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|
//! Declare various LLVM values.
//!
//! Prefer using functions and methods from this module rather than calling LLVM
//! functions directly. These functions do some additional work to ensure we do
//! the right thing given the preconceptions of codegen.
//!
//! Some useful guidelines:
//!
//! * Use declare_* family of methods if you are declaring, but are not
//! interested in defining the Value they return.
//! * Use define_* family of methods when you might be defining the Value.
//! * When in doubt, define.
use crate::abi::{FnAbi, FnAbiLlvmExt};
use crate::attributes;
use crate::context::CodegenCx;
use crate::llvm;
use crate::llvm::AttributePlace::Function;
use crate::type_::Type;
use crate::value::Value;
use rustc_codegen_ssa::traits::*;
use rustc_middle::ty::Ty;
use tracing::debug;
/// Declare a function.
///
/// If there’s a value with the same name already declared, the function will
/// update the declaration and return existing Value instead.
fn declare_raw_fn(
cx: &CodegenCx<'ll, '_>,
name: &str,
callconv: llvm::CallConv,
ty: &'ll Type,
) -> &'ll Value {
debug!("declare_raw_fn(name={:?}, ty={:?})", name, ty);
let llfn = unsafe {
llvm::LLVMRustGetOrInsertFunction(cx.llmod, name.as_ptr().cast(), name.len(), ty)
};
llvm::SetFunctionCallConv(llfn, callconv);
// Function addresses in Rust are never significant, allowing functions to
// be merged.
llvm::SetUnnamedAddress(llfn, llvm::UnnamedAddr::Global);
if cx.tcx.sess.opts.cg.no_redzone.unwrap_or(cx.tcx.sess.target.disable_redzone) {
llvm::Attribute::NoRedZone.apply_llfn(Function, llfn);
}
attributes::default_optimisation_attrs(cx.tcx.sess, llfn);
attributes::non_lazy_bind(cx.sess(), llfn);
llfn
}
impl CodegenCx<'ll, 'tcx> {
/// Declare a global value.
///
/// If there’s a value with the same name already declared, the function will
/// return its Value instead.
pub fn declare_global(&self, name: &str, ty: &'ll Type) -> &'ll Value {
debug!("declare_global(name={:?})", name);
unsafe { llvm::LLVMRustGetOrInsertGlobal(self.llmod, name.as_ptr().cast(), name.len(), ty) }
}
/// Declare a C ABI function.
///
/// Only use this for foreign function ABIs and glue. For Rust functions use
/// `declare_fn` instead.
///
/// If there’s a value with the same name already declared, the function will
/// update the declaration and return existing Value instead.
pub fn declare_cfn(&self, name: &str, fn_type: &'ll Type) -> &'ll Value {
declare_raw_fn(self, name, llvm::CCallConv, fn_type)
}
/// Declare a Rust function.
///
/// If there’s a value with the same name already declared, the function will
/// update the declaration and return existing Value instead.
pub fn declare_fn(&self, name: &str, fn_abi: &FnAbi<'tcx, Ty<'tcx>>) -> &'ll Value {
debug!("declare_rust_fn(name={:?}, fn_abi={:?})", name, fn_abi);
let llfn = declare_raw_fn(self, name, fn_abi.llvm_cconv(), fn_abi.llvm_type(self));
fn_abi.apply_attrs_llfn(self, llfn);
llfn
}
/// Declare a global with an intention to define it.
///
/// Use this function when you intend to define a global. This function will
/// return `None` if the name already has a definition associated with it. In that
/// case an error should be reported to the user, because it usually happens due
/// to user’s fault (e.g., misuse of `#[no_mangle]` or `#[export_name]` attributes).
pub fn define_global(&self, name: &str, ty: &'ll Type) -> Option<&'ll Value> {
if self.get_defined_value(name).is_some() {
None
} else {
Some(self.declare_global(name, ty))
}
}
/// Declare a private global
///
/// Use this function when you intend to define a global without a name.
pub fn define_private_global(&self, ty: &'ll Type) -> &'ll Value {
unsafe { llvm::LLVMRustInsertPrivateGlobal(self.llmod, ty) }
}
/// Gets declared value by name.
pub fn get_declared_value(&self, name: &str) -> Option<&'ll Value> {
debug!("get_declared_value(name={:?})", name);
unsafe { llvm::LLVMRustGetNamedValue(self.llmod, name.as_ptr().cast(), name.len()) }
}
/// Gets defined or externally defined (AvailableExternally linkage) value by
/// name.
pub fn get_defined_value(&self, name: &str) -> Option<&'ll Value> {
self.get_declared_value(name).and_then(|val| {
let declaration = unsafe { llvm::LLVMIsDeclaration(val) != 0 };
if !declaration { Some(val) } else { None }
})
}
}
|
