use rustc_hir as hir; use rustc_hir::lang_items::LangItem; use rustc_middle::ty::layout::{ fn_can_unwind, FnAbiError, HasParamEnv, HasTyCtxt, LayoutCx, LayoutOf, TyAndLayout, }; use rustc_middle::ty::{self, 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, }; use rustc_target::abi::*; use rustc_target::spec::abi::Abi as SpecAbi; use std::iter; pub fn provide(providers: &mut ty::query::Providers) { *providers = ty::query::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> { 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 // `src/test/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, substs) => tcx .bound_fn_sig(def_id) .map_bound(|fn_sig| { tcx.normalize_erasing_regions(tcx.param_env(def_id), fn_sig) }) .subst(tcx, substs), _ => 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] = tcx.mk_mut_ptr(inputs_and_output[0]); sig.inputs_and_output = tcx.intern_type_list(&inputs_and_output); sig }); } sig } ty::Closure(def_id, substs) => { let sig = substs.as_closure().sig(); let bound_vars = tcx.mk_bound_variable_kinds( 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::ReLateBound(ty::INNERMOST, br); let env_ty = tcx.closure_env_ty(def_id, substs, 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::Generator(_, substs, _) => { let sig = substs.as_generator().poly_sig(); let bound_vars = tcx.mk_bound_variable_kinds( 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::ReLateBound(ty::INNERMOST, br); let env_ty = tcx.mk_mut_ref(tcx.mk_region(env_region), ty); let pin_did = tcx.require_lang_item(LangItem::Pin, None); let pin_adt_ref = tcx.adt_def(pin_did); let pin_substs = tcx.intern_substs(&[env_ty.into()]); let env_ty = tcx.mk_adt(pin_adt_ref, pin_substs); let sig = sig.skip_binder(); let state_did = tcx.require_lang_item(LangItem::GeneratorState, None); let state_adt_ref = tcx.adt_def(state_did); let state_substs = tcx.intern_substs(&[sig.yield_ty.into(), sig.return_ty.into()]); let ret_ty = tcx.mk_adt(state_adt_ref, state_substs); ty::Binder::bind_with_vars( tcx.mk_fn_sig( [env_ty, sig.resume_ty].iter(), &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, RustCold => Conv::RustCold, // 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, 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>>, 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>>, 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 = if instance.def.requires_caller_location(tcx) { Some(tcx.caller_location_ty()) } else { None }; 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, ) { // 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; } // Scalars which have invalid values cannot be undef. if !scalar.is_always_valid(&cx) { attrs.set(ArgAttribute::NoUndef); } // Only pointer types handled below. let Scalar::Initialized { value: Pointer, valid_range} = scalar else { return }; if !valid_range.contains(0) { attrs.set(ArgAttribute::NonNull); } if let Some(pointee) = layout.pointee_info_at(&cx, offset) { if let Some(kind) = pointee.safe { attrs.pointee_align = Some(pointee.align); // `Box` (`UniqueBorrowed`) are not necessarily dereferenceable // for the entire duration of the function as they can be deallocated // at any time. Same for shared mutable references. If LLVM had a // way to say "dereferenceable on entry" we could use it here. attrs.pointee_size = match kind { PointerKind::UniqueBorrowed | PointerKind::UniqueBorrowedPinned | PointerKind::Frozen => pointee.size, PointerKind::SharedMutable | PointerKind::UniqueOwned => Size::ZERO, }; // `Box`, `&T`, and `&mut T` cannot be undef. // Note that this only applies to the value of the pointer itself; // this attribute doesn't make it UB for the pointed-to data to be undef. attrs.set(ArgAttribute::NoUndef); // 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.unwrap_or(true); // `&mut` pointer parameters never alias other parameters, // or mutable global data // // `&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 // // Due to past miscompiles in LLVM, we apply a separate NoAliasMutRef attribute // for UniqueBorrowed arguments, so that the codegen backend can decide whether // or not to actually emit the attribute. It can also be controlled with the // `-Zmutable-noalias` debugging option. let no_alias = match kind { PointerKind::SharedMutable | PointerKind::UniqueBorrowed | PointerKind::UniqueBorrowedPinned => false, PointerKind::UniqueOwned => noalias_for_box, PointerKind::Frozen => !is_return, }; if no_alias { attrs.set(ArgAttribute::NoAlias); } if kind == PointerKind::Frozen && !is_return { attrs.set(ArgAttribute::ReadOnly); } if kind == PointerKind::UniqueBorrowed && !is_return { attrs.set(ArgAttribute::NoAliasMutRef); } } } } // 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>>, 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 arg_of = |ty: Ty<'tcx>, arg_idx: Option| -> Result<_, FnAbiError<'tcx>> { let span = tracing::debug_span!("arg_of"); let _entered = span.enter(); let is_return = arg_idx.is_none(); let layout = cx.layout_of(ty)?; 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); 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); 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<(), 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| { 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, } let size = arg.layout.size; if arg.layout.is_unsized() || size > Pointer.size(cx) { arg.make_indirect(); } else { // We want to pass small aggregates as immediates, but using // a 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)?; } 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 tcx.mk_mut_ptr(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; 'descend_newtypes: while !fat_pointer_layout.ty.is_unsafe_ptr() && !fat_pointer_layout.ty.is_region_ptr() { for i in 0..fat_pointer_layout.fields.count() { let field_layout = fat_pointer_layout.field(cx, i); if !field_layout.is_zst() { fat_pointer_layout = field_layout; continue 'descend_newtypes; } } bug!("receiver has no non-zero-sized fields {:?}", fat_pointer_layout); } 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 = tcx.mk_mut_ptr(tcx.mk_unit()); 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() } }