rustc_codegen_llvm/
mono_item.rs
1use rustc_codegen_ssa::traits::*;
2use rustc_hir::def::DefKind;
3use rustc_hir::def_id::{DefId, LOCAL_CRATE};
4use rustc_middle::bug;
5use rustc_middle::mir::mono::{Linkage, Visibility};
6use rustc_middle::ty::layout::{FnAbiOf, HasTypingEnv, LayoutOf};
7use rustc_middle::ty::{self, Instance, TypeVisitableExt};
8use rustc_session::config::CrateType;
9use rustc_target::spec::RelocModel;
10use tracing::debug;
11
12use crate::context::CodegenCx;
13use crate::errors::SymbolAlreadyDefined;
14use crate::type_of::LayoutLlvmExt;
15use crate::{base, llvm};
16
17impl<'tcx> PreDefineCodegenMethods<'tcx> for CodegenCx<'_, 'tcx> {
18 fn predefine_static(
19 &self,
20 def_id: DefId,
21 linkage: Linkage,
22 visibility: Visibility,
23 symbol_name: &str,
24 ) {
25 let instance = Instance::mono(self.tcx, def_id);
26 let DefKind::Static { nested, .. } = self.tcx.def_kind(def_id) else { bug!() };
27 let ty =
30 if nested { self.tcx.types.unit } else { instance.ty(self.tcx, self.typing_env()) };
31 let llty = self.layout_of(ty).llvm_type(self);
32
33 let g = self.define_global(symbol_name, llty).unwrap_or_else(|| {
34 self.sess()
35 .dcx()
36 .emit_fatal(SymbolAlreadyDefined { span: self.tcx.def_span(def_id), symbol_name })
37 });
38
39 llvm::set_linkage(g, base::linkage_to_llvm(linkage));
40 llvm::set_visibility(g, base::visibility_to_llvm(visibility));
41 self.assume_dso_local(g, false);
42
43 self.instances.borrow_mut().insert(instance, g);
44 }
45
46 fn predefine_fn(
47 &self,
48 instance: Instance<'tcx>,
49 linkage: Linkage,
50 visibility: Visibility,
51 symbol_name: &str,
52 ) {
53 assert!(!instance.args.has_infer());
54
55 let fn_abi = self.fn_abi_of_instance(instance, ty::List::empty());
56 let lldecl = self.declare_fn(symbol_name, fn_abi, Some(instance));
57 llvm::set_linkage(lldecl, base::linkage_to_llvm(linkage));
58 let attrs = self.tcx.codegen_fn_attrs(instance.def_id());
59 base::set_link_section(lldecl, attrs);
60 if (linkage == Linkage::LinkOnceODR || linkage == Linkage::WeakODR)
61 && self.tcx.sess.target.supports_comdat()
62 {
63 llvm::SetUniqueComdat(self.llmod, lldecl);
64 }
65
66 if linkage != Linkage::Internal && self.tcx.is_compiler_builtins(LOCAL_CRATE) {
71 llvm::set_visibility(lldecl, llvm::Visibility::Hidden);
72 } else {
73 llvm::set_visibility(lldecl, base::visibility_to_llvm(visibility));
74 }
75
76 debug!("predefine_fn: instance = {:?}", instance);
77
78 self.assume_dso_local(lldecl, false);
79
80 self.instances.borrow_mut().insert(instance, lldecl);
81 }
82}
83
84impl CodegenCx<'_, '_> {
85 pub(crate) fn assume_dso_local(&self, llval: &llvm::Value, is_declaration: bool) -> bool {
89 let assume = self.should_assume_dso_local(llval, is_declaration);
90 if assume {
91 llvm::set_dso_local(llval);
92 }
93 assume
94 }
95
96 fn should_assume_dso_local(&self, llval: &llvm::Value, is_declaration: bool) -> bool {
97 let linkage = llvm::get_linkage(llval);
98 let visibility = llvm::get_visibility(llval);
99
100 if matches!(linkage, llvm::Linkage::InternalLinkage | llvm::Linkage::PrivateLinkage) {
101 return true;
102 }
103
104 if visibility != llvm::Visibility::Default && linkage != llvm::Linkage::ExternalWeakLinkage
105 {
106 return true;
107 }
108
109 let all_exe = self.tcx.crate_types().iter().all(|ty| *ty == CrateType::Executable);
111 let is_declaration_for_linker =
112 is_declaration || linkage == llvm::Linkage::AvailableExternallyLinkage;
113 if all_exe && !is_declaration_for_linker {
114 return true;
115 }
116
117 if matches!(&*self.tcx.sess.target.arch, "powerpc64" | "powerpc64le") {
119 return false;
120 }
121
122 if self.tcx.sess.target.is_like_osx {
124 return false;
125 }
126
127 if self.tcx.sess.relocation_model() == RelocModel::Pie && !is_declaration {
130 return true;
131 }
132
133 let is_thread_local_var = unsafe { llvm::LLVMIsAGlobalVariable(llval) }
135 .is_some_and(|v| unsafe { llvm::LLVMIsThreadLocal(v) } == llvm::True);
136 if is_thread_local_var {
137 return false;
138 }
139
140 if let Some(direct) = self.tcx.sess.direct_access_external_data() {
142 return direct;
143 }
144
145 self.tcx.sess.relocation_model() == RelocModel::Static
147 }
148}