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Rollup merge of rust-lang#76872 - khyperia:remove_declare_methods, r=…
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…eddyb

Remove DeclareMethods

Most of the `DeclareMethods` API was only used internally by rustc_codegen_llvm. As such, it makes no sense to require other backends to implement them.

(`get_declared_value` and `declare_cfn` were used, in one place, specific to the `main` symbol, which I've replaced with a more specialized function to allow more flexibility in implementation - the intent is that `declare_c_main` can go away once we do something more clever, e.g. @eddyb has ideas around having a MIR shim or somesuch we can explore in a follow-up PR)
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Dylan-DPC authored Sep 19, 2020
2 parents ad0ef4b + 0bc405e commit e1f3ce3
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Showing 6 changed files with 62 additions and 66 deletions.
11 changes: 11 additions & 0 deletions compiler/rustc_codegen_llvm/src/context.rs
Original file line number Diff line number Diff line change
Expand Up @@ -433,6 +433,17 @@ impl MiscMethods<'tcx> for CodegenCx<'ll, 'tcx> {
llvm::LLVMSetSection(g, section.as_ptr());
}
}

fn declare_c_main(&self, fn_type: Self::Type) -> Option<Self::Function> {
if self.get_declared_value("main").is_none() {
Some(self.declare_cfn("main", fn_type))
} else {
// If the symbol already exists, it is an error: for example, the user wrote
// #[no_mangle] extern "C" fn main(..) {..}
// instead of #[start]
None
}
}
}

impl CodegenCx<'b, 'tcx> {
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43 changes: 35 additions & 8 deletions compiler/rustc_codegen_llvm/src/declare.rs
Original file line number Diff line number Diff line change
Expand Up @@ -51,42 +51,69 @@ fn declare_raw_fn(
llfn
}

impl DeclareMethods<'tcx> for CodegenCx<'ll, 'tcx> {
fn declare_global(&self, name: &str, ty: &'ll Type) -> &'ll Value {
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) }
}

fn declare_cfn(&self, name: &str, fn_type: &'ll Type) -> &'ll Value {
/// 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)
}

fn declare_fn(&self, name: &str, fn_abi: &FnAbi<'tcx, Ty<'tcx>>) -> &'ll Value {
/// 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
}

fn define_global(&self, name: &str, ty: &'ll Type) -> Option<&'ll Value> {
/// 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))
}
}

fn define_private_global(&self, ty: &'ll Type) -> &'ll Value {
/// 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) }
}

fn get_declared_value(&self, name: &str) -> Option<&'ll Value> {
/// 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()) }
}

fn get_defined_value(&self, name: &str) -> Option<&'ll Value> {
/// 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 }
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22 changes: 12 additions & 10 deletions compiler/rustc_codegen_ssa/src/base.rs
Original file line number Diff line number Diff line change
Expand Up @@ -407,16 +407,18 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
// listing.
let main_ret_ty = cx.tcx().erase_regions(&main_ret_ty.no_bound_vars().unwrap());

if cx.get_declared_value("main").is_some() {
// FIXME: We should be smart and show a better diagnostic here.
cx.sess()
.struct_span_err(sp, "entry symbol `main` declared multiple times")
.help("did you use `#[no_mangle]` on `fn main`? Use `#[start]` instead")
.emit();
cx.sess().abort_if_errors();
bug!();
}
let llfn = cx.declare_cfn("main", llfty);
let llfn = match cx.declare_c_main(llfty) {
Some(llfn) => llfn,
None => {
// FIXME: We should be smart and show a better diagnostic here.
cx.sess()
.struct_span_err(sp, "entry symbol `main` declared multiple times")
.help("did you use `#[no_mangle]` on `fn main`? Use `#[start]` instead")
.emit();
cx.sess().abort_if_errors();
bug!();
}
};

// `main` should respect same config for frame pointer elimination as rest of code
cx.set_frame_pointer_elimination(llfn);
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46 changes: 1 addition & 45 deletions compiler/rustc_codegen_ssa/src/traits/declare.rs
Original file line number Diff line number Diff line change
@@ -1,51 +1,7 @@
use super::BackendTypes;
use rustc_hir::def_id::DefId;
use rustc_middle::mir::mono::{Linkage, Visibility};
use rustc_middle::ty::{Instance, Ty};
use rustc_target::abi::call::FnAbi;

pub trait DeclareMethods<'tcx>: BackendTypes {
/// Declare a global value.
///
/// If there’s a value with the same name already declared, the function will
/// return its Value instead.
fn declare_global(&self, name: &str, ty: Self::Type) -> Self::Value;

/// 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.
fn declare_cfn(&self, name: &str, fn_type: Self::Type) -> Self::Function;

/// 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.
fn declare_fn(&self, name: &str, fn_abi: &FnAbi<'tcx, Ty<'tcx>>) -> Self::Function;

/// 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).
fn define_global(&self, name: &str, ty: Self::Type) -> Option<Self::Value>;

/// Declare a private global
///
/// Use this function when you intend to define a global without a name.
fn define_private_global(&self, ty: Self::Type) -> Self::Value;

/// Gets declared value by name.
fn get_declared_value(&self, name: &str) -> Option<Self::Value>;

/// Gets defined or externally defined (AvailableExternally linkage) value by
/// name.
fn get_defined_value(&self, name: &str) -> Option<Self::Value>;
}
use rustc_middle::ty::Instance;

pub trait PreDefineMethods<'tcx>: BackendTypes {
fn predefine_static(
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2 changes: 2 additions & 0 deletions compiler/rustc_codegen_ssa/src/traits/misc.rs
Original file line number Diff line number Diff line change
Expand Up @@ -19,4 +19,6 @@ pub trait MiscMethods<'tcx>: BackendTypes {
fn set_frame_pointer_elimination(&self, llfn: Self::Function);
fn apply_target_cpu_attr(&self, llfn: Self::Function);
fn create_used_variable(&self);
/// Declares the extern "C" main function for the entry point. Returns None if the symbol already exists.
fn declare_c_main(&self, fn_type: Self::Type) -> Option<Self::Function>;
}
4 changes: 1 addition & 3 deletions compiler/rustc_codegen_ssa/src/traits/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -35,7 +35,7 @@ pub use self::builder::{BuilderMethods, OverflowOp};
pub use self::consts::ConstMethods;
pub use self::coverageinfo::{CoverageInfoBuilderMethods, CoverageInfoMethods};
pub use self::debuginfo::{DebugInfoBuilderMethods, DebugInfoMethods};
pub use self::declare::{DeclareMethods, PreDefineMethods};
pub use self::declare::PreDefineMethods;
pub use self::intrinsic::IntrinsicCallMethods;
pub use self::misc::MiscMethods;
pub use self::statics::{StaticBuilderMethods, StaticMethods};
Expand All @@ -60,7 +60,6 @@ pub trait CodegenMethods<'tcx>:
+ StaticMethods
+ CoverageInfoMethods
+ DebugInfoMethods<'tcx>
+ DeclareMethods<'tcx>
+ AsmMethods
+ PreDefineMethods<'tcx>
+ HasParamEnv<'tcx>
Expand All @@ -77,7 +76,6 @@ impl<'tcx, T> CodegenMethods<'tcx> for T where
+ StaticMethods
+ CoverageInfoMethods
+ DebugInfoMethods<'tcx>
+ DeclareMethods<'tcx>
+ AsmMethods
+ PreDefineMethods<'tcx>
+ HasParamEnv<'tcx>
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