1 //! Handling of `static`s, `const`s and promoted allocations
3 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
4 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
5 use rustc_middle::mir::interpret::{
6 read_target_uint, AllocId, ConstAllocation, ConstValue, ErrorHandled, GlobalAlloc, Scalar,
8 use rustc_middle::ty::ConstKind;
9 use rustc_span::DUMMY_SP;
11 use cranelift_codegen::ir::GlobalValueData;
12 use cranelift_module::*;
14 use crate::prelude::*;
16 pub(crate) struct ConstantCx {
18 done: FxHashSet<DataId>,
19 anon_allocs: FxHashMap<AllocId, DataId>,
22 #[derive(Copy, Clone, Debug)]
29 pub(crate) fn new() -> Self {
30 ConstantCx { todo: vec![], done: FxHashSet::default(), anon_allocs: FxHashMap::default() }
33 pub(crate) fn finalize(mut self, tcx: TyCtxt<'_>, module: &mut dyn Module) {
34 //println!("todo {:?}", self.todo);
35 define_all_allocs(tcx, module, &mut self);
36 //println!("done {:?}", self.done);
41 pub(crate) fn check_constants(fx: &mut FunctionCx<'_, '_, '_>) -> bool {
42 let mut all_constants_ok = true;
43 for constant in &fx.mir.required_consts {
44 let const_ = match fx.monomorphize(constant.literal) {
45 ConstantKind::Ty(ct) => ct,
46 ConstantKind::Val(..) => continue,
49 ConstKind::Value(_) => {}
50 ConstKind::Unevaluated(unevaluated) => {
52 fx.tcx.const_eval_resolve(ParamEnv::reveal_all(), unevaluated, None)
54 all_constants_ok = false;
56 ErrorHandled::Reported(_) | ErrorHandled::Linted => {
57 fx.tcx.sess.span_err(constant.span, "erroneous constant encountered");
59 ErrorHandled::TooGeneric => {
62 "codegen encountered polymorphic constant: {:?}",
71 | ConstKind::Bound(_, _)
72 | ConstKind::Placeholder(_)
73 | ConstKind::Error(_) => unreachable!("{:?}", const_),
79 pub(crate) fn codegen_static(tcx: TyCtxt<'_>, module: &mut dyn Module, def_id: DefId) {
80 let mut constants_cx = ConstantCx::new();
81 constants_cx.todo.push(TodoItem::Static(def_id));
82 constants_cx.finalize(tcx, module);
85 pub(crate) fn codegen_tls_ref<'tcx>(
86 fx: &mut FunctionCx<'_, '_, 'tcx>,
88 layout: TyAndLayout<'tcx>,
90 let data_id = data_id_for_static(fx.tcx, fx.module, def_id, false);
91 let local_data_id = fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
92 if fx.clif_comments.enabled() {
93 fx.add_comment(local_data_id, format!("tls {:?}", def_id));
95 let tls_ptr = fx.bcx.ins().tls_value(fx.pointer_type, local_data_id);
96 CValue::by_val(tls_ptr, layout)
99 fn codegen_static_ref<'tcx>(
100 fx: &mut FunctionCx<'_, '_, 'tcx>,
102 layout: TyAndLayout<'tcx>,
104 let data_id = data_id_for_static(fx.tcx, fx.module, def_id, false);
105 let local_data_id = fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
106 if fx.clif_comments.enabled() {
107 fx.add_comment(local_data_id, format!("{:?}", def_id));
109 let global_ptr = fx.bcx.ins().global_value(fx.pointer_type, local_data_id);
110 assert!(!layout.is_unsized(), "unsized statics aren't supported");
113 fx.bcx.func.global_values[local_data_id],
114 GlobalValueData::Symbol { tls: false, .. }
116 "tls static referenced without Rvalue::ThreadLocalRef"
118 CPlace::for_ptr(crate::pointer::Pointer::new(global_ptr), layout)
121 pub(crate) fn codegen_constant<'tcx>(
122 fx: &mut FunctionCx<'_, '_, 'tcx>,
123 constant: &Constant<'tcx>,
125 let const_ = match fx.monomorphize(constant.literal) {
126 ConstantKind::Ty(ct) => ct,
127 ConstantKind::Val(val, ty) => return codegen_const_value(fx, val, ty),
129 let const_val = match const_.kind() {
130 ConstKind::Value(valtree) => fx.tcx.valtree_to_const_val((const_.ty(), valtree)),
131 ConstKind::Unevaluated(ty::Unevaluated { def, substs, promoted })
132 if fx.tcx.is_static(def.did) =>
134 assert!(substs.is_empty());
135 assert!(promoted.is_none());
137 return codegen_static_ref(fx, def.did, fx.layout_of(const_.ty())).to_cvalue(fx);
139 ConstKind::Unevaluated(unevaluated) => {
140 match fx.tcx.const_eval_resolve(ParamEnv::reveal_all(), unevaluated, None) {
141 Ok(const_val) => const_val,
143 span_bug!(constant.span, "erroneous constant not captured by required_consts");
148 | ConstKind::Infer(_)
149 | ConstKind::Bound(_, _)
150 | ConstKind::Placeholder(_)
151 | ConstKind::Error(_) => unreachable!("{:?}", const_),
154 codegen_const_value(fx, const_val, const_.ty())
157 pub(crate) fn codegen_const_value<'tcx>(
158 fx: &mut FunctionCx<'_, '_, 'tcx>,
159 const_val: ConstValue<'tcx>,
162 let layout = fx.layout_of(ty);
163 assert!(!layout.is_unsized(), "sized const value");
166 return CValue::by_ref(crate::Pointer::dangling(layout.align.pref), layout);
170 ConstValue::ZeroSized => unreachable!(), // we already handles ZST above
171 ConstValue::Scalar(x) => match x {
172 Scalar::Int(int) => {
173 if fx.clif_type(layout.ty).is_some() {
174 return CValue::const_val(fx, layout, int);
176 let raw_val = int.to_bits(int.size()).unwrap();
177 let val = match int.size().bytes() {
178 1 => fx.bcx.ins().iconst(types::I8, raw_val as i64),
179 2 => fx.bcx.ins().iconst(types::I16, raw_val as i64),
180 4 => fx.bcx.ins().iconst(types::I32, raw_val as i64),
181 8 => fx.bcx.ins().iconst(types::I64, raw_val as i64),
183 let lsb = fx.bcx.ins().iconst(types::I64, raw_val as u64 as i64);
185 fx.bcx.ins().iconst(types::I64, (raw_val >> 64) as u64 as i64);
186 fx.bcx.ins().iconcat(lsb, msb)
191 let place = CPlace::new_stack_slot(fx, layout);
192 place.to_ptr().store(fx, val, MemFlags::trusted());
196 Scalar::Ptr(ptr, _size) => {
197 let (alloc_id, offset) = ptr.into_parts(); // we know the `offset` is relative
198 let base_addr = match fx.tcx.global_alloc(alloc_id) {
199 GlobalAlloc::Memory(alloc) => {
200 let data_id = data_id_for_alloc_id(
201 &mut fx.constants_cx,
204 alloc.inner().mutability,
207 fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
208 if fx.clif_comments.enabled() {
209 fx.add_comment(local_data_id, format!("{:?}", alloc_id));
211 fx.bcx.ins().global_value(fx.pointer_type, local_data_id)
213 GlobalAlloc::Function(instance) => {
214 let func_id = crate::abi::import_function(fx.tcx, fx.module, instance);
216 fx.module.declare_func_in_func(func_id, &mut fx.bcx.func);
217 fx.bcx.ins().func_addr(fx.pointer_type, local_func_id)
219 GlobalAlloc::VTable(ty, trait_ref) => {
220 let alloc_id = fx.tcx.vtable_allocation((ty, trait_ref));
221 let alloc = fx.tcx.global_alloc(alloc_id).unwrap_memory();
222 // FIXME: factor this common code with the `Memory` arm into a function?
223 let data_id = data_id_for_alloc_id(
224 &mut fx.constants_cx,
227 alloc.inner().mutability,
230 fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
231 fx.bcx.ins().global_value(fx.pointer_type, local_data_id)
233 GlobalAlloc::Static(def_id) => {
234 assert!(fx.tcx.is_static(def_id));
235 let data_id = data_id_for_static(fx.tcx, fx.module, def_id, false);
237 fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
238 if fx.clif_comments.enabled() {
239 fx.add_comment(local_data_id, format!("{:?}", def_id));
241 fx.bcx.ins().global_value(fx.pointer_type, local_data_id)
244 let val = if offset.bytes() != 0 {
245 fx.bcx.ins().iadd_imm(base_addr, i64::try_from(offset.bytes()).unwrap())
249 CValue::by_val(val, layout)
252 ConstValue::ByRef { alloc, offset } => CValue::by_ref(
253 pointer_for_allocation(fx, alloc)
254 .offset_i64(fx, i64::try_from(offset.bytes()).unwrap()),
257 ConstValue::Slice { data, start, end } => {
258 let ptr = pointer_for_allocation(fx, data)
259 .offset_i64(fx, i64::try_from(start).unwrap())
264 .iconst(fx.pointer_type, i64::try_from(end.checked_sub(start).unwrap()).unwrap());
265 CValue::by_val_pair(ptr, len, layout)
270 pub(crate) fn pointer_for_allocation<'tcx>(
271 fx: &mut FunctionCx<'_, '_, 'tcx>,
272 alloc: ConstAllocation<'tcx>,
273 ) -> crate::pointer::Pointer {
274 let alloc_id = fx.tcx.create_memory_alloc(alloc);
275 let data_id = data_id_for_alloc_id(
276 &mut fx.constants_cx,
279 alloc.inner().mutability,
282 let local_data_id = fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
283 if fx.clif_comments.enabled() {
284 fx.add_comment(local_data_id, format!("{:?}", alloc_id));
286 let global_ptr = fx.bcx.ins().global_value(fx.pointer_type, local_data_id);
287 crate::pointer::Pointer::new(global_ptr)
290 pub(crate) fn data_id_for_alloc_id(
292 module: &mut dyn Module,
294 mutability: rustc_hir::Mutability,
296 cx.todo.push(TodoItem::Alloc(alloc_id));
297 *cx.anon_allocs.entry(alloc_id).or_insert_with(|| {
298 module.declare_anonymous_data(mutability == rustc_hir::Mutability::Mut, false).unwrap()
302 fn data_id_for_static(
304 module: &mut dyn Module,
308 let rlinkage = tcx.codegen_fn_attrs(def_id).linkage;
309 let linkage = if definition {
310 crate::linkage::get_static_linkage(tcx, def_id)
311 } else if rlinkage == Some(rustc_middle::mir::mono::Linkage::ExternalWeak)
312 || rlinkage == Some(rustc_middle::mir::mono::Linkage::WeakAny)
319 let instance = Instance::mono(tcx, def_id).polymorphize(tcx);
320 let symbol_name = tcx.symbol_name(instance).name;
321 let ty = instance.ty(tcx, ParamEnv::reveal_all());
322 let is_mutable = if tcx.is_mutable_static(def_id) {
325 !ty.is_freeze(tcx.at(DUMMY_SP), ParamEnv::reveal_all())
327 let align = tcx.layout_of(ParamEnv::reveal_all().and(ty)).unwrap().align.pref.bytes();
329 let attrs = tcx.codegen_fn_attrs(def_id);
331 let data_id = match module.declare_data(
335 attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL),
337 Ok(data_id) => data_id,
338 Err(ModuleError::IncompatibleDeclaration(_)) => tcx.sess.fatal(&format!(
339 "attempt to declare `{symbol_name}` as static, but it was already declared as function"
341 Err(err) => Err::<_, _>(err).unwrap(),
344 if rlinkage.is_some() {
345 // Comment copied from https://github.com/rust-lang/rust/blob/45060c2a66dfd667f88bd8b94261b28a58d85bd5/src/librustc_codegen_llvm/consts.rs#L141
346 // Declare an internal global `extern_with_linkage_foo` which
347 // is initialized with the address of `foo`. If `foo` is
348 // discarded during linking (for example, if `foo` has weak
349 // linkage and there are no definitions), then
350 // `extern_with_linkage_foo` will instead be initialized to
353 let ref_name = format!("_rust_extern_with_linkage_{}", symbol_name);
354 let ref_data_id = module.declare_data(&ref_name, Linkage::Local, false, false).unwrap();
355 let mut data_ctx = DataContext::new();
356 data_ctx.set_align(align);
357 let data = module.declare_data_in_data(data_id, &mut data_ctx);
358 data_ctx.define(std::iter::repeat(0).take(pointer_ty(tcx).bytes() as usize).collect());
359 data_ctx.write_data_addr(0, data, 0);
360 match module.define_data(ref_data_id, &data_ctx) {
361 // Every time the static is referenced there will be another definition of this global,
362 // so duplicate definitions are expected and allowed.
363 Err(ModuleError::DuplicateDefinition(_)) => {}
372 fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut ConstantCx) {
373 while let Some(todo_item) = cx.todo.pop() {
374 let (data_id, alloc, section_name) = match todo_item {
375 TodoItem::Alloc(alloc_id) => {
376 let alloc = match tcx.global_alloc(alloc_id) {
377 GlobalAlloc::Memory(alloc) => alloc,
378 GlobalAlloc::Function(_) | GlobalAlloc::Static(_) | GlobalAlloc::VTable(..) => {
382 let data_id = *cx.anon_allocs.entry(alloc_id).or_insert_with(|| {
384 .declare_anonymous_data(
385 alloc.inner().mutability == rustc_hir::Mutability::Mut,
390 (data_id, alloc, None)
392 TodoItem::Static(def_id) => {
393 //println!("static {:?}", def_id);
395 let section_name = tcx.codegen_fn_attrs(def_id).link_section;
397 let alloc = tcx.eval_static_initializer(def_id).unwrap();
399 let data_id = data_id_for_static(tcx, module, def_id, true);
400 (data_id, alloc, section_name)
404 //("data_id {}", data_id);
405 if cx.done.contains(&data_id) {
409 let mut data_ctx = DataContext::new();
410 let alloc = alloc.inner();
411 data_ctx.set_align(alloc.align.bytes());
413 if let Some(section_name) = section_name {
414 let (segment_name, section_name) = if tcx.sess.target.is_like_osx {
415 let section_name = section_name.as_str();
416 if let Some(names) = section_name.split_once(',') {
419 tcx.sess.fatal(&format!(
420 "#[link_section = \"{}\"] is not valid for macos target: must be segment and section separated by comma",
425 ("", section_name.as_str())
427 data_ctx.set_segment_section(segment_name, section_name);
430 let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(0..alloc.len()).to_vec();
431 data_ctx.define(bytes.into_boxed_slice());
433 for &(offset, alloc_id) in alloc.provenance().iter() {
435 let endianness = tcx.data_layout.endian;
436 let offset = offset.bytes() as usize;
437 let ptr_size = tcx.data_layout.pointer_size;
438 let bytes = &alloc.inspect_with_uninit_and_ptr_outside_interpreter(
439 offset..offset + ptr_size.bytes() as usize,
441 read_target_uint(endianness, bytes).unwrap()
444 let reloc_target_alloc = tcx.global_alloc(alloc_id);
445 let data_id = match reloc_target_alloc {
446 GlobalAlloc::Function(instance) => {
447 assert_eq!(addend, 0);
449 crate::abi::import_function(tcx, module, instance.polymorphize(tcx));
450 let local_func_id = module.declare_func_in_data(func_id, &mut data_ctx);
451 data_ctx.write_function_addr(offset.bytes() as u32, local_func_id);
454 GlobalAlloc::Memory(target_alloc) => {
455 data_id_for_alloc_id(cx, module, alloc_id, target_alloc.inner().mutability)
457 GlobalAlloc::VTable(ty, trait_ref) => {
458 let alloc_id = tcx.vtable_allocation((ty, trait_ref));
459 data_id_for_alloc_id(cx, module, alloc_id, Mutability::Not)
461 GlobalAlloc::Static(def_id) => {
462 if tcx.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::THREAD_LOCAL)
464 tcx.sess.fatal(&format!(
465 "Allocation {:?} contains reference to TLS value {:?}",
470 // Don't push a `TodoItem::Static` here, as it will cause statics used by
471 // multiple crates to be duplicated between them. It isn't necessary anyway,
472 // as it will get pushed by `codegen_static` when necessary.
473 data_id_for_static(tcx, module, def_id, false)
477 let global_value = module.declare_data_in_data(data_id, &mut data_ctx);
478 data_ctx.write_data_addr(offset.bytes() as u32, global_value, addend as i64);
481 module.define_data(data_id, &data_ctx).unwrap();
482 cx.done.insert(data_id);
485 assert!(cx.todo.is_empty(), "{:?}", cx.todo);
488 pub(crate) fn mir_operand_get_const_val<'tcx>(
489 fx: &FunctionCx<'_, '_, 'tcx>,
490 operand: &Operand<'tcx>,
491 ) -> Option<ConstValue<'tcx>> {
493 Operand::Constant(const_) => match const_.literal {
494 ConstantKind::Ty(const_) => fx
495 .monomorphize(const_)
496 .eval_for_mir(fx.tcx, ParamEnv::reveal_all())
497 .try_to_value(fx.tcx),
498 ConstantKind::Val(val, _) => Some(val),
500 // FIXME(rust-lang/rust#85105): Casts like `IMM8 as u32` result in the const being stored
501 // inside a temporary before being passed to the intrinsic requiring the const argument.
502 // This code tries to find a single constant defining definition of the referenced local.
503 Operand::Copy(place) | Operand::Move(place) => {
504 if !place.projection.is_empty() {
507 let mut computed_const_val = None;
508 for bb_data in fx.mir.basic_blocks.iter() {
509 for stmt in &bb_data.statements {
511 StatementKind::Assign(local_and_rvalue) if &local_and_rvalue.0 == place => {
512 match &local_and_rvalue.1 {
513 Rvalue::Cast(CastKind::Misc, operand, ty) => {
514 if computed_const_val.is_some() {
515 return None; // local assigned twice
517 if !matches!(ty.kind(), ty::Uint(_) | ty::Int(_)) {
520 let const_val = mir_operand_get_const_val(fx, operand)?;
521 if fx.layout_of(*ty).size
522 != const_val.try_to_scalar_int()?.size()
526 computed_const_val = Some(const_val);
528 Rvalue::Use(operand) => {
529 computed_const_val = mir_operand_get_const_val(fx, operand)
534 StatementKind::SetDiscriminant { place: stmt_place, variant_index: _ }
535 if &**stmt_place == place =>
539 StatementKind::CopyNonOverlapping(_) => {
541 } // conservative handling
542 StatementKind::Assign(_)
543 | StatementKind::FakeRead(_)
544 | StatementKind::SetDiscriminant { .. }
545 | StatementKind::Deinit(_)
546 | StatementKind::StorageLive(_)
547 | StatementKind::StorageDead(_)
548 | StatementKind::Retag(_, _)
549 | StatementKind::AscribeUserType(_, _)
550 | StatementKind::Coverage(_)
551 | StatementKind::Nop => {}
554 match &bb_data.terminator().kind {
555 TerminatorKind::Goto { .. }
556 | TerminatorKind::SwitchInt { .. }
557 | TerminatorKind::Resume
558 | TerminatorKind::Abort
559 | TerminatorKind::Return
560 | TerminatorKind::Unreachable
561 | TerminatorKind::Drop { .. }
562 | TerminatorKind::Assert { .. } => {}
563 TerminatorKind::DropAndReplace { .. }
564 | TerminatorKind::Yield { .. }
565 | TerminatorKind::GeneratorDrop
566 | TerminatorKind::FalseEdge { .. }
567 | TerminatorKind::FalseUnwind { .. } => unreachable!(),
568 TerminatorKind::InlineAsm { .. } => return None,
569 TerminatorKind::Call { destination, target: Some(_), .. }
570 if destination == place =>
574 TerminatorKind::Call { .. } => {}