compiler/rustc_typeck/src/check/intrinsicck.rs

   1 use rustc_ast::InlineAsmTemplatePiece;
   2 use rustc_data_structures::stable_set::FxHashSet;
   3 use rustc_errors::struct_span_err;
   4 use rustc_hir as hir;
   5 use rustc_index::vec::Idx;
   6 use rustc_middle::ty::layout::{LayoutError, SizeSkeleton};
   7 use rustc_middle::ty::{self, Article, FloatTy, InferTy, IntTy, Ty, TyCtxt, TypeFoldable, UintTy};
   8 use rustc_session::lint;
   9 use rustc_span::{Span, Symbol, DUMMY_SP};
  10 use rustc_target::abi::{Pointer, VariantIdx};
  11 use rustc_target::asm::{InlineAsmReg, InlineAsmRegClass, InlineAsmRegOrRegClass, InlineAsmType};
  12 use rustc_trait_selection::infer::InferCtxtExt;
  13
  14 use super::FnCtxt;
  15
  16 /// If the type is `Option<T>`, it will return `T`, otherwise
  17 /// the type itself. Works on most `Option`-like types.
  18 fn unpack_option_like<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
  19     let ty::Adt(def, substs) = *ty.kind() else { return ty };
  20
  21     if def.variants().len() == 2 && !def.repr().c() && def.repr().int.is_none() {
  22         let data_idx;
  23
  24         let one = VariantIdx::new(1);
  25         let zero = VariantIdx::new(0);
  26
  27         if def.variant(zero).fields.is_empty() {
  28             data_idx = one;
  29         } else if def.variant(one).fields.is_empty() {
  30             data_idx = zero;
  31         } else {
  32             return ty;
  33         }
  34
  35         if def.variant(data_idx).fields.len() == 1 {
  36             return def.variant(data_idx).fields[0].ty(tcx, substs);
  37         }
  38     }
  39
  40     ty
  41 }
  42
  43 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  44     pub fn check_transmute(&self, span: Span, from: Ty<'tcx>, to: Ty<'tcx>) {
  45         let convert = |ty: Ty<'tcx>| {
  46             let ty = self.resolve_vars_if_possible(ty);
  47             let ty = self.tcx.normalize_erasing_regions(self.param_env, ty);
  48             (SizeSkeleton::compute(ty, self.tcx, self.param_env), ty)
  49         };
  50         let (sk_from, from) = convert(from);
  51         let (sk_to, to) = convert(to);
  52
  53         // Check for same size using the skeletons.
  54         if let (Ok(sk_from), Ok(sk_to)) = (sk_from, sk_to) {
  55             if sk_from.same_size(sk_to) {
  56                 return;
  57             }
  58
  59             // Special-case transmuting from `typeof(function)` and
  60             // `Option<typeof(function)>` to present a clearer error.
  61             let from = unpack_option_like(self.tcx, from);
  62             if let (&ty::FnDef(..), SizeSkeleton::Known(size_to)) = (from.kind(), sk_to) && size_to == Pointer.size(&self.tcx) {
  63                 struct_span_err!(self.tcx.sess, span, E0591, "can't transmute zero-sized type")
  64                     .note(&format!("source type: {from}"))
  65                     .note(&format!("target type: {to}"))
  66                     .help("cast with `as` to a pointer instead")
  67                     .emit();
  68                 return;
  69             }
  70         }
  71
  72         // Try to display a sensible error with as much information as possible.
  73         let skeleton_string = |ty: Ty<'tcx>, sk| match sk {
  74             Ok(SizeSkeleton::Known(size)) => format!("{} bits", size.bits()),
  75             Ok(SizeSkeleton::Pointer { tail, .. }) => format!("pointer to `{tail}`"),
  76             Err(LayoutError::Unknown(bad)) => {
  77                 if bad == ty {
  78                     "this type does not have a fixed size".to_owned()
  79                 } else {
  80                     format!("size can vary because of {bad}")
  81                 }
  82             }
  83             Err(err) => err.to_string(),
  84         };
  85
  86         let mut err = struct_span_err!(
  87             self.tcx.sess,
  88             span,
  89             E0512,
  90             "cannot transmute between types of different sizes, \
  91                                         or dependently-sized types"
  92         );
  93         if from == to {
  94             err.note(&format!("`{from}` does not have a fixed size"));
  95         } else {
  96             err.note(&format!("source type: `{}` ({})", from, skeleton_string(from, sk_from)))
  97                 .note(&format!("target type: `{}` ({})", to, skeleton_string(to, sk_to)));
  98         }
  99         err.emit();
 100     }
 101
 102     fn is_thin_ptr_ty(&self, ty: Ty<'tcx>) -> bool {
 103         if ty.is_sized(self.tcx.at(DUMMY_SP), self.param_env) {
 104             return true;
 105         }
 106         if let ty::Foreign(..) = ty.kind() {
 107             return true;
 108         }
 109         false
 110     }
 111
 112     fn check_asm_operand_type(
 113         &self,
 114         idx: usize,
 115         reg: InlineAsmRegOrRegClass,
 116         expr: &hir::Expr<'tcx>,
 117         template: &[InlineAsmTemplatePiece],
 118         is_input: bool,
 119         tied_input: Option<(&hir::Expr<'tcx>, Option<InlineAsmType>)>,
 120         target_features: &FxHashSet<Symbol>,
 121     ) -> Option<InlineAsmType> {
 122         // Check the type against the allowed types for inline asm.
 123         let ty = self.typeck_results.borrow().expr_ty_adjusted(expr);
 124         let ty = self.resolve_vars_if_possible(ty);
 125         let asm_ty_isize = match self.tcx.sess.target.pointer_width {
 126             16 => InlineAsmType::I16,
 127             32 => InlineAsmType::I32,
 128             64 => InlineAsmType::I64,
 129             _ => unreachable!(),
 130         };
 131         let asm_ty = match *ty.kind() {
 132             // `!` is allowed for input but not for output (issue #87802)
 133             ty::Never if is_input => return None,
 134             ty::Error(_) => return None,
 135             ty::Int(IntTy::I8) | ty::Uint(UintTy::U8) => Some(InlineAsmType::I8),
 136             ty::Int(IntTy::I16) | ty::Uint(UintTy::U16) => Some(InlineAsmType::I16),
 137             // Somewhat of a hack: fallback in the presence of errors does not actually
 138             // fall back to i32, but to ty::Error. For integer inference variables this
 139             // means that they don't get any fallback and stay as `{integer}`.
 140             // Since compilation can't succeed anyway, it's fine to use this to avoid printing
 141             // "cannot use value of type `{integer}`", even though that would absolutely
 142             // work due due i32 fallback if the current function had no other errors.
 143             ty::Infer(InferTy::IntVar(_)) => {
 144                 assert!(self.is_tainted_by_errors());
 145                 Some(InlineAsmType::I32)
 146             }
 147             ty::Int(IntTy::I32) | ty::Uint(UintTy::U32) => Some(InlineAsmType::I32),
 148             ty::Int(IntTy::I64) | ty::Uint(UintTy::U64) => Some(InlineAsmType::I64),
 149             ty::Int(IntTy::I128) | ty::Uint(UintTy::U128) => Some(InlineAsmType::I128),
 150             ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => Some(asm_ty_isize),
 151             ty::Infer(InferTy::FloatVar(_)) => {
 152                 assert!(self.is_tainted_by_errors());
 153                 Some(InlineAsmType::F32)
 154             }
 155             ty::Float(FloatTy::F32) => Some(InlineAsmType::F32),
 156             ty::Float(FloatTy::F64) => Some(InlineAsmType::F64),
 157             ty::FnPtr(_) => Some(asm_ty_isize),
 158             ty::RawPtr(ty::TypeAndMut { ty, mutbl: _ }) if self.is_thin_ptr_ty(ty) => {
 159                 Some(asm_ty_isize)
 160             }
 161             ty::Adt(adt, substs) if adt.repr().simd() => {
 162                 let fields = &adt.non_enum_variant().fields;
 163                 let elem_ty = fields[0].ty(self.tcx, substs);
 164                 match elem_ty.kind() {
 165                     ty::Never | ty::Error(_) => return None,
 166                     ty::Int(IntTy::I8) | ty::Uint(UintTy::U8) => {
 167                         Some(InlineAsmType::VecI8(fields.len() as u64))
 168                     }
 169                     ty::Int(IntTy::I16) | ty::Uint(UintTy::U16) => {
 170                         Some(InlineAsmType::VecI16(fields.len() as u64))
 171                     }
 172                     ty::Int(IntTy::I32) | ty::Uint(UintTy::U32) => {
 173                         Some(InlineAsmType::VecI32(fields.len() as u64))
 174                     }
 175                     ty::Int(IntTy::I64) | ty::Uint(UintTy::U64) => {
 176                         Some(InlineAsmType::VecI64(fields.len() as u64))
 177                     }
 178                     ty::Int(IntTy::I128) | ty::Uint(UintTy::U128) => {
 179                         Some(InlineAsmType::VecI128(fields.len() as u64))
 180                     }
 181                     ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => {
 182                         Some(match self.tcx.sess.target.pointer_width {
 183                             16 => InlineAsmType::VecI16(fields.len() as u64),
 184                             32 => InlineAsmType::VecI32(fields.len() as u64),
 185                             64 => InlineAsmType::VecI64(fields.len() as u64),
 186                             _ => unreachable!(),
 187                         })
 188                     }
 189                     ty::Float(FloatTy::F32) => Some(InlineAsmType::VecF32(fields.len() as u64)),
 190                     ty::Float(FloatTy::F64) => Some(InlineAsmType::VecF64(fields.len() as u64)),
 191                     _ => None,
 192                 }
 193             }
 194             _ => None,
 195         };
 196         let Some(asm_ty) = asm_ty else {
 197             let msg = &format!("cannot use value of type `{ty}` for inline assembly");
 198             let mut err = self.tcx.sess.struct_span_err(expr.span, msg);
 199             err.note(
 200                 "only integers, floats, SIMD vectors, pointers and function pointers \
 201                  can be used as arguments for inline assembly",
 202             );
 203             err.emit();
 204             return None;
 205         };
 206
 207         if ty.has_infer_types_or_consts() {
 208             assert!(self.is_tainted_by_errors());
 209             return None;
 210         }
 211
 212         // Check that the type implements Copy. The only case where this can
 213         // possibly fail is for SIMD types which don't #[derive(Copy)].
 214         if !self.infcx.type_is_copy_modulo_regions(self.param_env, ty, DUMMY_SP) {
 215             let msg = "arguments for inline assembly must be copyable";
 216             let mut err = self.tcx.sess.struct_span_err(expr.span, msg);
 217             err.note(&format!("`{ty}` does not implement the Copy trait"));
 218             err.emit();
 219         }
 220
 221         // Ideally we wouldn't need to do this, but LLVM's register allocator
 222         // really doesn't like it when tied operands have different types.
 223         //
 224         // This is purely an LLVM limitation, but we have to live with it since
 225         // there is no way to hide this with implicit conversions.
 226         //
 227         // For the purposes of this check we only look at the `InlineAsmType`,
 228         // which means that pointers and integers are treated as identical (modulo
 229         // size).
 230         if let Some((in_expr, Some(in_asm_ty))) = tied_input {
 231             if in_asm_ty != asm_ty {
 232                 let msg = "incompatible types for asm inout argument";
 233                 let mut err = self.tcx.sess.struct_span_err(vec![in_expr.span, expr.span], msg);
 234
 235                 let in_expr_ty = self.typeck_results.borrow().expr_ty_adjusted(in_expr);
 236                 let in_expr_ty = self.resolve_vars_if_possible(in_expr_ty);
 237                 err.span_label(in_expr.span, &format!("type `{in_expr_ty}`"));
 238                 err.span_label(expr.span, &format!("type `{ty}`"));
 239                 err.note(
 240                     "asm inout arguments must have the same type, \
 241                     unless they are both pointers or integers of the same size",
 242                 );
 243                 err.emit();
 244             }
 245
 246             // All of the later checks have already been done on the input, so
 247             // let's not emit errors and warnings twice.
 248             return Some(asm_ty);
 249         }
 250
 251         // Check the type against the list of types supported by the selected
 252         // register class.
 253         let asm_arch = self.tcx.sess.asm_arch.unwrap();
 254         let reg_class = reg.reg_class();
 255         let supported_tys = reg_class.supported_types(asm_arch);
 256         let Some((_, feature)) = supported_tys.iter().find(|&&(t, _)| t == asm_ty) else {
 257             let msg = &format!("type `{ty}` cannot be used with this register class");
 258             let mut err = self.tcx.sess.struct_span_err(expr.span, msg);
 259             let supported_tys: Vec<_> =
 260                 supported_tys.iter().map(|(t, _)| t.to_string()).collect();
 261             err.note(&format!(
 262                 "register class `{}` supports these types: {}",
 263                 reg_class.name(),
 264                 supported_tys.join(", "),
 265             ));
 266             if let Some(suggest) = reg_class.suggest_class(asm_arch, asm_ty) {
 267                 err.help(&format!(
 268                     "consider using the `{}` register class instead",
 269                     suggest.name()
 270                 ));
 271             }
 272             err.emit();
 273             return Some(asm_ty);
 274         };
 275
 276         // Check whether the selected type requires a target feature. Note that
 277         // this is different from the feature check we did earlier. While the
 278         // previous check checked that this register class is usable at all
 279         // with the currently enabled features, some types may only be usable
 280         // with a register class when a certain feature is enabled. We check
 281         // this here since it depends on the results of typeck.
 282         //
 283         // Also note that this check isn't run when the operand type is never
 284         // (!). In that case we still need the earlier check to verify that the
 285         // register class is usable at all.
 286         if let Some(feature) = feature {
 287             if !target_features.contains(&feature) {
 288                 let msg = &format!("`{}` target feature is not enabled", feature);
 289                 let mut err = self.tcx.sess.struct_span_err(expr.span, msg);
 290                 err.note(&format!(
 291                     "this is required to use type `{}` with register class `{}`",
 292                     ty,
 293                     reg_class.name(),
 294                 ));
 295                 err.emit();
 296                 return Some(asm_ty);
 297             }
 298         }
 299
 300         // Check whether a modifier is suggested for using this type.
 301         if let Some((suggested_modifier, suggested_result)) =
 302             reg_class.suggest_modifier(asm_arch, asm_ty)
 303         {
 304             // Search for any use of this operand without a modifier and emit
 305             // the suggestion for them.
 306             let mut spans = vec![];
 307             for piece in template {
 308                 if let &InlineAsmTemplatePiece::Placeholder { operand_idx, modifier, span } = piece
 309                 {
 310                     if operand_idx == idx && modifier.is_none() {
 311                         spans.push(span);
 312                     }
 313                 }
 314             }
 315             if !spans.is_empty() {
 316                 let (default_modifier, default_result) =
 317                     reg_class.default_modifier(asm_arch).unwrap();
 318                 self.tcx.struct_span_lint_hir(
 319                     lint::builtin::ASM_SUB_REGISTER,
 320                     expr.hir_id,
 321                     spans,
 322                     |lint| {
 323                         let msg = "formatting may not be suitable for sub-register argument";
 324                         let mut err = lint.build(msg);
 325                         err.span_label(expr.span, "for this argument");
 326                         err.help(&format!(
 327                             "use the `{suggested_modifier}` modifier to have the register formatted as `{suggested_result}`",
 328                         ));
 329                         err.help(&format!(
 330                             "or use the `{default_modifier}` modifier to keep the default formatting of `{default_result}`",
 331                         ));
 332                         err.emit();
 333                     },
 334                 );
 335             }
 336         }
 337
 338         Some(asm_ty)
 339     }
 340
 341     pub fn check_asm(&self, asm: &hir::InlineAsm<'tcx>, enclosing_id: hir::HirId) {
 342         let hir = self.tcx.hir();
 343         let enclosing_def_id = hir.local_def_id(enclosing_id).to_def_id();
 344         let target_features = self.tcx.asm_target_features(enclosing_def_id);
 345         let Some(asm_arch) = self.tcx.sess.asm_arch else {
 346             self.tcx.sess.delay_span_bug(DUMMY_SP, "target architecture does not support asm");
 347             return;
 348         };
 349         for (idx, (op, op_sp)) in asm.operands.iter().enumerate() {
 350             // Validate register classes against currently enabled target
 351             // features. We check that at least one type is available for
 352             // the enabled features.
 353             //
 354             // We ignore target feature requirements for clobbers: if the
 355             // feature is disabled then the compiler doesn't care what we
 356             // do with the registers.
 357             //
 358             // Note that this is only possible for explicit register
 359             // operands, which cannot be used in the asm string.
 360             if let Some(reg) = op.reg() {
 361                 // Some explicit registers cannot be used depending on the
 362                 // target. Reject those here.
 363                 if let InlineAsmRegOrRegClass::Reg(reg) = reg {
 364                     if let InlineAsmReg::Err = reg {
 365                         // `validate` will panic on `Err`, as an error must
 366                         // already have been reported.
 367                         continue;
 368                     }
 369                     if let Err(msg) = reg.validate(
 370                         asm_arch,
 371                         self.tcx.sess.relocation_model(),
 372                         &target_features,
 373                         &self.tcx.sess.target,
 374                         op.is_clobber(),
 375                     ) {
 376                         let msg = format!("cannot use register `{}`: {}", reg.name(), msg);
 377                         self.tcx.sess.struct_span_err(*op_sp, &msg).emit();
 378                         continue;
 379                     }
 380                 }
 381
 382                 if !op.is_clobber() {
 383                     let mut missing_required_features = vec![];
 384                     let reg_class = reg.reg_class();
 385                     if let InlineAsmRegClass::Err = reg_class {
 386                         continue;
 387                     }
 388                     for &(_, feature) in reg_class.supported_types(asm_arch) {
 389                         match feature {
 390                             Some(feature) => {
 391                                 if target_features.contains(&feature) {
 392                                     missing_required_features.clear();
 393                                     break;
 394                                 } else {
 395                                     missing_required_features.push(feature);
 396                                 }
 397                             }
 398                             None => {
 399                                 missing_required_features.clear();
 400                                 break;
 401                             }
 402                         }
 403                     }
 404
 405                     // We are sorting primitive strs here and can use unstable sort here
 406                     missing_required_features.sort_unstable();
 407                     missing_required_features.dedup();
 408                     match &missing_required_features[..] {
 409                         [] => {}
 410                         [feature] => {
 411                             let msg = format!(
 412                                 "register class `{}` requires the `{}` target feature",
 413                                 reg_class.name(),
 414                                 feature
 415                             );
 416                             self.tcx.sess.struct_span_err(*op_sp, &msg).emit();
 417                             // register isn't enabled, don't do more checks
 418                             continue;
 419                         }
 420                         features => {
 421                             let msg = format!(
 422                                 "register class `{}` requires at least one of the following target features: {}",
 423                                 reg_class.name(),
 424                                 features
 425                                     .iter()
 426                                     .map(|f| f.as_str())
 427                                     .intersperse(", ")
 428                                     .collect::<String>(),
 429                             );
 430                             self.tcx.sess.struct_span_err(*op_sp, &msg).emit();
 431                             // register isn't enabled, don't do more checks
 432                             continue;
 433                         }
 434                     }
 435                 }
 436             }
 437
 438             match *op {
 439                 hir::InlineAsmOperand::In { reg, ref expr } => {
 440                     self.check_asm_operand_type(
 441                         idx,
 442                         reg,
 443                         expr,
 444                         asm.template,
 445                         true,
 446                         None,
 447                         &target_features,
 448                     );
 449                 }
 450                 hir::InlineAsmOperand::Out { reg, late: _, ref expr } => {
 451                     if let Some(expr) = expr {
 452                         self.check_asm_operand_type(
 453                             idx,
 454                             reg,
 455                             expr,
 456                             asm.template,
 457                             false,
 458                             None,
 459                             &target_features,
 460                         );
 461                     }
 462                 }
 463                 hir::InlineAsmOperand::InOut { reg, late: _, ref expr } => {
 464                     self.check_asm_operand_type(
 465                         idx,
 466                         reg,
 467                         expr,
 468                         asm.template,
 469                         false,
 470                         None,
 471                         &target_features,
 472                     );
 473                 }
 474                 hir::InlineAsmOperand::SplitInOut { reg, late: _, ref in_expr, ref out_expr } => {
 475                     let in_ty = self.check_asm_operand_type(
 476                         idx,
 477                         reg,
 478                         in_expr,
 479                         asm.template,
 480                         true,
 481                         None,
 482                         &target_features,
 483                     );
 484                     if let Some(out_expr) = out_expr {
 485                         self.check_asm_operand_type(
 486                             idx,
 487                             reg,
 488                             out_expr,
 489                             asm.template,
 490                             false,
 491                             Some((in_expr, in_ty)),
 492                             &target_features,
 493                         );
 494                     }
 495                 }
 496                 // No special checking is needed for these:
 497                 // - Typeck has checked that Const operands are integers.
 498                 // - AST lowering guarantees that SymStatic points to a static.
 499                 hir::InlineAsmOperand::Const { .. } | hir::InlineAsmOperand::SymStatic { .. } => {}
 500                 // Check that sym actually points to a function. Later passes
 501                 // depend on this.
 502                 hir::InlineAsmOperand::SymFn { anon_const } => {
 503                     let ty = self.tcx.typeck_body(anon_const.body).node_type(anon_const.hir_id);
 504                     match ty.kind() {
 505                         ty::Never | ty::Error(_) => {}
 506                         ty::FnDef(..) => {}
 507                         _ => {
 508                             let mut err =
 509                                 self.tcx.sess.struct_span_err(*op_sp, "invalid `sym` operand");
 510                             err.span_label(
 511                                 self.tcx.hir().span(anon_const.body.hir_id),
 512                                 &format!("is {} `{}`", ty.kind().article(), ty),
 513                             );
 514                             err.help("`sym` operands must refer to either a function or a static");
 515                             err.emit();
 516                         }
 517                     };
 518                 }
 519             }
 520         }
 521     }
 522 }