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Commit | Line | Data |
---|---|---|
9fa01778 | 1 | use crate::base; |
dfeec247 XL |
2 | use crate::common::CodegenCx; |
3 | use crate::debuginfo; | |
ba9703b0 | 4 | use crate::llvm::{self, True}; |
9fa01778 XL |
5 | use crate::type_::Type; |
6 | use crate::type_of::LayoutLlvmExt; | |
7 | use crate::value::Value; | |
6a06907d | 8 | use cstr::cstr; |
8faf50e0 | 9 | use libc::c_uint; |
dfeec247 | 10 | use rustc_codegen_ssa::traits::*; |
dfeec247 | 11 | use rustc_hir::def_id::DefId; |
ba9703b0 XL |
12 | use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs}; |
13 | use rustc_middle::mir::interpret::{ | |
94222f64 XL |
14 | read_target_uint, Allocation, ErrorHandled, GlobalAlloc, InitChunk, Pointer, |
15 | Scalar as InterpScalar, | |
ba9703b0 XL |
16 | }; |
17 | use rustc_middle::mir::mono::MonoItem; | |
c295e0f8 | 18 | use rustc_middle::ty::layout::LayoutOf; |
ba9703b0 XL |
19 | use rustc_middle::ty::{self, Instance, Ty}; |
20 | use rustc_middle::{bug, span_bug}; | |
94222f64 | 21 | use rustc_target::abi::{ |
c295e0f8 | 22 | AddressSpace, Align, HasDataLayout, Primitive, Scalar, Size, WrappingRange, |
94222f64 XL |
23 | }; |
24 | use std::ops::Range; | |
3dfed10e | 25 | use tracing::debug; |
e9174d1e | 26 | |
a2a8927a | 27 | pub fn const_alloc_to_llvm<'ll>(cx: &CodegenCx<'ll, '_>, alloc: &Allocation) -> &'ll Value { |
e1599b0c | 28 | let mut llvals = Vec::with_capacity(alloc.relocations().len() + 1); |
a1dfa0c6 XL |
29 | let dl = cx.data_layout(); |
30 | let pointer_size = dl.pointer_size.bytes() as usize; | |
31 | ||
94222f64 XL |
32 | // Note: this function may call `inspect_with_uninit_and_ptr_outside_interpreter`, |
33 | // so `range` must be within the bounds of `alloc` and not contain or overlap a relocation. | |
34 | fn append_chunks_of_init_and_uninit_bytes<'ll, 'a, 'b>( | |
35 | llvals: &mut Vec<&'ll Value>, | |
36 | cx: &'a CodegenCx<'ll, 'b>, | |
37 | alloc: &'a Allocation, | |
38 | range: Range<usize>, | |
39 | ) { | |
40 | let mut chunks = alloc | |
41 | .init_mask() | |
42 | .range_as_init_chunks(Size::from_bytes(range.start), Size::from_bytes(range.end)); | |
43 | ||
44 | let chunk_to_llval = move |chunk| match chunk { | |
45 | InitChunk::Init(range) => { | |
46 | let range = (range.start.bytes() as usize)..(range.end.bytes() as usize); | |
47 | let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(range); | |
48 | cx.const_bytes(bytes) | |
49 | } | |
50 | InitChunk::Uninit(range) => { | |
51 | let len = range.end.bytes() - range.start.bytes(); | |
52 | cx.const_undef(cx.type_array(cx.type_i8(), len)) | |
53 | } | |
54 | }; | |
55 | ||
56 | // Generating partially-uninit consts inhibits optimizations, so it is disabled by default. | |
57 | // See https://github.com/rust-lang/rust/issues/84565. | |
58 | let allow_partially_uninit = | |
59 | match cx.sess().opts.debugging_opts.partially_uninit_const_threshold { | |
60 | Some(max) => range.len() <= max, | |
61 | None => false, | |
62 | }; | |
63 | ||
64 | if allow_partially_uninit { | |
65 | llvals.extend(chunks.map(chunk_to_llval)); | |
66 | } else { | |
67 | let llval = match (chunks.next(), chunks.next()) { | |
68 | (Some(chunk), None) => { | |
69 | // exactly one chunk, either fully init or fully uninit | |
70 | chunk_to_llval(chunk) | |
71 | } | |
72 | _ => { | |
73 | // partially uninit, codegen as if it was initialized | |
74 | // (using some arbitrary value for uninit bytes) | |
75 | let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(range); | |
76 | cx.const_bytes(bytes) | |
77 | } | |
78 | }; | |
79 | llvals.push(llval); | |
80 | } | |
81 | } | |
82 | ||
a1dfa0c6 | 83 | let mut next_offset = 0; |
136023e0 | 84 | for &(offset, alloc_id) in alloc.relocations().iter() { |
a1dfa0c6 XL |
85 | let offset = offset.bytes(); |
86 | assert_eq!(offset as usize as u64, offset); | |
87 | let offset = offset as usize; | |
88 | if offset > next_offset { | |
e1599b0c XL |
89 | // This `inspect` is okay since we have checked that it is not within a relocation, it |
90 | // is within the bounds of the allocation, and it doesn't affect interpreter execution | |
94222f64 XL |
91 | // (we inspect the result after interpreter execution). |
92 | append_chunks_of_init_and_uninit_bytes(&mut llvals, cx, alloc, next_offset..offset); | |
a1dfa0c6 XL |
93 | } |
94 | let ptr_offset = read_target_uint( | |
95 | dl.endian, | |
e1599b0c XL |
96 | // This `inspect` is okay since it is within the bounds of the allocation, it doesn't |
97 | // affect interpreter execution (we inspect the result after interpreter execution), | |
98 | // and we properly interpret the relocation as a relocation pointer offset. | |
3dfed10e | 99 | alloc.inspect_with_uninit_and_ptr_outside_interpreter(offset..(offset + pointer_size)), |
dfeec247 XL |
100 | ) |
101 | .expect("const_alloc_to_llvm: could not read relocation pointer") | |
102 | as u64; | |
3dfed10e XL |
103 | |
104 | let address_space = match cx.tcx.global_alloc(alloc_id) { | |
105 | GlobalAlloc::Function(..) => cx.data_layout().instruction_address_space, | |
106 | GlobalAlloc::Static(..) | GlobalAlloc::Memory(..) => AddressSpace::DATA, | |
107 | }; | |
108 | ||
a1dfa0c6 | 109 | llvals.push(cx.scalar_to_backend( |
136023e0 XL |
110 | InterpScalar::from_pointer( |
111 | Pointer::new(alloc_id, Size::from_bytes(ptr_offset)), | |
112 | &cx.tcx, | |
113 | ), | |
c295e0f8 | 114 | Scalar { value: Primitive::Pointer, valid_range: WrappingRange { start: 0, end: !0 } }, |
3dfed10e | 115 | cx.type_i8p_ext(address_space), |
a1dfa0c6 XL |
116 | )); |
117 | next_offset = offset + pointer_size; | |
1a4d82fc | 118 | } |
e1599b0c XL |
119 | if alloc.len() >= next_offset { |
120 | let range = next_offset..alloc.len(); | |
121 | // This `inspect` is okay since we have check that it is after all relocations, it is | |
122 | // within the bounds of the allocation, and it doesn't affect interpreter execution (we | |
94222f64 XL |
123 | // inspect the result after interpreter execution). |
124 | append_chunks_of_init_and_uninit_bytes(&mut llvals, cx, alloc, range); | |
a1dfa0c6 XL |
125 | } |
126 | ||
127 | cx.const_struct(&llvals, true) | |
1a4d82fc JJ |
128 | } |
129 | ||
a2a8927a | 130 | pub fn codegen_static_initializer<'ll, 'tcx>( |
a1dfa0c6 XL |
131 | cx: &CodegenCx<'ll, 'tcx>, |
132 | def_id: DefId, | |
133 | ) -> Result<(&'ll Value, &'tcx Allocation), ErrorHandled> { | |
1b1a35ee | 134 | let alloc = cx.tcx.eval_static_initializer(def_id)?; |
a1dfa0c6 | 135 | Ok((const_alloc_to_llvm(cx, alloc), alloc)) |
3b2f2976 XL |
136 | } |
137 | ||
a2a8927a | 138 | fn set_global_alignment<'ll>(cx: &CodegenCx<'ll, '_>, gv: &'ll Value, mut align: Align) { |
ea8adc8c XL |
139 | // The target may require greater alignment for globals than the type does. |
140 | // Note: GCC and Clang also allow `__attribute__((aligned))` on variables, | |
141 | // which can force it to be smaller. Rust doesn't support this yet. | |
29967ef6 | 142 | if let Some(min) = cx.sess().target.min_global_align { |
a1dfa0c6 | 143 | match Align::from_bits(min) { |
ff7c6d11 | 144 | Ok(min) => align = align.max(min), |
ea8adc8c | 145 | Err(err) => { |
2c00a5a8 | 146 | cx.sess().err(&format!("invalid minimum global alignment: {}", err)); |
ea8adc8c XL |
147 | } |
148 | } | |
149 | } | |
150 | unsafe { | |
a1dfa0c6 | 151 | llvm::LLVMSetAlignment(gv, align.bytes() as u32); |
ea8adc8c XL |
152 | } |
153 | } | |
154 | ||
a2a8927a | 155 | fn check_and_apply_linkage<'ll, 'tcx>( |
b7449926 | 156 | cx: &CodegenCx<'ll, 'tcx>, |
8faf50e0 XL |
157 | attrs: &CodegenFnAttrs, |
158 | ty: Ty<'tcx>, | |
3dfed10e | 159 | sym: &str, |
29967ef6 | 160 | span_def_id: DefId, |
b7449926 | 161 | ) -> &'ll Value { |
8faf50e0 XL |
162 | let llty = cx.layout_of(ty).llvm_type(cx); |
163 | if let Some(linkage) = attrs.linkage { | |
164 | debug!("get_static: sym={} linkage={:?}", sym, linkage); | |
165 | ||
166 | // If this is a static with a linkage specified, then we need to handle | |
167 | // it a little specially. The typesystem prevents things like &T and | |
168 | // extern "C" fn() from being non-null, so we can't just declare a | |
169 | // static and call it a day. Some linkages (like weak) will make it such | |
170 | // that the static actually has a null value. | |
1b1a35ee | 171 | let llty2 = if let ty::RawPtr(ref mt) = ty.kind() { |
0bf4aa26 XL |
172 | cx.layout_of(mt.ty).llvm_type(cx) |
173 | } else { | |
dc9dc135 | 174 | cx.sess().span_fatal( |
29967ef6 | 175 | cx.tcx.def_span(span_def_id), |
dfeec247 XL |
176 | "must have type `*const T` or `*mut T` due to `#[linkage]` attribute", |
177 | ) | |
8faf50e0 XL |
178 | }; |
179 | unsafe { | |
180 | // Declare a symbol `foo` with the desired linkage. | |
c295e0f8 | 181 | let g1 = cx.declare_global(sym, llty2); |
8faf50e0 XL |
182 | llvm::LLVMRustSetLinkage(g1, base::linkage_to_llvm(linkage)); |
183 | ||
184 | // Declare an internal global `extern_with_linkage_foo` which | |
185 | // is initialized with the address of `foo`. If `foo` is | |
186 | // discarded during linking (for example, if `foo` has weak | |
187 | // linkage and there are no definitions), then | |
188 | // `extern_with_linkage_foo` will instead be initialized to | |
189 | // zero. | |
190 | let mut real_name = "_rust_extern_with_linkage_".to_string(); | |
c295e0f8 | 191 | real_name.push_str(sym); |
dfeec247 | 192 | let g2 = cx.define_global(&real_name, llty).unwrap_or_else(|| { |
29967ef6 XL |
193 | cx.sess().span_fatal( |
194 | cx.tcx.def_span(span_def_id), | |
195 | &format!("symbol `{}` is already defined", &sym), | |
196 | ) | |
8faf50e0 XL |
197 | }); |
198 | llvm::LLVMRustSetLinkage(g2, llvm::Linkage::InternalLinkage); | |
199 | llvm::LLVMSetInitializer(g2, g1); | |
200 | g2 | |
201 | } | |
202 | } else { | |
203 | // Generate an external declaration. | |
204 | // FIXME(nagisa): investigate whether it can be changed into define_global | |
c295e0f8 | 205 | cx.declare_global(sym, llty) |
8faf50e0 XL |
206 | } |
207 | } | |
208 | ||
a2a8927a | 209 | pub fn ptrcast<'ll>(val: &'ll Value, ty: &'ll Type) -> &'ll Value { |
dfeec247 | 210 | unsafe { llvm::LLVMConstPointerCast(val, ty) } |
a1dfa0c6 | 211 | } |
c1a9b12d | 212 | |
a2a8927a | 213 | impl<'ll> CodegenCx<'ll, '_> { |
a1dfa0c6 | 214 | crate fn const_bitcast(&self, val: &'ll Value, ty: &'ll Type) -> &'ll Value { |
dfeec247 | 215 | unsafe { llvm::LLVMConstBitCast(val, ty) } |
a1dfa0c6 | 216 | } |
c1a9b12d | 217 | |
a1dfa0c6 XL |
218 | crate fn static_addr_of_mut( |
219 | &self, | |
220 | cv: &'ll Value, | |
221 | align: Align, | |
222 | kind: Option<&str>, | |
223 | ) -> &'ll Value { | |
224 | unsafe { | |
225 | let gv = match kind { | |
226 | Some(kind) if !self.tcx.sess.fewer_names() => { | |
227 | let name = self.generate_local_symbol_name(kind); | |
a2a8927a | 228 | let gv = self.define_global(&name, self.val_ty(cv)).unwrap_or_else(|| { |
dfeec247 | 229 | bug!("symbol `{}` is already defined", name); |
a1dfa0c6 XL |
230 | }); |
231 | llvm::LLVMRustSetLinkage(gv, llvm::Linkage::PrivateLinkage); | |
232 | gv | |
dfeec247 | 233 | } |
a1dfa0c6 XL |
234 | _ => self.define_private_global(self.val_ty(cv)), |
235 | }; | |
236 | llvm::LLVMSetInitializer(gv, cv); | |
c295e0f8 | 237 | set_global_alignment(self, gv, align); |
ba9703b0 | 238 | llvm::SetUnnamedAddress(gv, llvm::UnnamedAddr::Global); |
a1dfa0c6 XL |
239 | gv |
240 | } | |
241 | } | |
8faf50e0 | 242 | |
a1dfa0c6 XL |
243 | crate fn get_static(&self, def_id: DefId) -> &'ll Value { |
244 | let instance = Instance::mono(self.tcx, def_id); | |
245 | if let Some(&g) = self.instances.borrow().get(&instance) { | |
246 | return g; | |
247 | } | |
248 | ||
dfeec247 XL |
249 | let defined_in_current_codegen_unit = |
250 | self.codegen_unit.items().contains_key(&MonoItem::Static(def_id)); | |
251 | assert!( | |
252 | !defined_in_current_codegen_unit, | |
253 | "consts::get_static() should always hit the cache for \ | |
a1dfa0c6 | 254 | statics defined in the same CGU, but did not for `{:?}`", |
dfeec247 XL |
255 | def_id |
256 | ); | |
a1dfa0c6 | 257 | |
3dfed10e | 258 | let ty = instance.ty(self.tcx, ty::ParamEnv::reveal_all()); |
e74abb32 | 259 | let sym = self.tcx.symbol_name(instance).name; |
5869c6ff | 260 | let fn_attrs = self.tcx.codegen_fn_attrs(def_id); |
a1dfa0c6 | 261 | |
5869c6ff | 262 | debug!("get_static: sym={} instance={:?} fn_attrs={:?}", sym, instance, fn_attrs); |
a1dfa0c6 | 263 | |
5869c6ff | 264 | let g = if def_id.is_local() && !self.tcx.is_foreign_item(def_id) { |
a1dfa0c6 | 265 | let llty = self.layout_of(ty).llvm_type(self); |
5869c6ff XL |
266 | if let Some(g) = self.get_declared_value(sym) { |
267 | if self.val_ty(g) != self.type_ptr_to(llty) { | |
268 | span_bug!(self.tcx.def_span(def_id), "Conflicting types for static"); | |
a1dfa0c6 | 269 | } |
5869c6ff | 270 | } |
a1dfa0c6 | 271 | |
5869c6ff | 272 | let g = self.declare_global(sym, llty); |
a1dfa0c6 | 273 | |
5869c6ff XL |
274 | if !self.tcx.is_reachable_non_generic(def_id) { |
275 | unsafe { | |
276 | llvm::LLVMRustSetVisibility(g, llvm::Visibility::Hidden); | |
a1dfa0c6 XL |
277 | } |
278 | } | |
c1a9b12d | 279 | |
9e0c209e | 280 | g |
c1a9b12d | 281 | } else { |
c295e0f8 | 282 | check_and_apply_linkage(self, fn_attrs, ty, sym, def_id) |
5869c6ff | 283 | }; |
a1dfa0c6 | 284 | |
5869c6ff XL |
285 | // Thread-local statics in some other crate need to *always* be linked |
286 | // against in a thread-local fashion, so we need to be sure to apply the | |
287 | // thread-local attribute locally if it was present remotely. If we | |
288 | // don't do this then linker errors can be generated where the linker | |
289 | // complains that one object files has a thread local version of the | |
290 | // symbol and another one doesn't. | |
291 | if fn_attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL) { | |
292 | llvm::set_thread_local_mode(g, self.tls_model); | |
293 | } | |
a1dfa0c6 | 294 | |
5869c6ff | 295 | if !def_id.is_local() { |
dfeec247 | 296 | let needs_dll_storage_attr = self.use_dll_storage_attrs && !self.tcx.is_foreign_item(def_id) && |
a1dfa0c6 XL |
297 | // ThinLTO can't handle this workaround in all cases, so we don't |
298 | // emit the attrs. Instead we make them unnecessary by disallowing | |
9fa01778 XL |
299 | // dynamic linking when linker plugin based LTO is enabled. |
300 | !self.tcx.sess.opts.cg.linker_plugin_lto.enabled(); | |
a1dfa0c6 XL |
301 | |
302 | // If this assertion triggers, there's something wrong with commandline | |
303 | // argument validation. | |
dfeec247 XL |
304 | debug_assert!( |
305 | !(self.tcx.sess.opts.cg.linker_plugin_lto.enabled() | |
29967ef6 | 306 | && self.tcx.sess.target.is_like_windows |
dfeec247 XL |
307 | && self.tcx.sess.opts.cg.prefer_dynamic) |
308 | ); | |
a1dfa0c6 XL |
309 | |
310 | if needs_dll_storage_attr { | |
0731742a | 311 | // This item is external but not foreign, i.e., it originates from an external Rust |
a1dfa0c6 XL |
312 | // crate. Since we don't know whether this crate will be linked dynamically or |
313 | // statically in the final application, we always mark such symbols as 'dllimport'. | |
314 | // If final linkage happens to be static, we rely on compiler-emitted __imp_ stubs | |
315 | // to make things work. | |
316 | // | |
317 | // However, in some scenarios we defer emission of statics to downstream | |
318 | // crates, so there are cases where a static with an upstream DefId | |
319 | // is actually present in the current crate. We can find out via the | |
320 | // is_codegened_item query. | |
321 | if !self.tcx.is_codegened_item(def_id) { | |
322 | unsafe { | |
323 | llvm::LLVMSetDLLStorageClass(g, llvm::DLLStorageClass::DllImport); | |
324 | } | |
325 | } | |
326 | } | |
5869c6ff | 327 | } |
a1dfa0c6 XL |
328 | |
329 | if self.use_dll_storage_attrs && self.tcx.is_dllimport_foreign_item(def_id) { | |
330 | // For foreign (native) libs we know the exact storage type to use. | |
331 | unsafe { | |
332 | llvm::LLVMSetDLLStorageClass(g, llvm::DLLStorageClass::DllImport); | |
1a4d82fc JJ |
333 | } |
334 | } | |
c1a9b12d | 335 | |
17df50a5 XL |
336 | unsafe { |
337 | if self.should_assume_dso_local(g, true) { | |
338 | llvm::LLVMRustSetDSOLocal(g, true); | |
339 | } | |
340 | } | |
341 | ||
a1dfa0c6 XL |
342 | self.instances.borrow_mut().insert(instance, g); |
343 | g | |
344 | } | |
345 | } | |
346 | ||
a2a8927a | 347 | impl<'ll> StaticMethods for CodegenCx<'ll, '_> { |
dfeec247 | 348 | fn static_addr_of(&self, cv: &'ll Value, align: Align, kind: Option<&str>) -> &'ll Value { |
a1dfa0c6 XL |
349 | if let Some(&gv) = self.const_globals.borrow().get(&cv) { |
350 | unsafe { | |
351 | // Upgrade the alignment in cases where the same constant is used with different | |
352 | // alignment requirements | |
353 | let llalign = align.bytes() as u32; | |
354 | if llalign > llvm::LLVMGetAlignment(gv) { | |
355 | llvm::LLVMSetAlignment(gv, llalign); | |
356 | } | |
94b46f34 | 357 | } |
a1dfa0c6 XL |
358 | return gv; |
359 | } | |
360 | let gv = self.static_addr_of_mut(cv, align, kind); | |
361 | unsafe { | |
362 | llvm::LLVMSetGlobalConstant(gv, True); | |
c1a9b12d | 363 | } |
a1dfa0c6 XL |
364 | self.const_globals.borrow_mut().insert(cv, gv); |
365 | gv | |
366 | } | |
5bcae85e | 367 | |
dfeec247 | 368 | fn codegen_static(&self, def_id: DefId, is_mutable: bool) { |
a1dfa0c6 XL |
369 | unsafe { |
370 | let attrs = self.tcx.codegen_fn_attrs(def_id); | |
371 | ||
c295e0f8 | 372 | let (v, alloc) = match codegen_static_initializer(self, def_id) { |
a1dfa0c6 XL |
373 | Ok(v) => v, |
374 | // Error has already been reported | |
375 | Err(_) => return, | |
376 | }; | |
377 | ||
378 | let g = self.get_static(def_id); | |
379 | ||
380 | // boolean SSA values are i1, but they have to be stored in i8 slots, | |
381 | // otherwise some LLVM optimization passes don't work as expected | |
382 | let mut val_llty = self.val_ty(v); | |
383 | let v = if val_llty == self.type_i1() { | |
384 | val_llty = self.type_i8(); | |
385 | llvm::LLVMConstZExt(v, val_llty) | |
386 | } else { | |
387 | v | |
388 | }; | |
389 | ||
390 | let instance = Instance::mono(self.tcx, def_id); | |
3dfed10e | 391 | let ty = instance.ty(self.tcx, ty::ParamEnv::reveal_all()); |
a1dfa0c6 XL |
392 | let llty = self.layout_of(ty).llvm_type(self); |
393 | let g = if val_llty == llty { | |
394 | g | |
395 | } else { | |
396 | // If we created the global with the wrong type, | |
397 | // correct the type. | |
60c5eb7d XL |
398 | let name = llvm::get_value_name(g).to_vec(); |
399 | llvm::set_value_name(g, b""); | |
a1dfa0c6 XL |
400 | |
401 | let linkage = llvm::LLVMRustGetLinkage(g); | |
402 | let visibility = llvm::LLVMRustGetVisibility(g); | |
403 | ||
404 | let new_g = llvm::LLVMRustGetOrInsertGlobal( | |
dfeec247 XL |
405 | self.llmod, |
406 | name.as_ptr().cast(), | |
407 | name.len(), | |
408 | val_llty, | |
409 | ); | |
a1dfa0c6 XL |
410 | |
411 | llvm::LLVMRustSetLinkage(new_g, linkage); | |
412 | llvm::LLVMRustSetVisibility(new_g, visibility); | |
413 | ||
414 | // To avoid breaking any invariants, we leave around the old | |
415 | // global for the moment; we'll replace all references to it | |
416 | // with the new global later. (See base::codegen_backend.) | |
417 | self.statics_to_rauw.borrow_mut().push((g, new_g)); | |
418 | new_g | |
419 | }; | |
c295e0f8 | 420 | set_global_alignment(self, g, self.align_of(ty)); |
a1dfa0c6 XL |
421 | llvm::LLVMSetInitializer(g, v); |
422 | ||
17df50a5 XL |
423 | if self.should_assume_dso_local(g, true) { |
424 | llvm::LLVMRustSetDSOLocal(g, true); | |
425 | } | |
426 | ||
a1dfa0c6 XL |
427 | // As an optimization, all shared statics which do not have interior |
428 | // mutability are placed into read-only memory. | |
29967ef6 XL |
429 | if !is_mutable && self.type_is_freeze(ty) { |
430 | llvm::LLVMSetGlobalConstant(g, llvm::True); | |
a1dfa0c6 | 431 | } |
5bcae85e | 432 | |
c295e0f8 | 433 | debuginfo::create_global_var_metadata(self, def_id, g); |
a1dfa0c6 XL |
434 | |
435 | if attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL) { | |
436 | llvm::set_thread_local_mode(g, self.tls_model); | |
437 | ||
438 | // Do not allow LLVM to change the alignment of a TLS on macOS. | |
439 | // | |
440 | // By default a global's alignment can be freely increased. | |
441 | // This allows LLVM to generate more performant instructions | |
0731742a | 442 | // e.g., using load-aligned into a SIMD register. |
a1dfa0c6 XL |
443 | // |
444 | // However, on macOS 10.10 or below, the dynamic linker does not | |
445 | // respect any alignment given on the TLS (radar 24221680). | |
446 | // This will violate the alignment assumption, and causing segfault at runtime. | |
447 | // | |
448 | // This bug is very easy to trigger. In `println!` and `panic!`, | |
449 | // the `LOCAL_STDOUT`/`LOCAL_STDERR` handles are stored in a TLS, | |
450 | // which the values would be `mem::replace`d on initialization. | |
451 | // The implementation of `mem::replace` will use SIMD | |
452 | // whenever the size is 32 bytes or higher. LLVM notices SIMD is used | |
453 | // and tries to align `LOCAL_STDOUT`/`LOCAL_STDERR` to a 32-byte boundary, | |
454 | // which macOS's dyld disregarded and causing crashes | |
455 | // (see issues #51794, #51758, #50867, #48866 and #44056). | |
456 | // | |
457 | // To workaround the bug, we trick LLVM into not increasing | |
458 | // the global's alignment by explicitly assigning a section to it | |
459 | // (equivalent to automatically generating a `#[link_section]` attribute). | |
460 | // See the comment in the `GlobalValue::canIncreaseAlignment()` function | |
461 | // of `lib/IR/Globals.cpp` for why this works. | |
462 | // | |
463 | // When the alignment is not increased, the optimized `mem::replace` | |
464 | // will use load-unaligned instructions instead, and thus avoiding the crash. | |
465 | // | |
466 | // We could remove this hack whenever we decide to drop macOS 10.10 support. | |
29967ef6 | 467 | if self.tcx.sess.target.is_like_osx { |
ba9703b0 XL |
468 | // The `inspect` method is okay here because we checked relocations, and |
469 | // because we are doing this access to inspect the final interpreter state | |
470 | // (not as part of the interpreter execution). | |
471 | // | |
472 | // FIXME: This check requires that the (arbitrary) value of undefined bytes | |
473 | // happens to be zero. Instead, we should only check the value of defined bytes | |
474 | // and set all undefined bytes to zero if this allocation is headed for the | |
475 | // BSS. | |
476 | let all_bytes_are_zero = alloc.relocations().is_empty() | |
477 | && alloc | |
3dfed10e | 478 | .inspect_with_uninit_and_ptr_outside_interpreter(0..alloc.len()) |
e1599b0c | 479 | .iter() |
ba9703b0 XL |
480 | .all(|&byte| byte == 0); |
481 | ||
482 | let sect_name = if all_bytes_are_zero { | |
6a06907d | 483 | cstr!("__DATA,__thread_bss") |
a1dfa0c6 | 484 | } else { |
6a06907d | 485 | cstr!("__DATA,__thread_data") |
a1dfa0c6 XL |
486 | }; |
487 | llvm::LLVMSetSection(g, sect_name.as_ptr()); | |
488 | } | |
489 | } | |
490 | ||
a1dfa0c6 XL |
491 | // Wasm statics with custom link sections get special treatment as they |
492 | // go into custom sections of the wasm executable. | |
3c0e092e | 493 | if self.tcx.sess.target.is_like_wasm { |
a1dfa0c6 XL |
494 | if let Some(section) = attrs.link_section { |
495 | let section = llvm::LLVMMDStringInContext( | |
496 | self.llcx, | |
e74abb32 | 497 | section.as_str().as_ptr().cast(), |
a1dfa0c6 XL |
498 | section.as_str().len() as c_uint, |
499 | ); | |
e1599b0c XL |
500 | assert!(alloc.relocations().is_empty()); |
501 | ||
502 | // The `inspect` method is okay here because we checked relocations, and | |
503 | // because we are doing this access to inspect the final interpreter state (not | |
504 | // as part of the interpreter execution). | |
dfeec247 | 505 | let bytes = |
3dfed10e | 506 | alloc.inspect_with_uninit_and_ptr_outside_interpreter(0..alloc.len()); |
a1dfa0c6 XL |
507 | let alloc = llvm::LLVMMDStringInContext( |
508 | self.llcx, | |
e74abb32 | 509 | bytes.as_ptr().cast(), |
e1599b0c | 510 | bytes.len() as c_uint, |
a1dfa0c6 XL |
511 | ); |
512 | let data = [section, alloc]; | |
513 | let meta = llvm::LLVMMDNodeInContext(self.llcx, data.as_ptr(), 2); | |
514 | llvm::LLVMAddNamedMetadataOperand( | |
515 | self.llmod, | |
e74abb32 | 516 | "wasm.custom_sections\0".as_ptr().cast(), |
a1dfa0c6 XL |
517 | meta, |
518 | ); | |
519 | } | |
520 | } else { | |
c295e0f8 | 521 | base::set_link_section(g, attrs); |
8faf50e0 | 522 | } |
8faf50e0 | 523 | |
a1dfa0c6 | 524 | if attrs.flags.contains(CodegenFnAttrFlags::USED) { |
94222f64 XL |
525 | // The semantics of #[used] in Rust only require the symbol to make it into the |
526 | // object file. It is explicitly allowed for the linker to strip the symbol if it | |
527 | // is dead. As such, use llvm.compiler.used instead of llvm.used. | |
528 | // Additionally, https://reviews.llvm.org/D97448 in LLVM 13 started emitting unique | |
529 | // sections with SHF_GNU_RETAIN flag for llvm.used symbols, which may trigger bugs | |
530 | // in some versions of the gold linker. | |
531 | self.add_compiler_used_global(g); | |
a1dfa0c6 | 532 | } |
cc61c64b | 533 | } |
1a4d82fc | 534 | } |
3dfed10e XL |
535 | |
536 | /// Add a global value to a list to be stored in the `llvm.used` variable, an array of i8*. | |
537 | fn add_used_global(&self, global: &'ll Value) { | |
538 | let cast = unsafe { llvm::LLVMConstPointerCast(global, self.type_i8p()) }; | |
539 | self.used_statics.borrow_mut().push(cast); | |
540 | } | |
94222f64 XL |
541 | |
542 | /// Add a global value to a list to be stored in the `llvm.compiler.used` variable, | |
543 | /// an array of i8*. | |
544 | fn add_compiler_used_global(&self, global: &'ll Value) { | |
545 | let cast = unsafe { llvm::LLVMConstPointerCast(global, self.type_i8p()) }; | |
546 | self.compiler_used_statics.borrow_mut().push(cast); | |
547 | } | |
1a4d82fc | 548 | } |