use gccjit::{GlobalKind, LValue, RValue, ToRValue, Type}; use rustc_codegen_ssa::traits::{BaseTypeMethods, ConstMethods, DerivedTypeMethods, StaticMethods}; use rustc_hir as hir; use rustc_hir::Node; use rustc_middle::{bug, span_bug}; use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs}; use rustc_middle::mir::mono::MonoItem; use rustc_middle::ty::{self, Instance, Ty}; use rustc_middle::ty::layout::LayoutOf; use rustc_middle::mir::interpret::{self, ConstAllocation, ErrorHandled, Scalar as InterpScalar, read_target_uint}; use rustc_span::def_id::DefId; use rustc_target::abi::{self, Align, HasDataLayout, Primitive, Size, WrappingRange}; use crate::base; use crate::context::CodegenCx; use crate::type_of::LayoutGccExt; impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> { pub fn const_bitcast(&self, value: RValue<'gcc>, typ: Type<'gcc>) -> RValue<'gcc> { if value.get_type() == self.bool_type.make_pointer() { if let Some(pointee) = typ.get_pointee() { if pointee.dyncast_vector().is_some() { panic!() } } } // NOTE: since bitcast makes a value non-constant, don't bitcast if not necessary as some // SIMD builtins require a constant value. self.bitcast_if_needed(value, typ) } } impl<'gcc, 'tcx> StaticMethods for CodegenCx<'gcc, 'tcx> { fn static_addr_of(&self, cv: RValue<'gcc>, align: Align, kind: Option<&str>) -> RValue<'gcc> { // TODO(antoyo): implement a proper rvalue comparison in libgccjit instead of doing the // following: for (value, variable) in &*self.const_globals.borrow() { if format!("{:?}", value) == format!("{:?}", cv) { if let Some(global_variable) = self.global_lvalues.borrow().get(variable) { let alignment = align.bits() as i32; if alignment > global_variable.get_alignment() { global_variable.set_alignment(alignment); } } return *variable; } } let global_value = self.static_addr_of_mut(cv, align, kind); #[cfg(feature = "master")] self.global_lvalues.borrow().get(&global_value) .expect("`static_addr_of_mut` did not add the global to `self.global_lvalues`") .global_set_readonly(); self.const_globals.borrow_mut().insert(cv, global_value); global_value } fn codegen_static(&self, def_id: DefId, is_mutable: bool) { let attrs = self.tcx.codegen_fn_attrs(def_id); let value = match codegen_static_initializer(&self, def_id) { Ok((value, _)) => value, // Error has already been reported Err(_) => return, }; let global = self.get_static(def_id); // boolean SSA values are i1, but they have to be stored in i8 slots, // otherwise some LLVM optimization passes don't work as expected let val_llty = self.val_ty(value); let value = if val_llty == self.type_i1() { unimplemented!(); } else { value }; let instance = Instance::mono(self.tcx, def_id); let ty = instance.ty(self.tcx, ty::ParamEnv::reveal_all()); let gcc_type = self.layout_of(ty).gcc_type(self, true); // TODO(antoyo): set alignment. let value = self.bitcast_if_needed(value, gcc_type); global.global_set_initializer_rvalue(value); // As an optimization, all shared statics which do not have interior // mutability are placed into read-only memory. if !is_mutable { if self.type_is_freeze(ty) { #[cfg(feature = "master")] global.global_set_readonly(); } } if attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL) { // Do not allow LLVM to change the alignment of a TLS on macOS. // // By default a global's alignment can be freely increased. // This allows LLVM to generate more performant instructions // e.g., using load-aligned into a SIMD register. // // However, on macOS 10.10 or below, the dynamic linker does not // respect any alignment given on the TLS (radar 24221680). // This will violate the alignment assumption, and causing segfault at runtime. // // This bug is very easy to trigger. In `println!` and `panic!`, // the `LOCAL_STDOUT`/`LOCAL_STDERR` handles are stored in a TLS, // which the values would be `mem::replace`d on initialization. // The implementation of `mem::replace` will use SIMD // whenever the size is 32 bytes or higher. LLVM notices SIMD is used // and tries to align `LOCAL_STDOUT`/`LOCAL_STDERR` to a 32-byte boundary, // which macOS's dyld disregarded and causing crashes // (see issues #51794, #51758, #50867, #48866 and #44056). // // To workaround the bug, we trick LLVM into not increasing // the global's alignment by explicitly assigning a section to it // (equivalent to automatically generating a `#[link_section]` attribute). // See the comment in the `GlobalValue::canIncreaseAlignment()` function // of `lib/IR/Globals.cpp` for why this works. // // When the alignment is not increased, the optimized `mem::replace` // will use load-unaligned instructions instead, and thus avoiding the crash. // // We could remove this hack whenever we decide to drop macOS 10.10 support. if self.tcx.sess.target.options.is_like_osx { // The `inspect` method is okay here because we checked for provenance, and // because we are doing this access to inspect the final interpreter state // (not as part of the interpreter execution). // // FIXME: This check requires that the (arbitrary) value of undefined bytes // happens to be zero. Instead, we should only check the value of defined bytes // and set all undefined bytes to zero if this allocation is headed for the // BSS. unimplemented!(); } } // Wasm statics with custom link sections get special treatment as they // go into custom sections of the wasm executable. if self.tcx.sess.opts.target_triple.triple().starts_with("wasm32") { if let Some(_section) = attrs.link_section { unimplemented!(); } } else { // TODO(antoyo): set link section. } if attrs.flags.contains(CodegenFnAttrFlags::USED) || attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER) { self.add_used_global(global.to_rvalue()); } } /// Add a global value to a list to be stored in the `llvm.used` variable, an array of i8*. fn add_used_global(&self, _global: RValue<'gcc>) { // TODO(antoyo) } fn add_compiler_used_global(&self, _global: RValue<'gcc>) { // TODO(antoyo) } } impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> { pub fn static_addr_of_mut(&self, cv: RValue<'gcc>, align: Align, kind: Option<&str>) -> RValue<'gcc> { let global = match kind { Some(kind) if !self.tcx.sess.fewer_names() => { let name = self.generate_local_symbol_name(kind); // TODO(antoyo): check if it's okay that no link_section is set. let typ = self.val_ty(cv).get_aligned(align.bytes()); let global = self.declare_private_global(&name[..], typ); global } _ => { let typ = self.val_ty(cv).get_aligned(align.bytes()); let global = self.declare_unnamed_global(typ); global }, }; global.global_set_initializer_rvalue(cv); // TODO(antoyo): set unnamed address. let rvalue = global.get_address(None); self.global_lvalues.borrow_mut().insert(rvalue, global); rvalue } pub fn get_static(&self, def_id: DefId) -> LValue<'gcc> { let instance = Instance::mono(self.tcx, def_id); let fn_attrs = self.tcx.codegen_fn_attrs(def_id); if let Some(&global) = self.instances.borrow().get(&instance) { return global; } let defined_in_current_codegen_unit = self.codegen_unit.items().contains_key(&MonoItem::Static(def_id)); assert!( !defined_in_current_codegen_unit, "consts::get_static() should always hit the cache for \ statics defined in the same CGU, but did not for `{:?}`", def_id ); let ty = instance.ty(self.tcx, ty::ParamEnv::reveal_all()); let sym = self.tcx.symbol_name(instance).name; let global = if let Some(def_id) = def_id.as_local() { let id = self.tcx.hir().local_def_id_to_hir_id(def_id); let llty = self.layout_of(ty).gcc_type(self, true); // FIXME: refactor this to work without accessing the HIR let global = match self.tcx.hir().get(id) { Node::Item(&hir::Item { span, kind: hir::ItemKind::Static(..), .. }) => { if let Some(global) = self.get_declared_value(&sym) { if self.val_ty(global) != self.type_ptr_to(llty) { span_bug!(span, "Conflicting types for static"); } } let is_tls = fn_attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL); let global = self.declare_global( &sym, llty, GlobalKind::Exported, is_tls, fn_attrs.link_section, ); if !self.tcx.is_reachable_non_generic(def_id) { // TODO(antoyo): set visibility. } global } Node::ForeignItem(&hir::ForeignItem { span: _, kind: hir::ForeignItemKind::Static(..), .. }) => { let fn_attrs = self.tcx.codegen_fn_attrs(def_id); check_and_apply_linkage(&self, &fn_attrs, ty, sym) } item => bug!("get_static: expected static, found {:?}", item), }; global } else { // FIXME(nagisa): perhaps the map of externs could be offloaded to llvm somehow? //debug!("get_static: sym={} item_attr={:?}", sym, self.tcx.item_attrs(def_id)); let attrs = self.tcx.codegen_fn_attrs(def_id); let global = check_and_apply_linkage(&self, &attrs, ty, sym); let needs_dll_storage_attr = false; // TODO(antoyo) // If this assertion triggers, there's something wrong with commandline // argument validation. debug_assert!( !(self.tcx.sess.opts.cg.linker_plugin_lto.enabled() && self.tcx.sess.target.options.is_like_msvc && self.tcx.sess.opts.cg.prefer_dynamic) ); if needs_dll_storage_attr { // This item is external but not foreign, i.e., it originates from an external Rust // crate. Since we don't know whether this crate will be linked dynamically or // statically in the final application, we always mark such symbols as 'dllimport'. // If final linkage happens to be static, we rely on compiler-emitted __imp_ stubs // to make things work. // // However, in some scenarios we defer emission of statics to downstream // crates, so there are cases where a static with an upstream DefId // is actually present in the current crate. We can find out via the // is_codegened_item query. if !self.tcx.is_codegened_item(def_id) { unimplemented!(); } } global }; // TODO(antoyo): set dll storage class. self.instances.borrow_mut().insert(instance, global); global } } pub fn const_alloc_to_gcc<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, alloc: ConstAllocation<'tcx>) -> RValue<'gcc> { let alloc = alloc.inner(); let mut llvals = Vec::with_capacity(alloc.provenance().ptrs().len() + 1); let dl = cx.data_layout(); let pointer_size = dl.pointer_size.bytes() as usize; let mut next_offset = 0; for &(offset, alloc_id) in alloc.provenance().ptrs().iter() { let offset = offset.bytes(); assert_eq!(offset as usize as u64, offset); let offset = offset as usize; if offset > next_offset { // This `inspect` is okay since we have checked that it is not within a pointer with provenance, it // is within the bounds of the allocation, and it doesn't affect interpreter execution // (we inspect the result after interpreter execution). Any undef byte is replaced with // some arbitrary byte value. // // FIXME: relay undef bytes to codegen as undef const bytes let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(next_offset..offset); llvals.push(cx.const_bytes(bytes)); } let ptr_offset = read_target_uint( dl.endian, // This `inspect` is okay since it is within the bounds of the allocation, it doesn't // affect interpreter execution (we inspect the result after interpreter execution), // and we properly interpret the provenance as a relocation pointer offset. alloc.inspect_with_uninit_and_ptr_outside_interpreter(offset..(offset + pointer_size)), ) .expect("const_alloc_to_llvm: could not read relocation pointer") as u64; llvals.push(cx.scalar_to_backend( InterpScalar::from_pointer( interpret::Pointer::new(alloc_id, Size::from_bytes(ptr_offset)), &cx.tcx, ), abi::Scalar::Initialized { value: Primitive::Pointer, valid_range: WrappingRange::full(dl.pointer_size) }, cx.type_i8p(), )); next_offset = offset + pointer_size; } if alloc.len() >= next_offset { let range = next_offset..alloc.len(); // This `inspect` is okay since we have check that it is after all provenance, it is // within the bounds of the allocation, and it doesn't affect interpreter execution (we // inspect the result after interpreter execution). Any undef byte is replaced with some // arbitrary byte value. // // FIXME: relay undef bytes to codegen as undef const bytes let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(range); llvals.push(cx.const_bytes(bytes)); } cx.const_struct(&llvals, true) } pub fn codegen_static_initializer<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, def_id: DefId) -> Result<(RValue<'gcc>, ConstAllocation<'tcx>), ErrorHandled> { let alloc = cx.tcx.eval_static_initializer(def_id)?; Ok((const_alloc_to_gcc(cx, alloc), alloc)) } fn check_and_apply_linkage<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, attrs: &CodegenFnAttrs, ty: Ty<'tcx>, sym: &str) -> LValue<'gcc> { let is_tls = attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL); let llty = cx.layout_of(ty).gcc_type(cx, true); if let Some(linkage) = attrs.import_linkage { // Declare a symbol `foo` with the desired linkage. let global1 = cx.declare_global_with_linkage(&sym, cx.type_i8(), base::global_linkage_to_gcc(linkage)); // Declare an internal global `extern_with_linkage_foo` which // is initialized with the address of `foo`. If `foo` is // discarded during linking (for example, if `foo` has weak // linkage and there are no definitions), then // `extern_with_linkage_foo` will instead be initialized to // zero. let mut real_name = "_rust_extern_with_linkage_".to_string(); real_name.push_str(&sym); let global2 = cx.define_global(&real_name, llty, is_tls, attrs.link_section); // TODO(antoyo): set linkage. global2.global_set_initializer_rvalue(global1.get_address(None)); // TODO(antoyo): use global_set_initializer() when it will work. global2 } else { // Generate an external declaration. // FIXME(nagisa): investigate whether it can be changed into define_global // Thread-local statics in some other crate need to *always* be linked // against in a thread-local fashion, so we need to be sure to apply the // thread-local attribute locally if it was present remotely. If we // don't do this then linker errors can be generated where the linker // complains that one object files has a thread local version of the // symbol and another one doesn't. cx.declare_global(&sym, llty, GlobalKind::Imported, is_tls, attrs.link_section) } }