1 use crate::llvm
::{self, SetUnnamedAddr, True}
;
3 use crate::common
::CodegenCx
;
5 use crate::type_
::Type
;
6 use crate::type_of
::LayoutLlvmExt
;
7 use crate::value
::Value
;
9 use rustc
::hir
::def_id
::DefId
;
10 use rustc
::mir
::interpret
::{ConstValue
, Allocation
, read_target_uint
,
11 Pointer
, ErrorHandled
, GlobalId
};
12 use rustc
::mir
::mono
::MonoItem
;
14 use rustc_target
::abi
::HasDataLayout
;
15 use rustc
::ty
::{self, Ty, Instance}
;
16 use rustc_codegen_ssa
::traits
::*;
17 use syntax
::symbol
::{Symbol, sym}
;
20 use rustc
::ty
::layout
::{self, Size, Align, LayoutOf}
;
22 use rustc
::hir
::{self, CodegenFnAttrs, CodegenFnAttrFlags}
;
24 use std
::ffi
::{CStr, CString}
;
26 pub fn const_alloc_to_llvm(cx
: &CodegenCx
<'ll
, '_
>, alloc
: &Allocation
) -> &'ll Value
{
27 let mut llvals
= Vec
::with_capacity(alloc
.relocations().len() + 1);
28 let dl
= cx
.data_layout();
29 let pointer_size
= dl
.pointer_size
.bytes() as usize;
31 let mut next_offset
= 0;
32 for &(offset
, ((), alloc_id
)) in alloc
.relocations().iter() {
33 let offset
= offset
.bytes();
34 assert_eq
!(offset
as usize as u64, offset
);
35 let offset
= offset
as usize;
36 if offset
> next_offset
{
37 // This `inspect` is okay since we have checked that it is not within a relocation, it
38 // is within the bounds of the allocation, and it doesn't affect interpreter execution
39 // (we inspect the result after interpreter execution). Any undef byte is replaced with
40 // some arbitrary byte value.
42 // FIXME: relay undef bytes to codegen as undef const bytes
43 let bytes
= alloc
.inspect_with_undef_and_ptr_outside_interpreter(next_offset
..offset
);
44 llvals
.push(cx
.const_bytes(bytes
));
46 let ptr_offset
= read_target_uint(
48 // This `inspect` is okay since it is within the bounds of the allocation, it doesn't
49 // affect interpreter execution (we inspect the result after interpreter execution),
50 // and we properly interpret the relocation as a relocation pointer offset.
51 alloc
.inspect_with_undef_and_ptr_outside_interpreter(offset
..(offset
+ pointer_size
)),
52 ).expect("const_alloc_to_llvm: could not read relocation pointer") as u64;
53 llvals
.push(cx
.scalar_to_backend(
54 Pointer
::new(alloc_id
, Size
::from_bytes(ptr_offset
)).into(),
56 value
: layout
::Primitive
::Pointer
,
61 next_offset
= offset
+ pointer_size
;
63 if alloc
.len() >= next_offset
{
64 let range
= next_offset
..alloc
.len();
65 // This `inspect` is okay since we have check that it is after all relocations, it is
66 // within the bounds of the allocation, and it doesn't affect interpreter execution (we
67 // inspect the result after interpreter execution). Any undef byte is replaced with some
68 // arbitrary byte value.
70 // FIXME: relay undef bytes to codegen as undef const bytes
71 let bytes
= alloc
.inspect_with_undef_and_ptr_outside_interpreter(range
);
72 llvals
.push(cx
.const_bytes(bytes
));
75 cx
.const_struct(&llvals
, true)
78 pub fn codegen_static_initializer(
79 cx
: &CodegenCx
<'ll
, 'tcx
>,
81 ) -> Result
<(&'ll Value
, &'tcx Allocation
), ErrorHandled
> {
82 let instance
= ty
::Instance
::mono(cx
.tcx
, def_id
);
87 let param_env
= ty
::ParamEnv
::reveal_all();
88 let static_
= cx
.tcx
.const_eval(param_env
.and(cid
))?
;
90 let alloc
= match static_
.val
{
93 } if offset
.bytes() == 0 => {
96 _
=> bug
!("static const eval returned {:#?}", static_
),
98 Ok((const_alloc_to_llvm(cx
, alloc
), alloc
))
101 fn set_global_alignment(cx
: &CodegenCx
<'ll
, '_
>,
104 // The target may require greater alignment for globals than the type does.
105 // Note: GCC and Clang also allow `__attribute__((aligned))` on variables,
106 // which can force it to be smaller. Rust doesn't support this yet.
107 if let Some(min
) = cx
.sess().target
.target
.options
.min_global_align
{
108 match Align
::from_bits(min
) {
109 Ok(min
) => align
= align
.max(min
),
111 cx
.sess().err(&format
!("invalid minimum global alignment: {}", err
));
116 llvm
::LLVMSetAlignment(gv
, align
.bytes() as u32);
120 fn check_and_apply_linkage(
121 cx
: &CodegenCx
<'ll
, 'tcx
>,
122 attrs
: &CodegenFnAttrs
,
127 let llty
= cx
.layout_of(ty
).llvm_type(cx
);
128 let sym
= sym
.as_str();
129 if let Some(linkage
) = attrs
.linkage
{
130 debug
!("get_static: sym={} linkage={:?}", sym
, linkage
);
132 // If this is a static with a linkage specified, then we need to handle
133 // it a little specially. The typesystem prevents things like &T and
134 // extern "C" fn() from being non-null, so we can't just declare a
135 // static and call it a day. Some linkages (like weak) will make it such
136 // that the static actually has a null value.
137 let llty2
= if let ty
::RawPtr(ref mt
) = ty
.sty
{
138 cx
.layout_of(mt
.ty
).llvm_type(cx
)
140 cx
.sess().span_fatal(
141 span
, "must have type `*const T` or `*mut T` due to `#[linkage]` attribute")
144 // Declare a symbol `foo` with the desired linkage.
145 let g1
= cx
.declare_global(&sym
, llty2
);
146 llvm
::LLVMRustSetLinkage(g1
, base
::linkage_to_llvm(linkage
));
148 // Declare an internal global `extern_with_linkage_foo` which
149 // is initialized with the address of `foo`. If `foo` is
150 // discarded during linking (for example, if `foo` has weak
151 // linkage and there are no definitions), then
152 // `extern_with_linkage_foo` will instead be initialized to
154 let mut real_name
= "_rust_extern_with_linkage_".to_string();
155 real_name
.push_str(&sym
);
156 let g2
= cx
.define_global(&real_name
, llty
).unwrap_or_else(||{
157 cx
.sess().span_fatal(span
, &format
!("symbol `{}` is already defined", &sym
))
159 llvm
::LLVMRustSetLinkage(g2
, llvm
::Linkage
::InternalLinkage
);
160 llvm
::LLVMSetInitializer(g2
, g1
);
164 // Generate an external declaration.
165 // FIXME(nagisa): investigate whether it can be changed into define_global
166 cx
.declare_global(&sym
, llty
)
170 pub fn ptrcast(val
: &'ll Value
, ty
: &'ll Type
) -> &'ll Value
{
172 llvm
::LLVMConstPointerCast(val
, ty
)
176 impl CodegenCx
<'ll
, 'tcx
> {
177 crate fn const_bitcast(&self, val
: &'ll Value
, ty
: &'ll Type
) -> &'ll Value
{
179 llvm
::LLVMConstBitCast(val
, ty
)
183 crate fn static_addr_of_mut(
190 let gv
= match kind
{
191 Some(kind
) if !self.tcx
.sess
.fewer_names() => {
192 let name
= self.generate_local_symbol_name(kind
);
193 let gv
= self.define_global(&name
[..],
194 self.val_ty(cv
)).unwrap_or_else(||{
195 bug
!("symbol `{}` is already defined", name
);
197 llvm
::LLVMRustSetLinkage(gv
, llvm
::Linkage
::PrivateLinkage
);
200 _
=> self.define_private_global(self.val_ty(cv
)),
202 llvm
::LLVMSetInitializer(gv
, cv
);
203 set_global_alignment(&self, gv
, align
);
204 SetUnnamedAddr(gv
, true);
209 crate fn get_static(&self, def_id
: DefId
) -> &'ll Value
{
210 let instance
= Instance
::mono(self.tcx
, def_id
);
211 if let Some(&g
) = self.instances
.borrow().get(&instance
) {
215 let defined_in_current_codegen_unit
= self.codegen_unit
217 .contains_key(&MonoItem
::Static(def_id
));
218 assert
!(!defined_in_current_codegen_unit
,
219 "consts::get_static() should always hit the cache for \
220 statics defined in the same CGU, but did not for `{:?}`",
223 let ty
= instance
.ty(self.tcx
);
224 let sym
= self.tcx
.symbol_name(instance
).name
.as_symbol();
226 debug
!("get_static: sym={} instance={:?}", sym
, instance
);
228 let g
= if let Some(id
) = self.tcx
.hir().as_local_hir_id(def_id
) {
230 let llty
= self.layout_of(ty
).llvm_type(self);
231 let (g
, attrs
) = match self.tcx
.hir().get(id
) {
232 Node
::Item(&hir
::Item
{
233 ref attrs
, span
, node
: hir
::ItemKind
::Static(..), ..
235 let sym_str
= sym
.as_str();
236 if self.get_declared_value(&sym_str
).is_some() {
237 span_bug
!(span
, "Conflicting symbol names for static?");
240 let g
= self.define_global(&sym_str
, llty
).unwrap();
242 if !self.tcx
.is_reachable_non_generic(def_id
) {
244 llvm
::LLVMRustSetVisibility(g
, llvm
::Visibility
::Hidden
);
251 Node
::ForeignItem(&hir
::ForeignItem
{
252 ref attrs
, span
, node
: hir
::ForeignItemKind
::Static(..), ..
254 let fn_attrs
= self.tcx
.codegen_fn_attrs(def_id
);
255 (check_and_apply_linkage(&self, &fn_attrs
, ty
, sym
, span
), attrs
)
258 item
=> bug
!("get_static: expected static, found {:?}", item
)
261 debug
!("get_static: sym={} attrs={:?}", sym
, attrs
);
264 if attr
.check_name(sym
::thread_local
) {
265 llvm
::set_thread_local_mode(g
, self.tls_model
);
271 // FIXME(nagisa): perhaps the map of externs could be offloaded to llvm somehow?
272 debug
!("get_static: sym={} item_attr={:?}", sym
, self.tcx
.item_attrs(def_id
));
274 let attrs
= self.tcx
.codegen_fn_attrs(def_id
);
275 let span
= self.tcx
.def_span(def_id
);
276 let g
= check_and_apply_linkage(&self, &attrs
, ty
, sym
, span
);
278 // Thread-local statics in some other crate need to *always* be linked
279 // against in a thread-local fashion, so we need to be sure to apply the
280 // thread-local attribute locally if it was present remotely. If we
281 // don't do this then linker errors can be generated where the linker
282 // complains that one object files has a thread local version of the
283 // symbol and another one doesn't.
284 if attrs
.flags
.contains(CodegenFnAttrFlags
::THREAD_LOCAL
) {
285 llvm
::set_thread_local_mode(g
, self.tls_model
);
288 let needs_dll_storage_attr
=
289 self.use_dll_storage_attrs
&& !self.tcx
.is_foreign_item(def_id
) &&
290 // ThinLTO can't handle this workaround in all cases, so we don't
291 // emit the attrs. Instead we make them unnecessary by disallowing
292 // dynamic linking when linker plugin based LTO is enabled.
293 !self.tcx
.sess
.opts
.cg
.linker_plugin_lto
.enabled();
295 // If this assertion triggers, there's something wrong with commandline
296 // argument validation.
297 debug_assert
!(!(self.tcx
.sess
.opts
.cg
.linker_plugin_lto
.enabled() &&
298 self.tcx
.sess
.target
.target
.options
.is_like_msvc
&&
299 self.tcx
.sess
.opts
.cg
.prefer_dynamic
));
301 if needs_dll_storage_attr
{
302 // This item is external but not foreign, i.e., it originates from an external Rust
303 // crate. Since we don't know whether this crate will be linked dynamically or
304 // statically in the final application, we always mark such symbols as 'dllimport'.
305 // If final linkage happens to be static, we rely on compiler-emitted __imp_ stubs
306 // to make things work.
308 // However, in some scenarios we defer emission of statics to downstream
309 // crates, so there are cases where a static with an upstream DefId
310 // is actually present in the current crate. We can find out via the
311 // is_codegened_item query.
312 if !self.tcx
.is_codegened_item(def_id
) {
314 llvm
::LLVMSetDLLStorageClass(g
, llvm
::DLLStorageClass
::DllImport
);
321 if self.use_dll_storage_attrs
&& self.tcx
.is_dllimport_foreign_item(def_id
) {
322 // For foreign (native) libs we know the exact storage type to use.
324 llvm
::LLVMSetDLLStorageClass(g
, llvm
::DLLStorageClass
::DllImport
);
328 self.instances
.borrow_mut().insert(instance
, g
);
333 impl StaticMethods
for CodegenCx
<'ll
, 'tcx
> {
340 if let Some(&gv
) = self.const_globals
.borrow().get(&cv
) {
342 // Upgrade the alignment in cases where the same constant is used with different
343 // alignment requirements
344 let llalign
= align
.bytes() as u32;
345 if llalign
> llvm
::LLVMGetAlignment(gv
) {
346 llvm
::LLVMSetAlignment(gv
, llalign
);
351 let gv
= self.static_addr_of_mut(cv
, align
, kind
);
353 llvm
::LLVMSetGlobalConstant(gv
, True
);
355 self.const_globals
.borrow_mut().insert(cv
, gv
);
365 let attrs
= self.tcx
.codegen_fn_attrs(def_id
);
367 let (v
, alloc
) = match codegen_static_initializer(&self, def_id
) {
369 // Error has already been reported
373 let g
= self.get_static(def_id
);
375 // boolean SSA values are i1, but they have to be stored in i8 slots,
376 // otherwise some LLVM optimization passes don't work as expected
377 let mut val_llty
= self.val_ty(v
);
378 let v
= if val_llty
== self.type_i1() {
379 val_llty
= self.type_i8();
380 llvm
::LLVMConstZExt(v
, val_llty
)
385 let instance
= Instance
::mono(self.tcx
, def_id
);
386 let ty
= instance
.ty(self.tcx
);
387 let llty
= self.layout_of(ty
).llvm_type(self);
388 let g
= if val_llty
== llty
{
391 // If we created the global with the wrong type,
393 let empty_string
= const_cstr
!("");
394 let name_str_ref
= CStr
::from_ptr(llvm
::LLVMGetValueName(g
));
395 let name_string
= CString
::new(name_str_ref
.to_bytes()).unwrap();
396 llvm
::LLVMSetValueName(g
, empty_string
.as_ptr());
398 let linkage
= llvm
::LLVMRustGetLinkage(g
);
399 let visibility
= llvm
::LLVMRustGetVisibility(g
);
401 let new_g
= llvm
::LLVMRustGetOrInsertGlobal(
402 self.llmod
, name_string
.as_ptr(), val_llty
);
404 llvm
::LLVMRustSetLinkage(new_g
, linkage
);
405 llvm
::LLVMRustSetVisibility(new_g
, visibility
);
407 // To avoid breaking any invariants, we leave around the old
408 // global for the moment; we'll replace all references to it
409 // with the new global later. (See base::codegen_backend.)
410 self.statics_to_rauw
.borrow_mut().push((g
, new_g
));
413 set_global_alignment(&self, g
, self.align_of(ty
));
414 llvm
::LLVMSetInitializer(g
, v
);
416 // As an optimization, all shared statics which do not have interior
417 // mutability are placed into read-only memory.
419 if self.type_is_freeze(ty
) {
420 llvm
::LLVMSetGlobalConstant(g
, llvm
::True
);
424 debuginfo
::create_global_var_metadata(&self, def_id
, g
);
426 if attrs
.flags
.contains(CodegenFnAttrFlags
::THREAD_LOCAL
) {
427 llvm
::set_thread_local_mode(g
, self.tls_model
);
429 // Do not allow LLVM to change the alignment of a TLS on macOS.
431 // By default a global's alignment can be freely increased.
432 // This allows LLVM to generate more performant instructions
433 // e.g., using load-aligned into a SIMD register.
435 // However, on macOS 10.10 or below, the dynamic linker does not
436 // respect any alignment given on the TLS (radar 24221680).
437 // This will violate the alignment assumption, and causing segfault at runtime.
439 // This bug is very easy to trigger. In `println!` and `panic!`,
440 // the `LOCAL_STDOUT`/`LOCAL_STDERR` handles are stored in a TLS,
441 // which the values would be `mem::replace`d on initialization.
442 // The implementation of `mem::replace` will use SIMD
443 // whenever the size is 32 bytes or higher. LLVM notices SIMD is used
444 // and tries to align `LOCAL_STDOUT`/`LOCAL_STDERR` to a 32-byte boundary,
445 // which macOS's dyld disregarded and causing crashes
446 // (see issues #51794, #51758, #50867, #48866 and #44056).
448 // To workaround the bug, we trick LLVM into not increasing
449 // the global's alignment by explicitly assigning a section to it
450 // (equivalent to automatically generating a `#[link_section]` attribute).
451 // See the comment in the `GlobalValue::canIncreaseAlignment()` function
452 // of `lib/IR/Globals.cpp` for why this works.
454 // When the alignment is not increased, the optimized `mem::replace`
455 // will use load-unaligned instructions instead, and thus avoiding the crash.
457 // We could remove this hack whenever we decide to drop macOS 10.10 support.
458 if self.tcx
.sess
.target
.target
.options
.is_like_osx
{
459 assert_eq
!(alloc
.relocations().len(), 0);
462 // Treats undefined bytes as if they were defined with the byte value that
463 // happens to be currently assigned in mir. This is valid since reading
464 // undef bytes may yield arbitrary values.
466 // FIXME: ignore undef bytes even with representation `!= 0`.
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 alloc
.inspect_with_undef_and_ptr_outside_interpreter(0..alloc
.len())
475 let sect_name
= if is_zeroed
{
476 CStr
::from_bytes_with_nul_unchecked(b
"__DATA,__thread_bss\0")
478 CStr
::from_bytes_with_nul_unchecked(b
"__DATA,__thread_data\0")
480 llvm
::LLVMSetSection(g
, sect_name
.as_ptr());
485 // Wasm statics with custom link sections get special treatment as they
486 // go into custom sections of the wasm executable.
487 if self.tcx
.sess
.opts
.target_triple
.triple().starts_with("wasm32") {
488 if let Some(section
) = attrs
.link_section
{
489 let section
= llvm
::LLVMMDStringInContext(
491 section
.as_str().as_ptr() as *const _
,
492 section
.as_str().len() as c_uint
,
494 assert
!(alloc
.relocations().is_empty());
496 // The `inspect` method is okay here because we checked relocations, and
497 // because we are doing this access to inspect the final interpreter state (not
498 // as part of the interpreter execution).
499 let bytes
= alloc
.inspect_with_undef_and_ptr_outside_interpreter(
501 let alloc
= llvm
::LLVMMDStringInContext(
503 bytes
.as_ptr() as *const _
,
504 bytes
.len() as c_uint
,
506 let data
= [section
, alloc
];
507 let meta
= llvm
::LLVMMDNodeInContext(self.llcx
, data
.as_ptr(), 2);
508 llvm
::LLVMAddNamedMetadataOperand(
510 "wasm.custom_sections\0".as_ptr() as *const _
,
515 base
::set_link_section(g
, &attrs
);
518 if attrs
.flags
.contains(CodegenFnAttrFlags
::USED
) {
519 // This static will be stored in the llvm.used variable which is an array of i8*
520 let cast
= llvm
::LLVMConstPointerCast(g
, self.type_i8p());
521 self.used_statics
.borrow_mut().push(cast
);