src/shims/intrinsics.rs

   1 use std::iter;
   2
   3 use log::trace;
   4
   5 use rustc_apfloat::{Float, Round};
   6 use rustc_middle::ty::layout::{IntegerExt, LayoutOf};
   7 use rustc_middle::{mir, mir::BinOp, ty, ty::FloatTy};
   8 use rustc_target::abi::{Align, Integer};
   9
  10 use crate::*;
  11 use helpers::{bool_to_simd_element, check_arg_count, simd_element_to_bool};
  12
  13 pub enum AtomicOp {
  14     MirOp(mir::BinOp, bool),
  15     Max,
  16     Min,
  17 }
  18
  19 impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
  20 pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
  21     fn call_intrinsic(
  22         &mut self,
  23         instance: ty::Instance<'tcx>,
  24         args: &[OpTy<'tcx, Tag>],
  25         ret: Option<(&PlaceTy<'tcx, Tag>, mir::BasicBlock)>,
  26         _unwind: StackPopUnwind,
  27     ) -> InterpResult<'tcx> {
  28         let this = self.eval_context_mut();
  29
  30         if this.emulate_intrinsic(instance, args, ret)? {
  31             return Ok(());
  32         }
  33
  34         // All supported intrinsics have a return place.
  35         let intrinsic_name = this.tcx.item_name(instance.def_id());
  36         let intrinsic_name = intrinsic_name.as_str();
  37         let (dest, ret) = match ret {
  38             None => throw_unsup_format!("unimplemented (diverging) intrinsic: {}", intrinsic_name),
  39             Some(p) => p,
  40         };
  41
  42         // Then handle terminating intrinsics.
  43         match intrinsic_name {
  44             // Miri overwriting CTFE intrinsics.
  45             "ptr_guaranteed_eq" => {
  46                 let &[ref left, ref right] = check_arg_count(args)?;
  47                 let left = this.read_immediate(left)?;
  48                 let right = this.read_immediate(right)?;
  49                 this.binop_ignore_overflow(mir::BinOp::Eq, &left, &right, dest)?;
  50             }
  51             "ptr_guaranteed_ne" => {
  52                 let &[ref left, ref right] = check_arg_count(args)?;
  53                 let left = this.read_immediate(left)?;
  54                 let right = this.read_immediate(right)?;
  55                 this.binop_ignore_overflow(mir::BinOp::Ne, &left, &right, dest)?;
  56             }
  57             "const_allocate" => {
  58                 // For now, for compatibility with the run-time implementation of this, we just return null.
  59                 // See <https://github.com/rust-lang/rust/issues/93935>.
  60                 this.write_null(dest)?;
  61             }
  62             "const_deallocate" => {
  63                 // complete NOP
  64             }
  65
  66             // Raw memory accesses
  67             "volatile_load" => {
  68                 let &[ref place] = check_arg_count(args)?;
  69                 let place = this.deref_operand(place)?;
  70                 this.copy_op(&place.into(), dest)?;
  71             }
  72             "volatile_store" => {
  73                 let &[ref place, ref dest] = check_arg_count(args)?;
  74                 let place = this.deref_operand(place)?;
  75                 this.copy_op(dest, &place.into())?;
  76             }
  77
  78             "write_bytes" | "volatile_set_memory" => {
  79                 let &[ref ptr, ref val_byte, ref count] = check_arg_count(args)?;
  80                 let ty = instance.substs.type_at(0);
  81                 let ty_layout = this.layout_of(ty)?;
  82                 let val_byte = this.read_scalar(val_byte)?.to_u8()?;
  83                 let ptr = this.read_pointer(ptr)?;
  84                 let count = this.read_scalar(count)?.to_machine_usize(this)?;
  85                 let byte_count = ty_layout.size.checked_mul(count, this).ok_or_else(|| {
  86                     err_ub_format!("overflow computing total size of `{}`", intrinsic_name)
  87                 })?;
  88                 this.memory
  89                     .write_bytes(ptr, iter::repeat(val_byte).take(byte_count.bytes() as usize))?;
  90             }
  91
  92             // Floating-point operations
  93             #[rustfmt::skip]
  94             | "sinf32"
  95             | "fabsf32"
  96             | "cosf32"
  97             | "sqrtf32"
  98             | "expf32"
  99             | "exp2f32"
 100             | "logf32"
 101             | "log10f32"
 102             | "log2f32"
 103             | "floorf32"
 104             | "ceilf32"
 105             | "truncf32"
 106             | "roundf32"
 107             => {
 108                 let &[ref f] = check_arg_count(args)?;
 109                 // FIXME: Using host floats.
 110                 let f = f32::from_bits(this.read_scalar(f)?.to_u32()?);
 111                 let f = match intrinsic_name {
 112                     "sinf32" => f.sin(),
 113                     "fabsf32" => f.abs(),
 114                     "cosf32" => f.cos(),
 115                     "sqrtf32" => f.sqrt(),
 116                     "expf32" => f.exp(),
 117                     "exp2f32" => f.exp2(),
 118                     "logf32" => f.ln(),
 119                     "log10f32" => f.log10(),
 120                     "log2f32" => f.log2(),
 121                     "floorf32" => f.floor(),
 122                     "ceilf32" => f.ceil(),
 123                     "truncf32" => f.trunc(),
 124                     "roundf32" => f.round(),
 125                     _ => bug!(),
 126                 };
 127                 this.write_scalar(Scalar::from_u32(f.to_bits()), dest)?;
 128             }
 129
 130             #[rustfmt::skip]
 131             | "sinf64"
 132             | "fabsf64"
 133             | "cosf64"
 134             | "sqrtf64"
 135             | "expf64"
 136             | "exp2f64"
 137             | "logf64"
 138             | "log10f64"
 139             | "log2f64"
 140             | "floorf64"
 141             | "ceilf64"
 142             | "truncf64"
 143             | "roundf64"
 144             => {
 145                 let &[ref f] = check_arg_count(args)?;
 146                 // FIXME: Using host floats.
 147                 let f = f64::from_bits(this.read_scalar(f)?.to_u64()?);
 148                 let f = match intrinsic_name {
 149                     "sinf64" => f.sin(),
 150                     "fabsf64" => f.abs(),
 151                     "cosf64" => f.cos(),
 152                     "sqrtf64" => f.sqrt(),
 153                     "expf64" => f.exp(),
 154                     "exp2f64" => f.exp2(),
 155                     "logf64" => f.ln(),
 156                     "log10f64" => f.log10(),
 157                     "log2f64" => f.log2(),
 158                     "floorf64" => f.floor(),
 159                     "ceilf64" => f.ceil(),
 160                     "truncf64" => f.trunc(),
 161                     "roundf64" => f.round(),
 162                     _ => bug!(),
 163                 };
 164                 this.write_scalar(Scalar::from_u64(f.to_bits()), dest)?;
 165             }
 166
 167             #[rustfmt::skip]
 168             | "fadd_fast"
 169             | "fsub_fast"
 170             | "fmul_fast"
 171             | "fdiv_fast"
 172             | "frem_fast"
 173             => {
 174                 let &[ref a, ref b] = check_arg_count(args)?;
 175                 let a = this.read_immediate(a)?;
 176                 let b = this.read_immediate(b)?;
 177                 let op = match intrinsic_name {
 178                     "fadd_fast" => mir::BinOp::Add,
 179                     "fsub_fast" => mir::BinOp::Sub,
 180                     "fmul_fast" => mir::BinOp::Mul,
 181                     "fdiv_fast" => mir::BinOp::Div,
 182                     "frem_fast" => mir::BinOp::Rem,
 183                     _ => bug!(),
 184                 };
 185                 let float_finite = |x: ImmTy<'tcx, _>| -> InterpResult<'tcx, bool> {
 186                     Ok(match x.layout.ty.kind() {
 187                         ty::Float(FloatTy::F32) => x.to_scalar()?.to_f32()?.is_finite(),
 188                         ty::Float(FloatTy::F64) => x.to_scalar()?.to_f64()?.is_finite(),
 189                         _ => bug!(
 190                             "`{}` called with non-float input type {:?}",
 191                             intrinsic_name,
 192                             x.layout.ty
 193                         ),
 194                     })
 195                 };
 196                 match (float_finite(a)?, float_finite(b)?) {
 197                     (false, false) => throw_ub_format!(
 198                         "`{}` intrinsic called with non-finite value as both parameters",
 199                         intrinsic_name,
 200                     ),
 201                     (false, _) => throw_ub_format!(
 202                         "`{}` intrinsic called with non-finite value as first parameter",
 203                         intrinsic_name,
 204                     ),
 205                     (_, false) => throw_ub_format!(
 206                         "`{}` intrinsic called with non-finite value as second parameter",
 207                         intrinsic_name,
 208                     ),
 209                     _ => {}
 210                 }
 211                 this.binop_ignore_overflow(op, &a, &b, dest)?;
 212             }
 213
 214             #[rustfmt::skip]
 215             | "minnumf32"
 216             | "maxnumf32"
 217             | "copysignf32"
 218             => {
 219                 let &[ref a, ref b] = check_arg_count(args)?;
 220                 let a = this.read_scalar(a)?.to_f32()?;
 221                 let b = this.read_scalar(b)?.to_f32()?;
 222                 let res = match intrinsic_name {
 223                     "minnumf32" => a.min(b),
 224                     "maxnumf32" => a.max(b),
 225                     "copysignf32" => a.copy_sign(b),
 226                     _ => bug!(),
 227                 };
 228                 this.write_scalar(Scalar::from_f32(res), dest)?;
 229             }
 230
 231             #[rustfmt::skip]
 232             | "minnumf64"
 233             | "maxnumf64"
 234             | "copysignf64"
 235             => {
 236                 let &[ref a, ref b] = check_arg_count(args)?;
 237                 let a = this.read_scalar(a)?.to_f64()?;
 238                 let b = this.read_scalar(b)?.to_f64()?;
 239                 let res = match intrinsic_name {
 240                     "minnumf64" => a.min(b),
 241                     "maxnumf64" => a.max(b),
 242                     "copysignf64" => a.copy_sign(b),
 243                     _ => bug!(),
 244                 };
 245                 this.write_scalar(Scalar::from_f64(res), dest)?;
 246             }
 247
 248             "powf32" => {
 249                 let &[ref f, ref f2] = check_arg_count(args)?;
 250                 // FIXME: Using host floats.
 251                 let f = f32::from_bits(this.read_scalar(f)?.to_u32()?);
 252                 let f2 = f32::from_bits(this.read_scalar(f2)?.to_u32()?);
 253                 this.write_scalar(Scalar::from_u32(f.powf(f2).to_bits()), dest)?;
 254             }
 255
 256             "powf64" => {
 257                 let &[ref f, ref f2] = check_arg_count(args)?;
 258                 // FIXME: Using host floats.
 259                 let f = f64::from_bits(this.read_scalar(f)?.to_u64()?);
 260                 let f2 = f64::from_bits(this.read_scalar(f2)?.to_u64()?);
 261                 this.write_scalar(Scalar::from_u64(f.powf(f2).to_bits()), dest)?;
 262             }
 263
 264             "fmaf32" => {
 265                 let &[ref a, ref b, ref c] = check_arg_count(args)?;
 266                 let a = this.read_scalar(a)?.to_f32()?;
 267                 let b = this.read_scalar(b)?.to_f32()?;
 268                 let c = this.read_scalar(c)?.to_f32()?;
 269                 let res = a.mul_add(b, c).value;
 270                 this.write_scalar(Scalar::from_f32(res), dest)?;
 271             }
 272
 273             "fmaf64" => {
 274                 let &[ref a, ref b, ref c] = check_arg_count(args)?;
 275                 let a = this.read_scalar(a)?.to_f64()?;
 276                 let b = this.read_scalar(b)?.to_f64()?;
 277                 let c = this.read_scalar(c)?.to_f64()?;
 278                 let res = a.mul_add(b, c).value;
 279                 this.write_scalar(Scalar::from_f64(res), dest)?;
 280             }
 281
 282             "powif32" => {
 283                 let &[ref f, ref i] = check_arg_count(args)?;
 284                 // FIXME: Using host floats.
 285                 let f = f32::from_bits(this.read_scalar(f)?.to_u32()?);
 286                 let i = this.read_scalar(i)?.to_i32()?;
 287                 this.write_scalar(Scalar::from_u32(f.powi(i).to_bits()), dest)?;
 288             }
 289
 290             "powif64" => {
 291                 let &[ref f, ref i] = check_arg_count(args)?;
 292                 // FIXME: Using host floats.
 293                 let f = f64::from_bits(this.read_scalar(f)?.to_u64()?);
 294                 let i = this.read_scalar(i)?.to_i32()?;
 295                 this.write_scalar(Scalar::from_u64(f.powi(i).to_bits()), dest)?;
 296             }
 297
 298             "float_to_int_unchecked" => {
 299                 let &[ref val] = check_arg_count(args)?;
 300                 let val = this.read_immediate(val)?;
 301
 302                 let res = match val.layout.ty.kind() {
 303                     ty::Float(FloatTy::F32) =>
 304                         this.float_to_int_unchecked(val.to_scalar()?.to_f32()?, dest.layout.ty)?,
 305                     ty::Float(FloatTy::F64) =>
 306                         this.float_to_int_unchecked(val.to_scalar()?.to_f64()?, dest.layout.ty)?,
 307                     _ =>
 308                         bug!(
 309                             "`float_to_int_unchecked` called with non-float input type {:?}",
 310                             val.layout.ty
 311                         ),
 312                 };
 313
 314                 this.write_scalar(res, dest)?;
 315             }
 316
 317             // SIMD operations
 318             #[rustfmt::skip]
 319             | "simd_neg"
 320             | "simd_fabs" => {
 321                 let &[ref op] = check_arg_count(args)?;
 322                 let (op, op_len) = this.operand_to_simd(op)?;
 323                 let (dest, dest_len) = this.place_to_simd(dest)?;
 324
 325                 assert_eq!(dest_len, op_len);
 326
 327                 enum Op {
 328                     MirOp(mir::UnOp),
 329                     Abs,
 330                 }
 331                 let which = match intrinsic_name {
 332                     "simd_neg" => Op::MirOp(mir::UnOp::Neg),
 333                     "simd_fabs" => Op::Abs,
 334                     _ => unreachable!(),
 335                 };
 336
 337                 for i in 0..dest_len {
 338                     let op = this.read_immediate(&this.mplace_index(&op, i)?.into())?;
 339                     let dest = this.mplace_index(&dest, i)?;
 340                     let val = match which {
 341                         Op::MirOp(mir_op) => this.unary_op(mir_op, &op)?.to_scalar()?,
 342                         Op::Abs => {
 343                             // Works for f32 and f64.
 344                             let ty::Float(float_ty) = op.layout.ty.kind() else {
 345                                 bug!("simd_fabs operand is not a float")
 346                             };
 347                             let op = op.to_scalar()?;
 348                             // FIXME: Using host floats.
 349                             match float_ty {
 350                                 FloatTy::F32 => Scalar::from_f32(op.to_f32()?.abs()),
 351                                 FloatTy::F64 => Scalar::from_f64(op.to_f64()?.abs()),
 352                             }
 353                         }
 354                     };
 355                     this.write_scalar(val, &dest.into())?;
 356                 }
 357             }
 358             #[rustfmt::skip]
 359             | "simd_add"
 360             | "simd_sub"
 361             | "simd_mul"
 362             | "simd_div"
 363             | "simd_rem"
 364             | "simd_shl"
 365             | "simd_shr"
 366             | "simd_and"
 367             | "simd_or"
 368             | "simd_xor"
 369             | "simd_eq"
 370             | "simd_ne"
 371             | "simd_lt"
 372             | "simd_le"
 373             | "simd_gt"
 374             | "simd_ge" => {
 375                 use mir::BinOp;
 376
 377                 let &[ref left, ref right] = check_arg_count(args)?;
 378                 let (left, left_len) = this.operand_to_simd(left)?;
 379                 let (right, right_len) = this.operand_to_simd(right)?;
 380                 let (dest, dest_len) = this.place_to_simd(dest)?;
 381
 382                 assert_eq!(dest_len, left_len);
 383                 assert_eq!(dest_len, right_len);
 384
 385                 let mir_op = match intrinsic_name {
 386                     "simd_add" => BinOp::Add,
 387                     "simd_sub" => BinOp::Sub,
 388                     "simd_mul" => BinOp::Mul,
 389                     "simd_div" => BinOp::Div,
 390                     "simd_rem" => BinOp::Rem,
 391                     "simd_shl" => BinOp::Shl,
 392                     "simd_shr" => BinOp::Shr,
 393                     "simd_and" => BinOp::BitAnd,
 394                     "simd_or" => BinOp::BitOr,
 395                     "simd_xor" => BinOp::BitXor,
 396                     "simd_eq" => BinOp::Eq,
 397                     "simd_ne" => BinOp::Ne,
 398                     "simd_lt" => BinOp::Lt,
 399                     "simd_le" => BinOp::Le,
 400                     "simd_gt" => BinOp::Gt,
 401                     "simd_ge" => BinOp::Ge,
 402                     _ => unreachable!(),
 403                 };
 404
 405                 for i in 0..dest_len {
 406                     let left = this.read_immediate(&this.mplace_index(&left, i)?.into())?;
 407                     let right = this.read_immediate(&this.mplace_index(&right, i)?.into())?;
 408                     let dest = this.mplace_index(&dest, i)?;
 409                     let (val, overflowed, ty) = this.overflowing_binary_op(mir_op, &left, &right)?;
 410                     if matches!(mir_op, BinOp::Shl | BinOp::Shr) {
 411                         // Shifts have extra UB as SIMD operations that the MIR binop does not have.
 412                         // See <https://github.com/rust-lang/rust/issues/91237>.
 413                         if overflowed {
 414                             let r_val = right.to_scalar()?.to_bits(right.layout.size)?;
 415                             throw_ub_format!("overflowing shift by {} in `{}` in SIMD lane {}", r_val, intrinsic_name, i);
 416                         }
 417                     }
 418                     if matches!(mir_op, BinOp::Eq | BinOp::Ne | BinOp::Lt | BinOp::Le | BinOp::Gt | BinOp::Ge) {
 419                         // Special handling for boolean-returning operations
 420                         assert_eq!(ty, this.tcx.types.bool);
 421                         let val = val.to_bool().unwrap();
 422                         let val = bool_to_simd_element(val, dest.layout.size);
 423                         this.write_scalar(val, &dest.into())?;
 424                     } else {
 425                         assert_ne!(ty, this.tcx.types.bool);
 426                         assert_eq!(ty, dest.layout.ty);
 427                         this.write_scalar(val, &dest.into())?;
 428                     }
 429                 }
 430             }
 431             #[rustfmt::skip]
 432             | "simd_reduce_and"
 433             | "simd_reduce_or"
 434             | "simd_reduce_xor"
 435             | "simd_reduce_any"
 436             | "simd_reduce_all" => {
 437                 use mir::BinOp;
 438
 439                 let &[ref op] = check_arg_count(args)?;
 440                 let (op, op_len) = this.operand_to_simd(op)?;
 441
 442                 let imm_from_bool =
 443                     |b| ImmTy::from_scalar(Scalar::from_bool(b), this.machine.layouts.bool);
 444
 445                 enum Op {
 446                     MirOp(BinOp),
 447                     MirOpBool(BinOp),
 448                 }
 449                 // The initial value is the neutral element.
 450                 let (which, init) = match intrinsic_name {
 451                     "simd_reduce_and" => (Op::MirOp(BinOp::BitAnd), ImmTy::from_int(-1, dest.layout)),
 452                     "simd_reduce_or" => (Op::MirOp(BinOp::BitOr), ImmTy::from_int(0, dest.layout)),
 453                     "simd_reduce_xor" => (Op::MirOp(BinOp::BitXor), ImmTy::from_int(0, dest.layout)),
 454                     "simd_reduce_any" => (Op::MirOpBool(BinOp::BitOr), imm_from_bool(false)),
 455                     "simd_reduce_all" => (Op::MirOpBool(BinOp::BitAnd), imm_from_bool(true)),
 456                     _ => unreachable!(),
 457                 };
 458
 459                 let mut res = init;
 460                 for i in 0..op_len {
 461                     let op = this.read_immediate(&this.mplace_index(&op, i)?.into())?;
 462                     res = match which {
 463                         Op::MirOp(mir_op) => {
 464                             this.binary_op(mir_op, &res, &op)?
 465                         }
 466                         Op::MirOpBool(mir_op) => {
 467                             let op = imm_from_bool(simd_element_to_bool(op)?);
 468                             this.binary_op(mir_op, &res, &op)?
 469                         }
 470                     };
 471                 }
 472                 this.write_immediate(*res, dest)?;
 473             }
 474             #[rustfmt::skip]
 475             | "simd_reduce_add_ordered"
 476             | "simd_reduce_mul_ordered" => {
 477                 use mir::BinOp;
 478
 479                 let &[ref op, ref init] = check_arg_count(args)?;
 480                 let (op, op_len) = this.operand_to_simd(op)?;
 481                 let init = this.read_immediate(init)?;
 482
 483                 let mir_op = match intrinsic_name {
 484                     "simd_reduce_add_ordered" => BinOp::Add,
 485                     "simd_reduce_mul_ordered" => BinOp::Mul,
 486                     _ => unreachable!(),
 487                 };
 488
 489                 let mut res = init;
 490                 for i in 0..op_len {
 491                     let op = this.read_immediate(&this.mplace_index(&op, i)?.into())?;
 492                     res = this.binary_op(mir_op, &res, &op)?;
 493                 }
 494                 this.write_immediate(*res, dest)?;
 495             }
 496             "simd_select" => {
 497                 let &[ref mask, ref yes, ref no] = check_arg_count(args)?;
 498                 let (mask, mask_len) = this.operand_to_simd(mask)?;
 499                 let (yes, yes_len) = this.operand_to_simd(yes)?;
 500                 let (no, no_len) = this.operand_to_simd(no)?;
 501                 let (dest, dest_len) = this.place_to_simd(dest)?;
 502
 503                 assert_eq!(dest_len, mask_len);
 504                 assert_eq!(dest_len, yes_len);
 505                 assert_eq!(dest_len, no_len);
 506
 507                 for i in 0..dest_len {
 508                     let mask = this.read_immediate(&this.mplace_index(&mask, i)?.into())?;
 509                     let yes = this.read_immediate(&this.mplace_index(&yes, i)?.into())?;
 510                     let no = this.read_immediate(&this.mplace_index(&no, i)?.into())?;
 511                     let dest = this.mplace_index(&dest, i)?;
 512
 513                     let mask = simd_element_to_bool(mask)?;
 514                     let val = if mask { yes } else { no };
 515                     this.write_immediate(*val, &dest.into())?;
 516                 }
 517             }
 518             #[rustfmt::skip]
 519             "simd_cast" | "simd_as" => {
 520                 let &[ref op] = check_arg_count(args)?;
 521                 let (op, op_len) = this.operand_to_simd(op)?;
 522                 let (dest, dest_len) = this.place_to_simd(dest)?;
 523
 524                 assert_eq!(dest_len, op_len);
 525
 526                 let safe_cast = intrinsic_name == "simd_as";
 527
 528                 for i in 0..dest_len {
 529                     let op = this.read_immediate(&this.mplace_index(&op, i)?.into())?;
 530                     let dest = this.mplace_index(&dest, i)?;
 531
 532                     let val = match (op.layout.ty.kind(), dest.layout.ty.kind()) {
 533                         // Int-to-(int|float): always safe
 534                         (ty::Int(_) | ty::Uint(_), ty::Int(_) | ty::Uint(_) | ty::Float(_)) =>
 535                             this.misc_cast(&op, dest.layout.ty)?,
 536                         // Float-to-float: always safe
 537                         (ty::Float(_), ty::Float(_)) =>
 538                             this.misc_cast(&op, dest.layout.ty)?,
 539                         // Float-to-int in safe mode
 540                         (ty::Float(_), ty::Int(_) | ty::Uint(_)) if safe_cast =>
 541                             this.misc_cast(&op, dest.layout.ty)?,
 542                         // Float-to-int in unchecked mode
 543                         (ty::Float(FloatTy::F32), ty::Int(_) | ty::Uint(_)) if !safe_cast =>
 544                             this.float_to_int_unchecked(op.to_scalar()?.to_f32()?, dest.layout.ty)?.into(),
 545                         (ty::Float(FloatTy::F64), ty::Int(_) | ty::Uint(_)) if !safe_cast =>
 546                             this.float_to_int_unchecked(op.to_scalar()?.to_f64()?, dest.layout.ty)?.into(),
 547                         _ =>
 548                             throw_unsup_format!(
 549                                 "Unsupported SIMD cast from element type {} to {}",
 550                                 op.layout.ty,
 551                                 dest.layout.ty
 552                             ),
 553                     };
 554                     this.write_immediate(val, &dest.into())?;
 555                 }
 556             }
 557
 558             // Atomic operations
 559             "atomic_load" => this.atomic_load(args, dest, AtomicReadOp::SeqCst)?,
 560             "atomic_load_relaxed" => this.atomic_load(args, dest, AtomicReadOp::Relaxed)?,
 561             "atomic_load_acq" => this.atomic_load(args, dest, AtomicReadOp::Acquire)?,
 562
 563             "atomic_store" => this.atomic_store(args, AtomicWriteOp::SeqCst)?,
 564             "atomic_store_relaxed" => this.atomic_store(args, AtomicWriteOp::Relaxed)?,
 565             "atomic_store_rel" => this.atomic_store(args, AtomicWriteOp::Release)?,
 566
 567             "atomic_fence_acq" => this.atomic_fence(args, AtomicFenceOp::Acquire)?,
 568             "atomic_fence_rel" => this.atomic_fence(args, AtomicFenceOp::Release)?,
 569             "atomic_fence_acqrel" => this.atomic_fence(args, AtomicFenceOp::AcqRel)?,
 570             "atomic_fence" => this.atomic_fence(args, AtomicFenceOp::SeqCst)?,
 571
 572             "atomic_singlethreadfence_acq" => this.compiler_fence(args, AtomicFenceOp::Acquire)?,
 573             "atomic_singlethreadfence_rel" => this.compiler_fence(args, AtomicFenceOp::Release)?,
 574             "atomic_singlethreadfence_acqrel" =>
 575                 this.compiler_fence(args, AtomicFenceOp::AcqRel)?,
 576             "atomic_singlethreadfence" => this.compiler_fence(args, AtomicFenceOp::SeqCst)?,
 577
 578             "atomic_xchg" => this.atomic_exchange(args, dest, AtomicRwOp::SeqCst)?,
 579             "atomic_xchg_acq" => this.atomic_exchange(args, dest, AtomicRwOp::Acquire)?,
 580             "atomic_xchg_rel" => this.atomic_exchange(args, dest, AtomicRwOp::Release)?,
 581             "atomic_xchg_acqrel" => this.atomic_exchange(args, dest, AtomicRwOp::AcqRel)?,
 582             "atomic_xchg_relaxed" => this.atomic_exchange(args, dest, AtomicRwOp::Relaxed)?,
 583
 584             #[rustfmt::skip]
 585             "atomic_cxchg" =>
 586                 this.atomic_compare_exchange(args, dest, AtomicRwOp::SeqCst, AtomicReadOp::SeqCst)?,
 587             #[rustfmt::skip]
 588             "atomic_cxchg_acq" =>
 589                 this.atomic_compare_exchange(args, dest, AtomicRwOp::Acquire, AtomicReadOp::Acquire)?,
 590             #[rustfmt::skip]
 591             "atomic_cxchg_rel" =>
 592                 this.atomic_compare_exchange(args, dest, AtomicRwOp::Release, AtomicReadOp::Relaxed)?,
 593             #[rustfmt::skip]
 594             "atomic_cxchg_acqrel" =>
 595                 this.atomic_compare_exchange(args, dest, AtomicRwOp::AcqRel, AtomicReadOp::Acquire)?,
 596             #[rustfmt::skip]
 597             "atomic_cxchg_relaxed" =>
 598                 this.atomic_compare_exchange(args, dest, AtomicRwOp::Relaxed, AtomicReadOp::Relaxed)?,
 599             #[rustfmt::skip]
 600             "atomic_cxchg_acq_failrelaxed" =>
 601                 this.atomic_compare_exchange(args, dest, AtomicRwOp::Acquire, AtomicReadOp::Relaxed)?,
 602             #[rustfmt::skip]
 603             "atomic_cxchg_acqrel_failrelaxed" =>
 604                 this.atomic_compare_exchange(args, dest, AtomicRwOp::AcqRel, AtomicReadOp::Relaxed)?,
 605             #[rustfmt::skip]
 606             "atomic_cxchg_failrelaxed" =>
 607                 this.atomic_compare_exchange(args, dest, AtomicRwOp::SeqCst, AtomicReadOp::Relaxed)?,
 608             #[rustfmt::skip]
 609             "atomic_cxchg_failacq" =>
 610                 this.atomic_compare_exchange(args, dest, AtomicRwOp::SeqCst, AtomicReadOp::Acquire)?,
 611
 612             #[rustfmt::skip]
 613             "atomic_cxchgweak" =>
 614                 this.atomic_compare_exchange_weak(args, dest, AtomicRwOp::SeqCst, AtomicReadOp::SeqCst)?,
 615             #[rustfmt::skip]
 616             "atomic_cxchgweak_acq" =>
 617                 this.atomic_compare_exchange_weak(args, dest, AtomicRwOp::Acquire, AtomicReadOp::Acquire)?,
 618             #[rustfmt::skip]
 619             "atomic_cxchgweak_rel" =>
 620                 this.atomic_compare_exchange_weak(args, dest, AtomicRwOp::Release, AtomicReadOp::Relaxed)?,
 621             #[rustfmt::skip]
 622             "atomic_cxchgweak_acqrel" =>
 623                 this.atomic_compare_exchange_weak(args, dest, AtomicRwOp::AcqRel, AtomicReadOp::Acquire)?,
 624             #[rustfmt::skip]
 625             "atomic_cxchgweak_relaxed" =>
 626                 this.atomic_compare_exchange_weak(args, dest, AtomicRwOp::Relaxed, AtomicReadOp::Relaxed)?,
 627             #[rustfmt::skip]
 628             "atomic_cxchgweak_acq_failrelaxed" =>
 629                 this.atomic_compare_exchange_weak(args, dest, AtomicRwOp::Acquire, AtomicReadOp::Relaxed)?,
 630             #[rustfmt::skip]
 631             "atomic_cxchgweak_acqrel_failrelaxed" =>
 632                 this.atomic_compare_exchange_weak(args, dest, AtomicRwOp::AcqRel, AtomicReadOp::Relaxed)?,
 633             #[rustfmt::skip]
 634             "atomic_cxchgweak_failrelaxed" =>
 635                 this.atomic_compare_exchange_weak(args, dest, AtomicRwOp::SeqCst, AtomicReadOp::Relaxed)?,
 636             #[rustfmt::skip]
 637             "atomic_cxchgweak_failacq" =>
 638                 this.atomic_compare_exchange_weak(args, dest, AtomicRwOp::SeqCst, AtomicReadOp::Acquire)?,
 639
 640             #[rustfmt::skip]
 641             "atomic_or" =>
 642                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitOr, false), AtomicRwOp::SeqCst)?,
 643             #[rustfmt::skip]
 644             "atomic_or_acq" =>
 645                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitOr, false), AtomicRwOp::Acquire)?,
 646             #[rustfmt::skip]
 647             "atomic_or_rel" =>
 648                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitOr, false), AtomicRwOp::Release)?,
 649             #[rustfmt::skip]
 650             "atomic_or_acqrel" =>
 651                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitOr, false), AtomicRwOp::AcqRel)?,
 652             #[rustfmt::skip]
 653             "atomic_or_relaxed" =>
 654                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitOr, false), AtomicRwOp::Relaxed)?,
 655             #[rustfmt::skip]
 656             "atomic_xor" =>
 657                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitXor, false), AtomicRwOp::SeqCst)?,
 658             #[rustfmt::skip]
 659             "atomic_xor_acq" =>
 660                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitXor, false), AtomicRwOp::Acquire)?,
 661             #[rustfmt::skip]
 662             "atomic_xor_rel" =>
 663                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitXor, false), AtomicRwOp::Release)?,
 664             #[rustfmt::skip]
 665             "atomic_xor_acqrel" =>
 666                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitXor, false), AtomicRwOp::AcqRel)?,
 667             #[rustfmt::skip]
 668             "atomic_xor_relaxed" =>
 669                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitXor, false), AtomicRwOp::Relaxed)?,
 670             #[rustfmt::skip]
 671             "atomic_and" =>
 672                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, false), AtomicRwOp::SeqCst)?,
 673             #[rustfmt::skip]
 674             "atomic_and_acq" =>
 675                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, false), AtomicRwOp::Acquire)?,
 676             #[rustfmt::skip]
 677             "atomic_and_rel" =>
 678                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, false), AtomicRwOp::Release)?,
 679             #[rustfmt::skip]
 680             "atomic_and_acqrel" =>
 681                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, false), AtomicRwOp::AcqRel)?,
 682             #[rustfmt::skip]
 683             "atomic_and_relaxed" =>
 684                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, false), AtomicRwOp::Relaxed)?,
 685             #[rustfmt::skip]
 686             "atomic_nand" =>
 687                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, true), AtomicRwOp::SeqCst)?,
 688             #[rustfmt::skip]
 689             "atomic_nand_acq" =>
 690                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, true), AtomicRwOp::Acquire)?,
 691             #[rustfmt::skip]
 692             "atomic_nand_rel" =>
 693                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, true), AtomicRwOp::Release)?,
 694             #[rustfmt::skip]
 695             "atomic_nand_acqrel" =>
 696                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, true), AtomicRwOp::AcqRel)?,
 697             #[rustfmt::skip]
 698             "atomic_nand_relaxed" =>
 699                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, true), AtomicRwOp::Relaxed)?,
 700             #[rustfmt::skip]
 701             "atomic_xadd" =>
 702                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Add, false), AtomicRwOp::SeqCst)?,
 703             #[rustfmt::skip]
 704             "atomic_xadd_acq" =>
 705                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Add, false), AtomicRwOp::Acquire)?,
 706             #[rustfmt::skip]
 707             "atomic_xadd_rel" =>
 708                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Add, false), AtomicRwOp::Release)?,
 709             #[rustfmt::skip]
 710             "atomic_xadd_acqrel" =>
 711                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Add, false), AtomicRwOp::AcqRel)?,
 712             #[rustfmt::skip]
 713             "atomic_xadd_relaxed" =>
 714                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Add, false), AtomicRwOp::Relaxed)?,
 715             #[rustfmt::skip]
 716             "atomic_xsub" =>
 717                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Sub, false), AtomicRwOp::SeqCst)?,
 718             #[rustfmt::skip]
 719             "atomic_xsub_acq" =>
 720                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Sub, false), AtomicRwOp::Acquire)?,
 721             #[rustfmt::skip]
 722             "atomic_xsub_rel" =>
 723                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Sub, false), AtomicRwOp::Release)?,
 724             #[rustfmt::skip]
 725             "atomic_xsub_acqrel" =>
 726                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Sub, false), AtomicRwOp::AcqRel)?,
 727             #[rustfmt::skip]
 728             "atomic_xsub_relaxed" =>
 729                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Sub, false), AtomicRwOp::Relaxed)?,
 730             "atomic_min" => this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::SeqCst)?,
 731             "atomic_min_acq" => this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::Acquire)?,
 732             "atomic_min_rel" => this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::Release)?,
 733             "atomic_min_acqrel" => this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::AcqRel)?,
 734             "atomic_min_relaxed" =>
 735                 this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::Relaxed)?,
 736             "atomic_max" => this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::SeqCst)?,
 737             "atomic_max_acq" => this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::Acquire)?,
 738             "atomic_max_rel" => this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::Release)?,
 739             "atomic_max_acqrel" => this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::AcqRel)?,
 740             "atomic_max_relaxed" =>
 741                 this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::Relaxed)?,
 742             "atomic_umin" => this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::SeqCst)?,
 743             "atomic_umin_acq" => this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::Acquire)?,
 744             "atomic_umin_rel" => this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::Release)?,
 745             "atomic_umin_acqrel" =>
 746                 this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::AcqRel)?,
 747             "atomic_umin_relaxed" =>
 748                 this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::Relaxed)?,
 749             "atomic_umax" => this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::SeqCst)?,
 750             "atomic_umax_acq" => this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::Acquire)?,
 751             "atomic_umax_rel" => this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::Release)?,
 752             "atomic_umax_acqrel" =>
 753                 this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::AcqRel)?,
 754             "atomic_umax_relaxed" =>
 755                 this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::Relaxed)?,
 756
 757             // Other
 758             "exact_div" => {
 759                 let &[ref num, ref denom] = check_arg_count(args)?;
 760                 this.exact_div(&this.read_immediate(num)?, &this.read_immediate(denom)?, dest)?;
 761             }
 762
 763             "try" => return this.handle_try(args, dest, ret),
 764
 765             "breakpoint" => {
 766                 let &[] = check_arg_count(args)?;
 767                 // normally this would raise a SIGTRAP, which aborts if no debugger is connected
 768                 throw_machine_stop!(TerminationInfo::Abort("Trace/breakpoint trap".to_string()))
 769             }
 770
 771             name => throw_unsup_format!("unimplemented intrinsic: {}", name),
 772         }
 773
 774         trace!("{:?}", this.dump_place(**dest));
 775         this.go_to_block(ret);
 776         Ok(())
 777     }
 778
 779     fn atomic_load(
 780         &mut self,
 781         args: &[OpTy<'tcx, Tag>],
 782         dest: &PlaceTy<'tcx, Tag>,
 783         atomic: AtomicReadOp,
 784     ) -> InterpResult<'tcx> {
 785         let this = self.eval_context_mut();
 786
 787         let &[ref place] = check_arg_count(args)?;
 788         let place = this.deref_operand(place)?;
 789
 790         // make sure it fits into a scalar; otherwise it cannot be atomic
 791         let val = this.read_scalar_atomic(&place, atomic)?;
 792
 793         // Check alignment requirements. Atomics must always be aligned to their size,
 794         // even if the type they wrap would be less aligned (e.g. AtomicU64 on 32bit must
 795         // be 8-aligned).
 796         let align = Align::from_bytes(place.layout.size.bytes()).unwrap();
 797         this.memory.check_ptr_access_align(
 798             place.ptr,
 799             place.layout.size,
 800             align,
 801             CheckInAllocMsg::MemoryAccessTest,
 802         )?;
 803         // Perform regular access.
 804         this.write_scalar(val, dest)?;
 805         Ok(())
 806     }
 807
 808     fn atomic_store(
 809         &mut self,
 810         args: &[OpTy<'tcx, Tag>],
 811         atomic: AtomicWriteOp,
 812     ) -> InterpResult<'tcx> {
 813         let this = self.eval_context_mut();
 814
 815         let &[ref place, ref val] = check_arg_count(args)?;
 816         let place = this.deref_operand(place)?;
 817         let val = this.read_scalar(val)?; // make sure it fits into a scalar; otherwise it cannot be atomic
 818
 819         // Check alignment requirements. Atomics must always be aligned to their size,
 820         // even if the type they wrap would be less aligned (e.g. AtomicU64 on 32bit must
 821         // be 8-aligned).
 822         let align = Align::from_bytes(place.layout.size.bytes()).unwrap();
 823         this.memory.check_ptr_access_align(
 824             place.ptr,
 825             place.layout.size,
 826             align,
 827             CheckInAllocMsg::MemoryAccessTest,
 828         )?;
 829
 830         // Perform atomic store
 831         this.write_scalar_atomic(val, &place, atomic)?;
 832         Ok(())
 833     }
 834
 835     fn compiler_fence(
 836         &mut self,
 837         args: &[OpTy<'tcx, Tag>],
 838         atomic: AtomicFenceOp,
 839     ) -> InterpResult<'tcx> {
 840         let &[] = check_arg_count(args)?;
 841         let _ = atomic;
 842         //FIXME: compiler fences are currently ignored
 843         Ok(())
 844     }
 845
 846     fn atomic_fence(
 847         &mut self,
 848         args: &[OpTy<'tcx, Tag>],
 849         atomic: AtomicFenceOp,
 850     ) -> InterpResult<'tcx> {
 851         let this = self.eval_context_mut();
 852         let &[] = check_arg_count(args)?;
 853         this.validate_atomic_fence(atomic)?;
 854         Ok(())
 855     }
 856
 857     fn atomic_op(
 858         &mut self,
 859         args: &[OpTy<'tcx, Tag>],
 860         dest: &PlaceTy<'tcx, Tag>,
 861         atomic_op: AtomicOp,
 862         atomic: AtomicRwOp,
 863     ) -> InterpResult<'tcx> {
 864         let this = self.eval_context_mut();
 865
 866         let &[ref place, ref rhs] = check_arg_count(args)?;
 867         let place = this.deref_operand(place)?;
 868
 869         if !place.layout.ty.is_integral() {
 870             bug!("Atomic arithmetic operations only work on integer types");
 871         }
 872         let rhs = this.read_immediate(rhs)?;
 873
 874         // Check alignment requirements. Atomics must always be aligned to their size,
 875         // even if the type they wrap would be less aligned (e.g. AtomicU64 on 32bit must
 876         // be 8-aligned).
 877         let align = Align::from_bytes(place.layout.size.bytes()).unwrap();
 878         this.memory.check_ptr_access_align(
 879             place.ptr,
 880             place.layout.size,
 881             align,
 882             CheckInAllocMsg::MemoryAccessTest,
 883         )?;
 884
 885         match atomic_op {
 886             AtomicOp::Min => {
 887                 let old = this.atomic_min_max_scalar(&place, rhs, true, atomic)?;
 888                 this.write_immediate(*old, &dest)?; // old value is returned
 889                 Ok(())
 890             }
 891             AtomicOp::Max => {
 892                 let old = this.atomic_min_max_scalar(&place, rhs, false, atomic)?;
 893                 this.write_immediate(*old, &dest)?; // old value is returned
 894                 Ok(())
 895             }
 896             AtomicOp::MirOp(op, neg) => {
 897                 let old = this.atomic_op_immediate(&place, &rhs, op, neg, atomic)?;
 898                 this.write_immediate(*old, dest)?; // old value is returned
 899                 Ok(())
 900             }
 901         }
 902     }
 903
 904     fn atomic_exchange(
 905         &mut self,
 906         args: &[OpTy<'tcx, Tag>],
 907         dest: &PlaceTy<'tcx, Tag>,
 908         atomic: AtomicRwOp,
 909     ) -> InterpResult<'tcx> {
 910         let this = self.eval_context_mut();
 911
 912         let &[ref place, ref new] = check_arg_count(args)?;
 913         let place = this.deref_operand(place)?;
 914         let new = this.read_scalar(new)?;
 915
 916         // Check alignment requirements. Atomics must always be aligned to their size,
 917         // even if the type they wrap would be less aligned (e.g. AtomicU64 on 32bit must
 918         // be 8-aligned).
 919         let align = Align::from_bytes(place.layout.size.bytes()).unwrap();
 920         this.memory.check_ptr_access_align(
 921             place.ptr,
 922             place.layout.size,
 923             align,
 924             CheckInAllocMsg::MemoryAccessTest,
 925         )?;
 926
 927         let old = this.atomic_exchange_scalar(&place, new, atomic)?;
 928         this.write_scalar(old, dest)?; // old value is returned
 929         Ok(())
 930     }
 931
 932     fn atomic_compare_exchange_impl(
 933         &mut self,
 934         args: &[OpTy<'tcx, Tag>],
 935         dest: &PlaceTy<'tcx, Tag>,
 936         success: AtomicRwOp,
 937         fail: AtomicReadOp,
 938         can_fail_spuriously: bool,
 939     ) -> InterpResult<'tcx> {
 940         let this = self.eval_context_mut();
 941
 942         let &[ref place, ref expect_old, ref new] = check_arg_count(args)?;
 943         let place = this.deref_operand(place)?;
 944         let expect_old = this.read_immediate(expect_old)?; // read as immediate for the sake of `binary_op()`
 945         let new = this.read_scalar(new)?;
 946
 947         // Check alignment requirements. Atomics must always be aligned to their size,
 948         // even if the type they wrap would be less aligned (e.g. AtomicU64 on 32bit must
 949         // be 8-aligned).
 950         let align = Align::from_bytes(place.layout.size.bytes()).unwrap();
 951         this.memory.check_ptr_access_align(
 952             place.ptr,
 953             place.layout.size,
 954             align,
 955             CheckInAllocMsg::MemoryAccessTest,
 956         )?;
 957
 958         let old = this.atomic_compare_exchange_scalar(
 959             &place,
 960             &expect_old,
 961             new,
 962             success,
 963             fail,
 964             can_fail_spuriously,
 965         )?;
 966
 967         // Return old value.
 968         this.write_immediate(old, dest)?;
 969         Ok(())
 970     }
 971
 972     fn atomic_compare_exchange(
 973         &mut self,
 974         args: &[OpTy<'tcx, Tag>],
 975         dest: &PlaceTy<'tcx, Tag>,
 976         success: AtomicRwOp,
 977         fail: AtomicReadOp,
 978     ) -> InterpResult<'tcx> {
 979         self.atomic_compare_exchange_impl(args, dest, success, fail, false)
 980     }
 981
 982     fn atomic_compare_exchange_weak(
 983         &mut self,
 984         args: &[OpTy<'tcx, Tag>],
 985         dest: &PlaceTy<'tcx, Tag>,
 986         success: AtomicRwOp,
 987         fail: AtomicReadOp,
 988     ) -> InterpResult<'tcx> {
 989         self.atomic_compare_exchange_impl(args, dest, success, fail, true)
 990     }
 991
 992     fn float_to_int_unchecked<F>(
 993         &self,
 994         f: F,
 995         dest_ty: ty::Ty<'tcx>,
 996     ) -> InterpResult<'tcx, Scalar<Tag>>
 997     where
 998         F: Float + Into<Scalar<Tag>>,
 999     {
1000         let this = self.eval_context_ref();
1001
1002         // Step 1: cut off the fractional part of `f`. The result of this is
1003         // guaranteed to be precisely representable in IEEE floats.
1004         let f = f.round_to_integral(Round::TowardZero).value;
1005
1006         // Step 2: Cast the truncated float to the target integer type and see if we lose any information in this step.
1007         Ok(match dest_ty.kind() {
1008             // Unsigned
1009             ty::Uint(t) => {
1010                 let size = Integer::from_uint_ty(this, *t).size();
1011                 let res = f.to_u128(size.bits_usize());
1012                 if res.status.is_empty() {
1013                     // No status flags means there was no further rounding or other loss of precision.
1014                     Scalar::from_uint(res.value, size)
1015                 } else {
1016                     // `f` was not representable in this integer type.
1017                     throw_ub_format!(
1018                         "`float_to_int_unchecked` intrinsic called on {} which cannot be represented in target type `{:?}`",
1019                         f,
1020                         dest_ty,
1021                     );
1022                 }
1023             }
1024             // Signed
1025             ty::Int(t) => {
1026                 let size = Integer::from_int_ty(this, *t).size();
1027                 let res = f.to_i128(size.bits_usize());
1028                 if res.status.is_empty() {
1029                     // No status flags means there was no further rounding or other loss of precision.
1030                     Scalar::from_int(res.value, size)
1031                 } else {
1032                     // `f` was not representable in this integer type.
1033                     throw_ub_format!(
1034                         "`float_to_int_unchecked` intrinsic called on {} which cannot be represented in target type `{:?}`",
1035                         f,
1036                         dest_ty,
1037                     );
1038                 }
1039             }
1040             // Nothing else
1041             _ => bug!("`float_to_int_unchecked` called with non-int output type {:?}", dest_ty),
1042         })
1043     }
1044 }