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
+    }
+}