compiler/rustc_codegen_gcc/src/consts.rs - third_party/rust - Git at Google

 #[cfg(feature = "master")]
 use gccjit::{FnAttribute, VarAttribute, Visibility};
 use gccjit::{Function, GlobalKind, LValue, RValue, ToRValue, Type};
 use rustc_codegen_ssa::traits::{BaseTypeMethods, ConstMethods, StaticMethods};
 use rustc_hir::def::DefKind;
 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
 use rustc_middle::mir::interpret::{
     self, read_target_uint, ConstAllocation, ErrorHandled, Scalar as InterpScalar,
 };
 use rustc_middle::ty::layout::LayoutOf;
 use rustc_middle::ty::{self, Instance};
 use rustc_middle::{bug, span_bug};
 use rustc_span::def_id::DefId;
 use rustc_target::abi::{self, Align, HasDataLayout, Primitive, Size, WrappingRange};

 use crate::base;
 use crate::context::CodegenCx;
 use crate::errors::InvalidMinimumAlignment;
 use crate::type_of::LayoutGccExt;

 fn set_global_alignment<'gcc, 'tcx>(
     cx: &CodegenCx<'gcc, 'tcx>,
     gv: LValue<'gcc>,
     mut align: Align,
 ) {
     // The target may require greater alignment for globals than the type does.
     // Note: GCC and Clang also allow `__attribute__((aligned))` on variables,
     // which can force it to be smaller. Rust doesn't support this yet.
     if let Some(min) = cx.sess().target.min_global_align {
         match Align::from_bits(min) {
             Ok(min) => align = align.max(min),
             Err(err) => {
                 cx.sess().dcx().emit_err(InvalidMinimumAlignment { err: err.to_string() });
             }
         }
     }
     gv.set_alignment(align.bytes() as i32);
 }

 impl<'gcc, 'tcx> StaticMethods for CodegenCx<'gcc, 'tcx> {
     fn static_addr_of(&self, cv: RValue<'gcc>, align: Align, kind: Option<&str>) -> RValue<'gcc> {
         // TODO(antoyo): implement a proper rvalue comparison in libgccjit instead of doing the
         // following:
         for (value, variable) in &*self.const_globals.borrow() {
             if format!("{:?}", value) == format!("{:?}", cv) {
                 if let Some(global_variable) = self.global_lvalues.borrow().get(variable) {
                     let alignment = align.bits() as i32;
                     if alignment > global_variable.get_alignment() {
                         global_variable.set_alignment(alignment);
                     }
                 }
                 return *variable;
             }
         }
         let global_value = self.static_addr_of_mut(cv, align, kind);
         #[cfg(feature = "master")]
         self.global_lvalues
             .borrow()
             .get(&global_value)
             .expect("`static_addr_of_mut` did not add the global to `self.global_lvalues`")
             .global_set_readonly();
         self.const_globals.borrow_mut().insert(cv, global_value);
         global_value
     }

     #[cfg_attr(not(feature = "master"), allow(unused_mut))]
     fn codegen_static(&self, def_id: DefId) {
         let attrs = self.tcx.codegen_fn_attrs(def_id);

         let Ok((value, alloc)) = codegen_static_initializer(self, def_id) else {
             // Error has already been reported
             return;
         };
         let alloc = alloc.inner();

         // boolean SSA values are i1, but they have to be stored in i8 slots,
         // otherwise some LLVM optimization passes don't work as expected
         let val_llty = self.val_ty(value);
         if val_llty == self.type_i1() {
             unimplemented!();
         };

         let is_thread_local = attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL);
         let global = self.get_static_inner(def_id, val_llty);

         #[cfg(feature = "master")]
         if global.to_rvalue().get_type() != val_llty {
             global.to_rvalue().set_type(val_llty);
         }
         set_global_alignment(self, global, alloc.align);

         global.global_set_initializer_rvalue(value);

         // As an optimization, all shared statics which do not have interior
         // mutability are placed into read-only memory.
         if alloc.mutability.is_not() {
             #[cfg(feature = "master")]
             global.global_set_readonly();
         }

         if is_thread_local {
             // Do not allow LLVM to change the alignment of a TLS on macOS.
             //
             // By default a global's alignment can be freely increased.
             // This allows LLVM to generate more performant instructions
             // e.g., using load-aligned into a SIMD register.
             //
             // However, on macOS 10.10 or below, the dynamic linker does not
             // respect any alignment given on the TLS (radar 24221680).
             // This will violate the alignment assumption, and causing segfault at runtime.
             //
             // This bug is very easy to trigger. In `println!` and `panic!`,
             // the `LOCAL_STDOUT`/`LOCAL_STDERR` handles are stored in a TLS,
             // which the values would be `mem::replace`d on initialization.
             // The implementation of `mem::replace` will use SIMD
             // whenever the size is 32 bytes or higher. LLVM notices SIMD is used
             // and tries to align `LOCAL_STDOUT`/`LOCAL_STDERR` to a 32-byte boundary,
             // which macOS's dyld disregarded and causing crashes
             // (see issues #51794, #51758, #50867, #48866 and #44056).
             //
             // To workaround the bug, we trick LLVM into not increasing
             // the global's alignment by explicitly assigning a section to it
             // (equivalent to automatically generating a `#[link_section]` attribute).
             // See the comment in the `GlobalValue::canIncreaseAlignment()` function
             // of `lib/IR/Globals.cpp` for why this works.
             //
             // When the alignment is not increased, the optimized `mem::replace`
             // will use load-unaligned instructions instead, and thus avoiding the crash.
             //
             // We could remove this hack whenever we decide to drop macOS 10.10 support.
             if self.tcx.sess.target.options.is_like_osx {
                 // The `inspect` method is okay here because we checked for provenance, and
                 // because we are doing this access to inspect the final interpreter state
                 // (not as part of the interpreter execution).
                 //
                 // FIXME: This check requires that the (arbitrary) value of undefined bytes
                 // happens to be zero. Instead, we should only check the value of defined bytes
                 // and set all undefined bytes to zero if this allocation is headed for the
                 // BSS.
                 unimplemented!();
             }
         }

         // Wasm statics with custom link sections get special treatment as they
         // go into custom sections of the wasm executable.
         if self.tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
             if let Some(_section) = attrs.link_section {
                 unimplemented!();
             }
         } else {
             // TODO(antoyo): set link section.
         }

         if attrs.flags.contains(CodegenFnAttrFlags::USED)
             || attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER)
         {
             self.add_used_global(global.to_rvalue());
         }
     }

     /// Add a global value to a list to be stored in the `llvm.used` variable, an array of i8*.
     fn add_used_global(&self, _global: RValue<'gcc>) {
         // TODO(antoyo)
     }

     fn add_compiler_used_global(&self, global: RValue<'gcc>) {
         // NOTE: seems like GCC does not make the distinction between compiler.used and used.
         self.add_used_global(global);
     }
 }

 impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
     #[cfg_attr(not(feature = "master"), allow(unused_variables))]
     pub fn add_used_function(&self, function: Function<'gcc>) {
         #[cfg(feature = "master")]
         function.add_attribute(FnAttribute::Used);
     }

     pub fn static_addr_of_mut(
         &self,
         cv: RValue<'gcc>,
         align: Align,
         kind: Option<&str>,
     ) -> RValue<'gcc> {
         let global = match kind {
             Some(kind) if !self.tcx.sess.fewer_names() => {
                 let name = self.generate_local_symbol_name(kind);
                 // TODO(antoyo): check if it's okay that no link_section is set.

                 let typ = self.val_ty(cv).get_aligned(align.bytes());
                 let global = self.declare_private_global(&name[..], typ);
                 global
             }
             _ => {
                 let typ = self.val_ty(cv).get_aligned(align.bytes());
                 let global = self.declare_unnamed_global(typ);
                 global
             }
         };
         global.global_set_initializer_rvalue(cv);
         // TODO(antoyo): set unnamed address.
         let rvalue = global.get_address(None);
         self.global_lvalues.borrow_mut().insert(rvalue, global);
         rvalue
     }

     pub fn get_static(&self, def_id: DefId) -> LValue<'gcc> {
         let instance = Instance::mono(self.tcx, def_id);
         let DefKind::Static { nested, .. } = self.tcx.def_kind(def_id) else { bug!() };
         // Nested statics do not have a type, so pick a random type and let `define_static` figure out
         // the gcc type from the actual evaluated initializer.
         let gcc_type = if nested {
             self.type_i8()
         } else {
             let ty = instance.ty(self.tcx, ty::ParamEnv::reveal_all());
             self.layout_of(ty).gcc_type(self)
         };

         self.get_static_inner(def_id, gcc_type)
     }

     pub(crate) fn get_static_inner(&self, def_id: DefId, gcc_type: Type<'gcc>) -> LValue<'gcc> {
         let instance = Instance::mono(self.tcx, def_id);
         if let Some(&global) = self.instances.borrow().get(&instance) {
             trace!("used cached value");
             return global;
         }

         // FIXME: Once we stop removing globals in `codegen_static`, we can uncomment this code.
         // let defined_in_current_codegen_unit =
         //     self.codegen_unit.items().contains_key(&MonoItem::Static(def_id));
         // assert!(
         //     !defined_in_current_codegen_unit,
         //     "consts::get_static() should always hit the cache for \
         //          statics defined in the same CGU, but did not for `{:?}`",
         //     def_id
         // );
         let sym = self.tcx.symbol_name(instance).name;
         let fn_attrs = self.tcx.codegen_fn_attrs(def_id);

         let global = if def_id.is_local() && !self.tcx.is_foreign_item(def_id) {
             if let Some(global) = self.get_declared_value(sym) {
                 if self.val_ty(global) != self.type_ptr_to(gcc_type) {
                     span_bug!(self.tcx.def_span(def_id), "Conflicting types for static");
                 }
             }

             let is_tls = fn_attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL);
             let global = self.declare_global(
                 sym,
                 gcc_type,
                 GlobalKind::Exported,
                 is_tls,
                 fn_attrs.link_section,
             );

             if !self.tcx.is_reachable_non_generic(def_id) {
                 #[cfg(feature = "master")]
                 global.add_string_attribute(VarAttribute::Visibility(Visibility::Hidden));
             }

             global
         } else {
             check_and_apply_linkage(self, fn_attrs, gcc_type, sym)
         };

         if !def_id.is_local() {
             let needs_dll_storage_attr = false; // TODO(antoyo)

             // If this assertion triggers, there's something wrong with commandline
             // argument validation.
             debug_assert!(
                 !(self.tcx.sess.opts.cg.linker_plugin_lto.enabled()
                     && self.tcx.sess.target.options.is_like_msvc
                     && self.tcx.sess.opts.cg.prefer_dynamic)
             );

             if needs_dll_storage_attr {
                 // This item is external but not foreign, i.e., it originates from an external Rust
                 // crate. Since we don't know whether this crate will be linked dynamically or
                 // statically in the final application, we always mark such symbols as 'dllimport'.
                 // If final linkage happens to be static, we rely on compiler-emitted __imp_ stubs
                 // to make things work.
                 //
                 // However, in some scenarios we defer emission of statics to downstream
                 // crates, so there are cases where a static with an upstream DefId
                 // is actually present in the current crate. We can find out via the
                 // is_codegened_item query.
                 if !self.tcx.is_codegened_item(def_id) {
                     unimplemented!();
                 }
             }
         }

         // TODO(antoyo): set dll storage class.

         self.instances.borrow_mut().insert(instance, global);
         global
     }
 }

 pub fn const_alloc_to_gcc<'gcc, 'tcx>(
     cx: &CodegenCx<'gcc, 'tcx>,
     alloc: ConstAllocation<'tcx>,
 ) -> RValue<'gcc> {
     let alloc = alloc.inner();
     let mut llvals = Vec::with_capacity(alloc.provenance().ptrs().len() + 1);
     let dl = cx.data_layout();
     let pointer_size = dl.pointer_size.bytes() as usize;

     let mut next_offset = 0;
     for &(offset, prov) in alloc.provenance().ptrs().iter() {
         let alloc_id = prov.alloc_id();
         let offset = offset.bytes();
         assert_eq!(offset as usize as u64, offset);
         let offset = offset as usize;
         if offset > next_offset {
             // This `inspect` is okay since we have checked that it is not within a pointer with provenance, it
             // is within the bounds of the allocation, and it doesn't affect interpreter execution
             // (we inspect the result after interpreter execution). Any undef byte is replaced with
             // some arbitrary byte value.
             //
             // FIXME: relay undef bytes to codegen as undef const bytes
             let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(next_offset..offset);
             llvals.push(cx.const_bytes(bytes));
         }
         let ptr_offset = read_target_uint(
             dl.endian,
             // This `inspect` is okay since it is within the bounds of the allocation, it doesn't
             // affect interpreter execution (we inspect the result after interpreter execution),
             // and we properly interpret the provenance as a relocation pointer offset.
             alloc.inspect_with_uninit_and_ptr_outside_interpreter(offset..(offset + pointer_size)),
         )
         .expect("const_alloc_to_llvm: could not read relocation pointer")
             as u64;

         let address_space = cx.tcx.global_alloc(alloc_id).address_space(cx);

         llvals.push(cx.scalar_to_backend(
             InterpScalar::from_pointer(
                 interpret::Pointer::new(prov, Size::from_bytes(ptr_offset)),
                 &cx.tcx,
             ),
             abi::Scalar::Initialized {
                 value: Primitive::Pointer(address_space),
                 valid_range: WrappingRange::full(dl.pointer_size),
             },
             cx.type_i8p_ext(address_space),
         ));
         next_offset = offset + pointer_size;
     }
     if alloc.len() >= next_offset {
         let range = next_offset..alloc.len();
         // This `inspect` is okay since we have check that it is after all provenance, it is
         // within the bounds of the allocation, and it doesn't affect interpreter execution (we
         // inspect the result after interpreter execution). Any undef byte is replaced with some
         // arbitrary byte value.
         //
         // FIXME: relay undef bytes to codegen as undef const bytes
         let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(range);
         llvals.push(cx.const_bytes(bytes));
     }

     cx.const_struct(&llvals, true)
 }

 fn codegen_static_initializer<'gcc, 'tcx>(
     cx: &CodegenCx<'gcc, 'tcx>,
     def_id: DefId,
 ) -> Result<(RValue<'gcc>, ConstAllocation<'tcx>), ErrorHandled> {
     let alloc = cx.tcx.eval_static_initializer(def_id)?;
     Ok((const_alloc_to_gcc(cx, alloc), alloc))
 }

 fn check_and_apply_linkage<'gcc, 'tcx>(
     cx: &CodegenCx<'gcc, 'tcx>,
     attrs: &CodegenFnAttrs,
     gcc_type: Type<'gcc>,
     sym: &str,
 ) -> LValue<'gcc> {
     let is_tls = attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL);
     if let Some(linkage) = attrs.import_linkage {
         // Declare a symbol `foo` with the desired linkage.
         let global1 =
             cx.declare_global_with_linkage(sym, cx.type_i8(), base::global_linkage_to_gcc(linkage));

         // Declare an internal global `extern_with_linkage_foo` which
         // is initialized with the address of `foo`.  If `foo` is
         // discarded during linking (for example, if `foo` has weak
         // linkage and there are no definitions), then
         // `extern_with_linkage_foo` will instead be initialized to
         // zero.
         let mut real_name = "_rust_extern_with_linkage_".to_string();
         real_name.push_str(sym);
         let global2 = cx.define_global(&real_name, gcc_type, is_tls, attrs.link_section);
         // TODO(antoyo): set linkage.
         let value = cx.const_ptrcast(global1.get_address(None), gcc_type);
         global2.global_set_initializer_rvalue(value);
         // TODO(antoyo): use global_set_initializer() when it will work.
         global2
     } else {
         // Generate an external declaration.
         // FIXME(nagisa): investigate whether it can be changed into define_global

         // Thread-local statics in some other crate need to *always* be linked
         // against in a thread-local fashion, so we need to be sure to apply the
         // thread-local attribute locally if it was present remotely. If we
         // don't do this then linker errors can be generated where the linker
         // complains that one object files has a thread local version of the
         // symbol and another one doesn't.
         cx.declare_global(sym, gcc_type, GlobalKind::Imported, is_tls, attrs.link_section)
     }
 }
	#[cfg(feature = "master")]
	use gccjit::{FnAttribute, VarAttribute, Visibility};
	use gccjit::{Function, GlobalKind, LValue, RValue, ToRValue, Type};
	use rustc_codegen_ssa::traits::{BaseTypeMethods, ConstMethods, StaticMethods};
	use rustc_hir::def::DefKind;
	use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
	use rustc_middle::mir::interpret::{
	self, read_target_uint, ConstAllocation, ErrorHandled, Scalar as InterpScalar,
	};
	use rustc_middle::ty::layout::LayoutOf;
	use rustc_middle::ty::{self, Instance};
	use rustc_middle::{bug, span_bug};
	use rustc_span::def_id::DefId;
	use rustc_target::abi::{self, Align, HasDataLayout, Primitive, Size, WrappingRange};

	use crate::base;
	use crate::context::CodegenCx;
	use crate::errors::InvalidMinimumAlignment;
	use crate::type_of::LayoutGccExt;

	fn set_global_alignment<'gcc, 'tcx>(
	cx: &CodegenCx<'gcc, 'tcx>,
	gv: LValue<'gcc>,
	mut align: Align,
	) {
	// The target may require greater alignment for globals than the type does.
	// Note: GCC and Clang also allow `__attribute__((aligned))` on variables,
	// which can force it to be smaller. Rust doesn't support this yet.
	if let Some(min) = cx.sess().target.min_global_align {
	match Align::from_bits(min) {
	Ok(min) => align = align.max(min),
	Err(err) => {
	cx.sess().dcx().emit_err(InvalidMinimumAlignment { err: err.to_string() });
	}
	}
	}
	gv.set_alignment(align.bytes() as i32);
	}

	impl<'gcc, 'tcx> StaticMethods for CodegenCx<'gcc, 'tcx> {
	fn static_addr_of(&self, cv: RValue<'gcc>, align: Align, kind: Option<&str>) -> RValue<'gcc> {
	// TODO(antoyo): implement a proper rvalue comparison in libgccjit instead of doing the
	// following:
	for (value, variable) in &*self.const_globals.borrow() {
	if format!("{:?}", value) == format!("{:?}", cv) {
	if let Some(global_variable) = self.global_lvalues.borrow().get(variable) {
	let alignment = align.bits() as i32;
	if alignment > global_variable.get_alignment() {
	global_variable.set_alignment(alignment);
	}
	}
	return *variable;
	}
	}
	let global_value = self.static_addr_of_mut(cv, align, kind);
	#[cfg(feature = "master")]
	self.global_lvalues
	.borrow()
	.get(&global_value)
	.expect("`static_addr_of_mut` did not add the global to `self.global_lvalues`")
	.global_set_readonly();
	self.const_globals.borrow_mut().insert(cv, global_value);
	global_value
	}

	#[cfg_attr(not(feature = "master"), allow(unused_mut))]
	fn codegen_static(&self, def_id: DefId) {
	let attrs = self.tcx.codegen_fn_attrs(def_id);

	let Ok((value, alloc)) = codegen_static_initializer(self, def_id) else {
	// Error has already been reported
	return;
	};
	let alloc = alloc.inner();

	// boolean SSA values are i1, but they have to be stored in i8 slots,
	// otherwise some LLVM optimization passes don't work as expected
	let val_llty = self.val_ty(value);
	if val_llty == self.type_i1() {
	unimplemented!();
	};

	let is_thread_local = attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL);
	let global = self.get_static_inner(def_id, val_llty);

	#[cfg(feature = "master")]
	if global.to_rvalue().get_type() != val_llty {
	global.to_rvalue().set_type(val_llty);
	}
	set_global_alignment(self, global, alloc.align);

	global.global_set_initializer_rvalue(value);

	// As an optimization, all shared statics which do not have interior
	// mutability are placed into read-only memory.
	if alloc.mutability.is_not() {
	#[cfg(feature = "master")]
	global.global_set_readonly();
	}

	if is_thread_local {
	// Do not allow LLVM to change the alignment of a TLS on macOS.
	//
	// By default a global's alignment can be freely increased.
	// This allows LLVM to generate more performant instructions
	// e.g., using load-aligned into a SIMD register.
	//
	// However, on macOS 10.10 or below, the dynamic linker does not
	// respect any alignment given on the TLS (radar 24221680).
	// This will violate the alignment assumption, and causing segfault at runtime.
	//
	// This bug is very easy to trigger. In `println!` and `panic!`,
	// the `LOCAL_STDOUT`/`LOCAL_STDERR` handles are stored in a TLS,
	// which the values would be `mem::replace`d on initialization.
	// The implementation of `mem::replace` will use SIMD
	// whenever the size is 32 bytes or higher. LLVM notices SIMD is used
	// and tries to align `LOCAL_STDOUT`/`LOCAL_STDERR` to a 32-byte boundary,
	// which macOS's dyld disregarded and causing crashes
	// (see issues #51794, #51758, #50867, #48866 and #44056).
	//
	// To workaround the bug, we trick LLVM into not increasing
	// the global's alignment by explicitly assigning a section to it
	// (equivalent to automatically generating a `#[link_section]` attribute).
	// See the comment in the `GlobalValue::canIncreaseAlignment()` function
	// of `lib/IR/Globals.cpp` for why this works.
	//
	// When the alignment is not increased, the optimized `mem::replace`
	// will use load-unaligned instructions instead, and thus avoiding the crash.
	//
	// We could remove this hack whenever we decide to drop macOS 10.10 support.
	if self.tcx.sess.target.options.is_like_osx {
	// The `inspect` method is okay here because we checked for provenance, and
	// because we are doing this access to inspect the final interpreter state
	// (not as part of the interpreter execution).
	//
	// FIXME: This check requires that the (arbitrary) value of undefined bytes
	// happens to be zero. Instead, we should only check the value of defined bytes
	// and set all undefined bytes to zero if this allocation is headed for the
	// BSS.
	unimplemented!();
	}
	}

	// Wasm statics with custom link sections get special treatment as they
	// go into custom sections of the wasm executable.
	if self.tcx.sess.opts.target_triple.triple().starts_with("wasm32") {
	if let Some(_section) = attrs.link_section {
	unimplemented!();
	}
	} else {
	// TODO(antoyo): set link section.
	}

	if attrs.flags.contains(CodegenFnAttrFlags::USED)
	\|\| attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER)
	{
	self.add_used_global(global.to_rvalue());
	}
	}

	/// Add a global value to a list to be stored in the `llvm.used` variable, an array of i8*.
	fn add_used_global(&self, _global: RValue<'gcc>) {
	// TODO(antoyo)
	}

	fn add_compiler_used_global(&self, global: RValue<'gcc>) {
	// NOTE: seems like GCC does not make the distinction between compiler.used and used.
	self.add_used_global(global);
	}
	}

	impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
	#[cfg_attr(not(feature = "master"), allow(unused_variables))]
	pub fn add_used_function(&self, function: Function<'gcc>) {
	#[cfg(feature = "master")]
	function.add_attribute(FnAttribute::Used);
	}

	pub fn static_addr_of_mut(
	&self,
	cv: RValue<'gcc>,
	align: Align,
	kind: Option<&str>,
	) -> RValue<'gcc> {
	let global = match kind {
	Some(kind) if !self.tcx.sess.fewer_names() => {
	let name = self.generate_local_symbol_name(kind);
	// TODO(antoyo): check if it's okay that no link_section is set.

	let typ = self.val_ty(cv).get_aligned(align.bytes());
	let global = self.declare_private_global(&name[..], typ);
	global
	}
	_ => {
	let typ = self.val_ty(cv).get_aligned(align.bytes());
	let global = self.declare_unnamed_global(typ);
	global
	}
	};
	global.global_set_initializer_rvalue(cv);
	// TODO(antoyo): set unnamed address.
	let rvalue = global.get_address(None);
	self.global_lvalues.borrow_mut().insert(rvalue, global);
	rvalue
	}

	pub fn get_static(&self, def_id: DefId) -> LValue<'gcc> {
	let instance = Instance::mono(self.tcx, def_id);
	let DefKind::Static { nested, .. } = self.tcx.def_kind(def_id) else { bug!() };
	// Nested statics do not have a type, so pick a random type and let `define_static` figure out
	// the gcc type from the actual evaluated initializer.
	let gcc_type = if nested {
	self.type_i8()
	} else {
	let ty = instance.ty(self.tcx, ty::ParamEnv::reveal_all());
	self.layout_of(ty).gcc_type(self)
	};

	self.get_static_inner(def_id, gcc_type)
	}

	pub(crate) fn get_static_inner(&self, def_id: DefId, gcc_type: Type<'gcc>) -> LValue<'gcc> {
	let instance = Instance::mono(self.tcx, def_id);
	if let Some(&global) = self.instances.borrow().get(&instance) {
	trace!("used cached value");
	return global;
	}

	// FIXME: Once we stop removing globals in `codegen_static`, we can uncomment this code.
	// let defined_in_current_codegen_unit =
	// self.codegen_unit.items().contains_key(&MonoItem::Static(def_id));
	// assert!(
	// !defined_in_current_codegen_unit,
	// "consts::get_static() should always hit the cache for \
	// statics defined in the same CGU, but did not for `{:?}`",
	// def_id
	// );
	let sym = self.tcx.symbol_name(instance).name;
	let fn_attrs = self.tcx.codegen_fn_attrs(def_id);

	let global = if def_id.is_local() && !self.tcx.is_foreign_item(def_id) {
	if let Some(global) = self.get_declared_value(sym) {
	if self.val_ty(global) != self.type_ptr_to(gcc_type) {
	span_bug!(self.tcx.def_span(def_id), "Conflicting types for static");
	}
	}

	let is_tls = fn_attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL);
	let global = self.declare_global(
	sym,
	gcc_type,
	GlobalKind::Exported,
	is_tls,
	fn_attrs.link_section,
	);

	if !self.tcx.is_reachable_non_generic(def_id) {
	#[cfg(feature = "master")]
	global.add_string_attribute(VarAttribute::Visibility(Visibility::Hidden));
	}

	global
	} else {
	check_and_apply_linkage(self, fn_attrs, gcc_type, sym)
	};

	if !def_id.is_local() {
	let needs_dll_storage_attr = false; // TODO(antoyo)

	// If this assertion triggers, there's something wrong with commandline
	// argument validation.
	debug_assert!(
	!(self.tcx.sess.opts.cg.linker_plugin_lto.enabled()
	&& self.tcx.sess.target.options.is_like_msvc
	&& self.tcx.sess.opts.cg.prefer_dynamic)
	);

	if needs_dll_storage_attr {
	// This item is external but not foreign, i.e., it originates from an external Rust
	// crate. Since we don't know whether this crate will be linked dynamically or
	// statically in the final application, we always mark such symbols as 'dllimport'.
	// If final linkage happens to be static, we rely on compiler-emitted __imp_ stubs
	// to make things work.
	//
	// However, in some scenarios we defer emission of statics to downstream
	// crates, so there are cases where a static with an upstream DefId
	// is actually present in the current crate. We can find out via the
	// is_codegened_item query.
	if !self.tcx.is_codegened_item(def_id) {
	unimplemented!();
	}
	}
	}

	// TODO(antoyo): set dll storage class.

	self.instances.borrow_mut().insert(instance, global);
	global
	}
	}

	pub fn const_alloc_to_gcc<'gcc, 'tcx>(
	cx: &CodegenCx<'gcc, 'tcx>,
	alloc: ConstAllocation<'tcx>,
	) -> RValue<'gcc> {
	let alloc = alloc.inner();
	let mut llvals = Vec::with_capacity(alloc.provenance().ptrs().len() + 1);
	let dl = cx.data_layout();
	let pointer_size = dl.pointer_size.bytes() as usize;

	let mut next_offset = 0;
	for &(offset, prov) in alloc.provenance().ptrs().iter() {
	let alloc_id = prov.alloc_id();
	let offset = offset.bytes();
	assert_eq!(offset as usize as u64, offset);
	let offset = offset as usize;
	if offset > next_offset {
	// This `inspect` is okay since we have checked that it is not within a pointer with provenance, it
	// is within the bounds of the allocation, and it doesn't affect interpreter execution
	// (we inspect the result after interpreter execution). Any undef byte is replaced with
	// some arbitrary byte value.
	//
	// FIXME: relay undef bytes to codegen as undef const bytes
	let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(next_offset..offset);
	llvals.push(cx.const_bytes(bytes));
	}
	let ptr_offset = read_target_uint(
	dl.endian,
	// This `inspect` is okay since it is within the bounds of the allocation, it doesn't
	// affect interpreter execution (we inspect the result after interpreter execution),
	// and we properly interpret the provenance as a relocation pointer offset.
	alloc.inspect_with_uninit_and_ptr_outside_interpreter(offset..(offset + pointer_size)),
	)
	.expect("const_alloc_to_llvm: could not read relocation pointer")
	as u64;

	let address_space = cx.tcx.global_alloc(alloc_id).address_space(cx);

	llvals.push(cx.scalar_to_backend(
	InterpScalar::from_pointer(
	interpret::Pointer::new(prov, Size::from_bytes(ptr_offset)),
	&cx.tcx,
	),
	abi::Scalar::Initialized {
	value: Primitive::Pointer(address_space),
	valid_range: WrappingRange::full(dl.pointer_size),
	},
	cx.type_i8p_ext(address_space),
	));
	next_offset = offset + pointer_size;
	}
	if alloc.len() >= next_offset {
	let range = next_offset..alloc.len();
	// This `inspect` is okay since we have check that it is after all provenance, it is
	// within the bounds of the allocation, and it doesn't affect interpreter execution (we
	// inspect the result after interpreter execution). Any undef byte is replaced with some
	// arbitrary byte value.
	//
	// FIXME: relay undef bytes to codegen as undef const bytes
	let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(range);
	llvals.push(cx.const_bytes(bytes));
	}

	cx.const_struct(&llvals, true)
	}

	fn codegen_static_initializer<'gcc, 'tcx>(
	cx: &CodegenCx<'gcc, 'tcx>,
	def_id: DefId,
	) -> Result<(RValue<'gcc>, ConstAllocation<'tcx>), ErrorHandled> {
	let alloc = cx.tcx.eval_static_initializer(def_id)?;
	Ok((const_alloc_to_gcc(cx, alloc), alloc))
	}

	fn check_and_apply_linkage<'gcc, 'tcx>(
	cx: &CodegenCx<'gcc, 'tcx>,
	attrs: &CodegenFnAttrs,
	gcc_type: Type<'gcc>,
	sym: &str,
	) -> LValue<'gcc> {
	let is_tls = attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL);
	if let Some(linkage) = attrs.import_linkage {
	// Declare a symbol `foo` with the desired linkage.
	let global1 =
	cx.declare_global_with_linkage(sym, cx.type_i8(), base::global_linkage_to_gcc(linkage));

	// Declare an internal global `extern_with_linkage_foo` which
	// is initialized with the address of `foo`. If `foo` is
	// discarded during linking (for example, if `foo` has weak
	// linkage and there are no definitions), then
	// `extern_with_linkage_foo` will instead be initialized to
	// zero.
	let mut real_name = "_rust_extern_with_linkage_".to_string();
	real_name.push_str(sym);
	let global2 = cx.define_global(&real_name, gcc_type, is_tls, attrs.link_section);
	// TODO(antoyo): set linkage.
	let value = cx.const_ptrcast(global1.get_address(None), gcc_type);
	global2.global_set_initializer_rvalue(value);
	// TODO(antoyo): use global_set_initializer() when it will work.
	global2
	} else {
	// Generate an external declaration.
	// FIXME(nagisa): investigate whether it can be changed into define_global

	// Thread-local statics in some other crate need to always be linked
	// against in a thread-local fashion, so we need to be sure to apply the
	// thread-local attribute locally if it was present remotely. If we
	// don't do this then linker errors can be generated where the linker
	// complains that one object files has a thread local version of the
	// symbol and another one doesn't.
	cx.declare_global(sym, gcc_type, GlobalKind::Imported, is_tls, attrs.link_section)
	}
	}