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refactor: Remove LLVMRustInsertPrivateGlobal and define_private_global #147488

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Merged
merged 1 commit into from
Oct 9, 2025
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refactor: Remove LLVMRustInsertPrivateGlobal and define_private_global #147488

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6 changes: 4 additions & 2 deletions compiler/rustc_codegen_llvm/src/consts.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -240,11 +240,13 @@ impl<'ll> CodegenCx<'ll, '_> {
let gv = self.define_global(&name, self.val_ty(cv)).unwrap_or_else(|| {
bug!("symbol `{}` is already defined", name);
});
llvm::set_linkage(gv, llvm::Linkage::PrivateLinkage);
gv
}
_ => self.define_private_global(self.val_ty(cv)),
_ => self.define_global("", self.val_ty(cv)).unwrap_or_else(|| {
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@RalfJung RalfJung Oct 16, 2025 •
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What on Earth does it mean to give a global the empty string as the name?!? This is not documented anywhere that I could find. (I checked define_global and a few of the functions it calls.)

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The change done after @nikic's review comment doesn't seem to match what was suggested.

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@nikic nikic Oct 16, 2025 •
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An empty string name is how you create an anonymous symbol.

This is the same thing the old code did, it was just hidden behind a const Twine &Name = "" default value.

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@RalfJung RalfJung Oct 16, 2025 •
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Does "anonymous" mean "guaranteed fresh"?
And get_defined_value("") always returns None?

The bug! below this line makes it sound like "anonymous global symbol is already defined" is an actual error condition, but if it is truly fresh then that adds to my confusion.

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Yes. This kind of global is considered "unnamed" and will be rendered as @42 or similar when printed. The bug! here can't fail.

Do I understand correctly that the suggestion here is to replace the call to define_global() with declare_global(), which doesn't check existence of the global first, which also means we don't need this unwrap?

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I hadn't even though of that, but that sounds like a good idea -- together with documentation for declare_global that says what happens when the name is empty.

bug!("anonymous global symbol is already defined");
}),
};
llvm::set_linkage(gv, llvm::Linkage::PrivateLinkage);
llvm::set_initializer(gv, cv);
set_global_alignment(self, gv, align);
llvm::set_unnamed_address(gv, llvm::UnnamedAddr::Global);
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7 changes: 0 additions & 7 deletions compiler/rustc_codegen_llvm/src/declare.rs
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Expand Up @@ -230,13 +230,6 @@ impl<'ll, CX: Borrow<SCx<'ll>>> GenericCx<'ll, CX> {
}
}

/// Declare a private global
///
/// Use this function when you intend to define a global without a name.
pub(crate) fn define_private_global(&self, ty: &'ll Type) -> &'ll Value {
unsafe { llvm::LLVMRustInsertPrivateGlobal(self.llmod(), ty) }
}

/// Gets declared value by name.
pub(crate) fn get_declared_value(&self, name: &str) -> Option<&'ll Value> {
debug!("get_declared_value(name={:?})", name);
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1 change: 0 additions & 1 deletion compiler/rustc_codegen_llvm/src/llvm/ffi.rs
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Expand Up @@ -1954,7 +1954,6 @@ unsafe extern "C" {
NameLen: size_t,
T: &'a Type,
) -> &'a Value;
pub(crate) fn LLVMRustInsertPrivateGlobal<'a>(M: &'a Module, T: &'a Type) -> &'a Value;
pub(crate) fn LLVMRustGetNamedValue(
M: &Module,
Name: *const c_char,
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6 changes: 0 additions & 6 deletions compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
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Expand Up @@ -228,12 +228,6 @@ extern "C" LLVMValueRef LLVMRustGetOrInsertGlobal(LLVMModuleRef M,
return wrap(GV);
}

extern "C" LLVMValueRef LLVMRustInsertPrivateGlobal(LLVMModuleRef M,
LLVMTypeRef Ty) {
return wrap(new GlobalVariable(*unwrap(M), unwrap(Ty), false,
GlobalValue::PrivateLinkage, nullptr));
}

// Must match the layout of `rustc_codegen_llvm::llvm::ffi::AttributeKind`.
enum class LLVMRustAttributeKind {
AlwaysInline = 0,
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