1 use gccjit::{GlobalKind, LValue, RValue, ToRValue, Type};
2 use rustc_codegen_ssa::traits::{BaseTypeMethods, ConstMethods, DerivedTypeMethods, StaticMethods};
5 use rustc_middle::{bug, span_bug};
6 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
7 use rustc_middle::mir::mono::MonoItem;
8 use rustc_middle::ty::{self, Instance, Ty};
9 use rustc_middle::ty::layout::LayoutOf;
10 use rustc_middle::mir::interpret::{self, ConstAllocation, ErrorHandled, Scalar as InterpScalar, read_target_uint};
12 use rustc_span::def_id::DefId;
13 use rustc_target::abi::{self, Align, HasDataLayout, Primitive, Size, WrappingRange};
16 use crate::context::CodegenCx;
17 use crate::type_of::LayoutGccExt;
19 impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
20 pub fn const_bitcast(&self, value: RValue<'gcc>, typ: Type<'gcc>) -> RValue<'gcc> {
21 if value.get_type() == self.bool_type.make_pointer() {
22 if let Some(pointee) = typ.get_pointee() {
23 if pointee.dyncast_vector().is_some() {
28 self.context.new_bitcast(None, value, typ)
32 impl<'gcc, 'tcx> StaticMethods for CodegenCx<'gcc, 'tcx> {
33 fn static_addr_of(&self, cv: RValue<'gcc>, align: Align, kind: Option<&str>) -> RValue<'gcc> {
34 // TODO(antoyo): implement a proper rvalue comparison in libgccjit instead of doing the
36 for (value, variable) in &*self.const_globals.borrow() {
37 if format!("{:?}", value) == format!("{:?}", cv) {
38 if let Some(global_variable) = self.global_lvalues.borrow().get(variable) {
39 let alignment = align.bits() as i32;
40 if alignment > global_variable.get_alignment() {
41 global_variable.set_alignment(alignment);
47 let global_value = self.static_addr_of_mut(cv, align, kind);
48 // TODO(antoyo): set global constant.
49 self.const_globals.borrow_mut().insert(cv, global_value);
53 fn codegen_static(&self, def_id: DefId, is_mutable: bool) {
54 let attrs = self.tcx.codegen_fn_attrs(def_id);
57 match codegen_static_initializer(&self, def_id) {
58 Ok((value, _)) => value,
59 // Error has already been reported
63 let global = self.get_static(def_id);
65 // boolean SSA values are i1, but they have to be stored in i8 slots,
66 // otherwise some LLVM optimization passes don't work as expected
67 let val_llty = self.val_ty(value);
69 if val_llty == self.type_i1() {
76 let instance = Instance::mono(self.tcx, def_id);
77 let ty = instance.ty(self.tcx, ty::ParamEnv::reveal_all());
78 let gcc_type = self.layout_of(ty).gcc_type(self, true);
80 // TODO(antoyo): set alignment.
83 if value.get_type() != gcc_type {
84 self.context.new_bitcast(None, value, gcc_type)
89 global.global_set_initializer_rvalue(value);
91 // As an optimization, all shared statics which do not have interior
92 // mutability are placed into read-only memory.
94 if self.type_is_freeze(ty) {
95 // TODO(antoyo): set global constant.
99 if attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL) {
100 // Do not allow LLVM to change the alignment of a TLS on macOS.
102 // By default a global's alignment can be freely increased.
103 // This allows LLVM to generate more performant instructions
104 // e.g., using load-aligned into a SIMD register.
106 // However, on macOS 10.10 or below, the dynamic linker does not
107 // respect any alignment given on the TLS (radar 24221680).
108 // This will violate the alignment assumption, and causing segfault at runtime.
110 // This bug is very easy to trigger. In `println!` and `panic!`,
111 // the `LOCAL_STDOUT`/`LOCAL_STDERR` handles are stored in a TLS,
112 // which the values would be `mem::replace`d on initialization.
113 // The implementation of `mem::replace` will use SIMD
114 // whenever the size is 32 bytes or higher. LLVM notices SIMD is used
115 // and tries to align `LOCAL_STDOUT`/`LOCAL_STDERR` to a 32-byte boundary,
116 // which macOS's dyld disregarded and causing crashes
117 // (see issues #51794, #51758, #50867, #48866 and #44056).
119 // To workaround the bug, we trick LLVM into not increasing
120 // the global's alignment by explicitly assigning a section to it
121 // (equivalent to automatically generating a `#[link_section]` attribute).
122 // See the comment in the `GlobalValue::canIncreaseAlignment()` function
123 // of `lib/IR/Globals.cpp` for why this works.
125 // When the alignment is not increased, the optimized `mem::replace`
126 // will use load-unaligned instructions instead, and thus avoiding the crash.
128 // We could remove this hack whenever we decide to drop macOS 10.10 support.
129 if self.tcx.sess.target.options.is_like_osx {
130 // The `inspect` method is okay here because we checked relocations, and
131 // because we are doing this access to inspect the final interpreter state
132 // (not as part of the interpreter execution).
134 // FIXME: This check requires that the (arbitrary) value of undefined bytes
135 // happens to be zero. Instead, we should only check the value of defined bytes
136 // and set all undefined bytes to zero if this allocation is headed for the
142 // Wasm statics with custom link sections get special treatment as they
143 // go into custom sections of the wasm executable.
144 if self.tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
145 if let Some(_section) = attrs.link_section {
149 // TODO(antoyo): set link section.
152 if attrs.flags.contains(CodegenFnAttrFlags::USED) || attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER) {
153 self.add_used_global(global.to_rvalue());
157 /// Add a global value to a list to be stored in the `llvm.used` variable, an array of i8*.
158 fn add_used_global(&self, _global: RValue<'gcc>) {
162 fn add_compiler_used_global(&self, _global: RValue<'gcc>) {
167 impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
168 pub fn static_addr_of_mut(&self, cv: RValue<'gcc>, align: Align, kind: Option<&str>) -> RValue<'gcc> {
171 Some(kind) if !self.tcx.sess.fewer_names() => {
172 let name = self.generate_local_symbol_name(kind);
173 // TODO(antoyo): check if it's okay that no link_section is set.
174 // TODO(antoyo): set alignment here as well.
175 let global = self.declare_private_global(&name[..], self.val_ty(cv));
179 let typ = self.val_ty(cv).get_aligned(align.bytes());
180 let global = self.declare_unnamed_global(typ);
184 global.global_set_initializer_rvalue(cv);
185 // TODO(antoyo): set unnamed address.
186 let rvalue = global.get_address(None);
187 self.global_lvalues.borrow_mut().insert(rvalue, global);
191 pub fn get_static(&self, def_id: DefId) -> LValue<'gcc> {
192 let instance = Instance::mono(self.tcx, def_id);
193 let fn_attrs = self.tcx.codegen_fn_attrs(def_id);
194 if let Some(&global) = self.instances.borrow().get(&instance) {
198 let defined_in_current_codegen_unit =
199 self.codegen_unit.items().contains_key(&MonoItem::Static(def_id));
201 !defined_in_current_codegen_unit,
202 "consts::get_static() should always hit the cache for \
203 statics defined in the same CGU, but did not for `{:?}`",
207 let ty = instance.ty(self.tcx, ty::ParamEnv::reveal_all());
208 let sym = self.tcx.symbol_name(instance).name;
211 if let Some(def_id) = def_id.as_local() {
212 let id = self.tcx.hir().local_def_id_to_hir_id(def_id);
213 let llty = self.layout_of(ty).gcc_type(self, true);
214 // FIXME: refactor this to work without accessing the HIR
215 let global = match self.tcx.hir().get(id) {
216 Node::Item(&hir::Item { span, kind: hir::ItemKind::Static(..), .. }) => {
217 if let Some(global) = self.get_declared_value(&sym) {
218 if self.val_ty(global) != self.type_ptr_to(llty) {
219 span_bug!(span, "Conflicting types for static");
223 let is_tls = fn_attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL);
224 let global = self.declare_global(
227 GlobalKind::Exported,
229 fn_attrs.link_section,
232 if !self.tcx.is_reachable_non_generic(def_id) {
233 // TODO(antoyo): set visibility.
239 Node::ForeignItem(&hir::ForeignItem {
241 kind: hir::ForeignItemKind::Static(..),
244 let fn_attrs = self.tcx.codegen_fn_attrs(def_id);
245 check_and_apply_linkage(&self, &fn_attrs, ty, sym, span)
248 item => bug!("get_static: expected static, found {:?}", item),
254 // FIXME(nagisa): perhaps the map of externs could be offloaded to llvm somehow?
255 //debug!("get_static: sym={} item_attr={:?}", sym, self.tcx.item_attrs(def_id));
257 let attrs = self.tcx.codegen_fn_attrs(def_id);
258 let span = self.tcx.def_span(def_id);
259 let global = check_and_apply_linkage(&self, &attrs, ty, sym, span);
261 let needs_dll_storage_attr = false; // TODO(antoyo)
263 // If this assertion triggers, there's something wrong with commandline
264 // argument validation.
266 !(self.tcx.sess.opts.cg.linker_plugin_lto.enabled()
267 && self.tcx.sess.target.options.is_like_msvc
268 && self.tcx.sess.opts.cg.prefer_dynamic)
271 if needs_dll_storage_attr {
272 // This item is external but not foreign, i.e., it originates from an external Rust
273 // crate. Since we don't know whether this crate will be linked dynamically or
274 // statically in the final application, we always mark such symbols as 'dllimport'.
275 // If final linkage happens to be static, we rely on compiler-emitted __imp_ stubs
276 // to make things work.
278 // However, in some scenarios we defer emission of statics to downstream
279 // crates, so there are cases where a static with an upstream DefId
280 // is actually present in the current crate. We can find out via the
281 // is_codegened_item query.
282 if !self.tcx.is_codegened_item(def_id) {
289 // TODO(antoyo): set dll storage class.
291 self.instances.borrow_mut().insert(instance, global);
296 pub fn const_alloc_to_gcc<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, alloc: ConstAllocation<'tcx>) -> RValue<'gcc> {
297 let alloc = alloc.inner();
298 let mut llvals = Vec::with_capacity(alloc.relocations().len() + 1);
299 let dl = cx.data_layout();
300 let pointer_size = dl.pointer_size.bytes() as usize;
302 let mut next_offset = 0;
303 for &(offset, alloc_id) in alloc.relocations().iter() {
304 let offset = offset.bytes();
305 assert_eq!(offset as usize as u64, offset);
306 let offset = offset as usize;
307 if offset > next_offset {
308 // This `inspect` is okay since we have checked that it is not within a relocation, it
309 // is within the bounds of the allocation, and it doesn't affect interpreter execution
310 // (we inspect the result after interpreter execution). Any undef byte is replaced with
311 // some arbitrary byte value.
313 // FIXME: relay undef bytes to codegen as undef const bytes
314 let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(next_offset..offset);
315 llvals.push(cx.const_bytes(bytes));
318 read_target_uint( dl.endian,
319 // This `inspect` is okay since it is within the bounds of the allocation, it doesn't
320 // affect interpreter execution (we inspect the result after interpreter execution),
321 // and we properly interpret the relocation as a relocation pointer offset.
322 alloc.inspect_with_uninit_and_ptr_outside_interpreter(offset..(offset + pointer_size)),
324 .expect("const_alloc_to_llvm: could not read relocation pointer")
326 llvals.push(cx.scalar_to_backend(
327 InterpScalar::from_pointer(
328 interpret::Pointer::new(alloc_id, Size::from_bytes(ptr_offset)),
331 abi::Scalar { value: Primitive::Pointer, valid_range: WrappingRange { start: 0, end: !0 } },
334 next_offset = offset + pointer_size;
336 if alloc.len() >= next_offset {
337 let range = next_offset..alloc.len();
338 // This `inspect` is okay since we have check that it is after all relocations, it is
339 // within the bounds of the allocation, and it doesn't affect interpreter execution (we
340 // inspect the result after interpreter execution). Any undef byte is replaced with some
341 // arbitrary byte value.
343 // FIXME: relay undef bytes to codegen as undef const bytes
344 let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(range);
345 llvals.push(cx.const_bytes(bytes));
348 cx.const_struct(&llvals, true)
351 pub fn codegen_static_initializer<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, def_id: DefId) -> Result<(RValue<'gcc>, ConstAllocation<'tcx>), ErrorHandled> {
352 let alloc = cx.tcx.eval_static_initializer(def_id)?;
353 Ok((const_alloc_to_gcc(cx, alloc), alloc))
356 fn check_and_apply_linkage<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, attrs: &CodegenFnAttrs, ty: Ty<'tcx>, sym: &str, span: Span) -> LValue<'gcc> {
357 let is_tls = attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL);
358 let llty = cx.layout_of(ty).gcc_type(cx, true);
359 if let Some(linkage) = attrs.linkage {
360 // If this is a static with a linkage specified, then we need to handle
361 // it a little specially. The typesystem prevents things like &T and
362 // extern "C" fn() from being non-null, so we can't just declare a
363 // static and call it a day. Some linkages (like weak) will make it such
364 // that the static actually has a null value.
366 if let ty::RawPtr(ref mt) = ty.kind() {
367 cx.layout_of(mt.ty).gcc_type(cx, true)
370 cx.sess().span_fatal(
372 "must have type `*const T` or `*mut T` due to `#[linkage]` attribute",
375 // Declare a symbol `foo` with the desired linkage.
376 let global1 = cx.declare_global_with_linkage(&sym, llty2, base::global_linkage_to_gcc(linkage));
378 // Declare an internal global `extern_with_linkage_foo` which
379 // is initialized with the address of `foo`. If `foo` is
380 // discarded during linking (for example, if `foo` has weak
381 // linkage and there are no definitions), then
382 // `extern_with_linkage_foo` will instead be initialized to
384 let mut real_name = "_rust_extern_with_linkage_".to_string();
385 real_name.push_str(&sym);
386 let global2 = cx.define_global(&real_name, llty, is_tls, attrs.link_section);
387 // TODO(antoyo): set linkage.
388 global2.global_set_initializer_rvalue(global1.get_address(None));
389 // TODO(antoyo): use global_set_initializer() when it will work.
393 // Generate an external declaration.
394 // FIXME(nagisa): investigate whether it can be changed into define_global
396 // Thread-local statics in some other crate need to *always* be linked
397 // against in a thread-local fashion, so we need to be sure to apply the
398 // thread-local attribute locally if it was present remotely. If we
399 // don't do this then linker errors can be generated where the linker
400 // complains that one object files has a thread local version of the
401 // symbol and another one doesn't.
402 cx.declare_global(&sym, llty, GlobalKind::Imported, is_tls, attrs.link_section)