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
, InitChunk
, Pointer
,
15 Scalar
as InterpScalar
,
17 use rustc_middle
::mir
::mono
::MonoItem
;
18 use rustc_middle
::ty
::layout
::LayoutOf
;
19 use rustc_middle
::ty
::{self, Instance, Ty}
;
20 use rustc_middle
::{bug, span_bug}
;
21 use rustc_target
::abi
::{
22 AddressSpace
, Align
, HasDataLayout
, Primitive
, Scalar
, Size
, WrappingRange
,
27 pub fn const_alloc_to_llvm
<'ll
>(cx
: &CodegenCx
<'ll
, '_
>, alloc
: &Allocation
) -> &'ll Value
{
28 let mut llvals
= Vec
::with_capacity(alloc
.relocations().len() + 1);
29 let dl
= cx
.data_layout();
30 let pointer_size
= dl
.pointer_size
.bytes() as usize;
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
,
40 let mut chunks
= alloc
42 .range_as_init_chunks(Size
::from_bytes(range
.start
), Size
::from_bytes(range
.end
));
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
);
50 InitChunk
::Uninit(range
) => {
51 let len
= range
.end
.bytes() - range
.start
.bytes();
52 cx
.const_undef(cx
.type_array(cx
.type_i8(), len
))
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
,
64 if allow_partially_uninit
{
65 llvals
.extend(chunks
.map(chunk_to_llval
));
67 let llval
= match (chunks
.next(), chunks
.next()) {
68 (Some(chunk
), None
) => {
69 // exactly one chunk, either fully init or fully uninit
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
);
83 let mut next_offset
= 0;
84 for &(offset
, alloc_id
) in alloc
.relocations().iter() {
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
{
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
91 // (we inspect the result after interpreter execution).
92 append_chunks_of_init_and_uninit_bytes(&mut llvals
, cx
, alloc
, next_offset
..offset
);
94 let ptr_offset
= read_target_uint(
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.
99 alloc
.inspect_with_uninit_and_ptr_outside_interpreter(offset
..(offset
+ pointer_size
)),
101 .expect("const_alloc_to_llvm: could not read relocation pointer")
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
,
109 llvals
.push(cx
.scalar_to_backend(
110 InterpScalar
::from_pointer(
111 Pointer
::new(alloc_id
, Size
::from_bytes(ptr_offset
)),
114 Scalar { value: Primitive::Pointer, valid_range: WrappingRange { start: 0, end: !0 }
},
115 cx
.type_i8p_ext(address_space
),
117 next_offset
= offset
+ pointer_size
;
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
123 // inspect the result after interpreter execution).
124 append_chunks_of_init_and_uninit_bytes(&mut llvals
, cx
, alloc
, range
);
127 cx
.const_struct(&llvals
, true)
130 pub fn codegen_static_initializer
<'ll
, 'tcx
>(
131 cx
: &CodegenCx
<'ll
, 'tcx
>,
133 ) -> Result
<(&'ll Value
, &'tcx Allocation
), ErrorHandled
> {
134 let alloc
= cx
.tcx
.eval_static_initializer(def_id
)?
;
135 Ok((const_alloc_to_llvm(cx
, alloc
), alloc
))
138 fn set_global_alignment
<'ll
>(cx
: &CodegenCx
<'ll
, '_
>, gv
: &'ll Value
, mut align
: Align
) {
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.
142 if let Some(min
) = cx
.sess().target
.min_global_align
{
143 match Align
::from_bits(min
) {
144 Ok(min
) => align
= align
.max(min
),
146 cx
.sess().err(&format
!("invalid minimum global alignment: {}", err
));
151 llvm
::LLVMSetAlignment(gv
, align
.bytes() as u32);
155 fn check_and_apply_linkage
<'ll
, 'tcx
>(
156 cx
: &CodegenCx
<'ll
, 'tcx
>,
157 attrs
: &CodegenFnAttrs
,
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
);
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.
171 let llty2
= if let ty
::RawPtr(ref mt
) = ty
.kind() {
172 cx
.layout_of(mt
.ty
).llvm_type(cx
)
174 cx
.sess().span_fatal(
175 cx
.tcx
.def_span(span_def_id
),
176 "must have type `*const T` or `*mut T` due to `#[linkage]` attribute",
180 // Declare a symbol `foo` with the desired linkage.
181 let g1
= cx
.declare_global(sym
, llty2
);
182 llvm
::LLVMRustSetLinkage(g1
, base
::linkage_to_llvm(linkage
));
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
190 let mut real_name
= "_rust_extern_with_linkage_".to_string();
191 real_name
.push_str(sym
);
192 let g2
= cx
.define_global(&real_name
, llty
).unwrap_or_else(|| {
193 cx
.sess().span_fatal(
194 cx
.tcx
.def_span(span_def_id
),
195 &format
!("symbol `{}` is already defined", &sym
),
198 llvm
::LLVMRustSetLinkage(g2
, llvm
::Linkage
::InternalLinkage
);
199 llvm
::LLVMSetInitializer(g2
, g1
);
203 // Generate an external declaration.
204 // FIXME(nagisa): investigate whether it can be changed into define_global
205 cx
.declare_global(sym
, llty
)
209 pub fn ptrcast
<'ll
>(val
: &'ll Value
, ty
: &'ll Type
) -> &'ll Value
{
210 unsafe { llvm::LLVMConstPointerCast(val, ty) }
213 impl<'ll
> CodegenCx
<'ll
, '_
> {
214 crate fn const_bitcast(&self, val
: &'ll Value
, ty
: &'ll Type
) -> &'ll Value
{
215 unsafe { llvm::LLVMConstBitCast(val, ty) }
218 crate fn static_addr_of_mut(
225 let gv
= match kind
{
226 Some(kind
) if !self.tcx
.sess
.fewer_names() => {
227 let name
= self.generate_local_symbol_name(kind
);
228 let gv
= self.define_global(&name
, self.val_ty(cv
)).unwrap_or_else(|| {
229 bug
!("symbol `{}` is already defined", name
);
231 llvm
::LLVMRustSetLinkage(gv
, llvm
::Linkage
::PrivateLinkage
);
234 _
=> self.define_private_global(self.val_ty(cv
)),
236 llvm
::LLVMSetInitializer(gv
, cv
);
237 set_global_alignment(self, gv
, align
);
238 llvm
::SetUnnamedAddress(gv
, llvm
::UnnamedAddr
::Global
);
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
) {
249 let defined_in_current_codegen_unit
=
250 self.codegen_unit
.items().contains_key(&MonoItem
::Static(def_id
));
252 !defined_in_current_codegen_unit
,
253 "consts::get_static() should always hit the cache for \
254 statics defined in the same CGU, but did not for `{:?}`",
258 let ty
= instance
.ty(self.tcx
, ty
::ParamEnv
::reveal_all());
259 let sym
= self.tcx
.symbol_name(instance
).name
;
260 let fn_attrs
= self.tcx
.codegen_fn_attrs(def_id
);
262 debug
!("get_static: sym={} instance={:?} fn_attrs={:?}", sym
, instance
, fn_attrs
);
264 let g
= if def_id
.is_local() && !self.tcx
.is_foreign_item(def_id
) {
265 let llty
= self.layout_of(ty
).llvm_type(self);
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");
272 let g
= self.declare_global(sym
, llty
);
274 if !self.tcx
.is_reachable_non_generic(def_id
) {
276 llvm
::LLVMRustSetVisibility(g
, llvm
::Visibility
::Hidden
);
282 check_and_apply_linkage(self, fn_attrs
, ty
, sym
, def_id
)
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
);
295 if !def_id
.is_local() {
296 let needs_dll_storage_attr
= self.use_dll_storage_attrs
&& !self.tcx
.is_foreign_item(def_id
) &&
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
299 // dynamic linking when linker plugin based LTO is enabled.
300 !self.tcx
.sess
.opts
.cg
.linker_plugin_lto
.enabled();
302 // If this assertion triggers, there's something wrong with commandline
303 // argument validation.
305 !(self.tcx
.sess
.opts
.cg
.linker_plugin_lto
.enabled()
306 && self.tcx
.sess
.target
.is_like_windows
307 && self.tcx
.sess
.opts
.cg
.prefer_dynamic
)
310 if needs_dll_storage_attr
{
311 // This item is external but not foreign, i.e., it originates from an external Rust
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.
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
) {
323 llvm
::LLVMSetDLLStorageClass(g
, llvm
::DLLStorageClass
::DllImport
);
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.
332 llvm
::LLVMSetDLLStorageClass(g
, llvm
::DLLStorageClass
::DllImport
);
337 if self.should_assume_dso_local(g
, true) {
338 llvm
::LLVMRustSetDSOLocal(g
, true);
342 self.instances
.borrow_mut().insert(instance
, g
);
347 impl<'ll
> StaticMethods
for CodegenCx
<'ll
, '_
> {
348 fn static_addr_of(&self, cv
: &'ll Value
, align
: Align
, kind
: Option
<&str>) -> &'ll Value
{
349 if let Some(&gv
) = self.const_globals
.borrow().get(&cv
) {
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
);
360 let gv
= self.static_addr_of_mut(cv
, align
, kind
);
362 llvm
::LLVMSetGlobalConstant(gv
, True
);
364 self.const_globals
.borrow_mut().insert(cv
, gv
);
368 fn codegen_static(&self, def_id
: DefId
, is_mutable
: bool
) {
370 let attrs
= self.tcx
.codegen_fn_attrs(def_id
);
372 let (v
, alloc
) = match codegen_static_initializer(self, def_id
) {
374 // Error has already been reported
378 let g
= self.get_static(def_id
);
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
)
390 let instance
= Instance
::mono(self.tcx
, def_id
);
391 let ty
= instance
.ty(self.tcx
, ty
::ParamEnv
::reveal_all());
392 let llty
= self.layout_of(ty
).llvm_type(self);
393 let g
= if val_llty
== llty
{
396 // If we created the global with the wrong type,
398 let name
= llvm
::get_value_name(g
).to_vec();
399 llvm
::set_value_name(g
, b
"");
401 let linkage
= llvm
::LLVMRustGetLinkage(g
);
402 let visibility
= llvm
::LLVMRustGetVisibility(g
);
404 let new_g
= llvm
::LLVMRustGetOrInsertGlobal(
406 name
.as_ptr().cast(),
411 llvm
::LLVMRustSetLinkage(new_g
, linkage
);
412 llvm
::LLVMRustSetVisibility(new_g
, visibility
);
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
));
420 set_global_alignment(self, g
, self.align_of(ty
));
421 llvm
::LLVMSetInitializer(g
, v
);
423 if self.should_assume_dso_local(g
, true) {
424 llvm
::LLVMRustSetDSOLocal(g
, true);
427 // As an optimization, all shared statics which do not have interior
428 // mutability are placed into read-only memory.
429 if !is_mutable
&& self.type_is_freeze(ty
) {
430 llvm
::LLVMSetGlobalConstant(g
, llvm
::True
);
433 debuginfo
::create_global_var_metadata(self, def_id
, g
);
435 if attrs
.flags
.contains(CodegenFnAttrFlags
::THREAD_LOCAL
) {
436 llvm
::set_thread_local_mode(g
, self.tls_model
);
438 // Do not allow LLVM to change the alignment of a TLS on macOS.
440 // By default a global's alignment can be freely increased.
441 // This allows LLVM to generate more performant instructions
442 // e.g., using load-aligned into a SIMD register.
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.
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).
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.
463 // When the alignment is not increased, the optimized `mem::replace`
464 // will use load-unaligned instructions instead, and thus avoiding the crash.
466 // We could remove this hack whenever we decide to drop macOS 10.10 support.
467 if self.tcx
.sess
.target
.is_like_osx
{
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).
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
476 let all_bytes_are_zero
= alloc
.relocations().is_empty()
478 .inspect_with_uninit_and_ptr_outside_interpreter(0..alloc
.len())
480 .all(|&byte
| byte
== 0);
482 let sect_name
= if all_bytes_are_zero
{
483 cstr
!("__DATA,__thread_bss")
485 cstr
!("__DATA,__thread_data")
487 llvm
::LLVMSetSection(g
, sect_name
.as_ptr());
491 // Wasm statics with custom link sections get special treatment as they
492 // go into custom sections of the wasm executable.
493 if self.tcx
.sess
.target
.is_like_wasm
{
494 if let Some(section
) = attrs
.link_section
{
495 let section
= llvm
::LLVMMDStringInContext(
497 section
.as_str().as_ptr().cast(),
498 section
.as_str().len() as c_uint
,
500 assert
!(alloc
.relocations().is_empty());
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).
506 alloc
.inspect_with_uninit_and_ptr_outside_interpreter(0..alloc
.len());
507 let alloc
= llvm
::LLVMMDStringInContext(
509 bytes
.as_ptr().cast(),
510 bytes
.len() as c_uint
,
512 let data
= [section
, alloc
];
513 let meta
= llvm
::LLVMMDNodeInContext(self.llcx
, data
.as_ptr(), 2);
514 llvm
::LLVMAddNamedMetadataOperand(
516 "wasm.custom_sections\0".as_ptr().cast(),
521 base
::set_link_section(g
, attrs
);
524 if attrs
.flags
.contains(CodegenFnAttrFlags
::USED
) {
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
);
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
);
542 /// Add a global value to a list to be stored in the `llvm.compiler.used` variable,
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
);