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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
}
}
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