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Diffstat (limited to '')
-rw-r--r-- | compiler/rustc_codegen_llvm/src/mono_item.rs | 150 |
1 files changed, 150 insertions, 0 deletions
diff --git a/compiler/rustc_codegen_llvm/src/mono_item.rs b/compiler/rustc_codegen_llvm/src/mono_item.rs new file mode 100644 index 000000000..6e9428485 --- /dev/null +++ b/compiler/rustc_codegen_llvm/src/mono_item.rs @@ -0,0 +1,150 @@ +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 + } +} |