compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

   1 #![doc = include_str!("doc.md")]
   2
   3 use rustc_codegen_ssa::mir::debuginfo::VariableKind::*;
   4
   5 use self::metadata::{file_metadata, type_di_node};
   6 use self::metadata::{UNKNOWN_COLUMN_NUMBER, UNKNOWN_LINE_NUMBER};
   7 use self::namespace::mangled_name_of_instance;
   8 use self::utils::{create_DIArray, is_node_local_to_unit, DIB};
   9
  10 use crate::abi::FnAbi;
  11 use crate::builder::Builder;
  12 use crate::common::CodegenCx;
  13 use crate::llvm;
  14 use crate::llvm::debuginfo::{
  15     DIArray, DIBuilder, DIFile, DIFlags, DILexicalBlock, DILocation, DISPFlags, DIScope, DIType,
  16     DIVariable,
  17 };
  18 use crate::value::Value;
  19
  20 use rustc_codegen_ssa::debuginfo::type_names;
  21 use rustc_codegen_ssa::mir::debuginfo::{DebugScope, FunctionDebugContext, VariableKind};
  22 use rustc_codegen_ssa::traits::*;
  23 use rustc_data_structures::fx::FxHashMap;
  24 use rustc_data_structures::sync::Lrc;
  25 use rustc_hir::def_id::{DefId, DefIdMap};
  26 use rustc_index::vec::IndexVec;
  27 use rustc_middle::mir;
  28 use rustc_middle::ty::layout::LayoutOf;
  29 use rustc_middle::ty::subst::{GenericArgKind, SubstsRef};
  30 use rustc_middle::ty::{self, Instance, ParamEnv, Ty, TypeFoldable};
  31 use rustc_session::config::{self, DebugInfo};
  32 use rustc_session::Session;
  33 use rustc_span::symbol::Symbol;
  34 use rustc_span::{self, BytePos, Pos, SourceFile, SourceFileAndLine, Span};
  35 use rustc_target::abi::Size;
  36
  37 use libc::c_uint;
  38 use smallvec::SmallVec;
  39 use std::cell::RefCell;
  40 use std::iter;
  41 use std::lazy::OnceCell;
  42 use tracing::debug;
  43
  44 mod create_scope_map;
  45 pub mod gdb;
  46 pub mod metadata;
  47 mod namespace;
  48 mod utils;
  49
  50 pub use self::create_scope_map::compute_mir_scopes;
  51 pub use self::metadata::build_global_var_di_node;
  52 pub use self::metadata::extend_scope_to_file;
  53
  54 #[allow(non_upper_case_globals)]
  55 const DW_TAG_auto_variable: c_uint = 0x100;
  56 #[allow(non_upper_case_globals)]
  57 const DW_TAG_arg_variable: c_uint = 0x101;
  58
  59 /// A context object for maintaining all state needed by the debuginfo module.
  60 pub struct CodegenUnitDebugContext<'ll, 'tcx> {
  61     llcontext: &'ll llvm::Context,
  62     llmod: &'ll llvm::Module,
  63     builder: &'ll mut DIBuilder<'ll>,
  64     created_files: RefCell<FxHashMap<(Option<String>, Option<String>), &'ll DIFile>>,
  65
  66     type_map: metadata::TypeMap<'ll, 'tcx>,
  67     namespace_map: RefCell<DefIdMap<&'ll DIScope>>,
  68     recursion_marker_type: OnceCell<&'ll DIType>,
  69 }
  70
  71 impl Drop for CodegenUnitDebugContext<'_, '_> {
  72     fn drop(&mut self) {
  73         unsafe {
  74             llvm::LLVMRustDIBuilderDispose(&mut *(self.builder as *mut _));
  75         }
  76     }
  77 }
  78
  79 impl<'ll, 'tcx> CodegenUnitDebugContext<'ll, 'tcx> {
  80     pub fn new(llmod: &'ll llvm::Module) -> Self {
  81         debug!("CodegenUnitDebugContext::new");
  82         let builder = unsafe { llvm::LLVMRustDIBuilderCreate(llmod) };
  83         // DIBuilder inherits context from the module, so we'd better use the same one
  84         let llcontext = unsafe { llvm::LLVMGetModuleContext(llmod) };
  85         CodegenUnitDebugContext {
  86             llcontext,
  87             llmod,
  88             builder,
  89             created_files: Default::default(),
  90             type_map: Default::default(),
  91             namespace_map: RefCell::new(Default::default()),
  92             recursion_marker_type: OnceCell::new(),
  93         }
  94     }
  95
  96     pub fn finalize(&self, sess: &Session) {
  97         unsafe {
  98             llvm::LLVMRustDIBuilderFinalize(self.builder);
  99
 100             // Debuginfo generation in LLVM by default uses a higher
 101             // version of dwarf than macOS currently understands. We can
 102             // instruct LLVM to emit an older version of dwarf, however,
 103             // for macOS to understand. For more info see #11352
 104             // This can be overridden using --llvm-opts -dwarf-version,N.
 105             // Android has the same issue (#22398)
 106             if let Some(version) = sess.target.dwarf_version {
 107                 llvm::LLVMRustAddModuleFlag(
 108                     self.llmod,
 109                     llvm::LLVMModFlagBehavior::Warning,
 110                     "Dwarf Version\0".as_ptr().cast(),
 111                     version,
 112                 )
 113             }
 114
 115             // Indicate that we want CodeView debug information on MSVC
 116             if sess.target.is_like_msvc {
 117                 llvm::LLVMRustAddModuleFlag(
 118                     self.llmod,
 119                     llvm::LLVMModFlagBehavior::Warning,
 120                     "CodeView\0".as_ptr().cast(),
 121                     1,
 122                 )
 123             }
 124
 125             // Prevent bitcode readers from deleting the debug info.
 126             let ptr = "Debug Info Version\0".as_ptr();
 127             llvm::LLVMRustAddModuleFlag(
 128                 self.llmod,
 129                 llvm::LLVMModFlagBehavior::Warning,
 130                 ptr.cast(),
 131                 llvm::LLVMRustDebugMetadataVersion(),
 132             );
 133         }
 134     }
 135 }
 136
 137 /// Creates any deferred debug metadata nodes
 138 pub fn finalize(cx: &CodegenCx<'_, '_>) {
 139     if let Some(dbg_cx) = &cx.dbg_cx {
 140         debug!("finalize");
 141
 142         if gdb::needs_gdb_debug_scripts_section(cx) {
 143             // Add a .debug_gdb_scripts section to this compile-unit. This will
 144             // cause GDB to try and load the gdb_load_rust_pretty_printers.py file,
 145             // which activates the Rust pretty printers for binary this section is
 146             // contained in.
 147             gdb::get_or_insert_gdb_debug_scripts_section_global(cx);
 148         }
 149
 150         dbg_cx.finalize(cx.sess());
 151     }
 152 }
 153
 154 impl<'ll> DebugInfoBuilderMethods for Builder<'_, 'll, '_> {
 155     // FIXME(eddyb) find a common convention for all of the debuginfo-related
 156     // names (choose between `dbg`, `debug`, `debuginfo`, `debug_info` etc.).
 157     fn dbg_var_addr(
 158         &mut self,
 159         dbg_var: &'ll DIVariable,
 160         dbg_loc: &'ll DILocation,
 161         variable_alloca: Self::Value,
 162         direct_offset: Size,
 163         indirect_offsets: &[Size],
 164     ) {
 165         // Convert the direct and indirect offsets to address ops.
 166         // FIXME(eddyb) use `const`s instead of getting the values via FFI,
 167         // the values should match the ones in the DWARF standard anyway.
 168         let op_deref = || unsafe { llvm::LLVMRustDIBuilderCreateOpDeref() };
 169         let op_plus_uconst = || unsafe { llvm::LLVMRustDIBuilderCreateOpPlusUconst() };
 170         let mut addr_ops = SmallVec::<[u64; 8]>::new();
 171
 172         if direct_offset.bytes() > 0 {
 173             addr_ops.push(op_plus_uconst());
 174             addr_ops.push(direct_offset.bytes() as u64);
 175         }
 176         for &offset in indirect_offsets {
 177             addr_ops.push(op_deref());
 178             if offset.bytes() > 0 {
 179                 addr_ops.push(op_plus_uconst());
 180                 addr_ops.push(offset.bytes() as u64);
 181             }
 182         }
 183
 184         unsafe {
 185             // FIXME(eddyb) replace `llvm.dbg.declare` with `llvm.dbg.addr`.
 186             llvm::LLVMRustDIBuilderInsertDeclareAtEnd(
 187                 DIB(self.cx()),
 188                 variable_alloca,
 189                 dbg_var,
 190                 addr_ops.as_ptr(),
 191                 addr_ops.len() as c_uint,
 192                 dbg_loc,
 193                 self.llbb(),
 194             );
 195         }
 196     }
 197
 198     fn set_dbg_loc(&mut self, dbg_loc: &'ll DILocation) {
 199         unsafe {
 200             let dbg_loc_as_llval = llvm::LLVMRustMetadataAsValue(self.cx().llcx, dbg_loc);
 201             llvm::LLVMSetCurrentDebugLocation(self.llbuilder, dbg_loc_as_llval);
 202         }
 203     }
 204
 205     fn insert_reference_to_gdb_debug_scripts_section_global(&mut self) {
 206         gdb::insert_reference_to_gdb_debug_scripts_section_global(self)
 207     }
 208
 209     fn set_var_name(&mut self, value: &'ll Value, name: &str) {
 210         // Avoid wasting time if LLVM value names aren't even enabled.
 211         if self.sess().fewer_names() {
 212             return;
 213         }
 214
 215         // Only function parameters and instructions are local to a function,
 216         // don't change the name of anything else (e.g. globals).
 217         let param_or_inst = unsafe {
 218             llvm::LLVMIsAArgument(value).is_some() || llvm::LLVMIsAInstruction(value).is_some()
 219         };
 220         if !param_or_inst {
 221             return;
 222         }
 223
 224         // Avoid replacing the name if it already exists.
 225         // While we could combine the names somehow, it'd
 226         // get noisy quick, and the usefulness is dubious.
 227         if llvm::get_value_name(value).is_empty() {
 228             llvm::set_value_name(value, name.as_bytes());
 229         }
 230     }
 231 }
 232
 233 /// A source code location used to generate debug information.
 234 // FIXME(eddyb) rename this to better indicate it's a duplicate of
 235 // `rustc_span::Loc` rather than `DILocation`, perhaps by making
 236 // `lookup_char_pos` return the right information instead.
 237 pub struct DebugLoc {
 238     /// Information about the original source file.
 239     pub file: Lrc<SourceFile>,
 240     /// The (1-based) line number.
 241     pub line: u32,
 242     /// The (1-based) column number.
 243     pub col: u32,
 244 }
 245
 246 impl CodegenCx<'_, '_> {
 247     /// Looks up debug source information about a `BytePos`.
 248     // FIXME(eddyb) rename this to better indicate it's a duplicate of
 249     // `lookup_char_pos` rather than `dbg_loc`, perhaps by making
 250     // `lookup_char_pos` return the right information instead.
 251     pub fn lookup_debug_loc(&self, pos: BytePos) -> DebugLoc {
 252         let (file, line, col) = match self.sess().source_map().lookup_line(pos) {
 253             Ok(SourceFileAndLine { sf: file, line }) => {
 254                 let line_pos = file.line_begin_pos(pos);
 255
 256                 // Use 1-based indexing.
 257                 let line = (line + 1) as u32;
 258                 let col = (pos - line_pos).to_u32() + 1;
 259
 260                 (file, line, col)
 261             }
 262             Err(file) => (file, UNKNOWN_LINE_NUMBER, UNKNOWN_COLUMN_NUMBER),
 263         };
 264
 265         // For MSVC, omit the column number.
 266         // Otherwise, emit it. This mimics clang behaviour.
 267         // See discussion in https://github.com/rust-lang/rust/issues/42921
 268         if self.sess().target.is_like_msvc {
 269             DebugLoc { file, line, col: UNKNOWN_COLUMN_NUMBER }
 270         } else {
 271             DebugLoc { file, line, col }
 272         }
 273     }
 274 }
 275
 276 impl<'ll, 'tcx> DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
 277     fn create_function_debug_context(
 278         &self,
 279         instance: Instance<'tcx>,
 280         fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
 281         llfn: &'ll Value,
 282         mir: &mir::Body<'tcx>,
 283     ) -> Option<FunctionDebugContext<&'ll DIScope, &'ll DILocation>> {
 284         if self.sess().opts.debuginfo == DebugInfo::None {
 285             return None;
 286         }
 287
 288         // Initialize fn debug context (including scopes).
 289         // FIXME(eddyb) figure out a way to not need `Option` for `dbg_scope`.
 290         let empty_scope = DebugScope {
 291             dbg_scope: None,
 292             inlined_at: None,
 293             file_start_pos: BytePos(0),
 294             file_end_pos: BytePos(0),
 295         };
 296         let mut fn_debug_context =
 297             FunctionDebugContext { scopes: IndexVec::from_elem(empty_scope, &mir.source_scopes) };
 298
 299         // Fill in all the scopes, with the information from the MIR body.
 300         compute_mir_scopes(
 301             self,
 302             instance,
 303             mir,
 304             self.dbg_scope_fn(instance, fn_abi, Some(llfn)),
 305             &mut fn_debug_context,
 306         );
 307
 308         Some(fn_debug_context)
 309     }
 310
 311     fn dbg_scope_fn(
 312         &self,
 313         instance: Instance<'tcx>,
 314         fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
 315         maybe_definition_llfn: Option<&'ll Value>,
 316     ) -> &'ll DIScope {
 317         let tcx = self.tcx;
 318
 319         let def_id = instance.def_id();
 320         let containing_scope = get_containing_scope(self, instance);
 321         let span = tcx.def_span(def_id);
 322         let loc = self.lookup_debug_loc(span.lo());
 323         let file_metadata = file_metadata(self, &loc.file);
 324
 325         let function_type_metadata = unsafe {
 326             let fn_signature = get_function_signature(self, fn_abi);
 327             llvm::LLVMRustDIBuilderCreateSubroutineType(DIB(self), fn_signature)
 328         };
 329
 330         let mut name = String::new();
 331         type_names::push_item_name(tcx, def_id, false, &mut name);
 332
 333         // Find the enclosing function, in case this is a closure.
 334         let enclosing_fn_def_id = tcx.typeck_root_def_id(def_id);
 335
 336         // We look up the generics of the enclosing function and truncate the substs
 337         // to their length in order to cut off extra stuff that might be in there for
 338         // closures or generators.
 339         let generics = tcx.generics_of(enclosing_fn_def_id);
 340         let substs = instance.substs.truncate_to(tcx, generics);
 341
 342         type_names::push_generic_params(
 343             tcx,
 344             tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), substs),
 345             &mut name,
 346         );
 347
 348         let template_parameters = get_template_parameters(self, generics, substs);
 349
 350         let linkage_name = &mangled_name_of_instance(self, instance).name;
 351         // Omit the linkage_name if it is the same as subprogram name.
 352         let linkage_name = if &name == linkage_name { "" } else { linkage_name };
 353
 354         // FIXME(eddyb) does this need to be separate from `loc.line` for some reason?
 355         let scope_line = loc.line;
 356
 357         let mut flags = DIFlags::FlagPrototyped;
 358
 359         if fn_abi.ret.layout.abi.is_uninhabited() {
 360             flags |= DIFlags::FlagNoReturn;
 361         }
 362
 363         let mut spflags = DISPFlags::SPFlagDefinition;
 364         if is_node_local_to_unit(self, def_id) {
 365             spflags |= DISPFlags::SPFlagLocalToUnit;
 366         }
 367         if self.sess().opts.optimize != config::OptLevel::No {
 368             spflags |= DISPFlags::SPFlagOptimized;
 369         }
 370         if let Some((id, _)) = tcx.entry_fn(()) {
 371             if id == def_id {
 372                 spflags |= DISPFlags::SPFlagMainSubprogram;
 373             }
 374         }
 375
 376         unsafe {
 377             return llvm::LLVMRustDIBuilderCreateFunction(
 378                 DIB(self),
 379                 containing_scope,
 380                 name.as_ptr().cast(),
 381                 name.len(),
 382                 linkage_name.as_ptr().cast(),
 383                 linkage_name.len(),
 384                 file_metadata,
 385                 loc.line,
 386                 function_type_metadata,
 387                 scope_line,
 388                 flags,
 389                 spflags,
 390                 maybe_definition_llfn,
 391                 template_parameters,
 392                 None,
 393             );
 394         }
 395
 396         fn get_function_signature<'ll, 'tcx>(
 397             cx: &CodegenCx<'ll, 'tcx>,
 398             fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
 399         ) -> &'ll DIArray {
 400             if cx.sess().opts.debuginfo == DebugInfo::Limited {
 401                 return create_DIArray(DIB(cx), &[]);
 402             }
 403
 404             let mut signature = Vec::with_capacity(fn_abi.args.len() + 1);
 405
 406             // Return type -- llvm::DIBuilder wants this at index 0
 407             signature.push(if fn_abi.ret.is_ignore() {
 408                 None
 409             } else {
 410                 Some(type_di_node(cx, fn_abi.ret.layout.ty))
 411             });
 412
 413             // Arguments types
 414             if cx.sess().target.is_like_msvc {
 415                 // FIXME(#42800):
 416                 // There is a bug in MSDIA that leads to a crash when it encounters
 417                 // a fixed-size array of `u8` or something zero-sized in a
 418                 // function-type (see #40477).
 419                 // As a workaround, we replace those fixed-size arrays with a
 420                 // pointer-type. So a function `fn foo(a: u8, b: [u8; 4])` would
 421                 // appear as `fn foo(a: u8, b: *const u8)` in debuginfo,
 422                 // and a function `fn bar(x: [(); 7])` as `fn bar(x: *const ())`.
 423                 // This transformed type is wrong, but these function types are
 424                 // already inaccurate due to ABI adjustments (see #42800).
 425                 signature.extend(fn_abi.args.iter().map(|arg| {
 426                     let t = arg.layout.ty;
 427                     let t = match t.kind() {
 428                         ty::Array(ct, _)
 429                             if (*ct == cx.tcx.types.u8) || cx.layout_of(*ct).is_zst() =>
 430                         {
 431                             cx.tcx.mk_imm_ptr(*ct)
 432                         }
 433                         _ => t,
 434                     };
 435                     Some(type_di_node(cx, t))
 436                 }));
 437             } else {
 438                 signature
 439                     .extend(fn_abi.args.iter().map(|arg| Some(type_di_node(cx, arg.layout.ty))));
 440             }
 441
 442             create_DIArray(DIB(cx), &signature[..])
 443         }
 444
 445         fn get_template_parameters<'ll, 'tcx>(
 446             cx: &CodegenCx<'ll, 'tcx>,
 447             generics: &ty::Generics,
 448             substs: SubstsRef<'tcx>,
 449         ) -> &'ll DIArray {
 450             if substs.types().next().is_none() {
 451                 return create_DIArray(DIB(cx), &[]);
 452             }
 453
 454             // Again, only create type information if full debuginfo is enabled
 455             let template_params: Vec<_> = if cx.sess().opts.debuginfo == DebugInfo::Full {
 456                 let names = get_parameter_names(cx, generics);
 457                 iter::zip(substs, names)
 458                     .filter_map(|(kind, name)| {
 459                         if let GenericArgKind::Type(ty) = kind.unpack() {
 460                             let actual_type =
 461                                 cx.tcx.normalize_erasing_regions(ParamEnv::reveal_all(), ty);
 462                             let actual_type_metadata = type_di_node(cx, actual_type);
 463                             let name = name.as_str();
 464                             Some(unsafe {
 465                                 Some(llvm::LLVMRustDIBuilderCreateTemplateTypeParameter(
 466                                     DIB(cx),
 467                                     None,
 468                                     name.as_ptr().cast(),
 469                                     name.len(),
 470                                     actual_type_metadata,
 471                                 ))
 472                             })
 473                         } else {
 474                             None
 475                         }
 476                     })
 477                     .collect()
 478             } else {
 479                 vec![]
 480             };
 481
 482             create_DIArray(DIB(cx), &template_params)
 483         }
 484
 485         fn get_parameter_names(cx: &CodegenCx<'_, '_>, generics: &ty::Generics) -> Vec<Symbol> {
 486             let mut names = generics.parent.map_or_else(Vec::new, |def_id| {
 487                 get_parameter_names(cx, cx.tcx.generics_of(def_id))
 488             });
 489             names.extend(generics.params.iter().map(|param| param.name));
 490             names
 491         }
 492
 493         fn get_containing_scope<'ll, 'tcx>(
 494             cx: &CodegenCx<'ll, 'tcx>,
 495             instance: Instance<'tcx>,
 496         ) -> &'ll DIScope {
 497             // First, let's see if this is a method within an inherent impl. Because
 498             // if yes, we want to make the result subroutine DIE a child of the
 499             // subroutine's self-type.
 500             let self_type = cx.tcx.impl_of_method(instance.def_id()).and_then(|impl_def_id| {
 501                 // If the method does *not* belong to a trait, proceed
 502                 if cx.tcx.trait_id_of_impl(impl_def_id).is_none() {
 503                     let impl_self_ty = cx.tcx.subst_and_normalize_erasing_regions(
 504                         instance.substs,
 505                         ty::ParamEnv::reveal_all(),
 506                         cx.tcx.type_of(impl_def_id),
 507                     );
 508
 509                     // Only "class" methods are generally understood by LLVM,
 510                     // so avoid methods on other types (e.g., `<*mut T>::null`).
 511                     match impl_self_ty.kind() {
 512                         ty::Adt(def, ..) if !def.is_box() => {
 513                             // Again, only create type information if full debuginfo is enabled
 514                             if cx.sess().opts.debuginfo == DebugInfo::Full
 515                                 && !impl_self_ty.needs_subst()
 516                             {
 517                                 Some(type_di_node(cx, impl_self_ty))
 518                             } else {
 519                                 Some(namespace::item_namespace(cx, def.did()))
 520                             }
 521                         }
 522                         _ => None,
 523                     }
 524                 } else {
 525                     // For trait method impls we still use the "parallel namespace"
 526                     // strategy
 527                     None
 528                 }
 529             });
 530
 531             self_type.unwrap_or_else(|| {
 532                 namespace::item_namespace(
 533                     cx,
 534                     DefId {
 535                         krate: instance.def_id().krate,
 536                         index: cx
 537                             .tcx
 538                             .def_key(instance.def_id())
 539                             .parent
 540                             .expect("get_containing_scope: missing parent?"),
 541                     },
 542                 )
 543             })
 544         }
 545     }
 546
 547     fn dbg_loc(
 548         &self,
 549         scope: &'ll DIScope,
 550         inlined_at: Option<&'ll DILocation>,
 551         span: Span,
 552     ) -> &'ll DILocation {
 553         let DebugLoc { line, col, .. } = self.lookup_debug_loc(span.lo());
 554
 555         unsafe { llvm::LLVMRustDIBuilderCreateDebugLocation(line, col, scope, inlined_at) }
 556     }
 557
 558     fn create_vtable_debuginfo(
 559         &self,
 560         ty: Ty<'tcx>,
 561         trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
 562         vtable: Self::Value,
 563     ) {
 564         metadata::create_vtable_di_node(self, ty, trait_ref, vtable)
 565     }
 566
 567     fn extend_scope_to_file(
 568         &self,
 569         scope_metadata: &'ll DIScope,
 570         file: &rustc_span::SourceFile,
 571     ) -> &'ll DILexicalBlock {
 572         metadata::extend_scope_to_file(self, scope_metadata, file)
 573     }
 574
 575     fn debuginfo_finalize(&self) {
 576         finalize(self)
 577     }
 578
 579     // FIXME(eddyb) find a common convention for all of the debuginfo-related
 580     // names (choose between `dbg`, `debug`, `debuginfo`, `debug_info` etc.).
 581     fn create_dbg_var(
 582         &self,
 583         variable_name: Symbol,
 584         variable_type: Ty<'tcx>,
 585         scope_metadata: &'ll DIScope,
 586         variable_kind: VariableKind,
 587         span: Span,
 588     ) -> &'ll DIVariable {
 589         let loc = self.lookup_debug_loc(span.lo());
 590         let file_metadata = file_metadata(self, &loc.file);
 591
 592         let type_metadata = type_di_node(self, variable_type);
 593
 594         let (argument_index, dwarf_tag) = match variable_kind {
 595             ArgumentVariable(index) => (index as c_uint, DW_TAG_arg_variable),
 596             LocalVariable => (0, DW_TAG_auto_variable),
 597         };
 598         let align = self.align_of(variable_type);
 599
 600         let name = variable_name.as_str();
 601         unsafe {
 602             llvm::LLVMRustDIBuilderCreateVariable(
 603                 DIB(self),
 604                 dwarf_tag,
 605                 scope_metadata,
 606                 name.as_ptr().cast(),
 607                 name.len(),
 608                 file_metadata,
 609                 loc.line,
 610                 type_metadata,
 611                 true,
 612                 DIFlags::FlagZero,
 613                 argument_index,
 614                 align.bytes() as u32,
 615             )
 616         }
 617     }
 618 }