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             | "simd_reduce_max"
 438             | "simd_reduce_min" => {
 439                 use mir::BinOp;
 440
 441                 let &[ref op] = check_arg_count(args)?;
 442                 let (op, op_len) = this.operand_to_simd(op)?;
 443
 444                 let imm_from_bool =
 445                     |b| ImmTy::from_scalar(Scalar::from_bool(b), this.machine.layouts.bool);
 446
 447                 enum Op {
 448                     MirOp(BinOp),
 449                     MirOpBool(BinOp),
 450                     Max,
 451                     Min,
 452                 }
 453                 let which = match intrinsic_name {
 454                     "simd_reduce_and" => Op::MirOp(BinOp::BitAnd),
 455                     "simd_reduce_or" => Op::MirOp(BinOp::BitOr),
 456                     "simd_reduce_xor" => Op::MirOp(BinOp::BitXor),
 457                     "simd_reduce_any" => Op::MirOpBool(BinOp::BitOr),
 458                     "simd_reduce_all" => Op::MirOpBool(BinOp::BitAnd),
 459                     "simd_reduce_max" => Op::Max,
 460                     "simd_reduce_min" => Op::Min,
 461                     _ => unreachable!(),
 462                 };
 463
 464                 // Initialize with first lane, then proceed with the rest.
 465                 let mut res = this.read_immediate(&this.mplace_index(&op, 0)?.into())?;
 466                 if matches!(which, Op::MirOpBool(_)) {
 467                     // Convert to `bool` scalar.
 468                     res = imm_from_bool(simd_element_to_bool(res)?);
 469                 }
 470                 for i in 1..op_len {
 471                     let op = this.read_immediate(&this.mplace_index(&op, i)?.into())?;
 472                     res = match which {
 473                         Op::MirOp(mir_op) => {
 474                             this.binary_op(mir_op, &res, &op)?
 475                         }
 476                         Op::MirOpBool(mir_op) => {
 477                             let op = imm_from_bool(simd_element_to_bool(op)?);
 478                             this.binary_op(mir_op, &res, &op)?
 479                         }
 480                         Op::Max => {
 481                             // if `op > res`...
 482                             if this.binary_op(BinOp::Gt, &op, &res)?.to_scalar()?.to_bool()? {
 483                                 // update accumulator
 484                                 op
 485                             } else {
 486                                 // no change
 487                                 res
 488                             }
 489                         }
 490                         Op::Min => {
 491                             // if `op < res`...
 492                             if this.binary_op(BinOp::Lt, &op, &res)?.to_scalar()?.to_bool()? {
 493                                 // update accumulator
 494                                 op
 495                             } else {
 496                                 // no change
 497                                 res
 498                             }
 499                         }
 500                     };
 501                 }
 502                 this.write_immediate(*res, dest)?;
 503             }
 504             #[rustfmt::skip]
 505             | "simd_reduce_add_ordered"
 506             | "simd_reduce_mul_ordered" => {
 507                 use mir::BinOp;
 508
 509                 let &[ref op, ref init] = check_arg_count(args)?;
 510                 let (op, op_len) = this.operand_to_simd(op)?;
 511                 let init = this.read_immediate(init)?;
 512
 513                 let mir_op = match intrinsic_name {
 514                     "simd_reduce_add_ordered" => BinOp::Add,
 515                     "simd_reduce_mul_ordered" => BinOp::Mul,
 516                     _ => unreachable!(),
 517                 };
 518
 519                 let mut res = init;
 520                 for i in 0..op_len {
 521                     let op = this.read_immediate(&this.mplace_index(&op, i)?.into())?;
 522                     res = this.binary_op(mir_op, &res, &op)?;
 523                 }
 524                 this.write_immediate(*res, dest)?;
 525             }
 526             "simd_select" => {
 527                 let &[ref mask, ref yes, ref no] = check_arg_count(args)?;
 528                 let (mask, mask_len) = this.operand_to_simd(mask)?;
 529                 let (yes, yes_len) = this.operand_to_simd(yes)?;
 530                 let (no, no_len) = this.operand_to_simd(no)?;
 531                 let (dest, dest_len) = this.place_to_simd(dest)?;
 532
 533                 assert_eq!(dest_len, mask_len);
 534                 assert_eq!(dest_len, yes_len);
 535                 assert_eq!(dest_len, no_len);
 536
 537                 for i in 0..dest_len {
 538                     let mask = this.read_immediate(&this.mplace_index(&mask, i)?.into())?;
 539                     let yes = this.read_immediate(&this.mplace_index(&yes, i)?.into())?;
 540                     let no = this.read_immediate(&this.mplace_index(&no, i)?.into())?;
 541                     let dest = this.mplace_index(&dest, i)?;
 542
 543                     let mask = simd_element_to_bool(mask)?;
 544                     let val = if mask { yes } else { no };
 545                     this.write_immediate(*val, &dest.into())?;
 546                 }
 547             }
 548             #[rustfmt::skip]
 549             "simd_cast" | "simd_as" => {
 550                 let &[ref op] = check_arg_count(args)?;
 551                 let (op, op_len) = this.operand_to_simd(op)?;
 552                 let (dest, dest_len) = this.place_to_simd(dest)?;
 553
 554                 assert_eq!(dest_len, op_len);
 555
 556                 let safe_cast = intrinsic_name == "simd_as";
 557
 558                 for i in 0..dest_len {
 559                     let op = this.read_immediate(&this.mplace_index(&op, i)?.into())?;
 560                     let dest = this.mplace_index(&dest, i)?;
 561
 562                     let val = match (op.layout.ty.kind(), dest.layout.ty.kind()) {
 563                         // Int-to-(int|float): always safe
 564                         (ty::Int(_) | ty::Uint(_), ty::Int(_) | ty::Uint(_) | ty::Float(_)) =>
 565                             this.misc_cast(&op, dest.layout.ty)?,
 566                         // Float-to-float: always safe
 567                         (ty::Float(_), ty::Float(_)) =>
 568                             this.misc_cast(&op, dest.layout.ty)?,
 569                         // Float-to-int in safe mode
 570                         (ty::Float(_), ty::Int(_) | ty::Uint(_)) if safe_cast =>
 571                             this.misc_cast(&op, dest.layout.ty)?,
 572                         // Float-to-int in unchecked mode
 573                         (ty::Float(FloatTy::F32), ty::Int(_) | ty::Uint(_)) if !safe_cast =>
 574                             this.float_to_int_unchecked(op.to_scalar()?.to_f32()?, dest.layout.ty)?.into(),
 575                         (ty::Float(FloatTy::F64), ty::Int(_) | ty::Uint(_)) if !safe_cast =>
 576                             this.float_to_int_unchecked(op.to_scalar()?.to_f64()?, dest.layout.ty)?.into(),
 577                         _ =>
 578                             throw_unsup_format!(
 579                                 "Unsupported SIMD cast from element type {} to {}",
 580                                 op.layout.ty,
 581                                 dest.layout.ty
 582                             ),
 583                     };
 584                     this.write_immediate(val, &dest.into())?;
 585                 }
 586             }
 587
 588             // Atomic operations
 589             "atomic_load" => this.atomic_load(args, dest, AtomicReadOp::SeqCst)?,
 590             "atomic_load_relaxed" => this.atomic_load(args, dest, AtomicReadOp::Relaxed)?,
 591             "atomic_load_acq" => this.atomic_load(args, dest, AtomicReadOp::Acquire)?,
 592
 593             "atomic_store" => this.atomic_store(args, AtomicWriteOp::SeqCst)?,
 594             "atomic_store_relaxed" => this.atomic_store(args, AtomicWriteOp::Relaxed)?,
 595             "atomic_store_rel" => this.atomic_store(args, AtomicWriteOp::Release)?,
 596
 597             "atomic_fence_acq" => this.atomic_fence(args, AtomicFenceOp::Acquire)?,
 598             "atomic_fence_rel" => this.atomic_fence(args, AtomicFenceOp::Release)?,
 599             "atomic_fence_acqrel" => this.atomic_fence(args, AtomicFenceOp::AcqRel)?,
 600             "atomic_fence" => this.atomic_fence(args, AtomicFenceOp::SeqCst)?,
 601
 602             "atomic_singlethreadfence_acq" => this.compiler_fence(args, AtomicFenceOp::Acquire)?,
 603             "atomic_singlethreadfence_rel" => this.compiler_fence(args, AtomicFenceOp::Release)?,
 604             "atomic_singlethreadfence_acqrel" =>
 605                 this.compiler_fence(args, AtomicFenceOp::AcqRel)?,
 606             "atomic_singlethreadfence" => this.compiler_fence(args, AtomicFenceOp::SeqCst)?,
 607
 608             "atomic_xchg" => this.atomic_exchange(args, dest, AtomicRwOp::SeqCst)?,
 609             "atomic_xchg_acq" => this.atomic_exchange(args, dest, AtomicRwOp::Acquire)?,
 610             "atomic_xchg_rel" => this.atomic_exchange(args, dest, AtomicRwOp::Release)?,
 611             "atomic_xchg_acqrel" => this.atomic_exchange(args, dest, AtomicRwOp::AcqRel)?,
 612             "atomic_xchg_relaxed" => this.atomic_exchange(args, dest, AtomicRwOp::Relaxed)?,
 613
 614             #[rustfmt::skip]
 615             "atomic_cxchg" =>
 616                 this.atomic_compare_exchange(args, dest, AtomicRwOp::SeqCst, AtomicReadOp::SeqCst)?,
 617             #[rustfmt::skip]
 618             "atomic_cxchg_acq" =>
 619                 this.atomic_compare_exchange(args, dest, AtomicRwOp::Acquire, AtomicReadOp::Acquire)?,
 620             #[rustfmt::skip]
 621             "atomic_cxchg_rel" =>
 622                 this.atomic_compare_exchange(args, dest, AtomicRwOp::Release, AtomicReadOp::Relaxed)?,
 623             #[rustfmt::skip]
 624             "atomic_cxchg_acqrel" =>
 625                 this.atomic_compare_exchange(args, dest, AtomicRwOp::AcqRel, AtomicReadOp::Acquire)?,
 626             #[rustfmt::skip]
 627             "atomic_cxchg_relaxed" =>
 628                 this.atomic_compare_exchange(args, dest, AtomicRwOp::Relaxed, AtomicReadOp::Relaxed)?,
 629             #[rustfmt::skip]
 630             "atomic_cxchg_acq_failrelaxed" =>
 631                 this.atomic_compare_exchange(args, dest, AtomicRwOp::Acquire, AtomicReadOp::Relaxed)?,
 632             #[rustfmt::skip]
 633             "atomic_cxchg_acqrel_failrelaxed" =>
 634                 this.atomic_compare_exchange(args, dest, AtomicRwOp::AcqRel, AtomicReadOp::Relaxed)?,
 635             #[rustfmt::skip]
 636             "atomic_cxchg_failrelaxed" =>
 637                 this.atomic_compare_exchange(args, dest, AtomicRwOp::SeqCst, AtomicReadOp::Relaxed)?,
 638             #[rustfmt::skip]
 639             "atomic_cxchg_failacq" =>
 640                 this.atomic_compare_exchange(args, dest, AtomicRwOp::SeqCst, AtomicReadOp::Acquire)?,
 641
 642             #[rustfmt::skip]
 643             "atomic_cxchgweak" =>
 644                 this.atomic_compare_exchange_weak(args, dest, AtomicRwOp::SeqCst, AtomicReadOp::SeqCst)?,
 645             #[rustfmt::skip]
 646             "atomic_cxchgweak_acq" =>
 647                 this.atomic_compare_exchange_weak(args, dest, AtomicRwOp::Acquire, AtomicReadOp::Acquire)?,
 648             #[rustfmt::skip]
 649             "atomic_cxchgweak_rel" =>
 650                 this.atomic_compare_exchange_weak(args, dest, AtomicRwOp::Release, AtomicReadOp::Relaxed)?,
 651             #[rustfmt::skip]
 652             "atomic_cxchgweak_acqrel" =>
 653                 this.atomic_compare_exchange_weak(args, dest, AtomicRwOp::AcqRel, AtomicReadOp::Acquire)?,
 654             #[rustfmt::skip]
 655             "atomic_cxchgweak_relaxed" =>
 656                 this.atomic_compare_exchange_weak(args, dest, AtomicRwOp::Relaxed, AtomicReadOp::Relaxed)?,
 657             #[rustfmt::skip]
 658             "atomic_cxchgweak_acq_failrelaxed" =>
 659                 this.atomic_compare_exchange_weak(args, dest, AtomicRwOp::Acquire, AtomicReadOp::Relaxed)?,
 660             #[rustfmt::skip]
 661             "atomic_cxchgweak_acqrel_failrelaxed" =>
 662                 this.atomic_compare_exchange_weak(args, dest, AtomicRwOp::AcqRel, AtomicReadOp::Relaxed)?,
 663             #[rustfmt::skip]
 664             "atomic_cxchgweak_failrelaxed" =>
 665                 this.atomic_compare_exchange_weak(args, dest, AtomicRwOp::SeqCst, AtomicReadOp::Relaxed)?,
 666             #[rustfmt::skip]
 667             "atomic_cxchgweak_failacq" =>
 668                 this.atomic_compare_exchange_weak(args, dest, AtomicRwOp::SeqCst, AtomicReadOp::Acquire)?,
 669
 670             #[rustfmt::skip]
 671             "atomic_or" =>
 672                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitOr, false), AtomicRwOp::SeqCst)?,
 673             #[rustfmt::skip]
 674             "atomic_or_acq" =>
 675                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitOr, false), AtomicRwOp::Acquire)?,
 676             #[rustfmt::skip]
 677             "atomic_or_rel" =>
 678                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitOr, false), AtomicRwOp::Release)?,
 679             #[rustfmt::skip]
 680             "atomic_or_acqrel" =>
 681                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitOr, false), AtomicRwOp::AcqRel)?,
 682             #[rustfmt::skip]
 683             "atomic_or_relaxed" =>
 684                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitOr, false), AtomicRwOp::Relaxed)?,
 685             #[rustfmt::skip]
 686             "atomic_xor" =>
 687                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitXor, false), AtomicRwOp::SeqCst)?,
 688             #[rustfmt::skip]
 689             "atomic_xor_acq" =>
 690                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitXor, false), AtomicRwOp::Acquire)?,
 691             #[rustfmt::skip]
 692             "atomic_xor_rel" =>
 693                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitXor, false), AtomicRwOp::Release)?,
 694             #[rustfmt::skip]
 695             "atomic_xor_acqrel" =>
 696                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitXor, false), AtomicRwOp::AcqRel)?,
 697             #[rustfmt::skip]
 698             "atomic_xor_relaxed" =>
 699                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitXor, false), AtomicRwOp::Relaxed)?,
 700             #[rustfmt::skip]
 701             "atomic_and" =>
 702                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, false), AtomicRwOp::SeqCst)?,
 703             #[rustfmt::skip]
 704             "atomic_and_acq" =>
 705                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, false), AtomicRwOp::Acquire)?,
 706             #[rustfmt::skip]
 707             "atomic_and_rel" =>
 708                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, false), AtomicRwOp::Release)?,
 709             #[rustfmt::skip]
 710             "atomic_and_acqrel" =>
 711                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, false), AtomicRwOp::AcqRel)?,
 712             #[rustfmt::skip]
 713             "atomic_and_relaxed" =>
 714                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, false), AtomicRwOp::Relaxed)?,
 715             #[rustfmt::skip]
 716             "atomic_nand" =>
 717                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, true), AtomicRwOp::SeqCst)?,
 718             #[rustfmt::skip]
 719             "atomic_nand_acq" =>
 720                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, true), AtomicRwOp::Acquire)?,
 721             #[rustfmt::skip]
 722             "atomic_nand_rel" =>
 723                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, true), AtomicRwOp::Release)?,
 724             #[rustfmt::skip]
 725             "atomic_nand_acqrel" =>
 726                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, true), AtomicRwOp::AcqRel)?,
 727             #[rustfmt::skip]
 728             "atomic_nand_relaxed" =>
 729                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::BitAnd, true), AtomicRwOp::Relaxed)?,
 730             #[rustfmt::skip]
 731             "atomic_xadd" =>
 732                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Add, false), AtomicRwOp::SeqCst)?,
 733             #[rustfmt::skip]
 734             "atomic_xadd_acq" =>
 735                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Add, false), AtomicRwOp::Acquire)?,
 736             #[rustfmt::skip]
 737             "atomic_xadd_rel" =>
 738                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Add, false), AtomicRwOp::Release)?,
 739             #[rustfmt::skip]
 740             "atomic_xadd_acqrel" =>
 741                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Add, false), AtomicRwOp::AcqRel)?,
 742             #[rustfmt::skip]
 743             "atomic_xadd_relaxed" =>
 744                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Add, false), AtomicRwOp::Relaxed)?,
 745             #[rustfmt::skip]
 746             "atomic_xsub" =>
 747                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Sub, false), AtomicRwOp::SeqCst)?,
 748             #[rustfmt::skip]
 749             "atomic_xsub_acq" =>
 750                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Sub, false), AtomicRwOp::Acquire)?,
 751             #[rustfmt::skip]
 752             "atomic_xsub_rel" =>
 753                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Sub, false), AtomicRwOp::Release)?,
 754             #[rustfmt::skip]
 755             "atomic_xsub_acqrel" =>
 756                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Sub, false), AtomicRwOp::AcqRel)?,
 757             #[rustfmt::skip]
 758             "atomic_xsub_relaxed" =>
 759                 this.atomic_op(args, dest, AtomicOp::MirOp(BinOp::Sub, false), AtomicRwOp::Relaxed)?,
 760             "atomic_min" => this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::SeqCst)?,
 761             "atomic_min_acq" => this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::Acquire)?,
 762             "atomic_min_rel" => this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::Release)?,
 763             "atomic_min_acqrel" => this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::AcqRel)?,
 764             "atomic_min_relaxed" =>
 765                 this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::Relaxed)?,
 766             "atomic_max" => this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::SeqCst)?,
 767             "atomic_max_acq" => this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::Acquire)?,
 768             "atomic_max_rel" => this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::Release)?,
 769             "atomic_max_acqrel" => this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::AcqRel)?,
 770             "atomic_max_relaxed" =>
 771                 this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::Relaxed)?,
 772             "atomic_umin" => this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::SeqCst)?,
 773             "atomic_umin_acq" => this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::Acquire)?,
 774             "atomic_umin_rel" => this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::Release)?,
 775             "atomic_umin_acqrel" =>
 776                 this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::AcqRel)?,
 777             "atomic_umin_relaxed" =>
 778                 this.atomic_op(args, dest, AtomicOp::Min, AtomicRwOp::Relaxed)?,
 779             "atomic_umax" => this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::SeqCst)?,
 780             "atomic_umax_acq" => this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::Acquire)?,
 781             "atomic_umax_rel" => this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::Release)?,
 782             "atomic_umax_acqrel" =>
 783                 this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::AcqRel)?,
 784             "atomic_umax_relaxed" =>
 785                 this.atomic_op(args, dest, AtomicOp::Max, AtomicRwOp::Relaxed)?,
 786
 787             // Other
 788             "exact_div" => {
 789                 let &[ref num, ref denom] = check_arg_count(args)?;
 790                 this.exact_div(&this.read_immediate(num)?, &this.read_immediate(denom)?, dest)?;
 791             }
 792
 793             "try" => return this.handle_try(args, dest, ret),
 794
 795             "breakpoint" => {
 796                 let &[] = check_arg_count(args)?;
 797                 // normally this would raise a SIGTRAP, which aborts if no debugger is connected
 798                 throw_machine_stop!(TerminationInfo::Abort("Trace/breakpoint trap".to_string()))
 799             }
 800
 801             name => throw_unsup_format!("unimplemented intrinsic: {}", name),
 802         }
 803
 804         trace!("{:?}", this.dump_place(**dest));
 805         this.go_to_block(ret);
 806         Ok(())
 807     }
 808
 809     fn atomic_load(
 810         &mut self,
 811         args: &[OpTy<'tcx, Tag>],
 812         dest: &PlaceTy<'tcx, Tag>,
 813         atomic: AtomicReadOp,
 814     ) -> InterpResult<'tcx> {
 815         let this = self.eval_context_mut();
 816
 817         let &[ref place] = check_arg_count(args)?;
 818         let place = this.deref_operand(place)?;
 819
 820         // make sure it fits into a scalar; otherwise it cannot be atomic
 821         let val = this.read_scalar_atomic(&place, atomic)?;
 822
 823         // Check alignment requirements. Atomics must always be aligned to their size,
 824         // even if the type they wrap would be less aligned (e.g. AtomicU64 on 32bit must
 825         // be 8-aligned).
 826         let align = Align::from_bytes(place.layout.size.bytes()).unwrap();
 827         this.memory.check_ptr_access_align(
 828             place.ptr,
 829             place.layout.size,
 830             align,
 831             CheckInAllocMsg::MemoryAccessTest,
 832         )?;
 833         // Perform regular access.
 834         this.write_scalar(val, dest)?;
 835         Ok(())
 836     }
 837
 838     fn atomic_store(
 839         &mut self,
 840         args: &[OpTy<'tcx, Tag>],
 841         atomic: AtomicWriteOp,
 842     ) -> InterpResult<'tcx> {
 843         let this = self.eval_context_mut();
 844
 845         let &[ref place, ref val] = check_arg_count(args)?;
 846         let place = this.deref_operand(place)?;
 847         let val = this.read_scalar(val)?; // make sure it fits into a scalar; otherwise it cannot be atomic
 848
 849         // Check alignment requirements. Atomics must always be aligned to their size,
 850         // even if the type they wrap would be less aligned (e.g. AtomicU64 on 32bit must
 851         // be 8-aligned).
 852         let align = Align::from_bytes(place.layout.size.bytes()).unwrap();
 853         this.memory.check_ptr_access_align(
 854             place.ptr,
 855             place.layout.size,
 856             align,
 857             CheckInAllocMsg::MemoryAccessTest,
 858         )?;
 859
 860         // Perform atomic store
 861         this.write_scalar_atomic(val, &place, atomic)?;
 862         Ok(())
 863     }
 864
 865     fn compiler_fence(
 866         &mut self,
 867         args: &[OpTy<'tcx, Tag>],
 868         atomic: AtomicFenceOp,
 869     ) -> InterpResult<'tcx> {
 870         let &[] = check_arg_count(args)?;
 871         let _ = atomic;
 872         //FIXME: compiler fences are currently ignored
 873         Ok(())
 874     }
 875
 876     fn atomic_fence(
 877         &mut self,
 878         args: &[OpTy<'tcx, Tag>],
 879         atomic: AtomicFenceOp,
 880     ) -> InterpResult<'tcx> {
 881         let this = self.eval_context_mut();
 882         let &[] = check_arg_count(args)?;
 883         this.validate_atomic_fence(atomic)?;
 884         Ok(())
 885     }
 886
 887     fn atomic_op(
 888         &mut self,
 889         args: &[OpTy<'tcx, Tag>],
 890         dest: &PlaceTy<'tcx, Tag>,
 891         atomic_op: AtomicOp,
 892         atomic: AtomicRwOp,
 893     ) -> InterpResult<'tcx> {
 894         let this = self.eval_context_mut();
 895
 896         let &[ref place, ref rhs] = check_arg_count(args)?;
 897         let place = this.deref_operand(place)?;
 898
 899         if !place.layout.ty.is_integral() {
 900             bug!("Atomic arithmetic operations only work on integer types");
 901         }
 902         let rhs = this.read_immediate(rhs)?;
 903
 904         // Check alignment requirements. Atomics must always be aligned to their size,
 905         // even if the type they wrap would be less aligned (e.g. AtomicU64 on 32bit must
 906         // be 8-aligned).
 907         let align = Align::from_bytes(place.layout.size.bytes()).unwrap();
 908         this.memory.check_ptr_access_align(
 909             place.ptr,
 910             place.layout.size,
 911             align,
 912             CheckInAllocMsg::MemoryAccessTest,
 913         )?;
 914
 915         match atomic_op {
 916             AtomicOp::Min => {
 917                 let old = this.atomic_min_max_scalar(&place, rhs, true, atomic)?;
 918                 this.write_immediate(*old, &dest)?; // old value is returned
 919                 Ok(())
 920             }
 921             AtomicOp::Max => {
 922                 let old = this.atomic_min_max_scalar(&place, rhs, false, atomic)?;
 923                 this.write_immediate(*old, &dest)?; // old value is returned
 924                 Ok(())
 925             }
 926             AtomicOp::MirOp(op, neg) => {
 927                 let old = this.atomic_op_immediate(&place, &rhs, op, neg, atomic)?;
 928                 this.write_immediate(*old, dest)?; // old value is returned
 929                 Ok(())
 930             }
 931         }
 932     }
 933
 934     fn atomic_exchange(
 935         &mut self,
 936         args: &[OpTy<'tcx, Tag>],
 937         dest: &PlaceTy<'tcx, Tag>,
 938         atomic: AtomicRwOp,
 939     ) -> InterpResult<'tcx> {
 940         let this = self.eval_context_mut();
 941
 942         let &[ref place, ref new] = check_arg_count(args)?;
 943         let place = this.deref_operand(place)?;
 944         let new = this.read_scalar(new)?;
 945
 946         // Check alignment requirements. Atomics must always be aligned to their size,
 947         // even if the type they wrap would be less aligned (e.g. AtomicU64 on 32bit must
 948         // be 8-aligned).
 949         let align = Align::from_bytes(place.layout.size.bytes()).unwrap();
 950         this.memory.check_ptr_access_align(
 951             place.ptr,
 952             place.layout.size,
 953             align,
 954             CheckInAllocMsg::MemoryAccessTest,
 955         )?;
 956
 957         let old = this.atomic_exchange_scalar(&place, new, atomic)?;
 958         this.write_scalar(old, dest)?; // old value is returned
 959         Ok(())
 960     }
 961
 962     fn atomic_compare_exchange_impl(
 963         &mut self,
 964         args: &[OpTy<'tcx, Tag>],
 965         dest: &PlaceTy<'tcx, Tag>,
 966         success: AtomicRwOp,
 967         fail: AtomicReadOp,
 968         can_fail_spuriously: bool,
 969     ) -> InterpResult<'tcx> {
 970         let this = self.eval_context_mut();
 971
 972         let &[ref place, ref expect_old, ref new] = check_arg_count(args)?;
 973         let place = this.deref_operand(place)?;
 974         let expect_old = this.read_immediate(expect_old)?; // read as immediate for the sake of `binary_op()`
 975         let new = this.read_scalar(new)?;
 976
 977         // Check alignment requirements. Atomics must always be aligned to their size,
 978         // even if the type they wrap would be less aligned (e.g. AtomicU64 on 32bit must
 979         // be 8-aligned).
 980         let align = Align::from_bytes(place.layout.size.bytes()).unwrap();
 981         this.memory.check_ptr_access_align(
 982             place.ptr,
 983             place.layout.size,
 984             align,
 985             CheckInAllocMsg::MemoryAccessTest,
 986         )?;
 987
 988         let old = this.atomic_compare_exchange_scalar(
 989             &place,
 990             &expect_old,
 991             new,
 992             success,
 993             fail,
 994             can_fail_spuriously,
 995         )?;
 996
 997         // Return old value.
 998         this.write_immediate(old, dest)?;
 999         Ok(())
1000     }
1001
1002     fn atomic_compare_exchange(
1003         &mut self,
1004         args: &[OpTy<'tcx, Tag>],
1005         dest: &PlaceTy<'tcx, Tag>,
1006         success: AtomicRwOp,
1007         fail: AtomicReadOp,
1008     ) -> InterpResult<'tcx> {
1009         self.atomic_compare_exchange_impl(args, dest, success, fail, false)
1010     }
1011
1012     fn atomic_compare_exchange_weak(
1013         &mut self,
1014         args: &[OpTy<'tcx, Tag>],
1015         dest: &PlaceTy<'tcx, Tag>,
1016         success: AtomicRwOp,
1017         fail: AtomicReadOp,
1018     ) -> InterpResult<'tcx> {
1019         self.atomic_compare_exchange_impl(args, dest, success, fail, true)
1020     }
1021
1022     fn float_to_int_unchecked<F>(
1023         &self,
1024         f: F,
1025         dest_ty: ty::Ty<'tcx>,
1026     ) -> InterpResult<'tcx, Scalar<Tag>>
1027     where
1028         F: Float + Into<Scalar<Tag>>,
1029     {
1030         let this = self.eval_context_ref();
1031
1032         // Step 1: cut off the fractional part of `f`. The result of this is
1033         // guaranteed to be precisely representable in IEEE floats.
1034         let f = f.round_to_integral(Round::TowardZero).value;
1035
1036         // Step 2: Cast the truncated float to the target integer type and see if we lose any information in this step.
1037         Ok(match dest_ty.kind() {
1038             // Unsigned
1039             ty::Uint(t) => {
1040                 let size = Integer::from_uint_ty(this, *t).size();
1041                 let res = f.to_u128(size.bits_usize());
1042                 if res.status.is_empty() {
1043                     // No status flags means there was no further rounding or other loss of precision.
1044                     Scalar::from_uint(res.value, size)
1045                 } else {
1046                     // `f` was not representable in this integer type.
1047                     throw_ub_format!(
1048                         "`float_to_int_unchecked` intrinsic called on {} which cannot be represented in target type `{:?}`",
1049                         f,
1050                         dest_ty,
1051                     );
1052                 }
1053             }
1054             // Signed
1055             ty::Int(t) => {
1056                 let size = Integer::from_int_ty(this, *t).size();
1057                 let res = f.to_i128(size.bits_usize());
1058                 if res.status.is_empty() {
1059                     // No status flags means there was no further rounding or other loss of precision.
1060                     Scalar::from_int(res.value, size)
1061                 } else {
1062                     // `f` was not representable in this integer type.
1063                     throw_ub_format!(
1064                         "`float_to_int_unchecked` intrinsic called on {} which cannot be represented in target type `{:?}`",
1065                         f,
1066                         dest_ty,
1067                     );
1068                 }
1069             }
1070             // Nothing else
1071             _ => bug!("`float_to_int_unchecked` called with non-int output type {:?}", dest_ty),
1072         })
1073     }
1074 }