1 use gccjit::{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 // TODO(antoyo): upgrade alignment.
42 let global_value = self.static_addr_of_mut(cv, align, kind);
43 // TODO(antoyo): set global constant.
44 self.const_globals.borrow_mut().insert(cv, global_value);
48 fn codegen_static(&self, def_id: DefId, is_mutable: bool) {
49 let attrs = self.tcx.codegen_fn_attrs(def_id);
52 match codegen_static_initializer(&self, def_id) {
53 Ok((value, _)) => value,
54 // Error has already been reported
58 let global = self.get_static(def_id);
60 // boolean SSA values are i1, but they have to be stored in i8 slots,
61 // otherwise some LLVM optimization passes don't work as expected
62 let val_llty = self.val_ty(value);
64 if val_llty == self.type_i1() {
71 let instance = Instance::mono(self.tcx, def_id);
72 let ty = instance.ty(self.tcx, ty::ParamEnv::reveal_all());
73 let gcc_type = self.layout_of(ty).gcc_type(self, true);
75 // TODO(antoyo): set alignment.
78 if value.get_type() != gcc_type {
79 self.context.new_bitcast(None, value, gcc_type)
84 global.global_set_initializer_rvalue(value);
86 // As an optimization, all shared statics which do not have interior
87 // mutability are placed into read-only memory.
89 if self.type_is_freeze(ty) {
90 // TODO(antoyo): set global constant.
94 if attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL) {
95 // Do not allow LLVM to change the alignment of a TLS on macOS.
97 // By default a global's alignment can be freely increased.
98 // This allows LLVM to generate more performant instructions
99 // e.g., using load-aligned into a SIMD register.
101 // However, on macOS 10.10 or below, the dynamic linker does not
102 // respect any alignment given on the TLS (radar 24221680).
103 // This will violate the alignment assumption, and causing segfault at runtime.
105 // This bug is very easy to trigger. In `println!` and `panic!`,
106 // the `LOCAL_STDOUT`/`LOCAL_STDERR` handles are stored in a TLS,
107 // which the values would be `mem::replace`d on initialization.
108 // The implementation of `mem::replace` will use SIMD
109 // whenever the size is 32 bytes or higher. LLVM notices SIMD is used
110 // and tries to align `LOCAL_STDOUT`/`LOCAL_STDERR` to a 32-byte boundary,
111 // which macOS's dyld disregarded and causing crashes
112 // (see issues #51794, #51758, #50867, #48866 and #44056).
114 // To workaround the bug, we trick LLVM into not increasing
115 // the global's alignment by explicitly assigning a section to it
116 // (equivalent to automatically generating a `#[link_section]` attribute).
117 // See the comment in the `GlobalValue::canIncreaseAlignment()` function
118 // of `lib/IR/Globals.cpp` for why this works.
120 // When the alignment is not increased, the optimized `mem::replace`
121 // will use load-unaligned instructions instead, and thus avoiding the crash.
123 // We could remove this hack whenever we decide to drop macOS 10.10 support.
124 if self.tcx.sess.target.options.is_like_osx {
125 // The `inspect` method is okay here because we checked relocations, and
126 // because we are doing this access to inspect the final interpreter state
127 // (not as part of the interpreter execution).
129 // FIXME: This check requires that the (arbitrary) value of undefined bytes
130 // happens to be zero. Instead, we should only check the value of defined bytes
131 // and set all undefined bytes to zero if this allocation is headed for the
137 // Wasm statics with custom link sections get special treatment as they
138 // go into custom sections of the wasm executable.
139 if self.tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
140 if let Some(_section) = attrs.link_section {
144 // TODO(antoyo): set link section.
147 if attrs.flags.contains(CodegenFnAttrFlags::USED) || attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER) {
148 self.add_used_global(global.to_rvalue());
152 /// Add a global value to a list to be stored in the `llvm.used` variable, an array of i8*.
153 fn add_used_global(&self, _global: RValue<'gcc>) {
157 fn add_compiler_used_global(&self, _global: RValue<'gcc>) {
162 impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
163 pub fn static_addr_of_mut(&self, cv: RValue<'gcc>, align: Align, kind: Option<&str>) -> RValue<'gcc> {
166 Some(kind) if !self.tcx.sess.fewer_names() => {
167 let name = self.generate_local_symbol_name(kind);
168 // TODO(antoyo): check if it's okay that TLS is off here.
169 // TODO(antoyo): check if it's okay that link_section is None here.
170 // TODO(antoyo): set alignment here as well.
171 let global = self.define_global(&name[..], self.val_ty(cv), false, None);
172 // TODO(antoyo): set linkage.
176 let typ = self.val_ty(cv).get_aligned(align.bytes());
177 let global = self.declare_unnamed_global(typ);
181 // FIXME(antoyo): I think the name coming from generate_local_symbol_name() above cannot be used
183 global.global_set_initializer_rvalue(cv);
184 // TODO(antoyo): set unnamed address.
185 global.get_address(None)
188 pub fn get_static(&self, def_id: DefId) -> LValue<'gcc> {
189 let instance = Instance::mono(self.tcx, def_id);
190 let fn_attrs = self.tcx.codegen_fn_attrs(def_id);
191 if let Some(&global) = self.instances.borrow().get(&instance) {
195 let defined_in_current_codegen_unit =
196 self.codegen_unit.items().contains_key(&MonoItem::Static(def_id));
198 !defined_in_current_codegen_unit,
199 "consts::get_static() should always hit the cache for \
200 statics defined in the same CGU, but did not for `{:?}`",
204 let ty = instance.ty(self.tcx, ty::ParamEnv::reveal_all());
205 let sym = self.tcx.symbol_name(instance).name;
208 if let Some(def_id) = def_id.as_local() {
209 let id = self.tcx.hir().local_def_id_to_hir_id(def_id);
210 let llty = self.layout_of(ty).gcc_type(self, true);
211 // FIXME: refactor this to work without accessing the HIR
212 let global = match self.tcx.hir().get(id) {
213 Node::Item(&hir::Item { span, kind: hir::ItemKind::Static(..), .. }) => {
214 if let Some(global) = self.get_declared_value(&sym) {
215 if self.val_ty(global) != self.type_ptr_to(llty) {
216 span_bug!(span, "Conflicting types for static");
220 let is_tls = fn_attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL);
221 let global = self.declare_global(&sym, llty, is_tls, fn_attrs.link_section);
223 if !self.tcx.is_reachable_non_generic(def_id) {
224 // TODO(antoyo): set visibility.
230 Node::ForeignItem(&hir::ForeignItem {
232 kind: hir::ForeignItemKind::Static(..),
235 let fn_attrs = self.tcx.codegen_fn_attrs(def_id);
236 check_and_apply_linkage(&self, &fn_attrs, ty, sym, span)
239 item => bug!("get_static: expected static, found {:?}", item),
245 // FIXME(nagisa): perhaps the map of externs could be offloaded to llvm somehow?
246 //debug!("get_static: sym={} item_attr={:?}", sym, self.tcx.item_attrs(def_id));
248 let attrs = self.tcx.codegen_fn_attrs(def_id);
249 let span = self.tcx.def_span(def_id);
250 let global = check_and_apply_linkage(&self, &attrs, ty, sym, span);
252 let needs_dll_storage_attr = false; // TODO(antoyo)
254 // If this assertion triggers, there's something wrong with commandline
255 // argument validation.
257 !(self.tcx.sess.opts.cg.linker_plugin_lto.enabled()
258 && self.tcx.sess.target.options.is_like_msvc
259 && self.tcx.sess.opts.cg.prefer_dynamic)
262 if needs_dll_storage_attr {
263 // This item is external but not foreign, i.e., it originates from an external Rust
264 // crate. Since we don't know whether this crate will be linked dynamically or
265 // statically in the final application, we always mark such symbols as 'dllimport'.
266 // If final linkage happens to be static, we rely on compiler-emitted __imp_ stubs
267 // to make things work.
269 // However, in some scenarios we defer emission of statics to downstream
270 // crates, so there are cases where a static with an upstream DefId
271 // is actually present in the current crate. We can find out via the
272 // is_codegened_item query.
273 if !self.tcx.is_codegened_item(def_id) {
280 // TODO(antoyo): set dll storage class.
282 self.instances.borrow_mut().insert(instance, global);
287 pub fn const_alloc_to_gcc<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, alloc: ConstAllocation<'tcx>) -> RValue<'gcc> {
288 let alloc = alloc.inner();
289 let mut llvals = Vec::with_capacity(alloc.relocations().len() + 1);
290 let dl = cx.data_layout();
291 let pointer_size = dl.pointer_size.bytes() as usize;
293 let mut next_offset = 0;
294 for &(offset, alloc_id) in alloc.relocations().iter() {
295 let offset = offset.bytes();
296 assert_eq!(offset as usize as u64, offset);
297 let offset = offset as usize;
298 if offset > next_offset {
299 // This `inspect` is okay since we have checked that it is not within a relocation, it
300 // is within the bounds of the allocation, and it doesn't affect interpreter execution
301 // (we inspect the result after interpreter execution). Any undef byte is replaced with
302 // some arbitrary byte value.
304 // FIXME: relay undef bytes to codegen as undef const bytes
305 let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(next_offset..offset);
306 llvals.push(cx.const_bytes(bytes));
309 read_target_uint( dl.endian,
310 // This `inspect` is okay since it is within the bounds of the allocation, it doesn't
311 // affect interpreter execution (we inspect the result after interpreter execution),
312 // and we properly interpret the relocation as a relocation pointer offset.
313 alloc.inspect_with_uninit_and_ptr_outside_interpreter(offset..(offset + pointer_size)),
315 .expect("const_alloc_to_llvm: could not read relocation pointer")
317 llvals.push(cx.scalar_to_backend(
318 InterpScalar::from_pointer(
319 interpret::Pointer::new(alloc_id, Size::from_bytes(ptr_offset)),
322 abi::Scalar { value: Primitive::Pointer, valid_range: WrappingRange { start: 0, end: !0 } },
325 next_offset = offset + pointer_size;
327 if alloc.len() >= next_offset {
328 let range = next_offset..alloc.len();
329 // This `inspect` is okay since we have check that it is after all relocations, it is
330 // within the bounds of the allocation, and it doesn't affect interpreter execution (we
331 // inspect the result after interpreter execution). Any undef byte is replaced with some
332 // arbitrary byte value.
334 // FIXME: relay undef bytes to codegen as undef const bytes
335 let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(range);
336 llvals.push(cx.const_bytes(bytes));
339 cx.const_struct(&llvals, true)
342 pub fn codegen_static_initializer<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, def_id: DefId) -> Result<(RValue<'gcc>, ConstAllocation<'tcx>), ErrorHandled> {
343 let alloc = cx.tcx.eval_static_initializer(def_id)?;
344 Ok((const_alloc_to_gcc(cx, alloc), alloc))
347 fn check_and_apply_linkage<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, attrs: &CodegenFnAttrs, ty: Ty<'tcx>, sym: &str, span: Span) -> LValue<'gcc> {
348 let is_tls = attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL);
349 let llty = cx.layout_of(ty).gcc_type(cx, true);
350 if let Some(linkage) = attrs.linkage {
351 // If this is a static with a linkage specified, then we need to handle
352 // it a little specially. The typesystem prevents things like &T and
353 // extern "C" fn() from being non-null, so we can't just declare a
354 // static and call it a day. Some linkages (like weak) will make it such
355 // that the static actually has a null value.
357 if let ty::RawPtr(ref mt) = ty.kind() {
358 cx.layout_of(mt.ty).gcc_type(cx, true)
361 cx.sess().span_fatal(
363 "must have type `*const T` or `*mut T` due to `#[linkage]` attribute",
366 // Declare a symbol `foo` with the desired linkage.
367 let global1 = cx.declare_global_with_linkage(&sym, llty2, base::global_linkage_to_gcc(linkage));
369 // Declare an internal global `extern_with_linkage_foo` which
370 // is initialized with the address of `foo`. If `foo` is
371 // discarded during linking (for example, if `foo` has weak
372 // linkage and there are no definitions), then
373 // `extern_with_linkage_foo` will instead be initialized to
375 let mut real_name = "_rust_extern_with_linkage_".to_string();
376 real_name.push_str(&sym);
377 let global2 = cx.define_global(&real_name, llty, is_tls, attrs.link_section);
378 // TODO(antoyo): set linkage.
379 global2.global_set_initializer_rvalue(global1.get_address(None));
380 // TODO(antoyo): use global_set_initializer() when it will work.
384 // Generate an external declaration.
385 // FIXME(nagisa): investigate whether it can be changed into define_global
387 // Thread-local statics in some other crate need to *always* be linked
388 // against in a thread-local fashion, so we need to be sure to apply the
389 // thread-local attribute locally if it was present remotely. If we
390 // don't do this then linker errors can be generated where the linker
391 // complains that one object files has a thread local version of the
392 // symbol and another one doesn't.
393 cx.declare_global(&sym, llty, is_tls, attrs.link_section)