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,
13 use rustc_middle::ty::ConstKind;
15 use cranelift_codegen::ir::GlobalValueData;
16 use cranelift_module::*;
18 use crate::prelude::*;
20 pub(crate) struct ConstantCx {
22 done: FxHashSet<DataId>,
23 anon_allocs: FxHashMap<AllocId, DataId>,
26 #[derive(Copy, Clone, Debug)]
33 pub(crate) fn new() -> Self {
34 ConstantCx { todo: vec![], done: FxHashSet::default(), anon_allocs: FxHashMap::default() }
37 pub(crate) fn finalize(mut self, tcx: TyCtxt<'_>, module: &mut dyn Module) {
38 //println!("todo {:?}", self.todo);
39 define_all_allocs(tcx, module, &mut self);
40 //println!("done {:?}", self.done);
45 pub(crate) fn check_constants(fx: &mut FunctionCx<'_, '_, '_>) -> bool {
46 let mut all_constants_ok = true;
47 for constant in &fx.mir.required_consts {
48 let const_ = match fx.monomorphize(constant.literal) {
49 ConstantKind::Ty(ct) => ct,
50 ConstantKind::Val(..) => continue,
53 ConstKind::Value(_) => {}
54 ConstKind::Unevaluated(unevaluated) => {
56 fx.tcx.const_eval_resolve(ParamEnv::reveal_all(), unevaluated, None)
58 all_constants_ok = false;
60 ErrorHandled::Reported(ErrorReported) | ErrorHandled::Linted => {
61 fx.tcx.sess.span_err(constant.span, "erroneous constant encountered");
63 ErrorHandled::TooGeneric => {
66 "codgen encountered polymorphic constant: {:?}",
75 | ConstKind::Bound(_, _)
76 | ConstKind::Placeholder(_)
77 | ConstKind::Error(_) => unreachable!("{:?}", const_),
83 pub(crate) fn codegen_static(tcx: TyCtxt<'_>, module: &mut dyn Module, def_id: DefId) {
84 let mut constants_cx = ConstantCx::new();
85 constants_cx.todo.push(TodoItem::Static(def_id));
86 constants_cx.finalize(tcx, module);
89 pub(crate) fn codegen_tls_ref<'tcx>(
90 fx: &mut FunctionCx<'_, '_, 'tcx>,
92 layout: TyAndLayout<'tcx>,
94 let data_id = data_id_for_static(fx.tcx, fx.module, def_id, false);
95 let local_data_id = fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
96 if fx.clif_comments.enabled() {
97 fx.add_comment(local_data_id, format!("tls {:?}", def_id));
99 let tls_ptr = fx.bcx.ins().tls_value(fx.pointer_type, local_data_id);
100 CValue::by_val(tls_ptr, layout)
103 fn codegen_static_ref<'tcx>(
104 fx: &mut FunctionCx<'_, '_, 'tcx>,
106 layout: TyAndLayout<'tcx>,
108 let data_id = data_id_for_static(fx.tcx, fx.module, def_id, false);
109 let local_data_id = fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
110 if fx.clif_comments.enabled() {
111 fx.add_comment(local_data_id, format!("{:?}", def_id));
113 let global_ptr = fx.bcx.ins().global_value(fx.pointer_type, local_data_id);
114 assert!(!layout.is_unsized(), "unsized statics aren't supported");
117 fx.bcx.func.global_values[local_data_id],
118 GlobalValueData::Symbol { tls: false, .. }
120 "tls static referenced without Rvalue::ThreadLocalRef"
122 CPlace::for_ptr(crate::pointer::Pointer::new(global_ptr), layout)
125 pub(crate) fn codegen_constant<'tcx>(
126 fx: &mut FunctionCx<'_, '_, 'tcx>,
127 constant: &Constant<'tcx>,
129 let const_ = match fx.monomorphize(constant.literal) {
130 ConstantKind::Ty(ct) => ct,
131 ConstantKind::Val(val, ty) => return codegen_const_value(fx, val, ty),
133 let const_val = match const_.val {
134 ConstKind::Value(const_val) => const_val,
135 ConstKind::Unevaluated(ty::Unevaluated { def, substs, promoted })
136 if fx.tcx.is_static(def.did) =>
138 assert!(substs.is_empty());
139 assert!(promoted.is_none());
141 return codegen_static_ref(fx, def.did, fx.layout_of(const_.ty)).to_cvalue(fx);
143 ConstKind::Unevaluated(unevaluated) => {
144 match fx.tcx.const_eval_resolve(ParamEnv::reveal_all(), unevaluated, None) {
145 Ok(const_val) => const_val,
147 span_bug!(constant.span, "erroneous constant not captured by required_consts");
152 | ConstKind::Infer(_)
153 | ConstKind::Bound(_, _)
154 | ConstKind::Placeholder(_)
155 | ConstKind::Error(_) => unreachable!("{:?}", const_),
158 codegen_const_value(fx, const_val, const_.ty)
161 pub(crate) fn codegen_const_value<'tcx>(
162 fx: &mut FunctionCx<'_, '_, 'tcx>,
163 const_val: ConstValue<'tcx>,
166 let layout = fx.layout_of(ty);
167 assert!(!layout.is_unsized(), "sized const value");
170 return CValue::by_ref(crate::Pointer::dangling(layout.align.pref), layout);
174 ConstValue::Scalar(x) => {
175 if fx.clif_type(layout.ty).is_none() {
176 let (size, align) = (layout.size, layout.align.pref);
177 let mut alloc = Allocation::from_bytes(
178 std::iter::repeat(0).take(size.bytes_usize()).collect::<Vec<u8>>(),
182 alloc.write_scalar(fx, alloc_range(Size::ZERO, size), x.into()).unwrap();
183 let alloc = fx.tcx.intern_const_alloc(alloc);
184 return CValue::by_ref(pointer_for_allocation(fx, alloc), layout);
188 Scalar::Int(int) => CValue::const_val(fx, layout, int),
189 Scalar::Ptr(ptr) => {
190 let alloc_kind = fx.tcx.get_global_alloc(ptr.alloc_id);
191 let base_addr = match alloc_kind {
192 Some(GlobalAlloc::Memory(alloc)) => {
193 fx.constants_cx.todo.push(TodoItem::Alloc(ptr.alloc_id));
194 let data_id = data_id_for_alloc_id(
195 &mut fx.constants_cx,
201 fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
202 if fx.clif_comments.enabled() {
203 fx.add_comment(local_data_id, format!("{:?}", ptr.alloc_id));
205 fx.bcx.ins().global_value(fx.pointer_type, local_data_id)
207 Some(GlobalAlloc::Function(instance)) => {
208 let func_id = crate::abi::import_function(fx.tcx, fx.module, instance);
210 fx.module.declare_func_in_func(func_id, &mut fx.bcx.func);
211 fx.bcx.ins().func_addr(fx.pointer_type, local_func_id)
213 Some(GlobalAlloc::Static(def_id)) => {
214 assert!(fx.tcx.is_static(def_id));
215 let data_id = data_id_for_static(fx.tcx, fx.module, def_id, false);
217 fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
218 if fx.clif_comments.enabled() {
219 fx.add_comment(local_data_id, format!("{:?}", def_id));
221 fx.bcx.ins().global_value(fx.pointer_type, local_data_id)
223 None => bug!("missing allocation {:?}", ptr.alloc_id),
225 let val = if ptr.offset.bytes() != 0 {
226 fx.bcx.ins().iadd_imm(base_addr, i64::try_from(ptr.offset.bytes()).unwrap())
230 CValue::by_val(val, layout)
234 ConstValue::ByRef { alloc, offset } => CValue::by_ref(
235 pointer_for_allocation(fx, alloc)
236 .offset_i64(fx, i64::try_from(offset.bytes()).unwrap()),
239 ConstValue::Slice { data, start, end } => {
240 let ptr = pointer_for_allocation(fx, data)
241 .offset_i64(fx, i64::try_from(start).unwrap())
246 .iconst(fx.pointer_type, i64::try_from(end.checked_sub(start).unwrap()).unwrap());
247 CValue::by_val_pair(ptr, len, layout)
252 fn pointer_for_allocation<'tcx>(
253 fx: &mut FunctionCx<'_, '_, 'tcx>,
254 alloc: &'tcx Allocation,
255 ) -> crate::pointer::Pointer {
256 let alloc_id = fx.tcx.create_memory_alloc(alloc);
257 fx.constants_cx.todo.push(TodoItem::Alloc(alloc_id));
259 data_id_for_alloc_id(&mut fx.constants_cx, &mut *fx.module, alloc_id, alloc.mutability);
261 let local_data_id = fx.module.declare_data_in_func(data_id, &mut fx.bcx.func);
262 if fx.clif_comments.enabled() {
263 fx.add_comment(local_data_id, format!("{:?}", alloc_id));
265 let global_ptr = fx.bcx.ins().global_value(fx.pointer_type, local_data_id);
266 crate::pointer::Pointer::new(global_ptr)
269 fn data_id_for_alloc_id(
271 module: &mut dyn Module,
273 mutability: rustc_hir::Mutability,
275 *cx.anon_allocs.entry(alloc_id).or_insert_with(|| {
276 module.declare_anonymous_data(mutability == rustc_hir::Mutability::Mut, false).unwrap()
280 fn data_id_for_static(
282 module: &mut dyn Module,
286 let rlinkage = tcx.codegen_fn_attrs(def_id).linkage;
287 let linkage = if definition {
288 crate::linkage::get_static_linkage(tcx, def_id)
289 } else if rlinkage == Some(rustc_middle::mir::mono::Linkage::ExternalWeak)
290 || rlinkage == Some(rustc_middle::mir::mono::Linkage::WeakAny)
297 let instance = Instance::mono(tcx, def_id).polymorphize(tcx);
298 let symbol_name = tcx.symbol_name(instance).name;
299 let ty = instance.ty(tcx, ParamEnv::reveal_all());
300 let is_mutable = if tcx.is_mutable_static(def_id) {
303 !ty.is_freeze(tcx.at(DUMMY_SP), ParamEnv::reveal_all())
305 let align = tcx.layout_of(ParamEnv::reveal_all().and(ty)).unwrap().align.pref.bytes();
307 let attrs = tcx.codegen_fn_attrs(def_id);
314 attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL),
318 if rlinkage.is_some() {
319 // Comment copied from https://github.com/rust-lang/rust/blob/45060c2a66dfd667f88bd8b94261b28a58d85bd5/src/librustc_codegen_llvm/consts.rs#L141
320 // Declare an internal global `extern_with_linkage_foo` which
321 // is initialized with the address of `foo`. If `foo` is
322 // discarded during linking (for example, if `foo` has weak
323 // linkage and there are no definitions), then
324 // `extern_with_linkage_foo` will instead be initialized to
327 let ref_name = format!("_rust_extern_with_linkage_{}", symbol_name);
328 let ref_data_id = module.declare_data(&ref_name, Linkage::Local, false, false).unwrap();
329 let mut data_ctx = DataContext::new();
330 data_ctx.set_align(align);
331 let data = module.declare_data_in_data(data_id, &mut data_ctx);
332 data_ctx.define(std::iter::repeat(0).take(pointer_ty(tcx).bytes() as usize).collect());
333 data_ctx.write_data_addr(0, data, 0);
334 match module.define_data(ref_data_id, &data_ctx) {
335 // Every time the static is referenced there will be another definition of this global,
336 // so duplicate definitions are expected and allowed.
337 Err(ModuleError::DuplicateDefinition(_)) => {}
346 fn define_all_allocs(tcx: TyCtxt<'_>, module: &mut dyn Module, cx: &mut ConstantCx) {
347 while let Some(todo_item) = cx.todo.pop() {
348 let (data_id, alloc, section_name) = match todo_item {
349 TodoItem::Alloc(alloc_id) => {
350 //println!("alloc_id {}", alloc_id);
351 let alloc = match tcx.get_global_alloc(alloc_id).unwrap() {
352 GlobalAlloc::Memory(alloc) => alloc,
353 GlobalAlloc::Function(_) | GlobalAlloc::Static(_) => unreachable!(),
355 let data_id = data_id_for_alloc_id(cx, module, alloc_id, alloc.mutability);
356 (data_id, alloc, None)
358 TodoItem::Static(def_id) => {
359 //println!("static {:?}", def_id);
361 let section_name = tcx.codegen_fn_attrs(def_id).link_section.map(|s| s.as_str());
363 let alloc = tcx.eval_static_initializer(def_id).unwrap();
365 let data_id = data_id_for_static(tcx, module, def_id, true);
366 (data_id, alloc, section_name)
370 //("data_id {}", data_id);
371 if cx.done.contains(&data_id) {
375 let mut data_ctx = DataContext::new();
376 data_ctx.set_align(alloc.align.bytes());
378 if let Some(section_name) = section_name {
379 let (segment_name, section_name) = if tcx.sess.target.is_like_osx {
380 if let Some(names) = section_name.split_once(',') {
383 tcx.sess.fatal(&format!(
384 "#[link_section = \"{}\"] is not valid for macos target: must be segment and section separated by comma",
391 data_ctx.set_segment_section(segment_name, section_name);
394 let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(0..alloc.len()).to_vec();
395 data_ctx.define(bytes.into_boxed_slice());
397 for &(offset, (_tag, reloc)) in alloc.relocations().iter() {
399 let endianness = tcx.data_layout.endian;
400 let offset = offset.bytes() as usize;
401 let ptr_size = tcx.data_layout.pointer_size;
402 let bytes = &alloc.inspect_with_uninit_and_ptr_outside_interpreter(
403 offset..offset + ptr_size.bytes() as usize,
405 read_target_uint(endianness, bytes).unwrap()
408 let reloc_target_alloc = tcx.get_global_alloc(reloc).unwrap();
409 let data_id = match reloc_target_alloc {
410 GlobalAlloc::Function(instance) => {
411 assert_eq!(addend, 0);
412 let func_id = crate::abi::import_function(tcx, module, instance);
413 let local_func_id = module.declare_func_in_data(func_id, &mut data_ctx);
414 data_ctx.write_function_addr(offset.bytes() as u32, local_func_id);
417 GlobalAlloc::Memory(target_alloc) => {
418 cx.todo.push(TodoItem::Alloc(reloc));
419 data_id_for_alloc_id(cx, module, reloc, target_alloc.mutability)
421 GlobalAlloc::Static(def_id) => {
422 if tcx.codegen_fn_attrs(def_id).flags.contains(CodegenFnAttrFlags::THREAD_LOCAL)
424 tcx.sess.fatal(&format!(
425 "Allocation {:?} contains reference to TLS value {:?}",
430 // Don't push a `TodoItem::Static` here, as it will cause statics used by
431 // multiple crates to be duplicated between them. It isn't necessary anyway,
432 // as it will get pushed by `codegen_static` when necessary.
433 data_id_for_static(tcx, module, def_id, false)
437 let global_value = module.declare_data_in_data(data_id, &mut data_ctx);
438 data_ctx.write_data_addr(offset.bytes() as u32, global_value, addend as i64);
441 module.define_data(data_id, &data_ctx).unwrap();
442 cx.done.insert(data_id);
445 assert!(cx.todo.is_empty(), "{:?}", cx.todo);
448 pub(crate) fn mir_operand_get_const_val<'tcx>(
449 fx: &FunctionCx<'_, '_, 'tcx>,
450 operand: &Operand<'tcx>,
451 ) -> Option<ConstValue<'tcx>> {
453 Operand::Constant(const_) => match const_.literal {
454 ConstantKind::Ty(const_) => {
455 fx.monomorphize(const_).eval(fx.tcx, ParamEnv::reveal_all()).val.try_to_value()
457 ConstantKind::Val(val, _) => Some(val),
459 // FIXME(rust-lang/rust#85105): Casts like `IMM8 as u32` result in the const being stored
460 // inside a temporary before being passed to the intrinsic requiring the const argument.
461 // This code tries to find a single constant defining definition of the referenced local.
462 Operand::Copy(place) | Operand::Move(place) => {
463 if !place.projection.is_empty() {
466 let mut computed_const_val = None;
467 for bb_data in fx.mir.basic_blocks() {
468 for stmt in &bb_data.statements {
470 StatementKind::Assign(local_and_rvalue) if &local_and_rvalue.0 == place => {
471 match &local_and_rvalue.1 {
472 Rvalue::Cast(CastKind::Misc, operand, ty) => {
473 if computed_const_val.is_some() {
474 return None; // local assigned twice
476 if !matches!(ty.kind(), ty::Uint(_) | ty::Int(_)) {
479 let const_val = mir_operand_get_const_val(fx, operand)?;
480 if fx.layout_of(ty).size
481 != const_val.try_to_scalar_int()?.size()
485 computed_const_val = Some(const_val);
487 Rvalue::Use(operand) => {
488 computed_const_val = mir_operand_get_const_val(fx, operand)
493 StatementKind::SetDiscriminant { place: stmt_place, variant_index: _ }
494 if &**stmt_place == place =>
498 StatementKind::LlvmInlineAsm(_) | StatementKind::CopyNonOverlapping(_) => {
500 } // conservative handling
501 StatementKind::Assign(_)
502 | StatementKind::FakeRead(_)
503 | StatementKind::SetDiscriminant { .. }
504 | StatementKind::StorageLive(_)
505 | StatementKind::StorageDead(_)
506 | StatementKind::Retag(_, _)
507 | StatementKind::AscribeUserType(_, _)
508 | StatementKind::Coverage(_)
509 | StatementKind::Nop => {}
512 match &bb_data.terminator().kind {
513 TerminatorKind::Goto { .. }
514 | TerminatorKind::SwitchInt { .. }
515 | TerminatorKind::Resume
516 | TerminatorKind::Abort
517 | TerminatorKind::Return
518 | TerminatorKind::Unreachable
519 | TerminatorKind::Drop { .. }
520 | TerminatorKind::Assert { .. } => {}
521 TerminatorKind::DropAndReplace { .. }
522 | TerminatorKind::Yield { .. }
523 | TerminatorKind::GeneratorDrop
524 | TerminatorKind::FalseEdge { .. }
525 | TerminatorKind::FalseUnwind { .. } => unreachable!(),
526 TerminatorKind::InlineAsm { .. } => return None,
527 TerminatorKind::Call { destination: Some((call_place, _)), .. }
528 if call_place == place =>
532 TerminatorKind::Call { .. } => {}