Shrink some unsafe blocks in cg_llvm
This commit is contained in:
Oli Scherer
@@ -396,149 +396,148 @@ impl<'ll> CodegenCx<'ll, '_> {
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}
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fn codegen_static_item(&mut self, def_id: DefId) {
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unsafe {
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assert!(
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llvm::LLVMGetInitializer(
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self.instances.borrow().get(&Instance::mono(self.tcx, def_id)).unwrap()
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)
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.is_none()
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);
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let attrs = self.tcx.codegen_fn_attrs(def_id);
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assert!(
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llvm::LLVMGetInitializer(
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self.instances.borrow().get(&Instance::mono(self.tcx, def_id)).unwrap()
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)
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.is_none()
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);
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let attrs = self.tcx.codegen_fn_attrs(def_id);
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let Ok((v, alloc)) = codegen_static_initializer(self, def_id) else {
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// Error has already been reported
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return;
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};
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let alloc = alloc.inner();
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let Ok((v, alloc)) = codegen_static_initializer(self, def_id) else {
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// Error has already been reported
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return;
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};
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let alloc = alloc.inner();
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let val_llty = self.val_ty(v);
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let val_llty = self.val_ty(v);
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let g = self.get_static_inner(def_id, val_llty);
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let llty = self.get_type_of_global(g);
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let g = self.get_static_inner(def_id, val_llty);
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let llty = self.get_type_of_global(g);
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let g = if val_llty == llty {
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g
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} else {
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// codegen_static_initializer creates the global value just from the
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// `Allocation` data by generating one big struct value that is just
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// all the bytes and pointers after each other. This will almost never
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// match the type that the static was declared with. Unfortunately
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// we can't just LLVMConstBitCast our way out of it because that has very
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// specific rules on what can be cast. So instead of adding a new way to
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// generate static initializers that match the static's type, we picked
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// the easier option and retroactively change the type of the static item itself.
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let name = llvm::get_value_name(g);
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llvm::set_value_name(g, b"");
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let g = if val_llty == llty {
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g
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} else {
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// codegen_static_initializer creates the global value just from the
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// `Allocation` data by generating one big struct value that is just
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// all the bytes and pointers after each other. This will almost never
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// match the type that the static was declared with. Unfortunately
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// we can't just LLVMConstBitCast our way out of it because that has very
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// specific rules on what can be cast. So instead of adding a new way to
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// generate static initializers that match the static's type, we picked
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// the easier option and retroactively change the type of the static item itself.
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let name = String::from_utf8(llvm::get_value_name(g))
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.expect("we declare our statics with a utf8-valid name");
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llvm::set_value_name(g, b"");
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let linkage = llvm::get_linkage(g);
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let visibility = llvm::get_visibility(g);
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let linkage = llvm::get_linkage(g);
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let visibility = llvm::get_visibility(g);
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let new_g = llvm::LLVMRustGetOrInsertGlobal(
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self.llmod,
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name.as_c_char_ptr(),
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name.len(),
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val_llty,
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);
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let new_g = self.declare_global(&name, val_llty);
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llvm::set_linkage(new_g, linkage);
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llvm::set_visibility(new_g, visibility);
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llvm::set_linkage(new_g, linkage);
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llvm::set_visibility(new_g, visibility);
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// The old global has had its name removed but is returned by
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// get_static since it is in the instance cache. Provide an
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// alternative lookup that points to the new global so that
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// global_asm! can compute the correct mangled symbol name
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// for the global.
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self.renamed_statics.borrow_mut().insert(def_id, new_g);
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// The old global has had its name removed but is returned by
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// get_static since it is in the instance cache. Provide an
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// alternative lookup that points to the new global so that
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// global_asm! can compute the correct mangled symbol name
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// for the global.
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self.renamed_statics.borrow_mut().insert(def_id, new_g);
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// To avoid breaking any invariants, we leave around the old
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// global for the moment; we'll replace all references to it
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// with the new global later. (See base::codegen_backend.)
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self.statics_to_rauw.borrow_mut().push((g, new_g));
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new_g
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};
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set_global_alignment(self, g, alloc.align);
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llvm::set_initializer(g, v);
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// To avoid breaking any invariants, we leave around the old
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// global for the moment; we'll replace all references to it
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// with the new global later. (See base::codegen_backend.)
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self.statics_to_rauw.borrow_mut().push((g, new_g));
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new_g
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};
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set_global_alignment(self, g, alloc.align);
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llvm::set_initializer(g, v);
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self.assume_dso_local(g, true);
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self.assume_dso_local(g, true);
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// Forward the allocation's mutability (picked by the const interner) to LLVM.
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if alloc.mutability.is_not() {
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llvm::set_global_constant(g, true);
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}
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// Forward the allocation's mutability (picked by the const interner) to LLVM.
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if alloc.mutability.is_not() {
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llvm::set_global_constant(g, true);
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}
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debuginfo::build_global_var_di_node(self, def_id, g);
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debuginfo::build_global_var_di_node(self, def_id, g);
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if attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL) {
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llvm::set_thread_local_mode(g, self.tls_model);
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}
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if attrs.flags.contains(CodegenFnAttrFlags::THREAD_LOCAL) {
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llvm::set_thread_local_mode(g, self.tls_model);
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}
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// Wasm statics with custom link sections get special treatment as they
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// go into custom sections of the wasm executable. The exception to this
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// is the `.init_array` section which are treated specially by the wasm linker.
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if self.tcx.sess.target.is_like_wasm
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&& attrs
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.link_section
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.map(|link_section| !link_section.as_str().starts_with(".init_array"))
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.unwrap_or(true)
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{
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if let Some(section) = attrs.link_section {
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let section = llvm::LLVMMDStringInContext2(
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// Wasm statics with custom link sections get special treatment as they
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// go into custom sections of the wasm executable. The exception to this
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// is the `.init_array` section which are treated specially by the wasm linker.
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if self.tcx.sess.target.is_like_wasm
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&& attrs
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.link_section
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.map(|link_section| !link_section.as_str().starts_with(".init_array"))
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.unwrap_or(true)
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{
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if let Some(section) = attrs.link_section {
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let section = unsafe {
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llvm::LLVMMDStringInContext2(
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self.llcx,
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section.as_str().as_c_char_ptr(),
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section.as_str().len(),
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);
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assert!(alloc.provenance().ptrs().is_empty());
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)
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};
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assert!(alloc.provenance().ptrs().is_empty());
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// The `inspect` method is okay here because we checked for provenance, and
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// because we are doing this access to inspect the final interpreter state (not
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// as part of the interpreter execution).
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let bytes =
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alloc.inspect_with_uninit_and_ptr_outside_interpreter(0..alloc.len());
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let alloc =
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llvm::LLVMMDStringInContext2(self.llcx, bytes.as_c_char_ptr(), bytes.len());
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let data = [section, alloc];
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let meta = llvm::LLVMMDNodeInContext2(self.llcx, data.as_ptr(), data.len());
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let val = self.get_metadata_value(meta);
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// The `inspect` method is okay here because we checked for provenance, and
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// because we are doing this access to inspect the final interpreter state (not
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// as part of the interpreter execution).
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let bytes = alloc.inspect_with_uninit_and_ptr_outside_interpreter(0..alloc.len());
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let alloc = unsafe {
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llvm::LLVMMDStringInContext2(self.llcx, bytes.as_c_char_ptr(), bytes.len())
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};
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let data = [section, alloc];
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let meta =
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unsafe { llvm::LLVMMDNodeInContext2(self.llcx, data.as_ptr(), data.len()) };
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let val = self.get_metadata_value(meta);
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unsafe {
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llvm::LLVMAddNamedMetadataOperand(
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self.llmod,
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c"wasm.custom_sections".as_ptr(),
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val,
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);
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}
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} else {
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base::set_link_section(g, attrs);
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)
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};
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}
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} else {
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base::set_link_section(g, attrs);
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}
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base::set_variable_sanitizer_attrs(g, attrs);
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base::set_variable_sanitizer_attrs(g, attrs);
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if attrs.flags.contains(CodegenFnAttrFlags::USED_COMPILER) {
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// `USED` and `USED_LINKER` can't be used together.
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assert!(!attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER));
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if attrs.flags.contains(CodegenFnAttrFlags::USED_COMPILER) {
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// `USED` and `USED_LINKER` can't be used together.
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assert!(!attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER));
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// The semantics of #[used] in Rust only require the symbol to make it into the
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// object file. It is explicitly allowed for the linker to strip the symbol if it
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// is dead, which means we are allowed to use `llvm.compiler.used` instead of
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// `llvm.used` here.
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//
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// Additionally, https://reviews.llvm.org/D97448 in LLVM 13 started emitting unique
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// sections with SHF_GNU_RETAIN flag for llvm.used symbols, which may trigger bugs
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// in the handling of `.init_array` (the static constructor list) in versions of
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// the gold linker (prior to the one released with binutils 2.36).
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//
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// That said, we only ever emit these when `#[used(compiler)]` is explicitly
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// requested. This is to avoid similar breakage on other targets, in particular
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// MachO targets have *their* static constructor lists broken if `llvm.compiler.used`
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// is emitted rather than `llvm.used`. However, that check happens when assigning
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// the `CodegenFnAttrFlags` in the `codegen_fn_attrs` query, so we don't need to
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// take care of it here.
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self.add_compiler_used_global(g);
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}
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if attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER) {
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// `USED` and `USED_LINKER` can't be used together.
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assert!(!attrs.flags.contains(CodegenFnAttrFlags::USED_COMPILER));
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// The semantics of #[used] in Rust only require the symbol to make it into the
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// object file. It is explicitly allowed for the linker to strip the symbol if it
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// is dead, which means we are allowed to use `llvm.compiler.used` instead of
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// `llvm.used` here.
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//
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// Additionally, https://reviews.llvm.org/D97448 in LLVM 13 started emitting unique
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// sections with SHF_GNU_RETAIN flag for llvm.used symbols, which may trigger bugs
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// in the handling of `.init_array` (the static constructor list) in versions of
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// the gold linker (prior to the one released with binutils 2.36).
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//
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// That said, we only ever emit these when `#[used(compiler)]` is explicitly
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// requested. This is to avoid similar breakage on other targets, in particular
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// MachO targets have *their* static constructor lists broken if `llvm.compiler.used`
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// is emitted rather than `llvm.used`. However, that check happens when assigning
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// the `CodegenFnAttrFlags` in the `codegen_fn_attrs` query, so we don't need to
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// take care of it here.
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self.add_compiler_used_global(g);
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}
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if attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER) {
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// `USED` and `USED_LINKER` can't be used together.
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assert!(!attrs.flags.contains(CodegenFnAttrFlags::USED_COMPILER));
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self.add_used_global(g);
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}
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self.add_used_global(g);
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}
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}
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