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_metadata, TypeMap};
   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, FxHashSet};
  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::{Primitive, Size};
  36
  37 use libc::c_uint;
  38 use smallvec::SmallVec;
  39 use std::cell::RefCell;
  40 use std::iter;
  41 use tracing::debug;
  42
  43 mod create_scope_map;
  44 pub mod gdb;
  45 pub mod metadata;
  46 mod namespace;
  47 mod utils;
  48
  49 pub use self::create_scope_map::compute_mir_scopes;
  50 pub use self::metadata::create_global_var_metadata;
  51 pub use self::metadata::extend_scope_to_file;
  52
  53 #[allow(non_upper_case_globals)]
  54 const DW_TAG_auto_variable: c_uint = 0x100;
  55 #[allow(non_upper_case_globals)]
  56 const DW_TAG_arg_variable: c_uint = 0x101;
  57
  58 /// A context object for maintaining all state needed by the debuginfo module.
  59 pub struct CrateDebugContext<'a, 'tcx> {
  60     llcontext: &'a llvm::Context,
  61     llmod: &'a llvm::Module,
  62     builder: &'a mut DIBuilder<'a>,
  63     created_files: RefCell<FxHashMap<(Option<String>, Option<String>), &'a DIFile>>,
  64     created_enum_disr_types: RefCell<FxHashMap<(DefId, Primitive), &'a DIType>>,
  65
  66     type_map: RefCell<TypeMap<'a, 'tcx>>,
  67     namespace_map: RefCell<DefIdMap<&'a DIScope>>,
  68
  69     // This collection is used to assert that composite types (structs, enums,
  70     // ...) have their members only set once:
  71     composite_types_completed: RefCell<FxHashSet<&'a DIType>>,
  72 }
  73
  74 impl Drop for CrateDebugContext<'_, '_> {
  75     fn drop(&mut self) {
  76         unsafe {
  77             llvm::LLVMRustDIBuilderDispose(&mut *(self.builder as *mut _));
  78         }
  79     }
  80 }
  81
  82 impl<'a, 'tcx> CrateDebugContext<'a, 'tcx> {
  83     pub fn new(llmod: &'a llvm::Module) -> Self {
  84         debug!("CrateDebugContext::new");
  85         let builder = unsafe { llvm::LLVMRustDIBuilderCreate(llmod) };
  86         // DIBuilder inherits context from the module, so we'd better use the same one
  87         let llcontext = unsafe { llvm::LLVMGetModuleContext(llmod) };
  88         CrateDebugContext {
  89             llcontext,
  90             llmod,
  91             builder,
  92             created_files: Default::default(),
  93             created_enum_disr_types: Default::default(),
  94             type_map: Default::default(),
  95             namespace_map: RefCell::new(Default::default()),
  96             composite_types_completed: Default::default(),
  97         }
  98     }
  99
 100     pub fn finalize(&self, sess: &Session) {
 101         unsafe {
 102             llvm::LLVMRustDIBuilderFinalize(self.builder);
 103
 104             // Debuginfo generation in LLVM by default uses a higher
 105             // version of dwarf than macOS currently understands. We can
 106             // instruct LLVM to emit an older version of dwarf, however,
 107             // for macOS to understand. For more info see #11352
 108             // This can be overridden using --llvm-opts -dwarf-version,N.
 109             // Android has the same issue (#22398)
 110             if let Some(version) = sess.target.dwarf_version {
 111                 llvm::LLVMRustAddModuleFlag(
 112                     self.llmod,
 113                     llvm::LLVMModFlagBehavior::Warning,
 114                     "Dwarf Version\0".as_ptr().cast(),
 115                     version,
 116                 )
 117             }
 118
 119             // Indicate that we want CodeView debug information on MSVC
 120             if sess.target.is_like_msvc {
 121                 llvm::LLVMRustAddModuleFlag(
 122                     self.llmod,
 123                     llvm::LLVMModFlagBehavior::Warning,
 124                     "CodeView\0".as_ptr().cast(),
 125                     1,
 126                 )
 127             }
 128
 129             // Prevent bitcode readers from deleting the debug info.
 130             let ptr = "Debug Info Version\0".as_ptr();
 131             llvm::LLVMRustAddModuleFlag(
 132                 self.llmod,
 133                 llvm::LLVMModFlagBehavior::Warning,
 134                 ptr.cast(),
 135                 llvm::LLVMRustDebugMetadataVersion(),
 136             );
 137         }
 138     }
 139 }
 140
 141 /// Creates any deferred debug metadata nodes
 142 pub fn finalize(cx: &CodegenCx<'_, '_>) {
 143     if let Some(dbg_cx) = &cx.dbg_cx {
 144         debug!("finalize");
 145
 146         if gdb::needs_gdb_debug_scripts_section(cx) {
 147             // Add a .debug_gdb_scripts section to this compile-unit. This will
 148             // cause GDB to try and load the gdb_load_rust_pretty_printers.py file,
 149             // which activates the Rust pretty printers for binary this section is
 150             // contained in.
 151             gdb::get_or_insert_gdb_debug_scripts_section_global(cx);
 152         }
 153
 154         dbg_cx.finalize(cx.sess());
 155     }
 156 }
 157
 158 impl<'ll> DebugInfoBuilderMethods for Builder<'_, 'll, '_> {
 159     // FIXME(eddyb) find a common convention for all of the debuginfo-related
 160     // names (choose between `dbg`, `debug`, `debuginfo`, `debug_info` etc.).
 161     fn dbg_var_addr(
 162         &mut self,
 163         dbg_var: &'ll DIVariable,
 164         dbg_loc: &'ll DILocation,
 165         variable_alloca: Self::Value,
 166         direct_offset: Size,
 167         indirect_offsets: &[Size],
 168     ) {
 169         // Convert the direct and indirect offsets to address ops.
 170         // FIXME(eddyb) use `const`s instead of getting the values via FFI,
 171         // the values should match the ones in the DWARF standard anyway.
 172         let op_deref = || unsafe { llvm::LLVMRustDIBuilderCreateOpDeref() };
 173         let op_plus_uconst = || unsafe { llvm::LLVMRustDIBuilderCreateOpPlusUconst() };
 174         let mut addr_ops = SmallVec::<[u64; 8]>::new();
 175
 176         if direct_offset.bytes() > 0 {
 177             addr_ops.push(op_plus_uconst());
 178             addr_ops.push(direct_offset.bytes() as u64);
 179         }
 180         for &offset in indirect_offsets {
 181             addr_ops.push(op_deref());
 182             if offset.bytes() > 0 {
 183                 addr_ops.push(op_plus_uconst());
 184                 addr_ops.push(offset.bytes() as u64);
 185             }
 186         }
 187
 188         unsafe {
 189             // FIXME(eddyb) replace `llvm.dbg.declare` with `llvm.dbg.addr`.
 190             llvm::LLVMRustDIBuilderInsertDeclareAtEnd(
 191                 DIB(self.cx()),
 192                 variable_alloca,
 193                 dbg_var,
 194                 addr_ops.as_ptr(),
 195                 addr_ops.len() as c_uint,
 196                 dbg_loc,
 197                 self.llbb(),
 198             );
 199         }
 200     }
 201
 202     fn set_dbg_loc(&mut self, dbg_loc: &'ll DILocation) {
 203         unsafe {
 204             let dbg_loc_as_llval = llvm::LLVMRustMetadataAsValue(self.cx().llcx, dbg_loc);
 205             llvm::LLVMSetCurrentDebugLocation(self.llbuilder, dbg_loc_as_llval);
 206         }
 207     }
 208
 209     fn insert_reference_to_gdb_debug_scripts_section_global(&mut self) {
 210         gdb::insert_reference_to_gdb_debug_scripts_section_global(self)
 211     }
 212
 213     fn set_var_name(&mut self, value: &'ll Value, name: &str) {
 214         // Avoid wasting time if LLVM value names aren't even enabled.
 215         if self.sess().fewer_names() {
 216             return;
 217         }
 218
 219         // Only function parameters and instructions are local to a function,
 220         // don't change the name of anything else (e.g. globals).
 221         let param_or_inst = unsafe {
 222             llvm::LLVMIsAArgument(value).is_some() || llvm::LLVMIsAInstruction(value).is_some()
 223         };
 224         if !param_or_inst {
 225             return;
 226         }
 227
 228         // Avoid replacing the name if it already exists.
 229         // While we could combine the names somehow, it'd
 230         // get noisy quick, and the usefulness is dubious.
 231         if llvm::get_value_name(value).is_empty() {
 232             llvm::set_value_name(value, name.as_bytes());
 233         }
 234     }
 235 }
 236
 237 /// A source code location used to generate debug information.
 238 // FIXME(eddyb) rename this to better indicate it's a duplicate of
 239 // `rustc_span::Loc` rather than `DILocation`, perhaps by making
 240 // `lookup_char_pos` return the right information instead.
 241 pub struct DebugLoc {
 242     /// Information about the original source file.
 243     pub file: Lrc<SourceFile>,
 244     /// The (1-based) line number.
 245     pub line: u32,
 246     /// The (1-based) column number.
 247     pub col: u32,
 248 }
 249
 250 impl CodegenCx<'_, '_> {
 251     /// Looks up debug source information about a `BytePos`.
 252     // FIXME(eddyb) rename this to better indicate it's a duplicate of
 253     // `lookup_char_pos` rather than `dbg_loc`, perhaps by making
 254     // `lookup_char_pos` return the right information instead.
 255     pub fn lookup_debug_loc(&self, pos: BytePos) -> DebugLoc {
 256         let (file, line, col) = match self.sess().source_map().lookup_line(pos) {
 257             Ok(SourceFileAndLine { sf: file, line }) => {
 258                 let line_pos = file.line_begin_pos(pos);
 259
 260                 // Use 1-based indexing.
 261                 let line = (line + 1) as u32;
 262                 let col = (pos - line_pos).to_u32() + 1;
 263
 264                 (file, line, col)
 265             }
 266             Err(file) => (file, UNKNOWN_LINE_NUMBER, UNKNOWN_COLUMN_NUMBER),
 267         };
 268
 269         // For MSVC, omit the column number.
 270         // Otherwise, emit it. This mimics clang behaviour.
 271         // See discussion in https://github.com/rust-lang/rust/issues/42921
 272         if self.sess().target.is_like_msvc {
 273             DebugLoc { file, line, col: UNKNOWN_COLUMN_NUMBER }
 274         } else {
 275             DebugLoc { file, line, col }
 276         }
 277     }
 278 }
 279
 280 impl<'ll, 'tcx> DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
 281     fn create_function_debug_context(
 282         &self,
 283         instance: Instance<'tcx>,
 284         fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
 285         llfn: &'ll Value,
 286         mir: &mir::Body<'tcx>,
 287     ) -> Option<FunctionDebugContext<&'ll DIScope, &'ll DILocation>> {
 288         if self.sess().opts.debuginfo == DebugInfo::None {
 289             return None;
 290         }
 291
 292         // Initialize fn debug context (including scopes).
 293         // FIXME(eddyb) figure out a way to not need `Option` for `dbg_scope`.
 294         let empty_scope = DebugScope {
 295             dbg_scope: None,
 296             inlined_at: None,
 297             file_start_pos: BytePos(0),
 298             file_end_pos: BytePos(0),
 299         };
 300         let mut fn_debug_context =
 301             FunctionDebugContext { scopes: IndexVec::from_elem(empty_scope, &mir.source_scopes) };
 302
 303         // Fill in all the scopes, with the information from the MIR body.
 304         compute_mir_scopes(
 305             self,
 306             instance,
 307             mir,
 308             self.dbg_scope_fn(instance, fn_abi, Some(llfn)),
 309             &mut fn_debug_context,
 310         );
 311
 312         Some(fn_debug_context)
 313     }
 314
 315     fn dbg_scope_fn(
 316         &self,
 317         instance: Instance<'tcx>,
 318         fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
 319         maybe_definition_llfn: Option<&'ll Value>,
 320     ) -> &'ll DIScope {
 321         let tcx = self.tcx;
 322
 323         let def_id = instance.def_id();
 324         let containing_scope = get_containing_scope(self, instance);
 325         let span = tcx.def_span(def_id);
 326         let loc = self.lookup_debug_loc(span.lo());
 327         let file_metadata = file_metadata(self, &loc.file);
 328
 329         let function_type_metadata = unsafe {
 330             let fn_signature = get_function_signature(self, fn_abi);
 331             llvm::LLVMRustDIBuilderCreateSubroutineType(DIB(self), fn_signature)
 332         };
 333
 334         let mut name = String::new();
 335         type_names::push_item_name(tcx, def_id, false, &mut name);
 336
 337         // Find the enclosing function, in case this is a closure.
 338         let enclosing_fn_def_id = tcx.typeck_root_def_id(def_id);
 339
 340         // We look up the generics of the enclosing function and truncate the substs
 341         // to their length in order to cut off extra stuff that might be in there for
 342         // closures or generators.
 343         let generics = tcx.generics_of(enclosing_fn_def_id);
 344         let substs = instance.substs.truncate_to(tcx, generics);
 345
 346         type_names::push_generic_params(
 347             tcx,
 348             tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), substs),
 349             &mut name,
 350         );
 351
 352         let template_parameters = get_template_parameters(self, generics, substs);
 353
 354         let linkage_name = &mangled_name_of_instance(self, instance).name;
 355         // Omit the linkage_name if it is the same as subprogram name.
 356         let linkage_name = if &name == linkage_name { "" } else { linkage_name };
 357
 358         // FIXME(eddyb) does this need to be separate from `loc.line` for some reason?
 359         let scope_line = loc.line;
 360
 361         let mut flags = DIFlags::FlagPrototyped;
 362
 363         if fn_abi.ret.layout.abi.is_uninhabited() {
 364             flags |= DIFlags::FlagNoReturn;
 365         }
 366
 367         let mut spflags = DISPFlags::SPFlagDefinition;
 368         if is_node_local_to_unit(self, def_id) {
 369             spflags |= DISPFlags::SPFlagLocalToUnit;
 370         }
 371         if self.sess().opts.optimize != config::OptLevel::No {
 372             spflags |= DISPFlags::SPFlagOptimized;
 373         }
 374         if let Some((id, _)) = tcx.entry_fn(()) {
 375             if id == def_id {
 376                 spflags |= DISPFlags::SPFlagMainSubprogram;
 377             }
 378         }
 379
 380         unsafe {
 381             return llvm::LLVMRustDIBuilderCreateFunction(
 382                 DIB(self),
 383                 containing_scope,
 384                 name.as_ptr().cast(),
 385                 name.len(),
 386                 linkage_name.as_ptr().cast(),
 387                 linkage_name.len(),
 388                 file_metadata,
 389                 loc.line,
 390                 function_type_metadata,
 391                 scope_line,
 392                 flags,
 393                 spflags,
 394                 maybe_definition_llfn,
 395                 template_parameters,
 396                 None,
 397             );
 398         }
 399
 400         fn get_function_signature<'ll, 'tcx>(
 401             cx: &CodegenCx<'ll, 'tcx>,
 402             fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
 403         ) -> &'ll DIArray {
 404             if cx.sess().opts.debuginfo == DebugInfo::Limited {
 405                 return create_DIArray(DIB(cx), &[]);
 406             }
 407
 408             let mut signature = Vec::with_capacity(fn_abi.args.len() + 1);
 409
 410             // Return type -- llvm::DIBuilder wants this at index 0
 411             signature.push(if fn_abi.ret.is_ignore() {
 412                 None
 413             } else {
 414                 Some(type_metadata(cx, fn_abi.ret.layout.ty))
 415             });
 416
 417             // Arguments types
 418             if cx.sess().target.is_like_msvc {
 419                 // FIXME(#42800):
 420                 // There is a bug in MSDIA that leads to a crash when it encounters
 421                 // a fixed-size array of `u8` or something zero-sized in a
 422                 // function-type (see #40477).
 423                 // As a workaround, we replace those fixed-size arrays with a
 424                 // pointer-type. So a function `fn foo(a: u8, b: [u8; 4])` would
 425                 // appear as `fn foo(a: u8, b: *const u8)` in debuginfo,
 426                 // and a function `fn bar(x: [(); 7])` as `fn bar(x: *const ())`.
 427                 // This transformed type is wrong, but these function types are
 428                 // already inaccurate due to ABI adjustments (see #42800).
 429                 signature.extend(fn_abi.args.iter().map(|arg| {
 430                     let t = arg.layout.ty;
 431                     let t = match t.kind() {
 432                         ty::Array(ct, _)
 433                             if (*ct == cx.tcx.types.u8) || cx.layout_of(*ct).is_zst() =>
 434                         {
 435                             cx.tcx.mk_imm_ptr(*ct)
 436                         }
 437                         _ => t,
 438                     };
 439                     Some(type_metadata(cx, t))
 440                 }));
 441             } else {
 442                 signature
 443                     .extend(fn_abi.args.iter().map(|arg| Some(type_metadata(cx, arg.layout.ty))));
 444             }
 445
 446             create_DIArray(DIB(cx), &signature[..])
 447         }
 448
 449         fn get_template_parameters<'ll, 'tcx>(
 450             cx: &CodegenCx<'ll, 'tcx>,
 451             generics: &ty::Generics,
 452             substs: SubstsRef<'tcx>,
 453         ) -> &'ll DIArray {
 454             if substs.types().next().is_none() {
 455                 return create_DIArray(DIB(cx), &[]);
 456             }
 457
 458             // Again, only create type information if full debuginfo is enabled
 459             let template_params: Vec<_> = if cx.sess().opts.debuginfo == DebugInfo::Full {
 460                 let names = get_parameter_names(cx, generics);
 461                 iter::zip(substs, names)
 462                     .filter_map(|(kind, name)| {
 463                         if let GenericArgKind::Type(ty) = kind.unpack() {
 464                             let actual_type =
 465                                 cx.tcx.normalize_erasing_regions(ParamEnv::reveal_all(), ty);
 466                             let actual_type_metadata = type_metadata(cx, actual_type);
 467                             let name = name.as_str();
 468                             Some(unsafe {
 469                                 Some(llvm::LLVMRustDIBuilderCreateTemplateTypeParameter(
 470                                     DIB(cx),
 471                                     None,
 472                                     name.as_ptr().cast(),
 473                                     name.len(),
 474                                     actual_type_metadata,
 475                                 ))
 476                             })
 477                         } else {
 478                             None
 479                         }
 480                     })
 481                     .collect()
 482             } else {
 483                 vec![]
 484             };
 485
 486             create_DIArray(DIB(cx), &template_params)
 487         }
 488
 489         fn get_parameter_names(cx: &CodegenCx<'_, '_>, generics: &ty::Generics) -> Vec<Symbol> {
 490             let mut names = generics.parent.map_or_else(Vec::new, |def_id| {
 491                 get_parameter_names(cx, cx.tcx.generics_of(def_id))
 492             });
 493             names.extend(generics.params.iter().map(|param| param.name));
 494             names
 495         }
 496
 497         fn get_containing_scope<'ll, 'tcx>(
 498             cx: &CodegenCx<'ll, 'tcx>,
 499             instance: Instance<'tcx>,
 500         ) -> &'ll DIScope {
 501             // First, let's see if this is a method within an inherent impl. Because
 502             // if yes, we want to make the result subroutine DIE a child of the
 503             // subroutine's self-type.
 504             let self_type = cx.tcx.impl_of_method(instance.def_id()).and_then(|impl_def_id| {
 505                 // If the method does *not* belong to a trait, proceed
 506                 if cx.tcx.trait_id_of_impl(impl_def_id).is_none() {
 507                     let impl_self_ty = cx.tcx.subst_and_normalize_erasing_regions(
 508                         instance.substs,
 509                         ty::ParamEnv::reveal_all(),
 510                         cx.tcx.type_of(impl_def_id),
 511                     );
 512
 513                     // Only "class" methods are generally understood by LLVM,
 514                     // so avoid methods on other types (e.g., `<*mut T>::null`).
 515                     match impl_self_ty.kind() {
 516                         ty::Adt(def, ..) if !def.is_box() => {
 517                             // Again, only create type information if full debuginfo is enabled
 518                             if cx.sess().opts.debuginfo == DebugInfo::Full
 519                                 && !impl_self_ty.needs_subst()
 520                             {
 521                                 Some(type_metadata(cx, impl_self_ty))
 522                             } else {
 523                                 Some(namespace::item_namespace(cx, def.did))
 524                             }
 525                         }
 526                         _ => None,
 527                     }
 528                 } else {
 529                     // For trait method impls we still use the "parallel namespace"
 530                     // strategy
 531                     None
 532                 }
 533             });
 534
 535             self_type.unwrap_or_else(|| {
 536                 namespace::item_namespace(
 537                     cx,
 538                     DefId {
 539                         krate: instance.def_id().krate,
 540                         index: cx
 541                             .tcx
 542                             .def_key(instance.def_id())
 543                             .parent
 544                             .expect("get_containing_scope: missing parent?"),
 545                     },
 546                 )
 547             })
 548         }
 549     }
 550
 551     fn dbg_loc(
 552         &self,
 553         scope: &'ll DIScope,
 554         inlined_at: Option<&'ll DILocation>,
 555         span: Span,
 556     ) -> &'ll DILocation {
 557         let DebugLoc { line, col, .. } = self.lookup_debug_loc(span.lo());
 558
 559         unsafe { llvm::LLVMRustDIBuilderCreateDebugLocation(line, col, scope, inlined_at) }
 560     }
 561
 562     fn create_vtable_metadata(
 563         &self,
 564         ty: Ty<'tcx>,
 565         trait_ref: Option<ty::PolyExistentialTraitRef<'tcx>>,
 566         vtable: Self::Value,
 567     ) {
 568         metadata::create_vtable_metadata(self, ty, trait_ref, vtable)
 569     }
 570
 571     fn extend_scope_to_file(
 572         &self,
 573         scope_metadata: &'ll DIScope,
 574         file: &rustc_span::SourceFile,
 575     ) -> &'ll DILexicalBlock {
 576         metadata::extend_scope_to_file(self, scope_metadata, file)
 577     }
 578
 579     fn debuginfo_finalize(&self) {
 580         finalize(self)
 581     }
 582
 583     // FIXME(eddyb) find a common convention for all of the debuginfo-related
 584     // names (choose between `dbg`, `debug`, `debuginfo`, `debug_info` etc.).
 585     fn create_dbg_var(
 586         &self,
 587         variable_name: Symbol,
 588         variable_type: Ty<'tcx>,
 589         scope_metadata: &'ll DIScope,
 590         variable_kind: VariableKind,
 591         span: Span,
 592     ) -> &'ll DIVariable {
 593         let loc = self.lookup_debug_loc(span.lo());
 594         let file_metadata = file_metadata(self, &loc.file);
 595
 596         let type_metadata = type_metadata(self, variable_type);
 597
 598         let (argument_index, dwarf_tag) = match variable_kind {
 599             ArgumentVariable(index) => (index as c_uint, DW_TAG_arg_variable),
 600             LocalVariable => (0, DW_TAG_auto_variable),
 601         };
 602         let align = self.align_of(variable_type);
 603
 604         let name = variable_name.as_str();
 605         unsafe {
 606             llvm::LLVMRustDIBuilderCreateVariable(
 607                 DIB(self),
 608                 dwarf_tag,
 609                 scope_metadata,
 610                 name.as_ptr().cast(),
 611                 name.len(),
 612                 file_metadata,
 613                 loc.line,
 614                 type_metadata,
 615                 true,
 616                 DIFlags::FlagZero,
 617                 argument_index,
 618                 align.bytes() as u32,
 619             )
 620         }
 621     }
 622 }