use crate::attributes; use crate::base; use crate::context::CodegenCx; use crate::llvm; use crate::type_of::LayoutLlvmExt; use rustc_codegen_ssa::traits::*; use rustc_hir::def_id::{DefId, LOCAL_CRATE}; pub use rustc_middle::mir::mono::MonoItem; use rustc_middle::mir::mono::{Linkage, Visibility}; use rustc_middle::ty::layout::{FnAbiOf, LayoutOf}; use rustc_middle::ty::{self, Instance, TypeVisitable}; use rustc_session::config::CrateType; use rustc_target::spec::RelocModel; use tracing::debug; impl<'tcx> PreDefineMethods<'tcx> for CodegenCx<'_, 'tcx> { fn predefine_static( &self, def_id: DefId, linkage: Linkage, visibility: Visibility, symbol_name: &str, ) { let instance = Instance::mono(self.tcx, def_id); let ty = instance.ty(self.tcx, ty::ParamEnv::reveal_all()); let llty = self.layout_of(ty).llvm_type(self); let g = self.define_global(symbol_name, llty).unwrap_or_else(|| { self.sess().span_fatal( self.tcx.def_span(def_id), &format!("symbol `{}` is already defined", symbol_name), ) }); unsafe { llvm::LLVMRustSetLinkage(g, base::linkage_to_llvm(linkage)); llvm::LLVMRustSetVisibility(g, base::visibility_to_llvm(visibility)); if self.should_assume_dso_local(g, false) { llvm::LLVMRustSetDSOLocal(g, true); } } self.instances.borrow_mut().insert(instance, g); } fn predefine_fn( &self, instance: Instance<'tcx>, linkage: Linkage, visibility: Visibility, symbol_name: &str, ) { assert!(!instance.substs.needs_infer()); let fn_abi = self.fn_abi_of_instance(instance, ty::List::empty()); let lldecl = self.declare_fn(symbol_name, fn_abi); unsafe { llvm::LLVMRustSetLinkage(lldecl, base::linkage_to_llvm(linkage)) }; let attrs = self.tcx.codegen_fn_attrs(instance.def_id()); base::set_link_section(lldecl, attrs); if linkage == Linkage::LinkOnceODR || linkage == Linkage::WeakODR { llvm::SetUniqueComdat(self.llmod, lldecl); } // If we're compiling the compiler-builtins crate, e.g., the equivalent of // compiler-rt, then we want to implicitly compile everything with hidden // visibility as we're going to link this object all over the place but // don't want the symbols to get exported. if linkage != Linkage::Internal && linkage != Linkage::Private && self.tcx.is_compiler_builtins(LOCAL_CRATE) { unsafe { llvm::LLVMRustSetVisibility(lldecl, llvm::Visibility::Hidden); } } else { unsafe { llvm::LLVMRustSetVisibility(lldecl, base::visibility_to_llvm(visibility)); } } debug!("predefine_fn: instance = {:?}", instance); attributes::from_fn_attrs(self, lldecl, instance); unsafe { if self.should_assume_dso_local(lldecl, false) { llvm::LLVMRustSetDSOLocal(lldecl, true); } } self.instances.borrow_mut().insert(instance, lldecl); } } impl CodegenCx<'_, '_> { /// Whether a definition or declaration can be assumed to be local to a group of /// libraries that form a single DSO or executable. pub(crate) unsafe fn should_assume_dso_local( &self, llval: &llvm::Value, is_declaration: bool, ) -> bool { let linkage = llvm::LLVMRustGetLinkage(llval); let visibility = llvm::LLVMRustGetVisibility(llval); if matches!(linkage, llvm::Linkage::InternalLinkage | llvm::Linkage::PrivateLinkage) { return true; } if visibility != llvm::Visibility::Default && linkage != llvm::Linkage::ExternalWeakLinkage { return true; } // Symbols from executables can't really be imported any further. let all_exe = self.tcx.sess.crate_types().iter().all(|ty| *ty == CrateType::Executable); let is_declaration_for_linker = is_declaration || linkage == llvm::Linkage::AvailableExternallyLinkage; if all_exe && !is_declaration_for_linker { return true; } // PowerPC64 prefers TOC indirection to avoid copy relocations. if matches!(&*self.tcx.sess.target.arch, "powerpc64" | "powerpc64le") { return false; } // Thread-local variables generally don't support copy relocations. let is_thread_local_var = llvm::LLVMIsAGlobalVariable(llval) .map(|v| llvm::LLVMIsThreadLocal(v) == llvm::True) .unwrap_or(false); if is_thread_local_var { return false; } // Match clang by only supporting COFF and ELF for now. if self.tcx.sess.target.is_like_osx { return false; } // Static relocation model should force copy relocations everywhere. if self.tcx.sess.relocation_model() == RelocModel::Static { return true; } // With pie relocation model calls of functions defined in the translation // unit can use copy relocations. self.tcx.sess.relocation_model() == RelocModel::Pie && !is_declaration } }