind::AsyncGen(_) => { // The signature should be // `AsyncIterator::poll_next(_, &mut Context<'_>) -> Poll>` assert_eq!(sig.return_ty, tcx.types.unit); // Yield type is already `Poll>` let ret_ty = sig.yield_ty; // 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); (Some(context_mut_ref), ret_ty) } hir::CoroutineKind::Coroutine => { // The signature should be `Coroutine::resume(_, Resume) -> CoroutineState` 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); (Some(sig.resume_ty), ret_ty) } }; let fn_sig = if let Some(resume_ty) = resume_ty { tcx.mk_fn_sig( [env_ty, resume_ty], ret_ty, false, hir::Unsafety::Normal, rustc_target::spec::abi::Abi::Rust, ) } else { // `Iterator::next` doesn't have a `resume` argument. tcx.mk_fn_sig( [env_ty], ret_ty, false, hir::Unsafety::Normal, rustc_target::spec::abi::Abi::Rust, ) }; ty::Binder::bind_with_vars(fn_sig, 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>)>, ) -> 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>)>, ) -> 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>, ) { // 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 // ), and for mutable references to // potentially self-referential types (see // ). 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` 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` 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` 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 ). if no_alias && !is_return { attrs.set(ArgAttribute::NoAlias); } if matches!(kind, PointerKind::SharedRef { frozen: true }) && !is_return { attrs.set(ArgAttribute::ReadOnly); } } } } /// Ensure that the ABI makes basic sense. fn fn_abi_sanity_check<'tcx>( cx: &LayoutCx<'tcx, TyCtxt<'tcx>>, fn_abi: &FnAbi<'tcx, Ty<'tcx>>, spec_abi: SpecAbi, ) { fn fn_arg_sanity_check<'tcx>( cx: &LayoutCx<'tcx, TyCtxt<'tcx>>, fn_abi: &FnAbi<'tcx, Ty<'tcx>>, spec_abi: SpecAbi, arg: &ArgAbi<'tcx, Ty<'tcx>>, ) { match &arg.mode { PassMode::Ignore => {} PassMode::Direct(_) => { // Here the Rust type is used to determine the actual ABI, so we have to be very // careful. Scalar/ScalarPair is fine, since backends will generally use // `layout.abi` and ignore everything else. We should just reject `Aggregate` // entirely here, but some targets need to be fixed first. if matches!(arg.layout.abi, Abi::Aggregate { .. }) { // For an unsized type we'd only pass the sized prefix, so there is no universe // in which we ever want to allow this. assert!( arg.layout.is_sized(), "`PassMode::Direct` for unsized type in ABI: {:#?}", fn_abi ); // This really shouldn't happen even for sized aggregates, since // `immediate_llvm_type` will use `layout.fields` to turn this Rust type into an // LLVM type. This means all sorts of Rust type details leak into the ABI. // However wasm sadly *does* currently use this mode so we have to allow it -- // but we absolutely shouldn't let any more targets do that. // (Also see .) // // The unstable abi `PtxKernel` also uses Direct for now. // It needs to switch to something else before stabilization can happen. // (See issue: https://github.com/rust-lang/rust/issues/117271) assert!( matches!(&*cx.tcx.sess.target.arch, "wasm32" | "wasm64") || matches!(spec_abi, SpecAbi::PtxKernel | SpecAbi::Unadjusted), r#"`PassMode::Direct` for aggregates only allowed for "unadjusted" and "ptx-kernel" functions and on wasm\nProblematic type: {:#?}"#, arg.layout, ); } } PassMode::Pair(_, _) => { // Similar to `Direct`, we need to make sure that backends use `layout.abi` and // ignore the rest of the layout. assert!( matches!(arg.layout.abi, Abi::ScalarPair(..)), "PassMode::Pair for type {}", arg.layout.ty ); } PassMode::Cast { .. } => { // `Cast` means "transmute to `CastType`"; that only makes sense for sized types. assert!(arg.layout.is_sized()); } PassMode::Indirect { meta_attrs: None, .. } => { // No metadata, must be sized. // Conceptually, unsized arguments must be copied around, which requires dynamically // determining their size, which we cannot do without metadata. Consult // t-opsem before removing this check. assert!(arg.layout.is_sized()); } PassMode::Indirect { meta_attrs: Some(_), on_stack, .. } => { // With metadata. Must be unsized and not on the stack. assert!(arg.layout.is_unsized() && !on_stack); // Also, must not be `extern` type. let tail = cx.tcx.struct_tail_with_normalize(arg.layout.ty, |ty| ty, || {}); if matches!(tail.kind(), ty::Foreign(..)) { // These types do not have metadata, so having `meta_attrs` is bogus. // Conceptually, unsized arguments must be copied around, which requires dynamically // determining their size. Therefore, we cannot allow `extern` types here. Consult // t-opsem before removing this check. panic!("unsized arguments must not be `extern` types"); } } } } for arg in fn_abi.args.iter() { fn_arg_sanity_check(cx, fn_abi, spec_abi, arg); } fn_arg_sanity_check(cx, fn_abi, spec_abi, &fn_abi.ret); } // 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>, fn_def_id: Option, // 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| -> 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::>()?, 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); fn_abi_sanity_check(cx, &fn_abi, sig.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, ) -> Result<(), &'tcx FnAbiError<'tcx>> { if abi == SpecAbi::Unadjusted { // The "unadjusted" ABI passes aggregates in "direct" mode. That's fragile but needed for // some LLVM intrinsics. fn unadjust<'tcx>(arg: &mut ArgAbi<'tcx, Ty<'tcx>>) { // This still uses `PassMode::Pair` for ScalarPair types. That's unlikely to be intended, // but who knows what breaks if we change this now. if matches!(arg.layout.abi, Abi::Aggregate { .. }) { assert!( arg.layout.abi.is_sized(), "'unadjusted' ABI does not support unsized arguments" ); } arg.make_direct_deprecated(); } unadjust(&mut fn_abi.ret); for arg in fn_abi.args.iter_mut() { unadjust(arg); } 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| { 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, } // Compute `Aggregate` ABI. let is_indirect_not_on_stack = matches!(arg.mode, PassMode::Indirect { on_stack: false, .. }); assert!(is_indirect_not_on_stack, "{:?}", arg); let size = arg.layout.size; if !arg.layout.is_unsized() && size <= Pointer(AddressSpace::DATA).size(cx) { // 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, we need to explicitly pass a *mut RcBox // 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`, 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` // 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() } }