3 use crate::context::CodegenCx;
5 use crate::type_of::LayoutLlvmExt;
6 use rustc_codegen_ssa::traits::*;
7 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
8 pub use rustc_middle::mir::mono::MonoItem;
9 use rustc_middle::mir::mono::{Linkage, Visibility};
10 use rustc_middle::ty::layout::{FnAbiOf, LayoutOf};
11 use rustc_middle::ty::{self, Instance, TypeVisitable};
12 use rustc_session::config::CrateType;
13 use rustc_target::spec::RelocModel;
15 impl<'tcx> PreDefineMethods<'tcx> for CodegenCx<'_, 'tcx> {
20 visibility: Visibility,
23 let instance = Instance::mono(self.tcx, def_id);
24 let ty = instance.ty(self.tcx, ty::ParamEnv::reveal_all());
25 let llty = self.layout_of(ty).llvm_type(self);
27 let g = self.define_global(symbol_name, llty).unwrap_or_else(|| {
28 self.sess().span_fatal(
29 self.tcx.def_span(def_id),
30 &format!("symbol `{}` is already defined", symbol_name),
35 llvm::LLVMRustSetLinkage(g, base::linkage_to_llvm(linkage));
36 llvm::LLVMRustSetVisibility(g, base::visibility_to_llvm(visibility));
37 if self.should_assume_dso_local(g, false) {
38 llvm::LLVMRustSetDSOLocal(g, true);
42 self.instances.borrow_mut().insert(instance, g);
47 instance: Instance<'tcx>,
49 visibility: Visibility,
52 assert!(!instance.substs.needs_infer());
54 let fn_abi = self.fn_abi_of_instance(instance, ty::List::empty());
55 let lldecl = self.declare_fn(symbol_name, fn_abi);
56 unsafe { llvm::LLVMRustSetLinkage(lldecl, base::linkage_to_llvm(linkage)) };
57 let attrs = self.tcx.codegen_fn_attrs(instance.def_id());
58 base::set_link_section(lldecl, attrs);
59 if linkage == Linkage::LinkOnceODR || linkage == Linkage::WeakODR {
60 llvm::SetUniqueComdat(self.llmod, lldecl);
63 // If we're compiling the compiler-builtins crate, e.g., the equivalent of
64 // compiler-rt, then we want to implicitly compile everything with hidden
65 // visibility as we're going to link this object all over the place but
66 // don't want the symbols to get exported.
67 if linkage != Linkage::Internal
68 && linkage != Linkage::Private
69 && self.tcx.is_compiler_builtins(LOCAL_CRATE)
72 llvm::LLVMRustSetVisibility(lldecl, llvm::Visibility::Hidden);
76 llvm::LLVMRustSetVisibility(lldecl, base::visibility_to_llvm(visibility));
80 debug!("predefine_fn: instance = {:?}", instance);
82 attributes::from_fn_attrs(self, lldecl, instance);
85 if self.should_assume_dso_local(lldecl, false) {
86 llvm::LLVMRustSetDSOLocal(lldecl, true);
90 self.instances.borrow_mut().insert(instance, lldecl);
94 impl CodegenCx<'_, '_> {
95 /// Whether a definition or declaration can be assumed to be local to a group of
96 /// libraries that form a single DSO or executable.
97 pub(crate) unsafe fn should_assume_dso_local(
100 is_declaration: bool,
102 let linkage = llvm::LLVMRustGetLinkage(llval);
103 let visibility = llvm::LLVMRustGetVisibility(llval);
105 if matches!(linkage, llvm::Linkage::InternalLinkage | llvm::Linkage::PrivateLinkage) {
109 if visibility != llvm::Visibility::Default && linkage != llvm::Linkage::ExternalWeakLinkage
114 // Symbols from executables can't really be imported any further.
115 let all_exe = self.tcx.sess.crate_types().iter().all(|ty| *ty == CrateType::Executable);
116 let is_declaration_for_linker =
117 is_declaration || linkage == llvm::Linkage::AvailableExternallyLinkage;
118 if all_exe && !is_declaration_for_linker {
122 // PowerPC64 prefers TOC indirection to avoid copy relocations.
123 if matches!(&*self.tcx.sess.target.arch, "powerpc64" | "powerpc64le") {
127 // Thread-local variables generally don't support copy relocations.
128 let is_thread_local_var = llvm::LLVMIsAGlobalVariable(llval)
129 .map(|v| llvm::LLVMIsThreadLocal(v) == llvm::True)
131 if is_thread_local_var {
135 // Match clang by only supporting COFF and ELF for now.
136 if self.tcx.sess.target.is_like_osx {
140 // Static relocation model should force copy relocations everywhere.
141 if self.tcx.sess.relocation_model() == RelocModel::Static {
145 // With pie relocation model calls of functions defined in the translation
146 // unit can use copy relocations.
147 self.tcx.sess.relocation_model() == RelocModel::Pie && !is_declaration