src/intrinsic.rs

   1 use rustc::mir;
   2 use rustc::ty::layout::{self, LayoutOf, Size};
   3 use rustc::ty;
   4
   5 use rustc::mir::interpret::{EvalResult, PointerArithmetic};
   6
   7 use super::{
   8     PlaceTy, OpTy, Value, Scalar, ScalarMaybeUndef, Borrow,
   9     FalibleScalarExt, OperatorEvalContextExt
  10 };
  11
  12 pub trait EvalContextExt<'tcx> {
  13     fn call_intrinsic(
  14         &mut self,
  15         instance: ty::Instance<'tcx>,
  16         args: &[OpTy<'tcx, Borrow>],
  17         dest: PlaceTy<'tcx, Borrow>,
  18     ) -> EvalResult<'tcx>;
  19 }
  20
  21 impl<'a, 'mir, 'tcx> EvalContextExt<'tcx> for super::MiriEvalContext<'a, 'mir, 'tcx> {
  22     fn call_intrinsic(
  23         &mut self,
  24         instance: ty::Instance<'tcx>,
  25         args: &[OpTy<'tcx, Borrow>],
  26         dest: PlaceTy<'tcx, Borrow>,
  27     ) -> EvalResult<'tcx> {
  28         if self.emulate_intrinsic(instance, args, dest)? {
  29             return Ok(());
  30         }
  31
  32         let substs = instance.substs;
  33
  34         let intrinsic_name = &self.tcx.item_name(instance.def_id()).as_str()[..];
  35         match intrinsic_name {
  36             "arith_offset" => {
  37                 let offset = self.read_scalar(args[1])?.to_isize(&self)?;
  38                 let ptr = self.read_scalar(args[0])?.not_undef()?;
  39
  40                 let pointee_ty = substs.type_at(0);
  41                 let pointee_size = self.layout_of(pointee_ty)?.size.bytes() as i64;
  42                 let offset = offset.overflowing_mul(pointee_size).0;
  43                 let result_ptr = ptr.ptr_wrapping_signed_offset(offset, &self);
  44                 self.write_scalar(result_ptr, dest)?;
  45             }
  46
  47             "assume" => {
  48                 let cond = self.read_scalar(args[0])?.to_bool()?;
  49                 if !cond {
  50                     return err!(AssumptionNotHeld);
  51                 }
  52             }
  53
  54             "atomic_load" |
  55             "atomic_load_relaxed" |
  56             "atomic_load_acq" |
  57             "volatile_load" => {
  58                 let ptr = self.ref_to_mplace(self.read_value(args[0])?)?;
  59                 let val = self.read_scalar(ptr.into())?; // make sure it fits into a scalar; otherwise it cannot be atomic
  60                 self.write_scalar(val, dest)?;
  61             }
  62
  63             "atomic_store" |
  64             "atomic_store_relaxed" |
  65             "atomic_store_rel" |
  66             "volatile_store" => {
  67                 let ptr = self.ref_to_mplace(self.read_value(args[0])?)?;
  68                 let val = self.read_scalar(args[1])?; // make sure it fits into a scalar; otherwise it cannot be atomic
  69                 self.write_scalar(val, ptr.into())?;
  70             }
  71
  72             "atomic_fence_acq" => {
  73                 // we are inherently singlethreaded and singlecored, this is a nop
  74             }
  75
  76             _ if intrinsic_name.starts_with("atomic_xchg") => {
  77                 let ptr = self.ref_to_mplace(self.read_value(args[0])?)?;
  78                 let new = self.read_scalar(args[1])?;
  79                 let old = self.read_scalar(ptr.into())?;
  80                 self.write_scalar(old, dest)?; // old value is returned
  81                 self.write_scalar(new, ptr.into())?;
  82             }
  83
  84             _ if intrinsic_name.starts_with("atomic_cxchg") => {
  85                 let ptr = self.ref_to_mplace(self.read_value(args[0])?)?;
  86                 let expect_old = self.read_value(args[1])?; // read as value for the sake of `binary_op_val()`
  87                 let new = self.read_scalar(args[2])?;
  88                 let old = self.read_value(ptr.into())?; // read as value for the sake of `binary_op_val()`
  89                 // binary_op_val will bail if either of them is not a scalar
  90                 let (eq, _) = self.binary_op_val(mir::BinOp::Eq, old, expect_old)?;
  91                 let res = Value::ScalarPair(old.to_scalar_or_undef(), eq.into());
  92                 self.write_value(res, dest)?; // old value is returned
  93                 // update ptr depending on comparison
  94                 if eq.to_bool()? {
  95                     self.write_scalar(new, ptr.into())?;
  96                 }
  97             }
  98
  99             "atomic_or" |
 100             "atomic_or_acq" |
 101             "atomic_or_rel" |
 102             "atomic_or_acqrel" |
 103             "atomic_or_relaxed" |
 104             "atomic_xor" |
 105             "atomic_xor_acq" |
 106             "atomic_xor_rel" |
 107             "atomic_xor_acqrel" |
 108             "atomic_xor_relaxed" |
 109             "atomic_and" |
 110             "atomic_and_acq" |
 111             "atomic_and_rel" |
 112             "atomic_and_acqrel" |
 113             "atomic_and_relaxed" |
 114             "atomic_xadd" |
 115             "atomic_xadd_acq" |
 116             "atomic_xadd_rel" |
 117             "atomic_xadd_acqrel" |
 118             "atomic_xadd_relaxed" |
 119             "atomic_xsub" |
 120             "atomic_xsub_acq" |
 121             "atomic_xsub_rel" |
 122             "atomic_xsub_acqrel" |
 123             "atomic_xsub_relaxed" => {
 124                 let ptr = self.ref_to_mplace(self.read_value(args[0])?)?;
 125                 let rhs = self.read_value(args[1])?;
 126                 let old = self.read_value(ptr.into())?;
 127                 self.write_value(*old, dest)?; // old value is returned
 128                 let op = match intrinsic_name.split('_').nth(1).unwrap() {
 129                     "or" => mir::BinOp::BitOr,
 130                     "xor" => mir::BinOp::BitXor,
 131                     "and" => mir::BinOp::BitAnd,
 132                     "xadd" => mir::BinOp::Add,
 133                     "xsub" => mir::BinOp::Sub,
 134                     _ => bug!(),
 135                 };
 136                 // Atomics wrap around on overflow.
 137                 self.binop_ignore_overflow(op, old, rhs, ptr.into())?;
 138             }
 139
 140             "breakpoint" => unimplemented!(), // halt miri
 141
 142             "copy" |
 143             "copy_nonoverlapping" => {
 144                 let elem_ty = substs.type_at(0);
 145                 let elem_layout = self.layout_of(elem_ty)?;
 146                 let elem_size = elem_layout.size.bytes();
 147                 let count = self.read_scalar(args[2])?.to_usize(&self)?;
 148                 let elem_align = elem_layout.align;
 149                 let src = self.read_scalar(args[0])?.not_undef()?;
 150                 let dest = self.read_scalar(args[1])?.not_undef()?;
 151                 self.memory.copy(
 152                     src,
 153                     elem_align,
 154                     dest,
 155                     elem_align,
 156                     Size::from_bytes(count * elem_size),
 157                     intrinsic_name.ends_with("_nonoverlapping"),
 158                 )?;
 159             }
 160
 161             "discriminant_value" => {
 162                 let place = self.ref_to_mplace(self.read_value(args[0])?)?;
 163                 let discr_val = self.read_discriminant(place.into())?.0;
 164                 self.write_scalar(Scalar::from_uint(discr_val, dest.layout.size), dest)?;
 165             }
 166
 167             "sinf32" | "fabsf32" | "cosf32" | "sqrtf32" | "expf32" | "exp2f32" | "logf32" |
 168             "log10f32" | "log2f32" | "floorf32" | "ceilf32" | "truncf32" => {
 169                 let f = self.read_scalar(args[0])?.to_f32()?;
 170                 let f = match intrinsic_name {
 171                     "sinf32" => f.sin(),
 172                     "fabsf32" => f.abs(),
 173                     "cosf32" => f.cos(),
 174                     "sqrtf32" => f.sqrt(),
 175                     "expf32" => f.exp(),
 176                     "exp2f32" => f.exp2(),
 177                     "logf32" => f.ln(),
 178                     "log10f32" => f.log10(),
 179                     "log2f32" => f.log2(),
 180                     "floorf32" => f.floor(),
 181                     "ceilf32" => f.ceil(),
 182                     "truncf32" => f.trunc(),
 183                     _ => bug!(),
 184                 };
 185                 self.write_scalar(Scalar::from_f32(f), dest)?;
 186             }
 187
 188             "sinf64" | "fabsf64" | "cosf64" | "sqrtf64" | "expf64" | "exp2f64" | "logf64" |
 189             "log10f64" | "log2f64" | "floorf64" | "ceilf64" | "truncf64" => {
 190                 let f = self.read_scalar(args[0])?.to_f64()?;
 191                 let f = match intrinsic_name {
 192                     "sinf64" => f.sin(),
 193                     "fabsf64" => f.abs(),
 194                     "cosf64" => f.cos(),
 195                     "sqrtf64" => f.sqrt(),
 196                     "expf64" => f.exp(),
 197                     "exp2f64" => f.exp2(),
 198                     "logf64" => f.ln(),
 199                     "log10f64" => f.log10(),
 200                     "log2f64" => f.log2(),
 201                     "floorf64" => f.floor(),
 202                     "ceilf64" => f.ceil(),
 203                     "truncf64" => f.trunc(),
 204                     _ => bug!(),
 205                 };
 206                 self.write_scalar(Scalar::from_f64(f), dest)?;
 207             }
 208
 209             "fadd_fast" | "fsub_fast" | "fmul_fast" | "fdiv_fast" | "frem_fast" => {
 210                 let a = self.read_value(args[0])?;
 211                 let b = self.read_value(args[1])?;
 212                 let op = match intrinsic_name {
 213                     "fadd_fast" => mir::BinOp::Add,
 214                     "fsub_fast" => mir::BinOp::Sub,
 215                     "fmul_fast" => mir::BinOp::Mul,
 216                     "fdiv_fast" => mir::BinOp::Div,
 217                     "frem_fast" => mir::BinOp::Rem,
 218                     _ => bug!(),
 219                 };
 220                 self.binop_ignore_overflow(op, a, b, dest)?;
 221             }
 222
 223             "exact_div" => {
 224                 // Performs an exact division, resulting in undefined behavior where
 225                 // `x % y != 0` or `y == 0` or `x == T::min_value() && y == -1`
 226                 let a = self.read_value(args[0])?;
 227                 let b = self.read_value(args[1])?;
 228                 // check x % y != 0
 229                 if !self.binary_op_val(mir::BinOp::Rem, a, b)?.0.is_null() {
 230                     return err!(ValidationFailure(format!("exact_div: {:?} cannot be divided by {:?}", a, b)));
 231                 }
 232                 self.binop_ignore_overflow(mir::BinOp::Div, a, b, dest)?;
 233             },
 234
 235             "likely" | "unlikely" | "forget" => {}
 236
 237             "init" => {
 238                 // Check fast path: we don't want to force an allocation in case the destination is a simple value,
 239                 // but we also do not want to create a new allocation with 0s and then copy that over.
 240                 // FIXME: We do not properly validate in case of ZSTs and when doing it in memory!
 241                 // However, this only affects direct calls of the intrinsic; calls to the stable
 242                 // functions wrapping them do get their validation.
 243                 if !dest.layout.is_zst() { // nothing to do for ZST
 244                     match dest.layout.abi {
 245                         layout::Abi::Scalar(ref s) => {
 246                             let x = Scalar::from_int(0, s.value.size(&self));
 247                             self.write_value(Value::Scalar(x.into()), dest)?;
 248                         }
 249                         layout::Abi::ScalarPair(ref s1, ref s2) => {
 250                             let x = Scalar::from_int(0, s1.value.size(&self));
 251                             let y = Scalar::from_int(0, s2.value.size(&self));
 252                             self.write_value(Value::ScalarPair(x.into(), y.into()), dest)?;
 253                         }
 254                         _ => {
 255                             // Do it in memory
 256                             let mplace = self.force_allocation(dest)?;
 257                             assert!(mplace.meta.is_none());
 258                             self.memory.write_repeat(mplace.ptr, 0, dest.layout.size)?;
 259                         }
 260                     }
 261                 }
 262             }
 263
 264             "pref_align_of" => {
 265                 let ty = substs.type_at(0);
 266                 let layout = self.layout_of(ty)?;
 267                 let align = layout.align.pref();
 268                 let ptr_size = self.pointer_size();
 269                 let align_val = Scalar::from_uint(align as u128, ptr_size);
 270                 self.write_scalar(align_val, dest)?;
 271             }
 272
 273             "move_val_init" => {
 274                 let ptr = self.ref_to_mplace(self.read_value(args[0])?)?;
 275                 self.copy_op(args[1], ptr.into())?;
 276             }
 277
 278             "offset" => {
 279                 let offset = self.read_scalar(args[1])?.to_isize(&self)?;
 280                 let ptr = self.read_scalar(args[0])?.not_undef()?;
 281                 let result_ptr = self.pointer_offset_inbounds(ptr, substs.type_at(0), offset)?;
 282                 self.write_scalar(result_ptr, dest)?;
 283             }
 284
 285             "powf32" => {
 286                 let f = self.read_scalar(args[0])?.to_f32()?;
 287                 let f2 = self.read_scalar(args[1])?.to_f32()?;
 288                 self.write_scalar(
 289                     Scalar::from_f32(f.powf(f2)),
 290                     dest,
 291                 )?;
 292             }
 293
 294             "powf64" => {
 295                 let f = self.read_scalar(args[0])?.to_f64()?;
 296                 let f2 = self.read_scalar(args[1])?.to_f64()?;
 297                 self.write_scalar(
 298                     Scalar::from_f64(f.powf(f2)),
 299                     dest,
 300                 )?;
 301             }
 302
 303             "fmaf32" => {
 304                 let a = self.read_scalar(args[0])?.to_f32()?;
 305                 let b = self.read_scalar(args[1])?.to_f32()?;
 306                 let c = self.read_scalar(args[2])?.to_f32()?;
 307                 self.write_scalar(
 308                     Scalar::from_f32(a * b + c),
 309                     dest,
 310                 )?;
 311             }
 312
 313             "fmaf64" => {
 314                 let a = self.read_scalar(args[0])?.to_f64()?;
 315                 let b = self.read_scalar(args[1])?.to_f64()?;
 316                 let c = self.read_scalar(args[2])?.to_f64()?;
 317                 self.write_scalar(
 318                     Scalar::from_f64(a * b + c),
 319                     dest,
 320                 )?;
 321             }
 322
 323             "powif32" => {
 324                 let f = self.read_scalar(args[0])?.to_f32()?;
 325                 let i = self.read_scalar(args[1])?.to_i32()?;
 326                 self.write_scalar(
 327                     Scalar::from_f32(f.powi(i)),
 328                     dest,
 329                 )?;
 330             }
 331
 332             "powif64" => {
 333                 let f = self.read_scalar(args[0])?.to_f64()?;
 334                 let i = self.read_scalar(args[1])?.to_i32()?;
 335                 self.write_scalar(
 336                     Scalar::from_f64(f.powi(i)),
 337                     dest,
 338                 )?;
 339             }
 340
 341             "size_of_val" => {
 342                 let mplace = self.ref_to_mplace(self.read_value(args[0])?)?;
 343                 let (size, _) = self.size_and_align_of_mplace(mplace)?
 344                     .expect("size_of_val called on extern type");
 345                 let ptr_size = self.pointer_size();
 346                 self.write_scalar(
 347                     Scalar::from_uint(size.bytes() as u128, ptr_size),
 348                     dest,
 349                 )?;
 350             }
 351
 352             "min_align_of_val" |
 353             "align_of_val" => {
 354                 let mplace = self.ref_to_mplace(self.read_value(args[0])?)?;
 355                 let (_, align) = self.size_and_align_of_mplace(mplace)?
 356                     .expect("size_of_val called on extern type");
 357                 let ptr_size = self.pointer_size();
 358                 self.write_scalar(
 359                     Scalar::from_uint(align.abi(), ptr_size),
 360                     dest,
 361                 )?;
 362             }
 363
 364             "type_name" => {
 365                 let ty = substs.type_at(0);
 366                 let ty_name = ty.to_string();
 367                 let value = self.str_to_value(&ty_name)?;
 368                 self.write_value(value, dest)?;
 369             }
 370
 371             "unchecked_div" => {
 372                 let l = self.read_value(args[0])?;
 373                 let r = self.read_value(args[1])?;
 374                 let rval = r.to_scalar()?.to_bytes()?;
 375                 if rval == 0 {
 376                     return err!(Intrinsic(format!("Division by 0 in unchecked_div")));
 377                 }
 378                 self.binop_ignore_overflow(
 379                     mir::BinOp::Div,
 380                     l,
 381                     r,
 382                     dest,
 383                 )?;
 384             }
 385
 386             "unchecked_rem" => {
 387                 let l = self.read_value(args[0])?;
 388                 let r = self.read_value(args[1])?;
 389                 let rval = r.to_scalar()?.to_bytes()?;
 390                 if rval == 0 {
 391                     return err!(Intrinsic(format!("Division by 0 in unchecked_rem")));
 392                 }
 393                 self.binop_ignore_overflow(
 394                     mir::BinOp::Rem,
 395                     l,
 396                     r,
 397                     dest,
 398                 )?;
 399             }
 400
 401             "uninit" => {
 402                 // Check fast path: we don't want to force an allocation in case the destination is a simple value,
 403                 // but we also do not want to create a new allocation with 0s and then copy that over.
 404                 // FIXME: We do not properly validate in case of ZSTs and when doing it in memory!
 405                 // However, this only affects direct calls of the intrinsic; calls to the stable
 406                 // functions wrapping them do get their validation.
 407                 if !dest.layout.is_zst() { // nothing to do for ZST
 408                     match dest.layout.abi {
 409                         layout::Abi::Scalar(..) => {
 410                             let x = ScalarMaybeUndef::Undef;
 411                             self.write_value(Value::Scalar(x), dest)?;
 412                         }
 413                         layout::Abi::ScalarPair(..) => {
 414                             let x = ScalarMaybeUndef::Undef;
 415                             self.write_value(Value::ScalarPair(x, x), dest)?;
 416                         }
 417                         _ => {
 418                             // Do it in memory
 419                             let mplace = self.force_allocation(dest)?;
 420                             assert!(mplace.meta.is_none());
 421                             self.memory.mark_definedness(mplace.ptr.to_ptr()?, dest.layout.size, false)?;
 422                         }
 423                     }
 424                 }
 425             }
 426
 427             "write_bytes" => {
 428                 let ty = substs.type_at(0);
 429                 let ty_layout = self.layout_of(ty)?;
 430                 let val_byte = self.read_scalar(args[1])?.to_u8()?;
 431                 let ptr = self.read_scalar(args[0])?.not_undef()?;
 432                 let count = self.read_scalar(args[2])?.to_usize(&self)?;
 433                 self.memory.check_align(ptr, ty_layout.align)?;
 434                 self.memory.write_repeat(ptr, val_byte, ty_layout.size * count)?;
 435             }
 436
 437             name => return err!(Unimplemented(format!("unimplemented intrinsic: {}", name))),
 438         }
 439
 440         Ok(())
 441     }
 442 }