src/librustc_mir/interpret/operator.rs

   1 use std::convert::TryFrom;
   2
   3 use rustc_apfloat::Float;
   4 use rustc_ast::FloatTy;
   5 use rustc_middle::mir;
   6 use rustc_middle::mir::interpret::{InterpResult, Scalar};
   7 use rustc_middle::ty::{self, layout::TyAndLayout, Ty};
   8 use rustc_target::abi::LayoutOf;
   9
  10 use super::{ImmTy, Immediate, InterpCx, Machine, PlaceTy};
  11
  12 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
  13     /// Applies the binary operation `op` to the two operands and writes a tuple of the result
  14     /// and a boolean signifying the potential overflow to the destination.
  15     pub fn binop_with_overflow(
  16         &mut self,
  17         op: mir::BinOp,
  18         left: ImmTy<'tcx, M::PointerTag>,
  19         right: ImmTy<'tcx, M::PointerTag>,
  20         dest: PlaceTy<'tcx, M::PointerTag>,
  21     ) -> InterpResult<'tcx> {
  22         let (val, overflowed, ty) = self.overflowing_binary_op(op, left, right)?;
  23         debug_assert_eq!(
  24             self.tcx.intern_tup(&[ty, self.tcx.types.bool]),
  25             dest.layout.ty,
  26             "type mismatch for result of {:?}",
  27             op,
  28         );
  29         let val = Immediate::ScalarPair(val.into(), Scalar::from_bool(overflowed).into());
  30         self.write_immediate(val, dest)
  31     }
  32
  33     /// Applies the binary operation `op` to the arguments and writes the result to the
  34     /// destination.
  35     pub fn binop_ignore_overflow(
  36         &mut self,
  37         op: mir::BinOp,
  38         left: ImmTy<'tcx, M::PointerTag>,
  39         right: ImmTy<'tcx, M::PointerTag>,
  40         dest: PlaceTy<'tcx, M::PointerTag>,
  41     ) -> InterpResult<'tcx> {
  42         let (val, _overflowed, ty) = self.overflowing_binary_op(op, left, right)?;
  43         assert_eq!(ty, dest.layout.ty, "type mismatch for result of {:?}", op);
  44         self.write_scalar(val, dest)
  45     }
  46 }
  47
  48 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
  49     fn binary_char_op(
  50         &self,
  51         bin_op: mir::BinOp,
  52         l: char,
  53         r: char,
  54     ) -> (Scalar<M::PointerTag>, bool, Ty<'tcx>) {
  55         use rustc_middle::mir::BinOp::*;
  56
  57         let res = match bin_op {
  58             Eq => l == r,
  59             Ne => l != r,
  60             Lt => l < r,
  61             Le => l <= r,
  62             Gt => l > r,
  63             Ge => l >= r,
  64             _ => span_bug!(self.cur_span(), "Invalid operation on char: {:?}", bin_op),
  65         };
  66         (Scalar::from_bool(res), false, self.tcx.types.bool)
  67     }
  68
  69     fn binary_bool_op(
  70         &self,
  71         bin_op: mir::BinOp,
  72         l: bool,
  73         r: bool,
  74     ) -> (Scalar<M::PointerTag>, bool, Ty<'tcx>) {
  75         use rustc_middle::mir::BinOp::*;
  76
  77         let res = match bin_op {
  78             Eq => l == r,
  79             Ne => l != r,
  80             Lt => l < r,
  81             Le => l <= r,
  82             Gt => l > r,
  83             Ge => l >= r,
  84             BitAnd => l & r,
  85             BitOr => l | r,
  86             BitXor => l ^ r,
  87             _ => span_bug!(self.cur_span(), "Invalid operation on bool: {:?}", bin_op),
  88         };
  89         (Scalar::from_bool(res), false, self.tcx.types.bool)
  90     }
  91
  92     fn binary_float_op<F: Float + Into<Scalar<M::PointerTag>>>(
  93         &self,
  94         bin_op: mir::BinOp,
  95         ty: Ty<'tcx>,
  96         l: F,
  97         r: F,
  98     ) -> (Scalar<M::PointerTag>, bool, Ty<'tcx>) {
  99         use rustc_middle::mir::BinOp::*;
 100
 101         let (val, ty) = match bin_op {
 102             Eq => (Scalar::from_bool(l == r), self.tcx.types.bool),
 103             Ne => (Scalar::from_bool(l != r), self.tcx.types.bool),
 104             Lt => (Scalar::from_bool(l < r), self.tcx.types.bool),
 105             Le => (Scalar::from_bool(l <= r), self.tcx.types.bool),
 106             Gt => (Scalar::from_bool(l > r), self.tcx.types.bool),
 107             Ge => (Scalar::from_bool(l >= r), self.tcx.types.bool),
 108             Add => ((l + r).value.into(), ty),
 109             Sub => ((l - r).value.into(), ty),
 110             Mul => ((l * r).value.into(), ty),
 111             Div => ((l / r).value.into(), ty),
 112             Rem => ((l % r).value.into(), ty),
 113             _ => span_bug!(self.cur_span(), "invalid float op: `{:?}`", bin_op),
 114         };
 115         (val, false, ty)
 116     }
 117
 118     fn binary_int_op(
 119         &self,
 120         bin_op: mir::BinOp,
 121         // passing in raw bits
 122         l: u128,
 123         left_layout: TyAndLayout<'tcx>,
 124         r: u128,
 125         right_layout: TyAndLayout<'tcx>,
 126     ) -> InterpResult<'tcx, (Scalar<M::PointerTag>, bool, Ty<'tcx>)> {
 127         use rustc_middle::mir::BinOp::*;
 128
 129         // Shift ops can have an RHS with a different numeric type.
 130         if bin_op == Shl || bin_op == Shr {
 131             let signed = left_layout.abi.is_signed();
 132             let size = u128::from(left_layout.size.bits());
 133             let overflow = r >= size;
 134             let r = r % size; // mask to type size
 135             let r = u32::try_from(r).unwrap(); // we masked so this will always fit
 136             let result = if signed {
 137                 let l = self.sign_extend(l, left_layout) as i128;
 138                 let result = match bin_op {
 139                     Shl => l.checked_shl(r).unwrap(),
 140                     Shr => l.checked_shr(r).unwrap(),
 141                     _ => bug!("it has already been checked that this is a shift op"),
 142                 };
 143                 result as u128
 144             } else {
 145                 match bin_op {
 146                     Shl => l.checked_shl(r).unwrap(),
 147                     Shr => l.checked_shr(r).unwrap(),
 148                     _ => bug!("it has already been checked that this is a shift op"),
 149                 }
 150             };
 151             let truncated = self.truncate(result, left_layout);
 152             return Ok((Scalar::from_uint(truncated, left_layout.size), overflow, left_layout.ty));
 153         }
 154
 155         // For the remaining ops, the types must be the same on both sides
 156         if left_layout.ty != right_layout.ty {
 157             span_bug!(
 158                 self.cur_span(),
 159                 "invalid asymmetric binary op {:?}: {:?} ({:?}), {:?} ({:?})",
 160                 bin_op,
 161                 l,
 162                 left_layout.ty,
 163                 r,
 164                 right_layout.ty,
 165             )
 166         }
 167
 168         let size = left_layout.size;
 169
 170         // Operations that need special treatment for signed integers
 171         if left_layout.abi.is_signed() {
 172             let op: Option<fn(&i128, &i128) -> bool> = match bin_op {
 173                 Lt => Some(i128::lt),
 174                 Le => Some(i128::le),
 175                 Gt => Some(i128::gt),
 176                 Ge => Some(i128::ge),
 177                 _ => None,
 178             };
 179             if let Some(op) = op {
 180                 let l = self.sign_extend(l, left_layout) as i128;
 181                 let r = self.sign_extend(r, right_layout) as i128;
 182                 return Ok((Scalar::from_bool(op(&l, &r)), false, self.tcx.types.bool));
 183             }
 184             let op: Option<fn(i128, i128) -> (i128, bool)> = match bin_op {
 185                 Div if r == 0 => throw_ub!(DivisionByZero),
 186                 Rem if r == 0 => throw_ub!(RemainderByZero),
 187                 Div => Some(i128::overflowing_div),
 188                 Rem => Some(i128::overflowing_rem),
 189                 Add => Some(i128::overflowing_add),
 190                 Sub => Some(i128::overflowing_sub),
 191                 Mul => Some(i128::overflowing_mul),
 192                 _ => None,
 193             };
 194             if let Some(op) = op {
 195                 let r = self.sign_extend(r, right_layout) as i128;
 196                 // We need a special check for overflowing remainder:
 197                 // "int_min % -1" overflows and returns 0, but after casting things to a larger int
 198                 // type it does *not* overflow nor give an unrepresentable result!
 199                 if bin_op == Rem {
 200                     if r == -1 && l == (1 << (size.bits() - 1)) {
 201                         return Ok((Scalar::from_int(0, size), true, left_layout.ty));
 202                     }
 203                 }
 204                 let l = self.sign_extend(l, left_layout) as i128;
 205
 206                 let (result, oflo) = op(l, r);
 207                 // This may be out-of-bounds for the result type, so we have to truncate ourselves.
 208                 // If that truncation loses any information, we have an overflow.
 209                 let result = result as u128;
 210                 let truncated = self.truncate(result, left_layout);
 211                 return Ok((
 212                     Scalar::from_uint(truncated, size),
 213                     oflo || self.sign_extend(truncated, left_layout) != result,
 214                     left_layout.ty,
 215                 ));
 216             }
 217         }
 218
 219         let (val, ty) = match bin_op {
 220             Eq => (Scalar::from_bool(l == r), self.tcx.types.bool),
 221             Ne => (Scalar::from_bool(l != r), self.tcx.types.bool),
 222
 223             Lt => (Scalar::from_bool(l < r), self.tcx.types.bool),
 224             Le => (Scalar::from_bool(l <= r), self.tcx.types.bool),
 225             Gt => (Scalar::from_bool(l > r), self.tcx.types.bool),
 226             Ge => (Scalar::from_bool(l >= r), self.tcx.types.bool),
 227
 228             BitOr => (Scalar::from_uint(l | r, size), left_layout.ty),
 229             BitAnd => (Scalar::from_uint(l & r, size), left_layout.ty),
 230             BitXor => (Scalar::from_uint(l ^ r, size), left_layout.ty),
 231
 232             Add | Sub | Mul | Rem | Div => {
 233                 assert!(!left_layout.abi.is_signed());
 234                 let op: fn(u128, u128) -> (u128, bool) = match bin_op {
 235                     Add => u128::overflowing_add,
 236                     Sub => u128::overflowing_sub,
 237                     Mul => u128::overflowing_mul,
 238                     Div if r == 0 => throw_ub!(DivisionByZero),
 239                     Rem if r == 0 => throw_ub!(RemainderByZero),
 240                     Div => u128::overflowing_div,
 241                     Rem => u128::overflowing_rem,
 242                     _ => bug!(),
 243                 };
 244                 let (result, oflo) = op(l, r);
 245                 // Truncate to target type.
 246                 // If that truncation loses any information, we have an overflow.
 247                 let truncated = self.truncate(result, left_layout);
 248                 return Ok((
 249                     Scalar::from_uint(truncated, size),
 250                     oflo || truncated != result,
 251                     left_layout.ty,
 252                 ));
 253             }
 254
 255             _ => span_bug!(
 256                 self.cur_span(),
 257                 "invalid binary op {:?}: {:?}, {:?} (both {:?})",
 258                 bin_op,
 259                 l,
 260                 r,
 261                 right_layout.ty,
 262             ),
 263         };
 264
 265         Ok((val, false, ty))
 266     }
 267
 268     /// Returns the result of the specified operation, whether it overflowed, and
 269     /// the result type.
 270     pub fn overflowing_binary_op(
 271         &self,
 272         bin_op: mir::BinOp,
 273         left: ImmTy<'tcx, M::PointerTag>,
 274         right: ImmTy<'tcx, M::PointerTag>,
 275     ) -> InterpResult<'tcx, (Scalar<M::PointerTag>, bool, Ty<'tcx>)> {
 276         trace!(
 277             "Running binary op {:?}: {:?} ({:?}), {:?} ({:?})",
 278             bin_op,
 279             *left,
 280             left.layout.ty,
 281             *right,
 282             right.layout.ty
 283         );
 284
 285         match left.layout.ty.kind {
 286             ty::Char => {
 287                 assert_eq!(left.layout.ty, right.layout.ty);
 288                 let left = left.to_scalar()?;
 289                 let right = right.to_scalar()?;
 290                 Ok(self.binary_char_op(bin_op, left.to_char()?, right.to_char()?))
 291             }
 292             ty::Bool => {
 293                 assert_eq!(left.layout.ty, right.layout.ty);
 294                 let left = left.to_scalar()?;
 295                 let right = right.to_scalar()?;
 296                 Ok(self.binary_bool_op(bin_op, left.to_bool()?, right.to_bool()?))
 297             }
 298             ty::Float(fty) => {
 299                 assert_eq!(left.layout.ty, right.layout.ty);
 300                 let ty = left.layout.ty;
 301                 let left = left.to_scalar()?;
 302                 let right = right.to_scalar()?;
 303                 Ok(match fty {
 304                     FloatTy::F32 => {
 305                         self.binary_float_op(bin_op, ty, left.to_f32()?, right.to_f32()?)
 306                     }
 307                     FloatTy::F64 => {
 308                         self.binary_float_op(bin_op, ty, left.to_f64()?, right.to_f64()?)
 309                     }
 310                 })
 311             }
 312             _ if left.layout.ty.is_integral() => {
 313                 // the RHS type can be different, e.g. for shifts -- but it has to be integral, too
 314                 assert!(
 315                     right.layout.ty.is_integral(),
 316                     "Unexpected types for BinOp: {:?} {:?} {:?}",
 317                     left.layout.ty,
 318                     bin_op,
 319                     right.layout.ty
 320                 );
 321
 322                 let l = self.force_bits(left.to_scalar()?, left.layout.size)?;
 323                 let r = self.force_bits(right.to_scalar()?, right.layout.size)?;
 324                 self.binary_int_op(bin_op, l, left.layout, r, right.layout)
 325             }
 326             _ if left.layout.ty.is_any_ptr() => {
 327                 // The RHS type must be the same *or an integer type* (for `Offset`).
 328                 assert!(
 329                     right.layout.ty == left.layout.ty || right.layout.ty.is_integral(),
 330                     "Unexpected types for BinOp: {:?} {:?} {:?}",
 331                     left.layout.ty,
 332                     bin_op,
 333                     right.layout.ty
 334                 );
 335
 336                 M::binary_ptr_op(self, bin_op, left, right)
 337             }
 338             _ => span_bug!(
 339                 self.cur_span(),
 340                 "Invalid MIR: bad LHS type for binop: {:?}",
 341                 left.layout.ty
 342             ),
 343         }
 344     }
 345
 346     /// Typed version of `overflowing_binary_op`, returning an `ImmTy`. Also ignores overflows.
 347     #[inline]
 348     pub fn binary_op(
 349         &self,
 350         bin_op: mir::BinOp,
 351         left: ImmTy<'tcx, M::PointerTag>,
 352         right: ImmTy<'tcx, M::PointerTag>,
 353     ) -> InterpResult<'tcx, ImmTy<'tcx, M::PointerTag>> {
 354         let (val, _overflow, ty) = self.overflowing_binary_op(bin_op, left, right)?;
 355         Ok(ImmTy::from_scalar(val, self.layout_of(ty)?))
 356     }
 357
 358     /// Returns the result of the specified operation, whether it overflowed, and
 359     /// the result type.
 360     pub fn overflowing_unary_op(
 361         &self,
 362         un_op: mir::UnOp,
 363         val: ImmTy<'tcx, M::PointerTag>,
 364     ) -> InterpResult<'tcx, (Scalar<M::PointerTag>, bool, Ty<'tcx>)> {
 365         use rustc_middle::mir::UnOp::*;
 366
 367         let layout = val.layout;
 368         let val = val.to_scalar()?;
 369         trace!("Running unary op {:?}: {:?} ({:?})", un_op, val, layout.ty);
 370
 371         match layout.ty.kind {
 372             ty::Bool => {
 373                 let val = val.to_bool()?;
 374                 let res = match un_op {
 375                     Not => !val,
 376                     _ => span_bug!(self.cur_span(), "Invalid bool op {:?}", un_op),
 377                 };
 378                 Ok((Scalar::from_bool(res), false, self.tcx.types.bool))
 379             }
 380             ty::Float(fty) => {
 381                 let res = match (un_op, fty) {
 382                     (Neg, FloatTy::F32) => Scalar::from_f32(-val.to_f32()?),
 383                     (Neg, FloatTy::F64) => Scalar::from_f64(-val.to_f64()?),
 384                     _ => span_bug!(self.cur_span(), "Invalid float op {:?}", un_op),
 385                 };
 386                 Ok((res, false, layout.ty))
 387             }
 388             _ => {
 389                 assert!(layout.ty.is_integral());
 390                 let val = self.force_bits(val, layout.size)?;
 391                 let (res, overflow) = match un_op {
 392                     Not => (self.truncate(!val, layout), false), // bitwise negation, then truncate
 393                     Neg => {
 394                         // arithmetic negation
 395                         assert!(layout.abi.is_signed());
 396                         let val = self.sign_extend(val, layout) as i128;
 397                         let (res, overflow) = val.overflowing_neg();
 398                         let res = res as u128;
 399                         // Truncate to target type.
 400                         // If that truncation loses any information, we have an overflow.
 401                         let truncated = self.truncate(res, layout);
 402                         (truncated, overflow || self.sign_extend(truncated, layout) != res)
 403                     }
 404                 };
 405                 Ok((Scalar::from_uint(res, layout.size), overflow, layout.ty))
 406             }
 407         }
 408     }
 409
 410     pub fn unary_op(
 411         &self,
 412         un_op: mir::UnOp,
 413         val: ImmTy<'tcx, M::PointerTag>,
 414     ) -> InterpResult<'tcx, ImmTy<'tcx, M::PointerTag>> {
 415         let (val, _overflow, ty) = self.overflowing_unary_op(un_op, val)?;
 416         Ok(ImmTy::from_scalar(val, self.layout_of(ty)?))
 417     }
 418 }