compiler/rustc_codegen_ssa/src/mir/debuginfo.rs

   1 use crate::traits::*;
   2 use rustc_index::vec::IndexVec;
   3 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
   4 use rustc_middle::mir;
   5 use rustc_middle::ty;
   6 use rustc_middle::ty::layout::{HasTyCtxt, LayoutOf};
   7 use rustc_session::config::DebugInfo;
   8 use rustc_span::symbol::{kw, Symbol};
   9 use rustc_span::{BytePos, Span};
  10 use rustc_target::abi::Abi;
  11 use rustc_target::abi::Size;
  12
  13 use super::operand::{OperandRef, OperandValue};
  14 use super::place::PlaceRef;
  15 use super::{FunctionCx, LocalRef};
  16
  17 use std::ops::Range;
  18
  19 pub struct FunctionDebugContext<S, L> {
  20     pub scopes: IndexVec<mir::SourceScope, DebugScope<S, L>>,
  21 }
  22
  23 #[derive(Copy, Clone)]
  24 pub enum VariableKind {
  25     ArgumentVariable(usize /*index*/),
  26     LocalVariable,
  27 }
  28
  29 /// Like `mir::VarDebugInfo`, but within a `mir::Local`.
  30 #[derive(Clone)]
  31 pub struct PerLocalVarDebugInfo<'tcx, D> {
  32     pub name: Symbol,
  33     pub source_info: mir::SourceInfo,
  34
  35     /// `DIVariable` returned by `create_dbg_var`.
  36     pub dbg_var: Option<D>,
  37
  38     /// Byte range in the `dbg_var` covered by this fragment,
  39     /// if this is a fragment of a composite `VarDebugInfo`.
  40     pub fragment: Option<Range<Size>>,
  41
  42     /// `.place.projection` from `mir::VarDebugInfo`.
  43     pub projection: &'tcx ty::List<mir::PlaceElem<'tcx>>,
  44 }
  45
  46 #[derive(Clone, Copy, Debug)]
  47 pub struct DebugScope<S, L> {
  48     pub dbg_scope: S,
  49
  50     /// Call site location, if this scope was inlined from another function.
  51     pub inlined_at: Option<L>,
  52
  53     // Start and end offsets of the file to which this DIScope belongs.
  54     // These are used to quickly determine whether some span refers to the same file.
  55     pub file_start_pos: BytePos,
  56     pub file_end_pos: BytePos,
  57 }
  58
  59 impl<'tcx, S: Copy, L: Copy> DebugScope<S, L> {
  60     /// DILocations inherit source file name from the parent DIScope.  Due to macro expansions
  61     /// it may so happen that the current span belongs to a different file than the DIScope
  62     /// corresponding to span's containing source scope.  If so, we need to create a DIScope
  63     /// "extension" into that file.
  64     pub fn adjust_dbg_scope_for_span<Cx: CodegenMethods<'tcx, DIScope = S, DILocation = L>>(
  65         &self,
  66         cx: &Cx,
  67         span: Span,
  68     ) -> S {
  69         let pos = span.lo();
  70         if pos < self.file_start_pos || pos >= self.file_end_pos {
  71             let sm = cx.sess().source_map();
  72             cx.extend_scope_to_file(self.dbg_scope, &sm.lookup_char_pos(pos).file)
  73         } else {
  74             self.dbg_scope
  75         }
  76     }
  77 }
  78
  79 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
  80     pub fn set_debug_loc(&self, bx: &mut Bx, source_info: mir::SourceInfo) {
  81         bx.set_span(source_info.span);
  82         if let Some(dbg_loc) = self.dbg_loc(source_info) {
  83             bx.set_dbg_loc(dbg_loc);
  84         }
  85     }
  86
  87     fn dbg_loc(&self, source_info: mir::SourceInfo) -> Option<Bx::DILocation> {
  88         let (dbg_scope, inlined_at, span) = self.adjusted_span_and_dbg_scope(source_info)?;
  89         Some(self.cx.dbg_loc(dbg_scope, inlined_at, span))
  90     }
  91
  92     fn adjusted_span_and_dbg_scope(
  93         &self,
  94         source_info: mir::SourceInfo,
  95     ) -> Option<(Bx::DIScope, Option<Bx::DILocation>, Span)> {
  96         let span = self.adjust_span_for_debugging(source_info.span);
  97         let scope = &self.debug_context.as_ref()?.scopes[source_info.scope];
  98         Some((scope.adjust_dbg_scope_for_span(self.cx, span), scope.inlined_at, span))
  99     }
 100
 101     /// In order to have a good line stepping behavior in debugger, we overwrite debug
 102     /// locations of macro expansions with that of the outermost expansion site (when the macro is
 103     /// annotated with `#[collapse_debuginfo]` or when `-Zdebug-macros` is provided).
 104     fn adjust_span_for_debugging(&self, mut span: Span) -> Span {
 105         // Bail out if debug info emission is not enabled.
 106         if self.debug_context.is_none() {
 107             return span;
 108         }
 109
 110         if self.cx.tcx().should_collapse_debuginfo(span) {
 111             // Walk up the macro expansion chain until we reach a non-expanded span.
 112             // We also stop at the function body level because no line stepping can occur
 113             // at the level above that.
 114             // Use span of the outermost expansion site, while keeping the original lexical scope.
 115             span = rustc_span::hygiene::walk_chain(span, self.mir.span.ctxt());
 116         }
 117
 118         span
 119     }
 120
 121     fn spill_operand_to_stack(
 122         operand: &OperandRef<'tcx, Bx::Value>,
 123         name: Option<String>,
 124         bx: &mut Bx,
 125     ) -> PlaceRef<'tcx, Bx::Value> {
 126         // "Spill" the value onto the stack, for debuginfo,
 127         // without forcing non-debuginfo uses of the local
 128         // to also load from the stack every single time.
 129         // FIXME(#68817) use `llvm.dbg.value` instead,
 130         // at least for the cases which LLVM handles correctly.
 131         let spill_slot = PlaceRef::alloca(bx, operand.layout);
 132         if let Some(name) = name {
 133             bx.set_var_name(spill_slot.llval, &(name + ".dbg.spill"));
 134         }
 135         operand.val.store(bx, spill_slot);
 136         spill_slot
 137     }
 138
 139     /// Apply debuginfo and/or name, after creating the `alloca` for a local,
 140     /// or initializing the local with an operand (whichever applies).
 141     pub fn debug_introduce_local(&self, bx: &mut Bx, local: mir::Local) {
 142         let full_debug_info = bx.sess().opts.debuginfo == DebugInfo::Full;
 143
 144         // FIXME(eddyb) maybe name the return place as `_0` or `return`?
 145         if local == mir::RETURN_PLACE && !self.mir.local_decls[mir::RETURN_PLACE].is_user_variable()
 146         {
 147             return;
 148         }
 149
 150         let vars = match &self.per_local_var_debug_info {
 151             Some(per_local) => &per_local[local],
 152             None => return,
 153         };
 154         let whole_local_var = vars.iter().find(|var| var.projection.is_empty()).cloned();
 155         let has_proj = || vars.iter().any(|var| !var.projection.is_empty());
 156
 157         let fallback_var = if self.mir.local_kind(local) == mir::LocalKind::Arg {
 158             let arg_index = local.index() - 1;
 159
 160             // Add debuginfo even to unnamed arguments.
 161             // FIXME(eddyb) is this really needed?
 162             if arg_index == 0 && has_proj() {
 163                 // Hide closure environments from debuginfo.
 164                 // FIXME(eddyb) shouldn't `ArgumentVariable` indices
 165                 // be offset to account for the hidden environment?
 166                 None
 167             } else if whole_local_var.is_some() {
 168                 // No need to make up anything, there is a `mir::VarDebugInfo`
 169                 // covering the whole local.
 170                 // FIXME(eddyb) take `whole_local_var.source_info.scope` into
 171                 // account, just in case it doesn't use `ArgumentVariable`
 172                 // (after #67586 gets fixed).
 173                 None
 174             } else {
 175                 let name = kw::Empty;
 176                 let decl = &self.mir.local_decls[local];
 177                 let dbg_var = if full_debug_info {
 178                     self.adjusted_span_and_dbg_scope(decl.source_info).map(
 179                         |(dbg_scope, _, span)| {
 180                             // FIXME(eddyb) is this `+ 1` needed at all?
 181                             let kind = VariableKind::ArgumentVariable(arg_index + 1);
 182
 183                             let arg_ty = self.monomorphize(decl.ty);
 184
 185                             self.cx.create_dbg_var(name, arg_ty, dbg_scope, kind, span)
 186                         },
 187                     )
 188                 } else {
 189                     None
 190                 };
 191
 192                 Some(PerLocalVarDebugInfo {
 193                     name,
 194                     source_info: decl.source_info,
 195                     dbg_var,
 196                     fragment: None,
 197                     projection: ty::List::empty(),
 198                 })
 199             }
 200         } else {
 201             None
 202         };
 203
 204         let local_ref = &self.locals[local];
 205
 206         let name = if bx.sess().fewer_names() {
 207             None
 208         } else {
 209             Some(match whole_local_var.or(fallback_var.clone()) {
 210                 Some(var) if var.name != kw::Empty => var.name.to_string(),
 211                 _ => format!("{:?}", local),
 212             })
 213         };
 214
 215         if let Some(name) = &name {
 216             match local_ref {
 217                 LocalRef::Place(place) | LocalRef::UnsizedPlace(place) => {
 218                     bx.set_var_name(place.llval, name);
 219                 }
 220                 LocalRef::Operand(Some(operand)) => match operand.val {
 221                     OperandValue::Ref(x, ..) | OperandValue::Immediate(x) => {
 222                         bx.set_var_name(x, name);
 223                     }
 224                     OperandValue::Pair(a, b) => {
 225                         // FIXME(eddyb) these are scalar components,
 226                         // maybe extract the high-level fields?
 227                         bx.set_var_name(a, &(name.clone() + ".0"));
 228                         bx.set_var_name(b, &(name.clone() + ".1"));
 229                     }
 230                 },
 231                 LocalRef::Operand(None) => {}
 232             }
 233         }
 234
 235         if !full_debug_info || vars.is_empty() && fallback_var.is_none() {
 236             return;
 237         }
 238
 239         let base = match local_ref {
 240             LocalRef::Operand(None) => return,
 241
 242             LocalRef::Operand(Some(operand)) => {
 243                 // Don't spill operands onto the stack in naked functions.
 244                 // See: https://github.com/rust-lang/rust/issues/42779
 245                 let attrs = bx.tcx().codegen_fn_attrs(self.instance.def_id());
 246                 if attrs.flags.contains(CodegenFnAttrFlags::NAKED) {
 247                     return;
 248                 }
 249
 250                 Self::spill_operand_to_stack(operand, name, bx)
 251             }
 252
 253             LocalRef::Place(place) => *place,
 254
 255             // FIXME(eddyb) add debuginfo for unsized places too.
 256             LocalRef::UnsizedPlace(_) => return,
 257         };
 258
 259         let vars = vars.iter().cloned().chain(fallback_var);
 260
 261         for var in vars {
 262             let Some(dbg_var) = var.dbg_var else { continue };
 263             let Some(dbg_loc) = self.dbg_loc(var.source_info) else { continue };
 264
 265             let mut direct_offset = Size::ZERO;
 266             // FIXME(eddyb) use smallvec here.
 267             let mut indirect_offsets = vec![];
 268             let mut place = base;
 269
 270             for elem in &var.projection[..] {
 271                 match *elem {
 272                     mir::ProjectionElem::Deref => {
 273                         indirect_offsets.push(Size::ZERO);
 274                         place = bx.load_operand(place).deref(bx.cx());
 275                     }
 276                     mir::ProjectionElem::Field(field, _) => {
 277                         let i = field.index();
 278                         let offset = indirect_offsets.last_mut().unwrap_or(&mut direct_offset);
 279                         *offset += place.layout.fields.offset(i);
 280                         place = place.project_field(bx, i);
 281                     }
 282                     mir::ProjectionElem::Downcast(_, variant) => {
 283                         place = place.project_downcast(bx, variant);
 284                     }
 285                     _ => span_bug!(
 286                         var.source_info.span,
 287                         "unsupported var debuginfo place `{:?}`",
 288                         mir::Place { local, projection: var.projection },
 289                     ),
 290                 }
 291             }
 292
 293             // When targeting MSVC, create extra allocas for arguments instead of pointing multiple
 294             // dbg_var_addr() calls into the same alloca with offsets. MSVC uses CodeView records
 295             // not DWARF and LLVM doesn't support translating the resulting
 296             // [DW_OP_deref, DW_OP_plus_uconst, offset, DW_OP_deref] debug info to CodeView.
 297             // Creating extra allocas on the stack makes the resulting debug info simple enough
 298             // that LLVM can generate correct CodeView records and thus the values appear in the
 299             // debugger. (#83709)
 300             let should_create_individual_allocas = bx.cx().sess().target.is_like_msvc
 301                 && self.mir.local_kind(local) == mir::LocalKind::Arg
 302                 // LLVM can handle simple things but anything more complex than just a direct
 303                 // offset or one indirect offset of 0 is too complex for it to generate CV records
 304                 // correctly.
 305                 && (direct_offset != Size::ZERO
 306                     || !matches!(&indirect_offsets[..], [Size::ZERO] | []));
 307
 308             if should_create_individual_allocas {
 309                 // Create a variable which will be a pointer to the actual value
 310                 let ptr_ty = bx.tcx().mk_ty(ty::RawPtr(ty::TypeAndMut {
 311                     mutbl: mir::Mutability::Mut,
 312                     ty: place.layout.ty,
 313                 }));
 314                 let ptr_layout = bx.layout_of(ptr_ty);
 315                 let alloca = PlaceRef::alloca(bx, ptr_layout);
 316                 bx.set_var_name(alloca.llval, &(var.name.to_string() + ".dbg.spill"));
 317
 318                 // Write the pointer to the variable
 319                 bx.store(place.llval, alloca.llval, alloca.align);
 320
 321                 // Point the debug info to `*alloca` for the current variable
 322                 bx.dbg_var_addr(dbg_var, dbg_loc, alloca.llval, Size::ZERO, &[Size::ZERO], None);
 323             } else {
 324                 bx.dbg_var_addr(
 325                     dbg_var,
 326                     dbg_loc,
 327                     base.llval,
 328                     direct_offset,
 329                     &indirect_offsets,
 330                     None,
 331                 );
 332             }
 333         }
 334     }
 335
 336     pub fn debug_introduce_locals(&self, bx: &mut Bx) {
 337         if bx.sess().opts.debuginfo == DebugInfo::Full || !bx.sess().fewer_names() {
 338             for local in self.locals.indices() {
 339                 self.debug_introduce_local(bx, local);
 340             }
 341         }
 342     }
 343
 344     /// Partition all `VarDebugInfo` in `self.mir`, by their base `Local`.
 345     pub fn compute_per_local_var_debug_info(
 346         &self,
 347         bx: &mut Bx,
 348     ) -> Option<IndexVec<mir::Local, Vec<PerLocalVarDebugInfo<'tcx, Bx::DIVariable>>>> {
 349         let full_debug_info = self.cx.sess().opts.debuginfo == DebugInfo::Full;
 350
 351         let target_is_msvc = self.cx.sess().target.is_like_msvc;
 352
 353         if !full_debug_info && self.cx.sess().fewer_names() {
 354             return None;
 355         }
 356
 357         let mut per_local = IndexVec::from_elem(vec![], &self.mir.local_decls);
 358         for var in &self.mir.var_debug_info {
 359             let dbg_scope_and_span = if full_debug_info {
 360                 self.adjusted_span_and_dbg_scope(var.source_info)
 361             } else {
 362                 None
 363             };
 364
 365             let dbg_var = dbg_scope_and_span.map(|(dbg_scope, _, span)| {
 366                 let (var_ty, var_kind) = match var.value {
 367                     mir::VarDebugInfoContents::Place(place) => {
 368                         let var_ty = self.monomorphized_place_ty(place.as_ref());
 369                         let var_kind = if self.mir.local_kind(place.local) == mir::LocalKind::Arg
 370                             && place.projection.is_empty()
 371                             && var.source_info.scope == mir::OUTERMOST_SOURCE_SCOPE
 372                         {
 373                             let arg_index = place.local.index() - 1;
 374                             if target_is_msvc {
 375                                 // ScalarPair parameters are spilled to the stack so they need to
 376                                 // be marked as a `LocalVariable` for MSVC debuggers to visualize
 377                                 // their data correctly. (See #81894 & #88625)
 378                                 let var_ty_layout = self.cx.layout_of(var_ty);
 379                                 if let Abi::ScalarPair(_, _) = var_ty_layout.abi {
 380                                     VariableKind::LocalVariable
 381                                 } else {
 382                                     VariableKind::ArgumentVariable(arg_index + 1)
 383                                 }
 384                             } else {
 385                                 // FIXME(eddyb) shouldn't `ArgumentVariable` indices be
 386                                 // offset in closures to account for the hidden environment?
 387                                 // Also, is this `+ 1` needed at all?
 388                                 VariableKind::ArgumentVariable(arg_index + 1)
 389                             }
 390                         } else {
 391                             VariableKind::LocalVariable
 392                         };
 393                         (var_ty, var_kind)
 394                     }
 395                     mir::VarDebugInfoContents::Const(c) => {
 396                         let ty = self.monomorphize(c.ty());
 397                         (ty, VariableKind::LocalVariable)
 398                     }
 399                     mir::VarDebugInfoContents::Composite { ty, fragments: _ } => {
 400                         let ty = self.monomorphize(ty);
 401                         (ty, VariableKind::LocalVariable)
 402                     }
 403                 };
 404
 405                 self.cx.create_dbg_var(var.name, var_ty, dbg_scope, var_kind, span)
 406             });
 407
 408             match var.value {
 409                 mir::VarDebugInfoContents::Place(place) => {
 410                     per_local[place.local].push(PerLocalVarDebugInfo {
 411                         name: var.name,
 412                         source_info: var.source_info,
 413                         dbg_var,
 414                         fragment: None,
 415                         projection: place.projection,
 416                     });
 417                 }
 418                 mir::VarDebugInfoContents::Const(c) => {
 419                     if let Some(dbg_var) = dbg_var {
 420                         let Some(dbg_loc) = self.dbg_loc(var.source_info) else { continue };
 421
 422                         if let Ok(operand) = self.eval_mir_constant_to_operand(bx, &c) {
 423                             let base = Self::spill_operand_to_stack(
 424                                 &operand,
 425                                 Some(var.name.to_string()),
 426                                 bx,
 427                             );
 428
 429                             bx.dbg_var_addr(dbg_var, dbg_loc, base.llval, Size::ZERO, &[], None);
 430                         }
 431                     }
 432                 }
 433                 mir::VarDebugInfoContents::Composite { ty, ref fragments } => {
 434                     let var_ty = self.monomorphize(ty);
 435                     let var_layout = self.cx.layout_of(var_ty);
 436                     for fragment in fragments {
 437                         let mut fragment_start = Size::ZERO;
 438                         let mut fragment_layout = var_layout;
 439
 440                         for elem in &fragment.projection {
 441                             match *elem {
 442                                 mir::ProjectionElem::Field(field, _) => {
 443                                     let i = field.index();
 444                                     fragment_start += fragment_layout.fields.offset(i);
 445                                     fragment_layout = fragment_layout.field(self.cx, i);
 446                                 }
 447                                 _ => span_bug!(
 448                                     var.source_info.span,
 449                                     "unsupported fragment projection `{:?}`",
 450                                     elem,
 451                                 ),
 452                             }
 453                         }
 454
 455                         let place = fragment.contents;
 456                         per_local[place.local].push(PerLocalVarDebugInfo {
 457                             name: var.name,
 458                             source_info: var.source_info,
 459                             dbg_var,
 460                             fragment: if fragment_layout.size == var_layout.size {
 461                                 // Fragment covers entire variable, so as far as
 462                                 // DWARF is concerned, it's not really a fragment.
 463                                 None
 464                             } else {
 465                                 Some(fragment_start..fragment_start + fragment_layout.size)
 466                             },
 467                             projection: place.projection,
 468                         });
 469                     }
 470                 }
 471             }
 472         }
 473         Some(per_local)
 474     }
 475 }