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Manually set dso_local when its valid to do so

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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]: 3001d080c8/clang/lib/CodeGen/CodeGenModule.cpp (L945-L1039)
This commit is contained in:
Simonas Kazlauskas
2021-03-28 00:11:24 +02:00
parent 9b0edb7fdd
commit 2f000a78bf
30 changed files with 221 additions and 122 deletions
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19
compiler/rustc_codegen_llvm/src/callee.rs
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@@ -14,6 +14,7 @@ use tracing::debug;
use rustc_middle::ty::layout::{FnAbiExt, HasTyCtxt};
use rustc_middle::ty::{self, Instance, TypeFoldable};
use rustc_target::spec::RelocModel;
/// Codegens a reference to a fn/method item, monomorphizing and
/// inlining as it goes.
@@ -170,17 +171,19 @@ pub fn get_fn(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'tcx>) -> &'ll Value
}
}
}
}
// MinGW: For backward compatibility we rely on the linker to decide whether it
// should use dllimport for functions.
if cx.use_dll_storage_attrs
&& tcx.is_dllimport_foreign_item(instance_def_id)
&& tcx.sess.target.env != "gnu"
{
unsafe {
// MinGW: For backward compatibility we rely on the linker to decide whether it
// should use dllimport for functions.
if cx.use_dll_storage_attrs
&& tcx.is_dllimport_foreign_item(instance_def_id)
&& tcx.sess.target.env != "gnu"
{
llvm::LLVMSetDLLStorageClass(llfn, llvm::DLLStorageClass::DllImport);
}
if cx.tcx.sess.relocation_model() == RelocModel::Static {
llvm::LLVMRustSetDSOLocal(llfn, true);
}
}
llfn