compiler/rustc_typeck/src/check/intrinsicck.rs

   1 use rustc_ast::InlineAsmTemplatePiece;
   2 use rustc_data_structures::fx::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, IntTy, Ty, TyCtxt, TypeVisitable, 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
  13 use super::FnCtxt;
  14
  15 /// If the type is `Option<T>`, it will return `T`, otherwise
  16 /// the type itself. Works on most `Option`-like types.
  17 fn unpack_option_like<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
  18     let ty::Adt(def, substs) = *ty.kind() else { return ty };
  19
  20     if def.variants().len() == 2 && !def.repr().c() && def.repr().int.is_none() {
  21         let data_idx;
  22
  23         let one = VariantIdx::new(1);
  24         let zero = VariantIdx::new(0);
  25
  26         if def.variant(zero).fields.is_empty() {
  27             data_idx = one;
  28         } else if def.variant(one).fields.is_empty() {
  29             data_idx = zero;
  30         } else {
  31             return ty;
  32         }
  33
  34         if def.variant(data_idx).fields.len() == 1 {
  35             return def.variant(data_idx).fields[0].ty(tcx, substs);
  36         }
  37     }
  38
  39     ty
  40 }
  41
  42 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  43     pub fn check_transmute(&self, span: Span, from: Ty<'tcx>, to: Ty<'tcx>) {
  44         let convert = |ty: Ty<'tcx>| {
  45             let ty = self.resolve_vars_if_possible(ty);
  46             let ty = self.tcx.normalize_erasing_regions(self.param_env, ty);
  47             (SizeSkeleton::compute(ty, self.tcx, self.param_env), ty)
  48         };
  49         let (sk_from, from) = convert(from);
  50         let (sk_to, to) = convert(to);
  51
  52         // Check for same size using the skeletons.
  53         if let (Ok(sk_from), Ok(sk_to)) = (sk_from, sk_to) {
  54             if sk_from.same_size(sk_to) {
  55                 return;
  56             }
  57
  58             // Special-case transmuting from `typeof(function)` and
  59             // `Option<typeof(function)>` to present a clearer error.
  60             let from = unpack_option_like(self.tcx, from);
  61             if let (&ty::FnDef(..), SizeSkeleton::Known(size_to)) = (from.kind(), sk_to) && size_to == Pointer.size(&self.tcx) {
  62                 struct_span_err!(self.tcx.sess, span, E0591, "can't transmute zero-sized type")
  63                     .note(&format!("source type: {from}"))
  64                     .note(&format!("target type: {to}"))
  65                     .help("cast with `as` to a pointer instead")
  66                     .emit();
  67                 return;
  68             }
  69         }
  70
  71         // Try to display a sensible error with as much information as possible.
  72         let skeleton_string = |ty: Ty<'tcx>, sk| match sk {
  73             Ok(SizeSkeleton::Known(size)) => format!("{} bits", size.bits()),
  74             Ok(SizeSkeleton::Pointer { tail, .. }) => format!("pointer to `{tail}`"),
  75             Err(LayoutError::Unknown(bad)) => {
  76                 if bad == ty {
  77                     "this type does not have a fixed size".to_owned()
  78                 } else {
  79                     format!("size can vary because of {bad}")
  80                 }
  81             }
  82             Err(err) => err.to_string(),
  83         };
  84
  85         let mut err = struct_span_err!(
  86             self.tcx.sess,
  87             span,
  88             E0512,
  89             "cannot transmute between types of different sizes, \
  90                                         or dependently-sized types"
  91         );
  92         if from == to {
  93             err.note(&format!("`{from}` does not have a fixed size"));
  94         } else {
  95             err.note(&format!("source type: `{}` ({})", from, skeleton_string(from, sk_from)))
  96                 .note(&format!("target type: `{}` ({})", to, skeleton_string(to, sk_to)));
  97         }
  98         err.emit();
  99     }
 100 }
 101
 102 pub struct InlineAsmCtxt<'a, 'tcx> {
 103     tcx: TyCtxt<'tcx>,
 104     param_env: ty::ParamEnv<'tcx>,
 105     get_operand_ty: Box<dyn Fn(&'tcx hir::Expr<'tcx>) -> Ty<'tcx> + 'a>,
 106 }
 107
 108 impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
 109     pub fn new_global_asm(tcx: TyCtxt<'tcx>) -> Self {
 110         InlineAsmCtxt {
 111             tcx,
 112             param_env: ty::ParamEnv::empty(),
 113             get_operand_ty: Box::new(|e| bug!("asm operand in global asm: {e:?}")),
 114         }
 115     }
 116
 117     pub fn new_in_fn(
 118         tcx: TyCtxt<'tcx>,
 119         param_env: ty::ParamEnv<'tcx>,
 120         get_operand_ty: impl Fn(&'tcx hir::Expr<'tcx>) -> Ty<'tcx> + 'a,
 121     ) -> Self {
 122         InlineAsmCtxt { tcx, param_env, get_operand_ty: Box::new(get_operand_ty) }
 123     }
 124
 125     // FIXME(compiler-errors): This could use `<$ty as Pointee>::Metadata == ()`
 126     fn is_thin_ptr_ty(&self, ty: Ty<'tcx>) -> bool {
 127         // Type still may have region variables, but `Sized` does not depend
 128         // on those, so just erase them before querying.
 129         if ty.is_sized(self.tcx.at(DUMMY_SP), self.param_env) {
 130             return true;
 131         }
 132         if let ty::Foreign(..) = ty.kind() {
 133             return true;
 134         }
 135         false
 136     }
 137
 138     fn check_asm_operand_type(
 139         &self,
 140         idx: usize,
 141         reg: InlineAsmRegOrRegClass,
 142         expr: &'tcx hir::Expr<'tcx>,
 143         template: &[InlineAsmTemplatePiece],
 144         is_input: bool,
 145         tied_input: Option<(&'tcx hir::Expr<'tcx>, Option<InlineAsmType>)>,
 146         target_features: &FxHashSet<Symbol>,
 147     ) -> Option<InlineAsmType> {
 148         let ty = (self.get_operand_ty)(expr);
 149         if ty.has_infer_types_or_consts() {
 150             bug!("inference variable in asm operand ty: {:?} {:?}", expr, ty);
 151         }
 152         let asm_ty_isize = match self.tcx.sess.target.pointer_width {
 153             16 => InlineAsmType::I16,
 154             32 => InlineAsmType::I32,
 155             64 => InlineAsmType::I64,
 156             _ => unreachable!(),
 157         };
 158
 159         let asm_ty = match *ty.kind() {
 160             // `!` is allowed for input but not for output (issue #87802)
 161             ty::Never if is_input => return None,
 162             ty::Error(_) => return None,
 163             ty::Int(IntTy::I8) | ty::Uint(UintTy::U8) => Some(InlineAsmType::I8),
 164             ty::Int(IntTy::I16) | ty::Uint(UintTy::U16) => Some(InlineAsmType::I16),
 165             ty::Int(IntTy::I32) | ty::Uint(UintTy::U32) => Some(InlineAsmType::I32),
 166             ty::Int(IntTy::I64) | ty::Uint(UintTy::U64) => Some(InlineAsmType::I64),
 167             ty::Int(IntTy::I128) | ty::Uint(UintTy::U128) => Some(InlineAsmType::I128),
 168             ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => Some(asm_ty_isize),
 169             ty::Float(FloatTy::F32) => Some(InlineAsmType::F32),
 170             ty::Float(FloatTy::F64) => Some(InlineAsmType::F64),
 171             ty::FnPtr(_) => Some(asm_ty_isize),
 172             ty::RawPtr(ty::TypeAndMut { ty, mutbl: _ }) if self.is_thin_ptr_ty(ty) => {
 173                 Some(asm_ty_isize)
 174             }
 175             ty::Adt(adt, substs) if adt.repr().simd() => {
 176                 let fields = &adt.non_enum_variant().fields;
 177                 let elem_ty = fields[0].ty(self.tcx, substs);
 178                 match elem_ty.kind() {
 179                     ty::Never | ty::Error(_) => return None,
 180                     ty::Int(IntTy::I8) | ty::Uint(UintTy::U8) => {
 181                         Some(InlineAsmType::VecI8(fields.len() as u64))
 182                     }
 183                     ty::Int(IntTy::I16) | ty::Uint(UintTy::U16) => {
 184                         Some(InlineAsmType::VecI16(fields.len() as u64))
 185                     }
 186                     ty::Int(IntTy::I32) | ty::Uint(UintTy::U32) => {
 187                         Some(InlineAsmType::VecI32(fields.len() as u64))
 188                     }
 189                     ty::Int(IntTy::I64) | ty::Uint(UintTy::U64) => {
 190                         Some(InlineAsmType::VecI64(fields.len() as u64))
 191                     }
 192                     ty::Int(IntTy::I128) | ty::Uint(UintTy::U128) => {
 193                         Some(InlineAsmType::VecI128(fields.len() as u64))
 194                     }
 195                     ty::Int(IntTy::Isize) | ty::Uint(UintTy::Usize) => {
 196                         Some(match self.tcx.sess.target.pointer_width {
 197                             16 => InlineAsmType::VecI16(fields.len() as u64),
 198                             32 => InlineAsmType::VecI32(fields.len() as u64),
 199                             64 => InlineAsmType::VecI64(fields.len() as u64),
 200                             _ => unreachable!(),
 201                         })
 202                     }
 203                     ty::Float(FloatTy::F32) => Some(InlineAsmType::VecF32(fields.len() as u64)),
 204                     ty::Float(FloatTy::F64) => Some(InlineAsmType::VecF64(fields.len() as u64)),
 205                     _ => None,
 206                 }
 207             }
 208             ty::Infer(_) => unreachable!(),
 209             _ => None,
 210         };
 211         let Some(asm_ty) = asm_ty else {
 212             let msg = &format!("cannot use value of type `{ty}` for inline assembly");
 213             let mut err = self.tcx.sess.struct_span_err(expr.span, msg);
 214             err.note(
 215                 "only integers, floats, SIMD vectors, pointers and function pointers \
 216                  can be used as arguments for inline assembly",
 217             );
 218             err.emit();
 219             return None;
 220         };
 221
 222         // Check that the type implements Copy. The only case where this can
 223         // possibly fail is for SIMD types which don't #[derive(Copy)].
 224         if !ty.is_copy_modulo_regions(self.tcx.at(expr.span), self.param_env) {
 225             let msg = "arguments for inline assembly must be copyable";
 226             let mut err = self.tcx.sess.struct_span_err(expr.span, msg);
 227             err.note(&format!("`{ty}` does not implement the Copy trait"));
 228             err.emit();
 229         }
 230
 231         // Ideally we wouldn't need to do this, but LLVM's register allocator
 232         // really doesn't like it when tied operands have different types.
 233         //
 234         // This is purely an LLVM limitation, but we have to live with it since
 235         // there is no way to hide this with implicit conversions.
 236         //
 237         // For the purposes of this check we only look at the `InlineAsmType`,
 238         // which means that pointers and integers are treated as identical (modulo
 239         // size).
 240         if let Some((in_expr, Some(in_asm_ty))) = tied_input {
 241             if in_asm_ty != asm_ty {
 242                 let msg = "incompatible types for asm inout argument";
 243                 let mut err = self.tcx.sess.struct_span_err(vec![in_expr.span, expr.span], msg);
 244
 245                 let in_expr_ty = (self.get_operand_ty)(in_expr);
 246                 err.span_label(in_expr.span, &format!("type `{in_expr_ty}`"));
 247                 err.span_label(expr.span, &format!("type `{ty}`"));
 248                 err.note(
 249                     "asm inout arguments must have the same type, \
 250                     unless they are both pointers or integers of the same size",
 251                 );
 252                 err.emit();
 253             }
 254
 255             // All of the later checks have already been done on the input, so
 256             // let's not emit errors and warnings twice.
 257             return Some(asm_ty);
 258         }
 259
 260         // Check the type against the list of types supported by the selected
 261         // register class.
 262         let asm_arch = self.tcx.sess.asm_arch.unwrap();
 263         let reg_class = reg.reg_class();
 264         let supported_tys = reg_class.supported_types(asm_arch);
 265         let Some((_, feature)) = supported_tys.iter().find(|&&(t, _)| t == asm_ty) else {
 266             let msg = &format!("type `{ty}` cannot be used with this register class");
 267             let mut err = self.tcx.sess.struct_span_err(expr.span, msg);
 268             let supported_tys: Vec<_> =
 269                 supported_tys.iter().map(|(t, _)| t.to_string()).collect();
 270             err.note(&format!(
 271                 "register class `{}` supports these types: {}",
 272                 reg_class.name(),
 273                 supported_tys.join(", "),
 274             ));
 275             if let Some(suggest) = reg_class.suggest_class(asm_arch, asm_ty) {
 276                 err.help(&format!(
 277                     "consider using the `{}` register class instead",
 278                     suggest.name()
 279                 ));
 280             }
 281             err.emit();
 282             return Some(asm_ty);
 283         };
 284
 285         // Check whether the selected type requires a target feature. Note that
 286         // this is different from the feature check we did earlier. While the
 287         // previous check checked that this register class is usable at all
 288         // with the currently enabled features, some types may only be usable
 289         // with a register class when a certain feature is enabled. We check
 290         // this here since it depends on the results of typeck.
 291         //
 292         // Also note that this check isn't run when the operand type is never
 293         // (!). In that case we still need the earlier check to verify that the
 294         // register class is usable at all.
 295         if let Some(feature) = feature {
 296             if !target_features.contains(&feature) {
 297                 let msg = &format!("`{}` target feature is not enabled", feature);
 298                 let mut err = self.tcx.sess.struct_span_err(expr.span, msg);
 299                 err.note(&format!(
 300                     "this is required to use type `{}` with register class `{}`",
 301                     ty,
 302                     reg_class.name(),
 303                 ));
 304                 err.emit();
 305                 return Some(asm_ty);
 306             }
 307         }
 308
 309         // Check whether a modifier is suggested for using this type.
 310         if let Some((suggested_modifier, suggested_result)) =
 311             reg_class.suggest_modifier(asm_arch, asm_ty)
 312         {
 313             // Search for any use of this operand without a modifier and emit
 314             // the suggestion for them.
 315             let mut spans = vec![];
 316             for piece in template {
 317                 if let &InlineAsmTemplatePiece::Placeholder { operand_idx, modifier, span } = piece
 318                 {
 319                     if operand_idx == idx && modifier.is_none() {
 320                         spans.push(span);
 321                     }
 322                 }
 323             }
 324             if !spans.is_empty() {
 325                 let (default_modifier, default_result) =
 326                     reg_class.default_modifier(asm_arch).unwrap();
 327                 self.tcx.struct_span_lint_hir(
 328                     lint::builtin::ASM_SUB_REGISTER,
 329                     expr.hir_id,
 330                     spans,
 331                     |lint| {
 332                         let msg = "formatting may not be suitable for sub-register argument";
 333                         let mut err = lint.build(msg);
 334                         err.span_label(expr.span, "for this argument");
 335                         err.help(&format!(
 336                             "use `{{{idx}:{suggested_modifier}}}` to have the register formatted as `{suggested_result}`",
 337                         ));
 338                         err.help(&format!(
 339                             "or use `{{{idx}:{default_modifier}}}` to keep the default formatting of `{default_result}`",
 340                         ));
 341                         err.emit();
 342                     },
 343                 );
 344             }
 345         }
 346
 347         Some(asm_ty)
 348     }
 349
 350     pub fn check_asm(&self, asm: &hir::InlineAsm<'tcx>, enclosing_id: hir::HirId) {
 351         let hir = self.tcx.hir();
 352         let enclosing_def_id = hir.local_def_id(enclosing_id).to_def_id();
 353         let target_features = self.tcx.asm_target_features(enclosing_def_id);
 354         let Some(asm_arch) = self.tcx.sess.asm_arch else {
 355             self.tcx.sess.delay_span_bug(DUMMY_SP, "target architecture does not support asm");
 356             return;
 357         };
 358         for (idx, (op, op_sp)) in asm.operands.iter().enumerate() {
 359             // Validate register classes against currently enabled target
 360             // features. We check that at least one type is available for
 361             // the enabled features.
 362             //
 363             // We ignore target feature requirements for clobbers: if the
 364             // feature is disabled then the compiler doesn't care what we
 365             // do with the registers.
 366             //
 367             // Note that this is only possible for explicit register
 368             // operands, which cannot be used in the asm string.
 369             if let Some(reg) = op.reg() {
 370                 // Some explicit registers cannot be used depending on the
 371                 // target. Reject those here.
 372                 if let InlineAsmRegOrRegClass::Reg(reg) = reg {
 373                     if let InlineAsmReg::Err = reg {
 374                         // `validate` will panic on `Err`, as an error must
 375                         // already have been reported.
 376                         continue;
 377                     }
 378                     if let Err(msg) = reg.validate(
 379                         asm_arch,
 380                         self.tcx.sess.relocation_model(),
 381                         &target_features,
 382                         &self.tcx.sess.target,
 383                         op.is_clobber(),
 384                     ) {
 385                         let msg = format!("cannot use register `{}`: {}", reg.name(), msg);
 386                         self.tcx.sess.struct_span_err(*op_sp, &msg).emit();
 387                         continue;
 388                     }
 389                 }
 390
 391                 if !op.is_clobber() {
 392                     let mut missing_required_features = vec![];
 393                     let reg_class = reg.reg_class();
 394                     if let InlineAsmRegClass::Err = reg_class {
 395                         continue;
 396                     }
 397                     for &(_, feature) in reg_class.supported_types(asm_arch) {
 398                         match feature {
 399                             Some(feature) => {
 400                                 if target_features.contains(&feature) {
 401                                     missing_required_features.clear();
 402                                     break;
 403                                 } else {
 404                                     missing_required_features.push(feature);
 405                                 }
 406                             }
 407                             None => {
 408                                 missing_required_features.clear();
 409                                 break;
 410                             }
 411                         }
 412                     }
 413
 414                     // We are sorting primitive strs here and can use unstable sort here
 415                     missing_required_features.sort_unstable();
 416                     missing_required_features.dedup();
 417                     match &missing_required_features[..] {
 418                         [] => {}
 419                         [feature] => {
 420                             let msg = format!(
 421                                 "register class `{}` requires the `{}` target feature",
 422                                 reg_class.name(),
 423                                 feature
 424                             );
 425                             self.tcx.sess.struct_span_err(*op_sp, &msg).emit();
 426                             // register isn't enabled, don't do more checks
 427                             continue;
 428                         }
 429                         features => {
 430                             let msg = format!(
 431                                 "register class `{}` requires at least one of the following target features: {}",
 432                                 reg_class.name(),
 433                                 features
 434                                     .iter()
 435                                     .map(|f| f.as_str())
 436                                     .intersperse(", ")
 437                                     .collect::<String>(),
 438                             );
 439                             self.tcx.sess.struct_span_err(*op_sp, &msg).emit();
 440                             // register isn't enabled, don't do more checks
 441                             continue;
 442                         }
 443                     }
 444                 }
 445             }
 446
 447             match *op {
 448                 hir::InlineAsmOperand::In { reg, ref expr } => {
 449                     self.check_asm_operand_type(
 450                         idx,
 451                         reg,
 452                         expr,
 453                         asm.template,
 454                         true,
 455                         None,
 456                         &target_features,
 457                     );
 458                 }
 459                 hir::InlineAsmOperand::Out { reg, late: _, ref expr } => {
 460                     if let Some(expr) = expr {
 461                         self.check_asm_operand_type(
 462                             idx,
 463                             reg,
 464                             expr,
 465                             asm.template,
 466                             false,
 467                             None,
 468                             &target_features,
 469                         );
 470                     }
 471                 }
 472                 hir::InlineAsmOperand::InOut { reg, late: _, ref expr } => {
 473                     self.check_asm_operand_type(
 474                         idx,
 475                         reg,
 476                         expr,
 477                         asm.template,
 478                         false,
 479                         None,
 480                         &target_features,
 481                     );
 482                 }
 483                 hir::InlineAsmOperand::SplitInOut { reg, late: _, ref in_expr, ref out_expr } => {
 484                     let in_ty = self.check_asm_operand_type(
 485                         idx,
 486                         reg,
 487                         in_expr,
 488                         asm.template,
 489                         true,
 490                         None,
 491                         &target_features,
 492                     );
 493                     if let Some(out_expr) = out_expr {
 494                         self.check_asm_operand_type(
 495                             idx,
 496                             reg,
 497                             out_expr,
 498                             asm.template,
 499                             false,
 500                             Some((in_expr, in_ty)),
 501                             &target_features,
 502                         );
 503                     }
 504                 }
 505                 // No special checking is needed for these:
 506                 // - Typeck has checked that Const operands are integers.
 507                 // - AST lowering guarantees that SymStatic points to a static.
 508                 hir::InlineAsmOperand::Const { .. } | hir::InlineAsmOperand::SymStatic { .. } => {}
 509                 // Check that sym actually points to a function. Later passes
 510                 // depend on this.
 511                 hir::InlineAsmOperand::SymFn { anon_const } => {
 512                     let ty = self.tcx.typeck_body(anon_const.body).node_type(anon_const.hir_id);
 513                     match ty.kind() {
 514                         ty::Never | ty::Error(_) => {}
 515                         ty::FnDef(..) => {}
 516                         _ => {
 517                             let mut err =
 518                                 self.tcx.sess.struct_span_err(*op_sp, "invalid `sym` operand");
 519                             err.span_label(
 520                                 self.tcx.hir().span(anon_const.body.hir_id),
 521                                 &format!("is {} `{}`", ty.kind().article(), ty),
 522                             );
 523                             err.help("`sym` operands must refer to either a function or a static");
 524                             err.emit();
 525                         }
 526                     };
 527                 }
 528             }
 529         }
 530     }
 531 }