Manually set dso_local when its valid to do so

This should have no real effect in most cases, as e.g. `hidden`
visibility already implies `dso_local` (or at least LLVM IR does not
preserve the `dso_local` setting if the item is already `hidden`), but
it should fix `-Crelocation-model=static` and improve codegen in
executables.

Note that this PR does not exhaustively port the logic in [clang]. Only
the obviously correct portion and what is necessary to fix a regression
from LLVM 12 that relates to `-Crelocation_model=static`.

Fixes #83335

[clang]: https://github.com/llvm/llvm-project/blob/3001d080c813da20b329303bf8f45451480e5905/clang/lib/CodeGen/CodeGenModule.cpp#L945-L1039

1 files changed, 1 insertions, 0 deletions

diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index 82cd1be3b3b..84d4fbdec34 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -1031,6 +1031,7 @@ extern "C" {
     pub fn LLVMSetSection(Global: &Value, Section: *const c_char);
     pub fn LLVMRustGetVisibility(Global: &Value) -> Visibility;
     pub fn LLVMRustSetVisibility(Global: &Value, Viz: Visibility);
+    pub fn LLVMRustSetDSOLocal(Global: &Value, is_dso_local: bool);
     pub fn LLVMGetAlignment(Global: &Value) -> c_uint;
     pub fn LLVMSetAlignment(Global: &Value, Bytes: c_uint);
     pub fn LLVMSetDLLStorageClass(V: &Value, C: DLLStorageClass);