4 use crate::context::CodegenCx;
6 use crate::type_of::LayoutLlvmExt;
7 use rustc_codegen_ssa::traits::*;
8 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
9 pub use rustc_middle::mir::mono::MonoItem;
10 use rustc_middle::mir::mono::{Linkage, Visibility};
11 use rustc_middle::ty::layout::FnAbiExt;
12 use rustc_middle::ty::{self, Instance, TypeFoldable};
13 use rustc_session::config::CrateType;
14 use rustc_target::abi::LayoutOf;
15 use rustc_target::spec::RelocModel;
18 impl PreDefineMethods<'tcx> for CodegenCx<'ll, 'tcx> {
23 visibility: Visibility,
26 let instance = Instance::mono(self.tcx, def_id);
27 let ty = instance.ty(self.tcx, ty::ParamEnv::reveal_all());
28 let llty = self.layout_of(ty).llvm_type(self);
30 let g = self.define_global(symbol_name, llty).unwrap_or_else(|| {
31 self.sess().span_fatal(
32 self.tcx.def_span(def_id),
33 &format!("symbol `{}` is already defined", symbol_name),
38 llvm::LLVMRustSetLinkage(g, base::linkage_to_llvm(linkage));
39 llvm::LLVMRustSetVisibility(g, base::visibility_to_llvm(visibility));
40 if self.should_assume_dso_local(g, false) {
41 llvm::LLVMRustSetDSOLocal(g, true);
45 self.instances.borrow_mut().insert(instance, g);
50 instance: Instance<'tcx>,
52 visibility: Visibility,
55 assert!(!instance.substs.needs_infer());
57 let fn_abi = FnAbi::of_instance(self, instance, &[]);
58 let lldecl = self.declare_fn(symbol_name, &fn_abi);
59 unsafe { llvm::LLVMRustSetLinkage(lldecl, base::linkage_to_llvm(linkage)) };
60 let attrs = self.tcx.codegen_fn_attrs(instance.def_id());
61 base::set_link_section(lldecl, &attrs);
62 if linkage == Linkage::LinkOnceODR || linkage == Linkage::WeakODR {
63 llvm::SetUniqueComdat(self.llmod, lldecl);
66 // If we're compiling the compiler-builtins crate, e.g., the equivalent of
67 // compiler-rt, then we want to implicitly compile everything with hidden
68 // visibility as we're going to link this object all over the place but
69 // don't want the symbols to get exported.
70 if linkage != Linkage::Internal
71 && linkage != Linkage::Private
72 && self.tcx.is_compiler_builtins(LOCAL_CRATE)
75 llvm::LLVMRustSetVisibility(lldecl, llvm::Visibility::Hidden);
79 llvm::LLVMRustSetVisibility(lldecl, base::visibility_to_llvm(visibility));
83 debug!("predefine_fn: instance = {:?}", instance);
85 attributes::from_fn_attrs(self, lldecl, instance);
88 if self.should_assume_dso_local(lldecl, false) {
89 llvm::LLVMRustSetDSOLocal(lldecl, true);
93 self.instances.borrow_mut().insert(instance, lldecl);
97 impl CodegenCx<'ll, 'tcx> {
98 /// Whether a definition or declaration can be assumed to be local to a group of
99 /// libraries that form a single DSO or executable.
100 pub(crate) unsafe fn should_assume_dso_local(
103 is_declaration: bool,
105 let linkage = llvm::LLVMRustGetLinkage(llval);
106 let visibility = llvm::LLVMRustGetVisibility(llval);
108 if matches!(linkage, llvm::Linkage::InternalLinkage | llvm::Linkage::PrivateLinkage) {
112 if visibility != llvm::Visibility::Default && linkage != llvm::Linkage::ExternalWeakLinkage
117 // Symbols from executables can't really be imported any further.
118 let all_exe = self.tcx.sess.crate_types().iter().all(|ty| *ty == CrateType::Executable);
119 let is_declaration_for_linker =
120 is_declaration || linkage == llvm::Linkage::AvailableExternallyLinkage;
121 if all_exe && !is_declaration_for_linker {
125 // PowerPC64 prefers TOC indirection to avoid copy relocations.
126 if matches!(&*self.tcx.sess.target.arch, "powerpc64" | "powerpc64le") {
130 // Thread-local variables generally don't support copy relocations.
131 let is_thread_local_var = llvm::LLVMIsAGlobalVariable(llval)
132 .map(|v| llvm::LLVMIsThreadLocal(v) == llvm::True)
134 if is_thread_local_var {
138 // Static relocation model should force copy relocations everywhere.
139 if self.tcx.sess.relocation_model() == RelocModel::Static {