1 //! Declare various LLVM values.
3 //! Prefer using functions and methods from this module rather than calling LLVM
4 //! functions directly. These functions do some additional work to ensure we do
5 //! the right thing given the preconceptions of codegen.
7 //! Some useful guidelines:
9 //! * Use declare_* family of methods if you are declaring, but are not
10 //! interested in defining the Value they return.
11 //! * Use define_* family of methods when you might be defining the Value.
12 //! * When in doubt, define.
14 use crate::abi::{FnAbi, FnAbiLlvmExt};
15 use crate::attributes;
16 use crate::context::CodegenCx;
18 use crate::llvm::AttributePlace::Function;
19 use crate::type_::Type;
20 use crate::value::Value;
21 use rustc_codegen_ssa::traits::TypeMembershipMethods;
22 use rustc_middle::ty::Ty;
23 use rustc_symbol_mangling::typeid::typeid_for_fnabi;
24 use smallvec::SmallVec;
27 /// Declare a function.
29 /// If there’s a value with the same name already declared, the function will
30 /// update the declaration and return existing Value instead.
31 fn declare_raw_fn<'ll>(
32 cx: &CodegenCx<'ll, '_>,
34 callconv: llvm::CallConv,
35 unnamed: llvm::UnnamedAddr,
38 debug!("declare_raw_fn(name={:?}, ty={:?})", name, ty);
40 llvm::LLVMRustGetOrInsertFunction(cx.llmod, name.as_ptr().cast(), name.len(), ty)
43 llvm::SetFunctionCallConv(llfn, callconv);
44 llvm::SetUnnamedAddress(llfn, unnamed);
46 let mut attrs = SmallVec::<[_; 4]>::new();
48 if cx.tcx.sess.opts.cg.no_redzone.unwrap_or(cx.tcx.sess.target.disable_redzone) {
49 attrs.push(llvm::AttributeKind::NoRedZone.create_attr(cx.llcx));
52 attrs.extend(attributes::non_lazy_bind_attr(cx));
54 attributes::apply_to_llfn(llfn, Function, &attrs);
59 impl<'ll, 'tcx> CodegenCx<'ll, 'tcx> {
60 /// Declare a global value.
62 /// If there’s a value with the same name already declared, the function will
63 /// return its Value instead.
64 pub fn declare_global(&self, name: &str, ty: &'ll Type) -> &'ll Value {
65 debug!("declare_global(name={:?})", name);
66 unsafe { llvm::LLVMRustGetOrInsertGlobal(self.llmod, name.as_ptr().cast(), name.len(), ty) }
69 /// Declare a C ABI function.
71 /// Only use this for foreign function ABIs and glue. For Rust functions use
72 /// `declare_fn` instead.
74 /// If there’s a value with the same name already declared, the function will
75 /// update the declaration and return existing Value instead.
79 unnamed: llvm::UnnamedAddr,
82 declare_raw_fn(self, name, llvm::CCallConv, unnamed, fn_type)
85 /// Declare a Rust function.
87 /// If there’s a value with the same name already declared, the function will
88 /// update the declaration and return existing Value instead.
89 pub fn declare_fn(&self, name: &str, fn_abi: &FnAbi<'tcx, Ty<'tcx>>) -> &'ll Value {
90 debug!("declare_rust_fn(name={:?}, fn_abi={:?})", name, fn_abi);
92 // Function addresses in Rust are never significant, allowing functions to
94 let llfn = declare_raw_fn(
98 llvm::UnnamedAddr::Global,
99 fn_abi.llvm_type(self),
101 fn_abi.apply_attrs_llfn(self, llfn);
103 if self.tcx.sess.is_sanitizer_cfi_enabled() {
104 let typeid = typeid_for_fnabi(self.tcx, fn_abi);
105 self.set_type_metadata(llfn, typeid);
111 /// Declare a global with an intention to define it.
113 /// Use this function when you intend to define a global. This function will
114 /// return `None` if the name already has a definition associated with it. In that
115 /// case an error should be reported to the user, because it usually happens due
116 /// to user’s fault (e.g., misuse of `#[no_mangle]` or `#[export_name]` attributes).
117 pub fn define_global(&self, name: &str, ty: &'ll Type) -> Option<&'ll Value> {
118 if self.get_defined_value(name).is_some() {
121 Some(self.declare_global(name, ty))
125 /// Declare a private global
127 /// Use this function when you intend to define a global without a name.
128 pub fn define_private_global(&self, ty: &'ll Type) -> &'ll Value {
129 unsafe { llvm::LLVMRustInsertPrivateGlobal(self.llmod, ty) }
132 /// Gets declared value by name.
133 pub fn get_declared_value(&self, name: &str) -> Option<&'ll Value> {
134 debug!("get_declared_value(name={:?})", name);
135 unsafe { llvm::LLVMRustGetNamedValue(self.llmod, name.as_ptr().cast(), name.len()) }
138 /// Gets defined or externally defined (AvailableExternally linkage) value by
140 pub fn get_defined_value(&self, name: &str) -> Option<&'ll Value> {
141 self.get_declared_value(name).and_then(|val| {
142 let declaration = unsafe { llvm::LLVMIsDeclaration(val) != 0 };
143 if !declaration { Some(val) } else { None }