compiler/rustc_mir/src/interpret/intrinsics.rs

   1 //! Intrinsics and other functions that the miri engine executes without
   2 //! looking at their MIR. Intrinsics/functions supported here are shared by CTFE
   3 //! and miri.
   4
   5 use std::convert::TryFrom;
   6
   7 use rustc_hir::def_id::DefId;
   8 use rustc_middle::mir::{
   9     self,
  10     interpret::{uabs, ConstValue, GlobalId, InterpResult, Scalar},
  11     BinOp,
  12 };
  13 use rustc_middle::ty;
  14 use rustc_middle::ty::subst::SubstsRef;
  15 use rustc_middle::ty::{Ty, TyCtxt};
  16 use rustc_span::symbol::{sym, Symbol};
  17 use rustc_target::abi::{Abi, LayoutOf as _, Primitive, Size};
  18
  19 use super::{
  20     util::ensure_monomorphic_enough, CheckInAllocMsg, ImmTy, InterpCx, Machine, OpTy, PlaceTy,
  21 };
  22
  23 mod caller_location;
  24 mod type_name;
  25
  26 fn numeric_intrinsic<'tcx, Tag>(
  27     name: Symbol,
  28     bits: u128,
  29     kind: Primitive,
  30 ) -> InterpResult<'tcx, Scalar<Tag>> {
  31     let size = match kind {
  32         Primitive::Int(integer, _) => integer.size(),
  33         _ => bug!("invalid `{}` argument: {:?}", name, bits),
  34     };
  35     let extra = 128 - u128::from(size.bits());
  36     let bits_out = match name {
  37         sym::ctpop => u128::from(bits.count_ones()),
  38         sym::ctlz => u128::from(bits.leading_zeros()) - extra,
  39         sym::cttz => u128::from((bits << extra).trailing_zeros()) - extra,
  40         sym::bswap => (bits << extra).swap_bytes(),
  41         sym::bitreverse => (bits << extra).reverse_bits(),
  42         _ => bug!("not a numeric intrinsic: {}", name),
  43     };
  44     Ok(Scalar::from_uint(bits_out, size))
  45 }
  46
  47 /// The logic for all nullary intrinsics is implemented here. These intrinsics don't get evaluated
  48 /// inside an `InterpCx` and instead have their value computed directly from rustc internal info.
  49 crate fn eval_nullary_intrinsic<'tcx>(
  50     tcx: TyCtxt<'tcx>,
  51     param_env: ty::ParamEnv<'tcx>,
  52     def_id: DefId,
  53     substs: SubstsRef<'tcx>,
  54 ) -> InterpResult<'tcx, ConstValue<'tcx>> {
  55     let tp_ty = substs.type_at(0);
  56     let name = tcx.item_name(def_id);
  57     Ok(match name {
  58         sym::type_name => {
  59             ensure_monomorphic_enough(tcx, tp_ty)?;
  60             let alloc = type_name::alloc_type_name(tcx, tp_ty);
  61             ConstValue::Slice { data: alloc, start: 0, end: alloc.len() }
  62         }
  63         sym::needs_drop => ConstValue::from_bool(tp_ty.needs_drop(tcx, param_env)),
  64         sym::size_of | sym::min_align_of | sym::pref_align_of => {
  65             let layout = tcx.layout_of(param_env.and(tp_ty)).map_err(|e| err_inval!(Layout(e)))?;
  66             let n = match name {
  67                 sym::pref_align_of => layout.align.pref.bytes(),
  68                 sym::min_align_of => layout.align.abi.bytes(),
  69                 sym::size_of => layout.size.bytes(),
  70                 _ => bug!(),
  71             };
  72             ConstValue::from_machine_usize(n, &tcx)
  73         }
  74         sym::type_id => {
  75             ensure_monomorphic_enough(tcx, tp_ty)?;
  76             ConstValue::from_u64(tcx.type_id_hash(tp_ty))
  77         }
  78         sym::variant_count => match tp_ty.kind() {
  79             ty::Adt(ref adt, _) => ConstValue::from_machine_usize(adt.variants.len() as u64, &tcx),
  80             ty::Projection(_)
  81             | ty::Opaque(_, _)
  82             | ty::Param(_)
  83             | ty::Bound(_, _)
  84             | ty::Placeholder(_)
  85             | ty::Infer(_) => throw_inval!(TooGeneric),
  86             ty::Bool
  87             | ty::Char
  88             | ty::Int(_)
  89             | ty::Uint(_)
  90             | ty::Float(_)
  91             | ty::Foreign(_)
  92             | ty::Str
  93             | ty::Array(_, _)
  94             | ty::Slice(_)
  95             | ty::RawPtr(_)
  96             | ty::Ref(_, _, _)
  97             | ty::FnDef(_, _)
  98             | ty::FnPtr(_)
  99             | ty::Dynamic(_, _)
 100             | ty::Closure(_, _)
 101             | ty::Generator(_, _, _)
 102             | ty::GeneratorWitness(_)
 103             | ty::Never
 104             | ty::Tuple(_)
 105             | ty::Error(_) => ConstValue::from_machine_usize(0u64, &tcx),
 106         },
 107         other => bug!("`{}` is not a zero arg intrinsic", other),
 108     })
 109 }
 110
 111 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 112     /// Returns `true` if emulation happened.
 113     /// Here we implement the intrinsics that are common to all Miri instances; individual machines can add their own
 114     /// intrinsic handling.
 115     pub fn emulate_intrinsic(
 116         &mut self,
 117         instance: ty::Instance<'tcx>,
 118         args: &[OpTy<'tcx, M::PointerTag>],
 119         ret: Option<(PlaceTy<'tcx, M::PointerTag>, mir::BasicBlock)>,
 120     ) -> InterpResult<'tcx, bool> {
 121         let substs = instance.substs;
 122         let intrinsic_name = self.tcx.item_name(instance.def_id());
 123
 124         // First handle intrinsics without return place.
 125         let (dest, ret) = match ret {
 126             None => match intrinsic_name {
 127                 sym::transmute => throw_ub_format!("transmuting to uninhabited type"),
 128                 sym::unreachable => throw_ub!(Unreachable),
 129                 sym::abort => M::abort(self, "the program aborted execution".to_owned())?,
 130                 // Unsupported diverging intrinsic.
 131                 _ => return Ok(false),
 132             },
 133             Some(p) => p,
 134         };
 135
 136         // Keep the patterns in this match ordered the same as the list in
 137         // `src/librustc_middle/ty/constness.rs`
 138         match intrinsic_name {
 139             sym::caller_location => {
 140                 let span = self.find_closest_untracked_caller_location();
 141                 let location = self.alloc_caller_location_for_span(span);
 142                 self.write_scalar(location.ptr, dest)?;
 143             }
 144
 145             sym::min_align_of_val | sym::size_of_val => {
 146                 let place = self.deref_operand(args[0])?;
 147                 let (size, align) = self
 148                     .size_and_align_of(place.meta, place.layout)?
 149                     .ok_or_else(|| err_unsup_format!("`extern type` does not have known layout"))?;
 150
 151                 let result = match intrinsic_name {
 152                     sym::min_align_of_val => align.bytes(),
 153                     sym::size_of_val => size.bytes(),
 154                     _ => bug!(),
 155                 };
 156
 157                 self.write_scalar(Scalar::from_machine_usize(result, self), dest)?;
 158             }
 159
 160             sym::min_align_of
 161             | sym::pref_align_of
 162             | sym::needs_drop
 163             | sym::size_of
 164             | sym::type_id
 165             | sym::type_name
 166             | sym::variant_count => {
 167                 let gid = GlobalId { instance, promoted: None };
 168                 let ty = match intrinsic_name {
 169                     sym::min_align_of | sym::pref_align_of | sym::size_of | sym::variant_count => {
 170                         self.tcx.types.usize
 171                     }
 172                     sym::needs_drop => self.tcx.types.bool,
 173                     sym::type_id => self.tcx.types.u64,
 174                     sym::type_name => self.tcx.mk_static_str(),
 175                     _ => bug!("already checked for nullary intrinsics"),
 176                 };
 177                 let val =
 178                     self.tcx.const_eval_global_id(self.param_env, gid, Some(self.tcx.span))?;
 179                 let const_ = ty::Const { val: ty::ConstKind::Value(val), ty };
 180                 let val = self.const_to_op(&const_, None)?;
 181                 self.copy_op(val, dest)?;
 182             }
 183
 184             sym::ctpop
 185             | sym::cttz
 186             | sym::cttz_nonzero
 187             | sym::ctlz
 188             | sym::ctlz_nonzero
 189             | sym::bswap
 190             | sym::bitreverse => {
 191                 let ty = substs.type_at(0);
 192                 let layout_of = self.layout_of(ty)?;
 193                 let val = self.read_scalar(args[0])?.check_init()?;
 194                 let bits = self.force_bits(val, layout_of.size)?;
 195                 let kind = match layout_of.abi {
 196                     Abi::Scalar(ref scalar) => scalar.value,
 197                     _ => span_bug!(
 198                         self.cur_span(),
 199                         "{} called on invalid type {:?}",
 200                         intrinsic_name,
 201                         ty
 202                     ),
 203                 };
 204                 let (nonzero, intrinsic_name) = match intrinsic_name {
 205                     sym::cttz_nonzero => (true, sym::cttz),
 206                     sym::ctlz_nonzero => (true, sym::ctlz),
 207                     other => (false, other),
 208                 };
 209                 if nonzero && bits == 0 {
 210                     throw_ub_format!("`{}_nonzero` called on 0", intrinsic_name);
 211                 }
 212                 let out_val = numeric_intrinsic(intrinsic_name, bits, kind)?;
 213                 self.write_scalar(out_val, dest)?;
 214             }
 215             sym::wrapping_add
 216             | sym::wrapping_sub
 217             | sym::wrapping_mul
 218             | sym::add_with_overflow
 219             | sym::sub_with_overflow
 220             | sym::mul_with_overflow => {
 221                 let lhs = self.read_immediate(args[0])?;
 222                 let rhs = self.read_immediate(args[1])?;
 223                 let (bin_op, ignore_overflow) = match intrinsic_name {
 224                     sym::wrapping_add => (BinOp::Add, true),
 225                     sym::wrapping_sub => (BinOp::Sub, true),
 226                     sym::wrapping_mul => (BinOp::Mul, true),
 227                     sym::add_with_overflow => (BinOp::Add, false),
 228                     sym::sub_with_overflow => (BinOp::Sub, false),
 229                     sym::mul_with_overflow => (BinOp::Mul, false),
 230                     _ => bug!("Already checked for int ops"),
 231                 };
 232                 if ignore_overflow {
 233                     self.binop_ignore_overflow(bin_op, lhs, rhs, dest)?;
 234                 } else {
 235                     self.binop_with_overflow(bin_op, lhs, rhs, dest)?;
 236                 }
 237             }
 238             sym::saturating_add | sym::saturating_sub => {
 239                 let l = self.read_immediate(args[0])?;
 240                 let r = self.read_immediate(args[1])?;
 241                 let is_add = intrinsic_name == sym::saturating_add;
 242                 let (val, overflowed, _ty) =
 243                     self.overflowing_binary_op(if is_add { BinOp::Add } else { BinOp::Sub }, l, r)?;
 244                 let val = if overflowed {
 245                     let num_bits = l.layout.size.bits();
 246                     if l.layout.abi.is_signed() {
 247                         // For signed ints the saturated value depends on the sign of the first
 248                         // term since the sign of the second term can be inferred from this and
 249                         // the fact that the operation has overflowed (if either is 0 no
 250                         // overflow can occur)
 251                         let first_term: u128 = self.force_bits(l.to_scalar()?, l.layout.size)?;
 252                         let first_term_positive = first_term & (1 << (num_bits - 1)) == 0;
 253                         if first_term_positive {
 254                             // Negative overflow not possible since the positive first term
 255                             // can only increase an (in range) negative term for addition
 256                             // or corresponding negated positive term for subtraction
 257                             Scalar::from_uint(
 258                                 (1u128 << (num_bits - 1)) - 1, // max positive
 259                                 Size::from_bits(num_bits),
 260                             )
 261                         } else {
 262                             // Positive overflow not possible for similar reason
 263                             // max negative
 264                             Scalar::from_uint(1u128 << (num_bits - 1), Size::from_bits(num_bits))
 265                         }
 266                     } else {
 267                         // unsigned
 268                         if is_add {
 269                             // max unsigned
 270                             Scalar::from_uint(
 271                                 u128::MAX >> (128 - num_bits),
 272                                 Size::from_bits(num_bits),
 273                             )
 274                         } else {
 275                             // underflow to 0
 276                             Scalar::from_uint(0u128, Size::from_bits(num_bits))
 277                         }
 278                     }
 279                 } else {
 280                     val
 281                 };
 282                 self.write_scalar(val, dest)?;
 283             }
 284             sym::discriminant_value => {
 285                 let place = self.deref_operand(args[0])?;
 286                 let discr_val = self.read_discriminant(place.into())?.0;
 287                 self.write_scalar(discr_val, dest)?;
 288             }
 289             sym::unchecked_shl
 290             | sym::unchecked_shr
 291             | sym::unchecked_add
 292             | sym::unchecked_sub
 293             | sym::unchecked_mul
 294             | sym::unchecked_div
 295             | sym::unchecked_rem => {
 296                 let l = self.read_immediate(args[0])?;
 297                 let r = self.read_immediate(args[1])?;
 298                 let bin_op = match intrinsic_name {
 299                     sym::unchecked_shl => BinOp::Shl,
 300                     sym::unchecked_shr => BinOp::Shr,
 301                     sym::unchecked_add => BinOp::Add,
 302                     sym::unchecked_sub => BinOp::Sub,
 303                     sym::unchecked_mul => BinOp::Mul,
 304                     sym::unchecked_div => BinOp::Div,
 305                     sym::unchecked_rem => BinOp::Rem,
 306                     _ => bug!("Already checked for int ops"),
 307                 };
 308                 let (val, overflowed, _ty) = self.overflowing_binary_op(bin_op, l, r)?;
 309                 if overflowed {
 310                     let layout = self.layout_of(substs.type_at(0))?;
 311                     let r_val = self.force_bits(r.to_scalar()?, layout.size)?;
 312                     if let sym::unchecked_shl | sym::unchecked_shr = intrinsic_name {
 313                         throw_ub_format!("overflowing shift by {} in `{}`", r_val, intrinsic_name);
 314                     } else {
 315                         throw_ub_format!("overflow executing `{}`", intrinsic_name);
 316                     }
 317                 }
 318                 self.write_scalar(val, dest)?;
 319             }
 320             sym::rotate_left | sym::rotate_right => {
 321                 // rotate_left: (X << (S % BW)) | (X >> ((BW - S) % BW))
 322                 // rotate_right: (X << ((BW - S) % BW)) | (X >> (S % BW))
 323                 let layout = self.layout_of(substs.type_at(0))?;
 324                 let val = self.read_scalar(args[0])?.check_init()?;
 325                 let val_bits = self.force_bits(val, layout.size)?;
 326                 let raw_shift = self.read_scalar(args[1])?.check_init()?;
 327                 let raw_shift_bits = self.force_bits(raw_shift, layout.size)?;
 328                 let width_bits = u128::from(layout.size.bits());
 329                 let shift_bits = raw_shift_bits % width_bits;
 330                 let inv_shift_bits = (width_bits - shift_bits) % width_bits;
 331                 let result_bits = if intrinsic_name == sym::rotate_left {
 332                     (val_bits << shift_bits) | (val_bits >> inv_shift_bits)
 333                 } else {
 334                     (val_bits >> shift_bits) | (val_bits << inv_shift_bits)
 335                 };
 336                 let truncated_bits = self.truncate(result_bits, layout);
 337                 let result = Scalar::from_uint(truncated_bits, layout.size);
 338                 self.write_scalar(result, dest)?;
 339             }
 340             sym::offset => {
 341                 let ptr = self.read_scalar(args[0])?.check_init()?;
 342                 let offset_count = self.read_scalar(args[1])?.to_machine_isize(self)?;
 343                 let pointee_ty = substs.type_at(0);
 344
 345                 let offset_ptr = self.ptr_offset_inbounds(ptr, pointee_ty, offset_count)?;
 346                 self.write_scalar(offset_ptr, dest)?;
 347             }
 348             sym::arith_offset => {
 349                 let ptr = self.read_scalar(args[0])?.check_init()?;
 350                 let offset_count = self.read_scalar(args[1])?.to_machine_isize(self)?;
 351                 let pointee_ty = substs.type_at(0);
 352
 353                 let pointee_size = i64::try_from(self.layout_of(pointee_ty)?.size.bytes()).unwrap();
 354                 let offset_bytes = offset_count.wrapping_mul(pointee_size);
 355                 let offset_ptr = ptr.ptr_wrapping_signed_offset(offset_bytes, self);
 356                 self.write_scalar(offset_ptr, dest)?;
 357             }
 358             sym::ptr_offset_from => {
 359                 let a = self.read_immediate(args[0])?.to_scalar()?;
 360                 let b = self.read_immediate(args[1])?.to_scalar()?;
 361
 362                 // Special case: if both scalars are *equal integers*
 363                 // and not NULL, we pretend there is an allocation of size 0 right there,
 364                 // and their offset is 0. (There's never a valid object at NULL, making it an
 365                 // exception from the exception.)
 366                 // This is the dual to the special exception for offset-by-0
 367                 // in the inbounds pointer offset operation (see the Miri code, `src/operator.rs`).
 368                 //
 369                 // Control flow is weird because we cannot early-return (to reach the
 370                 // `go_to_block` at the end).
 371                 let done = if a.is_bits() && b.is_bits() {
 372                     let a = a.to_machine_usize(self)?;
 373                     let b = b.to_machine_usize(self)?;
 374                     if a == b && a != 0 {
 375                         self.write_scalar(Scalar::from_machine_isize(0, self), dest)?;
 376                         true
 377                     } else {
 378                         false
 379                     }
 380                 } else {
 381                     false
 382                 };
 383
 384                 if !done {
 385                     // General case: we need two pointers.
 386                     let a = self.force_ptr(a)?;
 387                     let b = self.force_ptr(b)?;
 388                     if a.alloc_id != b.alloc_id {
 389                         throw_ub_format!(
 390                             "ptr_offset_from cannot compute offset of pointers into different \
 391                             allocations.",
 392                         );
 393                     }
 394                     let usize_layout = self.layout_of(self.tcx.types.usize)?;
 395                     let isize_layout = self.layout_of(self.tcx.types.isize)?;
 396                     let a_offset = ImmTy::from_uint(a.offset.bytes(), usize_layout);
 397                     let b_offset = ImmTy::from_uint(b.offset.bytes(), usize_layout);
 398                     let (val, _overflowed, _ty) =
 399                         self.overflowing_binary_op(BinOp::Sub, a_offset, b_offset)?;
 400                     let pointee_layout = self.layout_of(substs.type_at(0))?;
 401                     let val = ImmTy::from_scalar(val, isize_layout);
 402                     let size = ImmTy::from_int(pointee_layout.size.bytes(), isize_layout);
 403                     self.exact_div(val, size, dest)?;
 404                 }
 405             }
 406
 407             sym::transmute => {
 408                 self.copy_op_transmute(args[0], dest)?;
 409             }
 410             sym::assert_inhabited => {
 411                 let ty = instance.substs.type_at(0);
 412                 let layout = self.layout_of(ty)?;
 413
 414                 if layout.abi.is_uninhabited() {
 415                     // The run-time intrinsic panics just to get a good backtrace; here we abort
 416                     // since there is no problem showing a backtrace even for aborts.
 417                     M::abort(self, format!("attempted to instantiate uninhabited type `{}`", ty))?;
 418                 }
 419             }
 420             sym::simd_insert => {
 421                 let index = u64::from(self.read_scalar(args[1])?.to_u32()?);
 422                 let elem = args[2];
 423                 let input = args[0];
 424                 let (len, e_ty) = input.layout.ty.simd_size_and_type(*self.tcx);
 425                 assert!(
 426                     index < len,
 427                     "Index `{}` must be in bounds of vector type `{}`: `[0, {})`",
 428                     index,
 429                     e_ty,
 430                     len
 431                 );
 432                 assert_eq!(
 433                     input.layout, dest.layout,
 434                     "Return type `{}` must match vector type `{}`",
 435                     dest.layout.ty, input.layout.ty
 436                 );
 437                 assert_eq!(
 438                     elem.layout.ty, e_ty,
 439                     "Scalar element type `{}` must match vector element type `{}`",
 440                     elem.layout.ty, e_ty
 441                 );
 442
 443                 for i in 0..len {
 444                     let place = self.place_index(dest, i)?;
 445                     let value = if i == index { elem } else { self.operand_index(input, i)? };
 446                     self.copy_op(value, place)?;
 447                 }
 448             }
 449             sym::simd_extract => {
 450                 let index = u64::from(self.read_scalar(args[1])?.to_u32()?);
 451                 let (len, e_ty) = args[0].layout.ty.simd_size_and_type(*self.tcx);
 452                 assert!(
 453                     index < len,
 454                     "index `{}` is out-of-bounds of vector type `{}` with length `{}`",
 455                     index,
 456                     e_ty,
 457                     len
 458                 );
 459                 assert_eq!(
 460                     e_ty, dest.layout.ty,
 461                     "Return type `{}` must match vector element type `{}`",
 462                     dest.layout.ty, e_ty
 463                 );
 464                 self.copy_op(self.operand_index(args[0], index)?, dest)?;
 465             }
 466             sym::likely | sym::unlikely => {
 467                 // These just return their argument
 468                 self.copy_op(args[0], dest)?;
 469             }
 470             sym::assume => {
 471                 let cond = self.read_scalar(args[0])?.check_init()?.to_bool()?;
 472                 if !cond {
 473                     throw_ub_format!("`assume` intrinsic called with `false`");
 474                 }
 475             }
 476             _ => return Ok(false),
 477         }
 478
 479         trace!("{:?}", self.dump_place(*dest));
 480         self.go_to_block(ret);
 481         Ok(true)
 482     }
 483
 484     pub fn exact_div(
 485         &mut self,
 486         a: ImmTy<'tcx, M::PointerTag>,
 487         b: ImmTy<'tcx, M::PointerTag>,
 488         dest: PlaceTy<'tcx, M::PointerTag>,
 489     ) -> InterpResult<'tcx> {
 490         // Performs an exact division, resulting in undefined behavior where
 491         // `x % y != 0` or `y == 0` or `x == T::MIN && y == -1`.
 492         // First, check x % y != 0 (or if that computation overflows).
 493         let (res, overflow, _ty) = self.overflowing_binary_op(BinOp::Rem, a, b)?;
 494         if overflow || res.assert_bits(a.layout.size) != 0 {
 495             // Then, check if `b` is -1, which is the "MIN / -1" case.
 496             let minus1 = Scalar::from_int(-1, dest.layout.size);
 497             let b_scalar = b.to_scalar().unwrap();
 498             if b_scalar == minus1 {
 499                 throw_ub_format!("exact_div: result of dividing MIN by -1 cannot be represented")
 500             } else {
 501                 throw_ub_format!("exact_div: {} cannot be divided by {} without remainder", a, b,)
 502             }
 503         }
 504         // `Rem` says this is all right, so we can let `Div` do its job.
 505         self.binop_ignore_overflow(BinOp::Div, a, b, dest)
 506     }
 507
 508     /// Offsets a pointer by some multiple of its type, returning an error if the pointer leaves its
 509     /// allocation. For integer pointers, we consider each of them their own tiny allocation of size
 510     /// 0, so offset-by-0 (and only 0) is okay -- except that NULL cannot be offset by _any_ value.
 511     pub fn ptr_offset_inbounds(
 512         &self,
 513         ptr: Scalar<M::PointerTag>,
 514         pointee_ty: Ty<'tcx>,
 515         offset_count: i64,
 516     ) -> InterpResult<'tcx, Scalar<M::PointerTag>> {
 517         // We cannot overflow i64 as a type's size must be <= isize::MAX.
 518         let pointee_size = i64::try_from(self.layout_of(pointee_ty)?.size.bytes()).unwrap();
 519         // The computed offset, in bytes, cannot overflow an isize.
 520         let offset_bytes =
 521             offset_count.checked_mul(pointee_size).ok_or(err_ub!(PointerArithOverflow))?;
 522         // The offset being in bounds cannot rely on "wrapping around" the address space.
 523         // So, first rule out overflows in the pointer arithmetic.
 524         let offset_ptr = ptr.ptr_signed_offset(offset_bytes, self)?;
 525         // ptr and offset_ptr must be in bounds of the same allocated object. This means all of the
 526         // memory between these pointers must be accessible. Note that we do not require the
 527         // pointers to be properly aligned (unlike a read/write operation).
 528         let min_ptr = if offset_bytes >= 0 { ptr } else { offset_ptr };
 529         let size: u64 = uabs(offset_bytes);
 530         // This call handles checking for integer/NULL pointers.
 531         self.memory.check_ptr_access_align(
 532             min_ptr,
 533             Size::from_bytes(size),
 534             None,
 535             CheckInAllocMsg::InboundsTest,
 536         )?;
 537         Ok(offset_ptr)
 538     }
 539 }