2 use crate::common::CodegenCx;
4 use crate::llvm::{self, SetUnnamedAddr, True};
5 use crate::type_::Type;
6 use crate::type_of::LayoutLlvmExt;
7 use crate::value::Value;
10 use rustc::hir::def_id::DefId;
11 use rustc::hir::{self, Node};
12 use rustc::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
13 use rustc::mir::interpret::{read_target_uint, Allocation, ConstValue, ErrorHandled, Pointer};
14 use rustc::mir::mono::MonoItem;
15 use rustc::ty::layout::{self, Align, LayoutOf, Size};
16 use rustc::ty::{self, Instance, Ty};
17 use rustc::{bug, span_bug};
18 use rustc_codegen_ssa::traits::*;
19 use rustc_span::symbol::{sym, Symbol};
21 use rustc_target::abi::HasDataLayout;
25 pub fn const_alloc_to_llvm(cx: &CodegenCx<'ll, '_>, alloc: &Allocation) -> &'ll Value {
26 let mut llvals = Vec::with_capacity(alloc.relocations().len() + 1);
27 let dl = cx.data_layout();
28 let pointer_size = dl.pointer_size.bytes() as usize;
30 let mut next_offset = 0;
31 for &(offset, ((), alloc_id)) in alloc.relocations().iter() {
32 let offset = offset.bytes();
33 assert_eq!(offset as usize as u64, offset);
34 let offset = offset as usize;
35 if offset > next_offset {
36 // This `inspect` is okay since we have checked that it is not within a relocation, it
37 // is within the bounds of the allocation, and it doesn't affect interpreter execution
38 // (we inspect the result after interpreter execution). Any undef byte is replaced with
39 // some arbitrary byte value.
41 // FIXME: relay undef bytes to codegen as undef const bytes
42 let bytes = alloc.inspect_with_undef_and_ptr_outside_interpreter(next_offset..offset);
43 llvals.push(cx.const_bytes(bytes));
45 let ptr_offset = read_target_uint(
47 // This `inspect` is okay since it is within the bounds of the allocation, it doesn't
48 // affect interpreter execution (we inspect the result after interpreter execution),
49 // and we properly interpret the relocation as a relocation pointer offset.
50 alloc.inspect_with_undef_and_ptr_outside_interpreter(offset..(offset + pointer_size)),
52 .expect("const_alloc_to_llvm: could not read relocation pointer")
54 llvals.push(cx.scalar_to_backend(
55 Pointer::new(alloc_id, Size::from_bytes(ptr_offset)).into(),
56 &layout::Scalar { value: layout::Primitive::Pointer, valid_range: 0..=!0 },
59 next_offset = offset + pointer_size;
61 if alloc.len() >= next_offset {
62 let range = next_offset..alloc.len();
63 // This `inspect` is okay since we have check that it is after all relocations, it is
64 // within the bounds of the allocation, and it doesn't affect interpreter execution (we
65 // inspect the result after interpreter execution). Any undef byte is replaced with some
66 // arbitrary byte value.
68 // FIXME: relay undef bytes to codegen as undef const bytes
69 let bytes = alloc.inspect_with_undef_and_ptr_outside_interpreter(range);
70 llvals.push(cx.const_bytes(bytes));
73 cx.const_struct(&llvals, true)
76 pub fn codegen_static_initializer(
77 cx: &CodegenCx<'ll, 'tcx>,
79 ) -> Result<(&'ll Value, &'tcx Allocation), ErrorHandled> {
80 let static_ = cx.tcx.const_eval_poly(def_id)?;
82 let alloc = match static_.val {
83 ty::ConstKind::Value(ConstValue::ByRef { alloc, offset }) if offset.bytes() == 0 => alloc,
84 _ => bug!("static const eval returned {:#?}", static_),
86 Ok((const_alloc_to_llvm(cx, alloc), alloc))
89 fn set_global_alignment(cx: &CodegenCx<'ll, '_>, gv: &'ll Value, mut align: Align) {
90 // The target may require greater alignment for globals than the type does.
91 // Note: GCC and Clang also allow `__attribute__((aligned))` on variables,
92 // which can force it to be smaller. Rust doesn't support this yet.
93 if let Some(min) = cx.sess().target.target.options.min_global_align {
94 match Align::from_bits(min) {
95 Ok(min) => align = align.max(min),
97 cx.sess().err(&format!("invalid minimum global alignment: {}", err));
102 llvm::LLVMSetAlignment(gv, align.bytes() as u32);
106 fn check_and_apply_linkage(
107 cx: &CodegenCx<'ll, 'tcx>,
108 attrs: &CodegenFnAttrs,
113 let llty = cx.layout_of(ty).llvm_type(cx);
114 let sym = sym.as_str();
115 if let Some(linkage) = attrs.linkage {
116 debug!("get_static: sym={} linkage={:?}", sym, linkage);
118 // If this is a static with a linkage specified, then we need to handle
119 // it a little specially. The typesystem prevents things like &T and
120 // extern "C" fn() from being non-null, so we can't just declare a
121 // static and call it a day. Some linkages (like weak) will make it such
122 // that the static actually has a null value.
123 let llty2 = if let ty::RawPtr(ref mt) = ty.kind {
124 cx.layout_of(mt.ty).llvm_type(cx)
126 cx.sess().span_fatal(
128 "must have type `*const T` or `*mut T` due to `#[linkage]` attribute",
132 // Declare a symbol `foo` with the desired linkage.
133 let g1 = cx.declare_global(&sym, llty2);
134 llvm::LLVMRustSetLinkage(g1, base::linkage_to_llvm(linkage));
136 // Declare an internal global `extern_with_linkage_foo` which
137 // is initialized with the address of `foo`. If `foo` is
138 // discarded during linking (for example, if `foo` has weak
139 // linkage and there are no definitions), then
140 // `extern_with_linkage_foo` will instead be initialized to
142 let mut real_name = "_rust_extern_with_linkage_".to_string();
143 real_name.push_str(&sym);
144 let g2 = cx.define_global(&real_name, llty).unwrap_or_else(|| {
145 cx.sess().span_fatal(span, &format!("symbol `{}` is already defined", &sym))
147 llvm::LLVMRustSetLinkage(g2, llvm::Linkage::InternalLinkage);
148 llvm::LLVMSetInitializer(g2, g1);
152 // Generate an external declaration.
153 // FIXME(nagisa): investigate whether it can be changed into define_global
154 cx.declare_global(&sym, llty)
158 pub fn ptrcast(val: &'ll Value, ty: &'ll Type) -> &'ll Value {
159 unsafe { llvm::LLVMConstPointerCast(val, ty) }
162 impl CodegenCx<'ll, 'tcx> {
163 crate fn const_bitcast(&self, val: &'ll Value, ty: &'ll Type) -> &'ll Value {
164 unsafe { llvm::LLVMConstBitCast(val, ty) }
167 crate fn static_addr_of_mut(
174 let gv = match kind {
175 Some(kind) if !self.tcx.sess.fewer_names() => {
176 let name = self.generate_local_symbol_name(kind);
177 let gv = self.define_global(&name[..], self.val_ty(cv)).unwrap_or_else(|| {
178 bug!("symbol `{}` is already defined", name);
180 llvm::LLVMRustSetLinkage(gv, llvm::Linkage::PrivateLinkage);
183 _ => self.define_private_global(self.val_ty(cv)),
185 llvm::LLVMSetInitializer(gv, cv);
186 set_global_alignment(&self, gv, align);
187 SetUnnamedAddr(gv, true);
192 crate fn get_static(&self, def_id: DefId) -> &'ll Value {
193 let instance = Instance::mono(self.tcx, def_id);
194 if let Some(&g) = 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.monomorphic_ty(self.tcx);
208 let sym = self.tcx.symbol_name(instance).name;
210 debug!("get_static: sym={} instance={:?}", sym, instance);
212 let g = if let Some(id) = self.tcx.hir().as_local_hir_id(def_id) {
213 let llty = self.layout_of(ty).llvm_type(self);
214 let (g, attrs) = match self.tcx.hir().get(id) {
215 Node::Item(&hir::Item { attrs, span, kind: hir::ItemKind::Static(..), .. }) => {
216 let sym_str = sym.as_str();
217 if let Some(g) = self.get_declared_value(&sym_str) {
218 if self.val_ty(g) != self.type_ptr_to(llty) {
219 span_bug!(span, "Conflicting types for static");
223 let g = self.declare_global(&sym_str, llty);
225 if !self.tcx.is_reachable_non_generic(def_id) {
227 llvm::LLVMRustSetVisibility(g, llvm::Visibility::Hidden);
234 Node::ForeignItem(&hir::ForeignItem {
237 kind: hir::ForeignItemKind::Static(..),
240 let fn_attrs = self.tcx.codegen_fn_attrs(def_id);
241 (check_and_apply_linkage(&self, &fn_attrs, ty, sym, span), &**attrs)
244 item => bug!("get_static: expected static, found {:?}", item),
247 debug!("get_static: sym={} attrs={:?}", sym, attrs);
250 if attr.check_name(sym::thread_local) {
251 llvm::set_thread_local_mode(g, self.tls_model);
257 // FIXME(nagisa): perhaps the map of externs could be offloaded to llvm somehow?
258 debug!("get_static: sym={} item_attr={:?}", sym, self.tcx.item_attrs(def_id));
260 let attrs = self.tcx.codegen_fn_attrs(def_id);
261 let span = self.tcx.def_span(def_id);
262 let g = check_and_apply_linkage(&self, &attrs, ty, sym, span);
264 // Thread-local statics in some other crate need to *always* be linked
265 // against in a thread-local fashion, so we need to be sure to apply the
266 // thread-local attribute locally if it was present remotely. If we
267 // don't do this then linker errors can be generated where the linker
268 // complains that one object files has a thread local version of the
269 // symbol and another one doesn't.
270 if attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL) {
271 llvm::set_thread_local_mode(g, self.tls_model);
274 let needs_dll_storage_attr = self.use_dll_storage_attrs && !self.tcx.is_foreign_item(def_id) &&
275 // ThinLTO can't handle this workaround in all cases, so we don't
276 // emit the attrs. Instead we make them unnecessary by disallowing
277 // dynamic linking when linker plugin based LTO is enabled.
278 !self.tcx.sess.opts.cg.linker_plugin_lto.enabled();
280 // If this assertion triggers, there's something wrong with commandline
281 // argument validation.
283 !(self.tcx.sess.opts.cg.linker_plugin_lto.enabled()
284 && self.tcx.sess.target.target.options.is_like_msvc
285 && self.tcx.sess.opts.cg.prefer_dynamic)
288 if needs_dll_storage_attr {
289 // This item is external but not foreign, i.e., it originates from an external Rust
290 // crate. Since we don't know whether this crate will be linked dynamically or
291 // statically in the final application, we always mark such symbols as 'dllimport'.
292 // If final linkage happens to be static, we rely on compiler-emitted __imp_ stubs
293 // to make things work.
295 // However, in some scenarios we defer emission of statics to downstream
296 // crates, so there are cases where a static with an upstream DefId
297 // is actually present in the current crate. We can find out via the
298 // is_codegened_item query.
299 if !self.tcx.is_codegened_item(def_id) {
301 llvm::LLVMSetDLLStorageClass(g, llvm::DLLStorageClass::DllImport);
308 if self.use_dll_storage_attrs && self.tcx.is_dllimport_foreign_item(def_id) {
309 // For foreign (native) libs we know the exact storage type to use.
311 llvm::LLVMSetDLLStorageClass(g, llvm::DLLStorageClass::DllImport);
315 self.instances.borrow_mut().insert(instance, g);
320 impl StaticMethods for CodegenCx<'ll, 'tcx> {
321 fn static_addr_of(&self, cv: &'ll Value, align: Align, kind: Option<&str>) -> &'ll Value {
322 if let Some(&gv) = self.const_globals.borrow().get(&cv) {
324 // Upgrade the alignment in cases where the same constant is used with different
325 // alignment requirements
326 let llalign = align.bytes() as u32;
327 if llalign > llvm::LLVMGetAlignment(gv) {
328 llvm::LLVMSetAlignment(gv, llalign);
333 let gv = self.static_addr_of_mut(cv, align, kind);
335 llvm::LLVMSetGlobalConstant(gv, True);
337 self.const_globals.borrow_mut().insert(cv, gv);
341 fn codegen_static(&self, def_id: DefId, is_mutable: bool) {
343 let attrs = self.tcx.codegen_fn_attrs(def_id);
345 let (v, alloc) = match codegen_static_initializer(&self, def_id) {
347 // Error has already been reported
351 let g = self.get_static(def_id);
353 // boolean SSA values are i1, but they have to be stored in i8 slots,
354 // otherwise some LLVM optimization passes don't work as expected
355 let mut val_llty = self.val_ty(v);
356 let v = if val_llty == self.type_i1() {
357 val_llty = self.type_i8();
358 llvm::LLVMConstZExt(v, val_llty)
363 let instance = Instance::mono(self.tcx, def_id);
364 let ty = instance.monomorphic_ty(self.tcx);
365 let llty = self.layout_of(ty).llvm_type(self);
366 let g = if val_llty == llty {
369 // If we created the global with the wrong type,
371 let name = llvm::get_value_name(g).to_vec();
372 llvm::set_value_name(g, b"");
374 let linkage = llvm::LLVMRustGetLinkage(g);
375 let visibility = llvm::LLVMRustGetVisibility(g);
377 let new_g = llvm::LLVMRustGetOrInsertGlobal(
379 name.as_ptr().cast(),
384 llvm::LLVMRustSetLinkage(new_g, linkage);
385 llvm::LLVMRustSetVisibility(new_g, visibility);
387 // To avoid breaking any invariants, we leave around the old
388 // global for the moment; we'll replace all references to it
389 // with the new global later. (See base::codegen_backend.)
390 self.statics_to_rauw.borrow_mut().push((g, new_g));
393 set_global_alignment(&self, g, self.align_of(ty));
394 llvm::LLVMSetInitializer(g, v);
396 // As an optimization, all shared statics which do not have interior
397 // mutability are placed into read-only memory.
399 if self.type_is_freeze(ty) {
400 llvm::LLVMSetGlobalConstant(g, llvm::True);
404 debuginfo::create_global_var_metadata(&self, def_id, g);
406 if attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL) {
407 llvm::set_thread_local_mode(g, self.tls_model);
409 // Do not allow LLVM to change the alignment of a TLS on macOS.
411 // By default a global's alignment can be freely increased.
412 // This allows LLVM to generate more performant instructions
413 // e.g., using load-aligned into a SIMD register.
415 // However, on macOS 10.10 or below, the dynamic linker does not
416 // respect any alignment given on the TLS (radar 24221680).
417 // This will violate the alignment assumption, and causing segfault at runtime.
419 // This bug is very easy to trigger. In `println!` and `panic!`,
420 // the `LOCAL_STDOUT`/`LOCAL_STDERR` handles are stored in a TLS,
421 // which the values would be `mem::replace`d on initialization.
422 // The implementation of `mem::replace` will use SIMD
423 // whenever the size is 32 bytes or higher. LLVM notices SIMD is used
424 // and tries to align `LOCAL_STDOUT`/`LOCAL_STDERR` to a 32-byte boundary,
425 // which macOS's dyld disregarded and causing crashes
426 // (see issues #51794, #51758, #50867, #48866 and #44056).
428 // To workaround the bug, we trick LLVM into not increasing
429 // the global's alignment by explicitly assigning a section to it
430 // (equivalent to automatically generating a `#[link_section]` attribute).
431 // See the comment in the `GlobalValue::canIncreaseAlignment()` function
432 // of `lib/IR/Globals.cpp` for why this works.
434 // When the alignment is not increased, the optimized `mem::replace`
435 // will use load-unaligned instructions instead, and thus avoiding the crash.
437 // We could remove this hack whenever we decide to drop macOS 10.10 support.
438 if self.tcx.sess.target.target.options.is_like_osx {
439 assert_eq!(alloc.relocations().len(), 0);
442 // Treats undefined bytes as if they were defined with the byte value that
443 // happens to be currently assigned in mir. This is valid since reading
444 // undef bytes may yield arbitrary values.
446 // FIXME: ignore undef bytes even with representation `!= 0`.
448 // The `inspect` method is okay here because we checked relocations, and
449 // because we are doing this access to inspect the final interpreter state
450 // (not as part of the interpreter execution).
452 .inspect_with_undef_and_ptr_outside_interpreter(0..alloc.len())
456 let sect_name = if is_zeroed {
457 CStr::from_bytes_with_nul_unchecked(b"__DATA,__thread_bss\0")
459 CStr::from_bytes_with_nul_unchecked(b"__DATA,__thread_data\0")
461 llvm::LLVMSetSection(g, sect_name.as_ptr());
465 // Wasm statics with custom link sections get special treatment as they
466 // go into custom sections of the wasm executable.
467 if self.tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
468 if let Some(section) = attrs.link_section {
469 let section = llvm::LLVMMDStringInContext(
471 section.as_str().as_ptr().cast(),
472 section.as_str().len() as c_uint,
474 assert!(alloc.relocations().is_empty());
476 // The `inspect` method is okay here because we checked relocations, and
477 // because we are doing this access to inspect the final interpreter state (not
478 // as part of the interpreter execution).
480 alloc.inspect_with_undef_and_ptr_outside_interpreter(0..alloc.len());
481 let alloc = llvm::LLVMMDStringInContext(
483 bytes.as_ptr().cast(),
484 bytes.len() as c_uint,
486 let data = [section, alloc];
487 let meta = llvm::LLVMMDNodeInContext(self.llcx, data.as_ptr(), 2);
488 llvm::LLVMAddNamedMetadataOperand(
490 "wasm.custom_sections\0".as_ptr().cast(),
495 base::set_link_section(g, &attrs);
498 if attrs.flags.contains(CodegenFnAttrFlags::USED) {
499 // This static will be stored in the llvm.used variable which is an array of i8*
500 let cast = llvm::LLVMConstPointerCast(g, self.type_i8p());
501 self.used_statics.borrow_mut().push(cast);