1 //! Handling of `static`s, `const`s and promoted allocations
3 use rustc_span::DUMMY_SP;
5 use rustc_ast::Mutability;
6 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
7 use rustc_errors::ErrorReported;
8 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
9 use rustc_middle::mir::interpret::{
10 alloc_range, read_target_uint, AllocId, Allocation, ConstValue, ErrorHandled, GlobalAlloc, Scalar,
12 use rustc_middle::ty::ConstKind;
14 use cranelift_codegen::ir::GlobalValueData;
15 use cranelift_module::*;
17 use crate::prelude::*;
19 pub(crate) struct ConstantCx {
21 done: FxHashSet<DataId>,
22 anon_allocs: FxHashMap<AllocId, DataId>,
25 #[derive(Copy, Clone, Debug)]
32 pub(crate) fn new() -> Self {
33 ConstantCx { todo: vec![], done: FxHashSet::default(), anon_allocs: FxHashMap::default() }
36 pub(crate) fn finalize(mut self, tcx: TyCtxt<'_>, module: &mut dyn Module) {
37 //println!("todo {:?}", self.todo);
38 define_all_allocs(tcx, module, &mut self);
39 //println!("done {:?}", self.done);
44 pub(crate) fn check_constants(fx: &mut FunctionCx<'_, '_, '_>) -> bool {
45 let mut all_constants_ok = true;
46 for constant in &fx.mir.required_consts {
47 let const_ = match fx.monomorphize(constant.literal) {
48 ConstantKind::Ty(ct) => ct,
49 ConstantKind::Val(..) => continue,
52 ConstKind::Value(_) => {}
53 ConstKind::Unevaluated(unevaluated) => {
55 fx.tcx.const_eval_resolve(ParamEnv::reveal_all(), unevaluated, None)
57 all_constants_ok = false;
59 ErrorHandled::Reported(ErrorReported) | ErrorHandled::Linted => {
60 fx.tcx.sess.span_err(constant.span, "erroneous constant encountered");
62 ErrorHandled::TooGeneric => {
65 "codgen encountered polymorphic constant: {:?}",
74 | ConstKind::Bound(_, _)
75 | ConstKind::Placeholder(_)
76 | ConstKind::Error(_) => unreachable!("{:?}", const_),
82 pub(crate) fn codegen_static(tcx: TyCtxt<'_>, module: &mut dyn Module, def_id: DefId) {
83 let mut constants_cx = ConstantCx::new();
84 constants_cx.todo.push(TodoItem::Static(def_id));
85 constants_cx.finalize(tcx, module);
88 pub(crate) fn codegen_tls_ref<'tcx>(
89 fx: &mut FunctionCx<'_, '_, 'tcx>,
91 layout: TyAndLayout<'tcx>,
93 let data_id = data_id_for_static(fx.tcx, fx.module, def_id, false);
94 let local_data_id = fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
95 if fx.clif_comments.enabled() {
96 fx.add_comment(local_data_id, format!("tls {:?}", def_id));
98 let tls_ptr = fx.bcx.ins().tls_value(fx.pointer_type, local_data_id);
99 CValue::by_val(tls_ptr, layout)
102 fn codegen_static_ref<'tcx>(
103 fx: &mut FunctionCx<'_, '_, 'tcx>,
105 layout: TyAndLayout<'tcx>,
107 let data_id = data_id_for_static(fx.tcx, fx.module, def_id, false);
108 let local_data_id = fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
109 if fx.clif_comments.enabled() {
110 fx.add_comment(local_data_id, format!("{:?}", def_id));
112 let global_ptr = fx.bcx.ins().global_value(fx.pointer_type, local_data_id);
113 assert!(!layout.is_unsized(), "unsized statics aren't supported");
116 fx.bcx.func.global_values[local_data_id],
117 GlobalValueData::Symbol { tls: false, .. }
119 "tls static referenced without Rvalue::ThreadLocalRef"
121 CPlace::for_ptr(crate::pointer::Pointer::new(global_ptr), layout)
124 pub(crate) fn codegen_constant<'tcx>(
125 fx: &mut FunctionCx<'_, '_, 'tcx>,
126 constant: &Constant<'tcx>,
128 let const_ = match fx.monomorphize(constant.literal) {
129 ConstantKind::Ty(ct) => ct,
130 ConstantKind::Val(val, ty) => return codegen_const_value(fx, val, ty),
132 let const_val = match const_.val {
133 ConstKind::Value(const_val) => const_val,
134 ConstKind::Unevaluated(ty::Unevaluated { def, substs, promoted })
135 if fx.tcx.is_static(def.did) =>
137 assert!(substs.is_empty());
138 assert!(promoted.is_none());
140 return codegen_static_ref(fx, def.did, fx.layout_of(const_.ty)).to_cvalue(fx);
142 ConstKind::Unevaluated(unevaluated) => {
143 match fx.tcx.const_eval_resolve(ParamEnv::reveal_all(), unevaluated, None) {
144 Ok(const_val) => const_val,
146 span_bug!(constant.span, "erroneous constant not captured by required_consts");
151 | ConstKind::Infer(_)
152 | ConstKind::Bound(_, _)
153 | ConstKind::Placeholder(_)
154 | ConstKind::Error(_) => unreachable!("{:?}", const_),
157 codegen_const_value(fx, const_val, const_.ty)
160 pub(crate) fn codegen_const_value<'tcx>(
161 fx: &mut FunctionCx<'_, '_, 'tcx>,
162 const_val: ConstValue<'tcx>,
165 let layout = fx.layout_of(ty);
166 assert!(!layout.is_unsized(), "sized const value");
169 return CValue::by_ref(crate::Pointer::dangling(layout.align.pref), layout);
173 ConstValue::Scalar(x) => {
174 if fx.clif_type(layout.ty).is_none() {
175 let (size, align) = (layout.size, layout.align.pref);
176 let mut alloc = Allocation::from_bytes(
177 std::iter::repeat(0).take(size.bytes_usize()).collect::<Vec<u8>>(),
181 alloc.write_scalar(fx, alloc_range(Size::ZERO, size), x.into()).unwrap();
182 let alloc = fx.tcx.intern_const_alloc(alloc);
183 return CValue::by_ref(pointer_for_allocation(fx, alloc), layout);
187 Scalar::Int(int) => CValue::const_val(fx, layout, int),
188 Scalar::Ptr(ptr) => {
189 let alloc_kind = fx.tcx.get_global_alloc(ptr.alloc_id);
190 let base_addr = match alloc_kind {
191 Some(GlobalAlloc::Memory(alloc)) => {
192 fx.constants_cx.todo.push(TodoItem::Alloc(ptr.alloc_id));
193 let data_id = data_id_for_alloc_id(
194 &mut fx.constants_cx,
200 fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
201 if fx.clif_comments.enabled() {
202 fx.add_comment(local_data_id, format!("{:?}", ptr.alloc_id));
204 fx.bcx.ins().global_value(fx.pointer_type, local_data_id)
206 Some(GlobalAlloc::Function(instance)) => {
207 let func_id = crate::abi::import_function(fx.tcx, fx.module, instance);
209 fx.module.declare_func_in_func(func_id, &mut fx.bcx.func);
210 fx.bcx.ins().func_addr(fx.pointer_type, local_func_id)
212 Some(GlobalAlloc::Static(def_id)) => {
213 assert!(fx.tcx.is_static(def_id));
214 let data_id = data_id_for_static(fx.tcx, fx.module, def_id, false);
216 fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
217 if fx.clif_comments.enabled() {
218 fx.add_comment(local_data_id, format!("{:?}", def_id));
220 fx.bcx.ins().global_value(fx.pointer_type, local_data_id)
222 None => bug!("missing allocation {:?}", ptr.alloc_id),
224 let val = if ptr.offset.bytes() != 0 {
225 fx.bcx.ins().iadd_imm(base_addr, i64::try_from(ptr.offset.bytes()).unwrap())
229 CValue::by_val(val, layout)
233 ConstValue::ByRef { alloc, offset } => CValue::by_ref(
234 pointer_for_allocation(fx, alloc)
235 .offset_i64(fx, i64::try_from(offset.bytes()).unwrap()),
238 ConstValue::Slice { data, start, end } => {
239 let ptr = pointer_for_allocation(fx, data)
240 .offset_i64(fx, i64::try_from(start).unwrap())
245 .iconst(fx.pointer_type, i64::try_from(end.checked_sub(start).unwrap()).unwrap());
246 CValue::by_val_pair(ptr, len, layout)
251 fn pointer_for_allocation<'tcx>(
252 fx: &mut FunctionCx<'_, '_, 'tcx>,
253 alloc: &'tcx Allocation,
254 ) -> crate::pointer::Pointer {
255 let alloc_id = fx.tcx.create_memory_alloc(alloc);
256 fx.constants_cx.todo.push(TodoItem::Alloc(alloc_id));
258 data_id_for_alloc_id(&mut fx.constants_cx, &mut *fx.module, alloc_id, alloc.mutability);
260 let local_data_id = fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
261 if fx.clif_comments.enabled() {
262 fx.add_comment(local_data_id, format!("{:?}", alloc_id));
264 let global_ptr = fx.bcx.ins().global_value(fx.pointer_type, local_data_id);
265 crate::pointer::Pointer::new(global_ptr)
268 fn data_id_for_alloc_id(
270 module: &mut dyn Module,
272 mutability: rustc_hir::Mutability,
274 *cx.anon_allocs.entry(alloc_id).or_insert_with(|| {
275 module.declare_anonymous_data(mutability == rustc_hir::Mutability::Mut, false).unwrap()
279 fn data_id_for_static(
281 module: &mut dyn Module,
285 let rlinkage = tcx.codegen_fn_attrs(def_id).linkage;
286 let linkage = if definition {
287 crate::linkage::get_static_linkage(tcx, def_id)
288 } else if rlinkage == Some(rustc_middle::mir::mono::Linkage::ExternalWeak)
289 || rlinkage == Some(rustc_middle::mir::mono::Linkage::WeakAny)
296 let instance = Instance::mono(tcx, def_id).polymorphize(tcx);
297 let symbol_name = tcx.symbol_name(instance).name;
298 let ty = instance.ty(tcx, ParamEnv::reveal_all());
299 let is_mutable = if tcx.is_mutable_static(def_id) {
302 !ty.is_freeze(tcx.at(DUMMY_SP), ParamEnv::reveal_all())
304 let align = tcx.layout_of(ParamEnv::reveal_all().and(ty)).unwrap().align.pref.bytes();
306 let attrs = tcx.codegen_fn_attrs(def_id);
313 attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL),
317 if rlinkage.is_some() {
318 // Comment copied from https://github.com/rust-lang/rust/blob/45060c2a66dfd667f88bd8b94261b28a58d85bd5/src/librustc_codegen_llvm/consts.rs#L141
319 // Declare an internal global `extern_with_linkage_foo` which
320 // is initialized with the address of `foo`. If `foo` is
321 // discarded during linking (for example, if `foo` has weak
322 // linkage and there are no definitions), then
323 // `extern_with_linkage_foo` will instead be initialized to
326 let ref_name = format!("_rust_extern_with_linkage_{}", symbol_name);
327 let ref_data_id = module.declare_data(&ref_name, Linkage::Local, false, false).unwrap();
328 let mut data_ctx = DataContext::new();
329 data_ctx.set_align(align);
330 let data = module.declare_data_in_data(data_id, &mut data_ctx);
331 data_ctx.define(std::iter::repeat(0).take(pointer_ty(tcx).bytes() as usize).collect());
332 data_ctx.write_data_addr(0, data, 0);
333 match module.define_data(ref_data_id, &data_ctx) {
334 // Every time the static is referenced there will be another definition of this global,
335 // so duplicate definitions are expected and allowed.
336 Err(ModuleError::DuplicateDefinition(_)) => {}
345 fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut ConstantCx) {
346 while let Some(todo_item) = cx.todo.pop() {
347 let (data_id, alloc, section_name) = match todo_item {
348 TodoItem::Alloc(alloc_id) => {
349 //println!("alloc_id {}", alloc_id);
350 let alloc = match tcx.get_global_alloc(alloc_id).unwrap() {
351 GlobalAlloc::Memory(alloc) => alloc,
352 GlobalAlloc::Function(_) | GlobalAlloc::Static(_) => unreachable!(),
354 let data_id = data_id_for_alloc_id(cx, module, alloc_id, alloc.mutability);
355 (data_id, alloc, None)
357 TodoItem::Static(def_id) => {
358 //println!("static {:?}", def_id);
360 let section_name = tcx.codegen_fn_attrs(def_id).link_section.map(|s| s.as_str());
362 let alloc = tcx.eval_static_initializer(def_id).unwrap();
364 let data_id = data_id_for_static(tcx, module, def_id, true);
365 (data_id, alloc, section_name)
369 //("data_id {}", data_id);
370 if cx.done.contains(&data_id) {
374 let mut data_ctx = DataContext::new();
375 data_ctx.set_align(alloc.align.bytes());
377 if let Some(section_name) = section_name {
378 let (segment_name, section_name) = if tcx.sess.target.is_like_osx {
379 if let Some(names) = section_name.split_once(',') {
382 tcx.sess.fatal(&format!(
383 "#[link_section = \"{}\"] is not valid for macos target: must be segment and section separated by comma",
390 data_ctx.set_segment_section(segment_name, section_name);
393 let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(0..alloc.len()).to_vec();
394 data_ctx.define(bytes.into_boxed_slice());
396 for &(offset, (_tag, reloc)) in alloc.relocations().iter() {
398 let endianness = tcx.data_layout.endian;
399 let offset = offset.bytes() as usize;
400 let ptr_size = tcx.data_layout.pointer_size;
401 let bytes = &alloc.inspect_with_uninit_and_ptr_outside_interpreter(
402 offset..offset + ptr_size.bytes() as usize,
404 read_target_uint(endianness, bytes).unwrap()
407 let reloc_target_alloc = tcx.get_global_alloc(reloc).unwrap();
408 let data_id = match reloc_target_alloc {
409 GlobalAlloc::Function(instance) => {
410 assert_eq!(addend, 0);
411 let func_id = crate::abi::import_function(tcx, module, instance);
412 let local_func_id = module.declare_func_in_data(func_id, &mut data_ctx);
413 data_ctx.write_function_addr(offset.bytes() as u32, local_func_id);
416 GlobalAlloc::Memory(target_alloc) => {
417 cx.todo.push(TodoItem::Alloc(reloc));
418 data_id_for_alloc_id(cx, module, reloc, target_alloc.mutability)
420 GlobalAlloc::Static(def_id) => {
421 if tcx.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::THREAD_LOCAL)
423 tcx.sess.fatal(&format!(
424 "Allocation {:?} contains reference to TLS value {:?}",
429 // Don't push a `TodoItem::Static` here, as it will cause statics used by
430 // multiple crates to be duplicated between them. It isn't necessary anyway,
431 // as it will get pushed by `codegen_static` when necessary.
432 data_id_for_static(tcx, module, def_id, false)
436 let global_value = module.declare_data_in_data(data_id, &mut data_ctx);
437 data_ctx.write_data_addr(offset.bytes() as u32, global_value, addend as i64);
440 module.define_data(data_id, &data_ctx).unwrap();
441 cx.done.insert(data_id);
444 assert!(cx.todo.is_empty(), "{:?}", cx.todo);
447 pub(crate) fn mir_operand_get_const_val<'tcx>(
448 fx: &FunctionCx<'_, '_, 'tcx>,
449 operand: &Operand<'tcx>,
450 ) -> Option<ConstValue<'tcx>> {
452 Operand::Constant(const_) => match const_.literal {
453 ConstantKind::Ty(const_) => {
454 fx.monomorphize(const_).eval(fx.tcx, ParamEnv::reveal_all()).val.try_to_value()
456 ConstantKind::Val(val, _) => Some(val),
458 // FIXME(rust-lang/rust#85105): Casts like `IMM8 as u32` result in the const being stored
459 // inside a temporary before being passed to the intrinsic requiring the const argument.
460 // This code tries to find a single constant defining definition of the referenced local.
461 Operand::Copy(place) | Operand::Move(place) => {
462 if !place.projection.is_empty() {
465 let mut computed_const_val = None;
466 for bb_data in fx.mir.basic_blocks() {
467 for stmt in &bb_data.statements {
469 StatementKind::Assign(local_and_rvalue) if &local_and_rvalue.0 == place => {
470 match &local_and_rvalue.1 {
471 Rvalue::Cast(CastKind::Misc, operand, ty) => {
472 if computed_const_val.is_some() {
473 return None; // local assigned twice
475 if !matches!(ty.kind(), ty::Uint(_) | ty::Int(_)) {
478 let const_val = mir_operand_get_const_val(fx, operand)?;
479 if fx.layout_of(ty).size
480 != const_val.try_to_scalar_int()?.size()
484 computed_const_val = Some(const_val);
486 Rvalue::Use(operand) => {
487 computed_const_val = mir_operand_get_const_val(fx, operand)
492 StatementKind::SetDiscriminant { place: stmt_place, variant_index: _ }
493 if &**stmt_place == place =>
497 StatementKind::LlvmInlineAsm(_) | StatementKind::CopyNonOverlapping(_) => {
499 } // conservative handling
500 StatementKind::Assign(_)
501 | StatementKind::FakeRead(_)
502 | StatementKind::SetDiscriminant { .. }
503 | StatementKind::StorageLive(_)
504 | StatementKind::StorageDead(_)
505 | StatementKind::Retag(_, _)
506 | StatementKind::AscribeUserType(_, _)
507 | StatementKind::Coverage(_)
508 | StatementKind::Nop => {}
511 match &bb_data.terminator().kind {
512 TerminatorKind::Goto { .. }
513 | TerminatorKind::SwitchInt { .. }
514 | TerminatorKind::Resume
515 | TerminatorKind::Abort
516 | TerminatorKind::Return
517 | TerminatorKind::Unreachable
518 | TerminatorKind::Drop { .. }
519 | TerminatorKind::Assert { .. } => {}
520 TerminatorKind::DropAndReplace { .. }
521 | TerminatorKind::Yield { .. }
522 | TerminatorKind::GeneratorDrop
523 | TerminatorKind::FalseEdge { .. }
524 | TerminatorKind::FalseUnwind { .. } => unreachable!(),
525 TerminatorKind::InlineAsm { .. } => return None,
526 TerminatorKind::Call { destination: Some((call_place, _)), .. }
527 if call_place == place =>
531 TerminatorKind::Call { .. } => {}