2 use crate::common
::CodegenCx
;
4 use crate::llvm
::{self, True}
;
5 use crate::type_
::Type
;
6 use crate::type_of
::LayoutLlvmExt
;
7 use crate::value
::Value
;
10 use rustc_codegen_ssa
::traits
::*;
11 use rustc_hir
::def_id
::DefId
;
12 use rustc_middle
::middle
::codegen_fn_attrs
::{CodegenFnAttrFlags, CodegenFnAttrs}
;
13 use rustc_middle
::mir
::interpret
::{
14 read_target_uint
, Allocation
, ErrorHandled
, GlobalAlloc
, Pointer
,
16 use rustc_middle
::mir
::mono
::MonoItem
;
17 use rustc_middle
::ty
::{self, Instance, Ty}
;
18 use rustc_middle
::{bug, span_bug}
;
19 use rustc_target
::abi
::{AddressSpace, Align, HasDataLayout, LayoutOf, Primitive, Scalar, Size}
;
22 pub fn const_alloc_to_llvm(cx
: &CodegenCx
<'ll
, '_
>, alloc
: &Allocation
) -> &'ll Value
{
23 let mut llvals
= Vec
::with_capacity(alloc
.relocations().len() + 1);
24 let dl
= cx
.data_layout();
25 let pointer_size
= dl
.pointer_size
.bytes() as usize;
27 let mut next_offset
= 0;
28 for &(offset
, ((), alloc_id
)) in alloc
.relocations().iter() {
29 let offset
= offset
.bytes();
30 assert_eq
!(offset
as usize as u64, offset
);
31 let offset
= offset
as usize;
32 if offset
> next_offset
{
33 // This `inspect` is okay since we have checked that it is not within a relocation, it
34 // is within the bounds of the allocation, and it doesn't affect interpreter execution
35 // (we inspect the result after interpreter execution). Any undef byte is replaced with
36 // some arbitrary byte value.
38 // FIXME: relay undef bytes to codegen as undef const bytes
39 let bytes
= alloc
.inspect_with_uninit_and_ptr_outside_interpreter(next_offset
..offset
);
40 llvals
.push(cx
.const_bytes(bytes
));
42 let ptr_offset
= read_target_uint(
44 // This `inspect` is okay since it is within the bounds of the allocation, it doesn't
45 // affect interpreter execution (we inspect the result after interpreter execution),
46 // and we properly interpret the relocation as a relocation pointer offset.
47 alloc
.inspect_with_uninit_and_ptr_outside_interpreter(offset
..(offset
+ pointer_size
)),
49 .expect("const_alloc_to_llvm: could not read relocation pointer")
52 let address_space
= match cx
.tcx
.global_alloc(alloc_id
) {
53 GlobalAlloc
::Function(..) => cx
.data_layout().instruction_address_space
,
54 GlobalAlloc
::Static(..) | GlobalAlloc
::Memory(..) => AddressSpace
::DATA
,
57 llvals
.push(cx
.scalar_to_backend(
58 Pointer
::new(alloc_id
, Size
::from_bytes(ptr_offset
)).into(),
59 &Scalar { value: Primitive::Pointer, valid_range: 0..=!0 }
,
60 cx
.type_i8p_ext(address_space
),
62 next_offset
= offset
+ pointer_size
;
64 if alloc
.len() >= next_offset
{
65 let range
= next_offset
..alloc
.len();
66 // This `inspect` is okay since we have check that it is after all relocations, it is
67 // within the bounds of the allocation, and it doesn't affect interpreter execution (we
68 // inspect the result after interpreter execution). Any undef byte is replaced with some
69 // arbitrary byte value.
71 // FIXME: relay undef bytes to codegen as undef const bytes
72 let bytes
= alloc
.inspect_with_uninit_and_ptr_outside_interpreter(range
);
73 llvals
.push(cx
.const_bytes(bytes
));
76 cx
.const_struct(&llvals
, true)
79 pub fn codegen_static_initializer(
80 cx
: &CodegenCx
<'ll
, 'tcx
>,
82 ) -> Result
<(&'ll Value
, &'tcx Allocation
), ErrorHandled
> {
83 let alloc
= cx
.tcx
.eval_static_initializer(def_id
)?
;
84 Ok((const_alloc_to_llvm(cx
, alloc
), alloc
))
87 fn set_global_alignment(cx
: &CodegenCx
<'ll
, '_
>, gv
: &'ll Value
, mut align
: Align
) {
88 // The target may require greater alignment for globals than the type does.
89 // Note: GCC and Clang also allow `__attribute__((aligned))` on variables,
90 // which can force it to be smaller. Rust doesn't support this yet.
91 if let Some(min
) = cx
.sess().target
.min_global_align
{
92 match Align
::from_bits(min
) {
93 Ok(min
) => align
= align
.max(min
),
95 cx
.sess().err(&format
!("invalid minimum global alignment: {}", err
));
100 llvm
::LLVMSetAlignment(gv
, align
.bytes() as u32);
104 fn check_and_apply_linkage(
105 cx
: &CodegenCx
<'ll
, 'tcx
>,
106 attrs
: &CodegenFnAttrs
,
111 let llty
= cx
.layout_of(ty
).llvm_type(cx
);
112 if let Some(linkage
) = attrs
.linkage
{
113 debug
!("get_static: sym={} linkage={:?}", sym
, linkage
);
115 // If this is a static with a linkage specified, then we need to handle
116 // it a little specially. The typesystem prevents things like &T and
117 // extern "C" fn() from being non-null, so we can't just declare a
118 // static and call it a day. Some linkages (like weak) will make it such
119 // that the static actually has a null value.
120 let llty2
= if let ty
::RawPtr(ref mt
) = ty
.kind() {
121 cx
.layout_of(mt
.ty
).llvm_type(cx
)
123 cx
.sess().span_fatal(
124 cx
.tcx
.def_span(span_def_id
),
125 "must have type `*const T` or `*mut T` due to `#[linkage]` attribute",
129 // Declare a symbol `foo` with the desired linkage.
130 let g1
= cx
.declare_global(&sym
, llty2
);
131 llvm
::LLVMRustSetLinkage(g1
, base
::linkage_to_llvm(linkage
));
133 // Declare an internal global `extern_with_linkage_foo` which
134 // is initialized with the address of `foo`. If `foo` is
135 // discarded during linking (for example, if `foo` has weak
136 // linkage and there are no definitions), then
137 // `extern_with_linkage_foo` will instead be initialized to
139 let mut real_name
= "_rust_extern_with_linkage_".to_string();
140 real_name
.push_str(&sym
);
141 let g2
= cx
.define_global(&real_name
, llty
).unwrap_or_else(|| {
142 cx
.sess().span_fatal(
143 cx
.tcx
.def_span(span_def_id
),
144 &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 llvm
::SetUnnamedAddress(gv
, llvm
::UnnamedAddr
::Global
);
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
.ty(self.tcx
, ty
::ParamEnv
::reveal_all());
208 let sym
= self.tcx
.symbol_name(instance
).name
;
209 let fn_attrs
= self.tcx
.codegen_fn_attrs(def_id
);
211 debug
!("get_static: sym={} instance={:?} fn_attrs={:?}", sym
, instance
, fn_attrs
);
213 let g
= if def_id
.is_local() && !self.tcx
.is_foreign_item(def_id
) {
214 let llty
= self.layout_of(ty
).llvm_type(self);
215 if let Some(g
) = self.get_declared_value(sym
) {
216 if self.val_ty(g
) != self.type_ptr_to(llty
) {
217 span_bug
!(self.tcx
.def_span(def_id
), "Conflicting types for static");
221 let g
= self.declare_global(sym
, llty
);
223 if !self.tcx
.is_reachable_non_generic(def_id
) {
225 llvm
::LLVMRustSetVisibility(g
, llvm
::Visibility
::Hidden
);
231 check_and_apply_linkage(&self, &fn_attrs
, ty
, sym
, def_id
)
234 // Thread-local statics in some other crate need to *always* be linked
235 // against in a thread-local fashion, so we need to be sure to apply the
236 // thread-local attribute locally if it was present remotely. If we
237 // don't do this then linker errors can be generated where the linker
238 // complains that one object files has a thread local version of the
239 // symbol and another one doesn't.
240 if fn_attrs
.flags
.contains(CodegenFnAttrFlags
::THREAD_LOCAL
) {
241 llvm
::set_thread_local_mode(g
, self.tls_model
);
244 if !def_id
.is_local() {
245 let needs_dll_storage_attr
= self.use_dll_storage_attrs
&& !self.tcx
.is_foreign_item(def_id
) &&
246 // ThinLTO can't handle this workaround in all cases, so we don't
247 // emit the attrs. Instead we make them unnecessary by disallowing
248 // dynamic linking when linker plugin based LTO is enabled.
249 !self.tcx
.sess
.opts
.cg
.linker_plugin_lto
.enabled();
251 // If this assertion triggers, there's something wrong with commandline
252 // argument validation.
254 !(self.tcx
.sess
.opts
.cg
.linker_plugin_lto
.enabled()
255 && self.tcx
.sess
.target
.is_like_windows
256 && self.tcx
.sess
.opts
.cg
.prefer_dynamic
)
259 if needs_dll_storage_attr
{
260 // This item is external but not foreign, i.e., it originates from an external Rust
261 // crate. Since we don't know whether this crate will be linked dynamically or
262 // statically in the final application, we always mark such symbols as 'dllimport'.
263 // If final linkage happens to be static, we rely on compiler-emitted __imp_ stubs
264 // to make things work.
266 // However, in some scenarios we defer emission of statics to downstream
267 // crates, so there are cases where a static with an upstream DefId
268 // is actually present in the current crate. We can find out via the
269 // is_codegened_item query.
270 if !self.tcx
.is_codegened_item(def_id
) {
272 llvm
::LLVMSetDLLStorageClass(g
, llvm
::DLLStorageClass
::DllImport
);
278 if self.use_dll_storage_attrs
&& self.tcx
.is_dllimport_foreign_item(def_id
) {
279 // For foreign (native) libs we know the exact storage type to use.
281 llvm
::LLVMSetDLLStorageClass(g
, llvm
::DLLStorageClass
::DllImport
);
285 self.instances
.borrow_mut().insert(instance
, g
);
290 impl StaticMethods
for CodegenCx
<'ll
, 'tcx
> {
291 fn static_addr_of(&self, cv
: &'ll Value
, align
: Align
, kind
: Option
<&str>) -> &'ll Value
{
292 if let Some(&gv
) = self.const_globals
.borrow().get(&cv
) {
294 // Upgrade the alignment in cases where the same constant is used with different
295 // alignment requirements
296 let llalign
= align
.bytes() as u32;
297 if llalign
> llvm
::LLVMGetAlignment(gv
) {
298 llvm
::LLVMSetAlignment(gv
, llalign
);
303 let gv
= self.static_addr_of_mut(cv
, align
, kind
);
305 llvm
::LLVMSetGlobalConstant(gv
, True
);
307 self.const_globals
.borrow_mut().insert(cv
, gv
);
311 fn codegen_static(&self, def_id
: DefId
, is_mutable
: bool
) {
313 let attrs
= self.tcx
.codegen_fn_attrs(def_id
);
315 let (v
, alloc
) = match codegen_static_initializer(&self, def_id
) {
317 // Error has already been reported
321 let g
= self.get_static(def_id
);
323 // boolean SSA values are i1, but they have to be stored in i8 slots,
324 // otherwise some LLVM optimization passes don't work as expected
325 let mut val_llty
= self.val_ty(v
);
326 let v
= if val_llty
== self.type_i1() {
327 val_llty
= self.type_i8();
328 llvm
::LLVMConstZExt(v
, val_llty
)
333 let instance
= Instance
::mono(self.tcx
, def_id
);
334 let ty
= instance
.ty(self.tcx
, ty
::ParamEnv
::reveal_all());
335 let llty
= self.layout_of(ty
).llvm_type(self);
336 let g
= if val_llty
== llty
{
339 // If we created the global with the wrong type,
341 let name
= llvm
::get_value_name(g
).to_vec();
342 llvm
::set_value_name(g
, b
"");
344 let linkage
= llvm
::LLVMRustGetLinkage(g
);
345 let visibility
= llvm
::LLVMRustGetVisibility(g
);
347 let new_g
= llvm
::LLVMRustGetOrInsertGlobal(
349 name
.as_ptr().cast(),
354 llvm
::LLVMRustSetLinkage(new_g
, linkage
);
355 llvm
::LLVMRustSetVisibility(new_g
, visibility
);
357 // To avoid breaking any invariants, we leave around the old
358 // global for the moment; we'll replace all references to it
359 // with the new global later. (See base::codegen_backend.)
360 self.statics_to_rauw
.borrow_mut().push((g
, new_g
));
363 set_global_alignment(&self, g
, self.align_of(ty
));
364 llvm
::LLVMSetInitializer(g
, v
);
366 // As an optimization, all shared statics which do not have interior
367 // mutability are placed into read-only memory.
368 if !is_mutable
&& self.type_is_freeze(ty
) {
369 llvm
::LLVMSetGlobalConstant(g
, llvm
::True
);
372 debuginfo
::create_global_var_metadata(&self, def_id
, g
);
374 if attrs
.flags
.contains(CodegenFnAttrFlags
::THREAD_LOCAL
) {
375 llvm
::set_thread_local_mode(g
, self.tls_model
);
377 // Do not allow LLVM to change the alignment of a TLS on macOS.
379 // By default a global's alignment can be freely increased.
380 // This allows LLVM to generate more performant instructions
381 // e.g., using load-aligned into a SIMD register.
383 // However, on macOS 10.10 or below, the dynamic linker does not
384 // respect any alignment given on the TLS (radar 24221680).
385 // This will violate the alignment assumption, and causing segfault at runtime.
387 // This bug is very easy to trigger. In `println!` and `panic!`,
388 // the `LOCAL_STDOUT`/`LOCAL_STDERR` handles are stored in a TLS,
389 // which the values would be `mem::replace`d on initialization.
390 // The implementation of `mem::replace` will use SIMD
391 // whenever the size is 32 bytes or higher. LLVM notices SIMD is used
392 // and tries to align `LOCAL_STDOUT`/`LOCAL_STDERR` to a 32-byte boundary,
393 // which macOS's dyld disregarded and causing crashes
394 // (see issues #51794, #51758, #50867, #48866 and #44056).
396 // To workaround the bug, we trick LLVM into not increasing
397 // the global's alignment by explicitly assigning a section to it
398 // (equivalent to automatically generating a `#[link_section]` attribute).
399 // See the comment in the `GlobalValue::canIncreaseAlignment()` function
400 // of `lib/IR/Globals.cpp` for why this works.
402 // When the alignment is not increased, the optimized `mem::replace`
403 // will use load-unaligned instructions instead, and thus avoiding the crash.
405 // We could remove this hack whenever we decide to drop macOS 10.10 support.
406 if self.tcx
.sess
.target
.is_like_osx
{
407 // The `inspect` method is okay here because we checked relocations, and
408 // because we are doing this access to inspect the final interpreter state
409 // (not as part of the interpreter execution).
411 // FIXME: This check requires that the (arbitrary) value of undefined bytes
412 // happens to be zero. Instead, we should only check the value of defined bytes
413 // and set all undefined bytes to zero if this allocation is headed for the
415 let all_bytes_are_zero
= alloc
.relocations().is_empty()
417 .inspect_with_uninit_and_ptr_outside_interpreter(0..alloc
.len())
419 .all(|&byte
| byte
== 0);
421 let sect_name
= if all_bytes_are_zero
{
422 cstr
!("__DATA,__thread_bss")
424 cstr
!("__DATA,__thread_data")
426 llvm
::LLVMSetSection(g
, sect_name
.as_ptr());
430 // Wasm statics with custom link sections get special treatment as they
431 // go into custom sections of the wasm executable.
432 if self.tcx
.sess
.opts
.target_triple
.triple().starts_with("wasm32") {
433 if let Some(section
) = attrs
.link_section
{
434 let section
= llvm
::LLVMMDStringInContext(
436 section
.as_str().as_ptr().cast(),
437 section
.as_str().len() as c_uint
,
439 assert
!(alloc
.relocations().is_empty());
441 // The `inspect` method is okay here because we checked relocations, and
442 // because we are doing this access to inspect the final interpreter state (not
443 // as part of the interpreter execution).
445 alloc
.inspect_with_uninit_and_ptr_outside_interpreter(0..alloc
.len());
446 let alloc
= llvm
::LLVMMDStringInContext(
448 bytes
.as_ptr().cast(),
449 bytes
.len() as c_uint
,
451 let data
= [section
, alloc
];
452 let meta
= llvm
::LLVMMDNodeInContext(self.llcx
, data
.as_ptr(), 2);
453 llvm
::LLVMAddNamedMetadataOperand(
455 "wasm.custom_sections\0".as_ptr().cast(),
460 base
::set_link_section(g
, &attrs
);
463 if attrs
.flags
.contains(CodegenFnAttrFlags
::USED
) {
464 self.add_used_global(g
);
469 /// Add a global value to a list to be stored in the `llvm.used` variable, an array of i8*.
470 fn add_used_global(&self, global
: &'ll Value
) {
471 let cast
= unsafe { llvm::LLVMConstPointerCast(global, self.type_i8p()) }
;
472 self.used_statics
.borrow_mut().push(cast
);