compiler/rustc_const_eval/src/interpret/operator.rs

   1 use std::convert::TryFrom;
   2
   3 use rustc_apfloat::Float;
   4 use rustc_middle::mir;
   5 use rustc_middle::mir::interpret::{InterpResult, Scalar};
   6 use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
   7 use rustc_middle::ty::{self, FloatTy, Ty};
   8
   9 use super::{ImmTy, Immediate, InterpCx, Machine, PlaceTy};
  10
  11 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
  12     /// Applies the binary operation `op` to the two operands and writes a tuple of the result
  13     /// and a boolean signifying the potential overflow to the destination.
  14     pub fn binop_with_overflow(
  15         &mut self,
  16         op: mir::BinOp,
  17         left: &ImmTy<'tcx, M::PointerTag>,
  18         right: &ImmTy<'tcx, M::PointerTag>,
  19         dest: &PlaceTy<'tcx, M::PointerTag>,
  20     ) -> InterpResult<'tcx> {
  21         let (val, overflowed, ty) = self.overflowing_binary_op(op, &left, &right)?;
  22         debug_assert_eq!(
  23             self.tcx.intern_tup(&[ty, self.tcx.types.bool]),
  24             dest.layout.ty,
  25             "type mismatch for result of {:?}",
  26             op,
  27         );
  28         let val = Immediate::ScalarPair(val.into(), Scalar::from_bool(overflowed).into());
  29         self.write_immediate(val, dest)
  30     }
  31
  32     /// Applies the binary operation `op` to the arguments and writes the result to the
  33     /// destination.
  34     pub fn binop_ignore_overflow(
  35         &mut self,
  36         op: mir::BinOp,
  37         left: &ImmTy<'tcx, M::PointerTag>,
  38         right: &ImmTy<'tcx, M::PointerTag>,
  39         dest: &PlaceTy<'tcx, M::PointerTag>,
  40     ) -> InterpResult<'tcx> {
  41         let (val, _overflowed, ty) = self.overflowing_binary_op(op, left, right)?;
  42         assert_eq!(ty, dest.layout.ty, "type mismatch for result of {:?}", op);
  43         self.write_scalar(val, dest)
  44     }
  45 }
  46
  47 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
  48     fn binary_char_op(
  49         &self,
  50         bin_op: mir::BinOp,
  51         l: char,
  52         r: char,
  53     ) -> (Scalar<M::PointerTag>, bool, Ty<'tcx>) {
  54         use rustc_middle::mir::BinOp::*;
  55
  56         let res = match bin_op {
  57             Eq => l == r,
  58             Ne => l != r,
  59             Lt => l < r,
  60             Le => l <= r,
  61             Gt => l > r,
  62             Ge => l >= r,
  63             _ => span_bug!(self.cur_span(), "Invalid operation on char: {:?}", bin_op),
  64         };
  65         (Scalar::from_bool(res), false, self.tcx.types.bool)
  66     }
  67
  68     fn binary_bool_op(
  69         &self,
  70         bin_op: mir::BinOp,
  71         l: bool,
  72         r: bool,
  73     ) -> (Scalar<M::PointerTag>, bool, Ty<'tcx>) {
  74         use rustc_middle::mir::BinOp::*;
  75
  76         let res = match bin_op {
  77             Eq => l == r,
  78             Ne => l != r,
  79             Lt => l < r,
  80             Le => l <= r,
  81             Gt => l > r,
  82             Ge => l >= r,
  83             BitAnd => l & r,
  84             BitOr => l | r,
  85             BitXor => l ^ r,
  86             _ => span_bug!(self.cur_span(), "Invalid operation on bool: {:?}", bin_op),
  87         };
  88         (Scalar::from_bool(res), false, self.tcx.types.bool)
  89     }
  90
  91     fn binary_float_op<F: Float + Into<Scalar<M::PointerTag>>>(
  92         &self,
  93         bin_op: mir::BinOp,
  94         ty: Ty<'tcx>,
  95         l: F,
  96         r: F,
  97     ) -> (Scalar<M::PointerTag>, bool, Ty<'tcx>) {
  98         use rustc_middle::mir::BinOp::*;
  99
 100         let (val, ty) = match bin_op {
 101             Eq => (Scalar::from_bool(l == r), self.tcx.types.bool),
 102             Ne => (Scalar::from_bool(l != r), self.tcx.types.bool),
 103             Lt => (Scalar::from_bool(l < r), self.tcx.types.bool),
 104             Le => (Scalar::from_bool(l <= r), self.tcx.types.bool),
 105             Gt => (Scalar::from_bool(l > r), self.tcx.types.bool),
 106             Ge => (Scalar::from_bool(l >= r), self.tcx.types.bool),
 107             Add => ((l + r).value.into(), ty),
 108             Sub => ((l - r).value.into(), ty),
 109             Mul => ((l * r).value.into(), ty),
 110             Div => ((l / r).value.into(), ty),
 111             Rem => ((l % r).value.into(), ty),
 112             _ => span_bug!(self.cur_span(), "invalid float op: `{:?}`", bin_op),
 113         };
 114         (val, false, ty)
 115     }
 116
 117     fn binary_int_op(
 118         &self,
 119         bin_op: mir::BinOp,
 120         // passing in raw bits
 121         l: u128,
 122         left_layout: TyAndLayout<'tcx>,
 123         r: u128,
 124         right_layout: TyAndLayout<'tcx>,
 125     ) -> InterpResult<'tcx, (Scalar<M::PointerTag>, bool, Ty<'tcx>)> {
 126         use rustc_middle::mir::BinOp::*;
 127
 128         // Shift ops can have an RHS with a different numeric type.
 129         if bin_op == Shl || bin_op == Shr {
 130             let signed = left_layout.abi.is_signed();
 131             let size = u128::from(left_layout.size.bits());
 132             let overflow = r >= size;
 133             // The shift offset is implicitly masked to the type size, to make sure this operation
 134             // is always defined. This is the one MIR operator that does *not* directly map to a
 135             // single LLVM operation. See
 136             // <https://github.com/rust-lang/rust/blob/a3b9405ae7bb6ab4e8103b414e75c44598a10fd2/compiler/rustc_codegen_ssa/src/common.rs#L131-L158>
 137             // for the corresponding truncation in our codegen backends.
 138             let r = r % size;
 139             let r = u32::try_from(r).unwrap(); // we masked so this will always fit
 140             let result = if signed {
 141                 let l = self.sign_extend(l, left_layout) as i128;
 142                 let result = match bin_op {
 143                     Shl => l.checked_shl(r).unwrap(),
 144                     Shr => l.checked_shr(r).unwrap(),
 145                     _ => bug!("it has already been checked that this is a shift op"),
 146                 };
 147                 result as u128
 148             } else {
 149                 match bin_op {
 150                     Shl => l.checked_shl(r).unwrap(),
 151                     Shr => l.checked_shr(r).unwrap(),
 152                     _ => bug!("it has already been checked that this is a shift op"),
 153                 }
 154             };
 155             let truncated = self.truncate(result, left_layout);
 156             return Ok((Scalar::from_uint(truncated, left_layout.size), overflow, left_layout.ty));
 157         }
 158
 159         // For the remaining ops, the types must be the same on both sides
 160         if left_layout.ty != right_layout.ty {
 161             span_bug!(
 162                 self.cur_span(),
 163                 "invalid asymmetric binary op {:?}: {:?} ({:?}), {:?} ({:?})",
 164                 bin_op,
 165                 l,
 166                 left_layout.ty,
 167                 r,
 168                 right_layout.ty,
 169             )
 170         }
 171
 172         let size = left_layout.size;
 173
 174         // Operations that need special treatment for signed integers
 175         if left_layout.abi.is_signed() {
 176             let op: Option<fn(&i128, &i128) -> bool> = match bin_op {
 177                 Lt => Some(i128::lt),
 178                 Le => Some(i128::le),
 179                 Gt => Some(i128::gt),
 180                 Ge => Some(i128::ge),
 181                 _ => None,
 182             };
 183             if let Some(op) = op {
 184                 let l = self.sign_extend(l, left_layout) as i128;
 185                 let r = self.sign_extend(r, right_layout) as i128;
 186                 return Ok((Scalar::from_bool(op(&l, &r)), false, self.tcx.types.bool));
 187             }
 188             let op: Option<fn(i128, i128) -> (i128, bool)> = match bin_op {
 189                 Div if r == 0 => throw_ub!(DivisionByZero),
 190                 Rem if r == 0 => throw_ub!(RemainderByZero),
 191                 Div => Some(i128::overflowing_div),
 192                 Rem => Some(i128::overflowing_rem),
 193                 Add => Some(i128::overflowing_add),
 194                 Sub => Some(i128::overflowing_sub),
 195                 Mul => Some(i128::overflowing_mul),
 196                 _ => None,
 197             };
 198             if let Some(op) = op {
 199                 let r = self.sign_extend(r, right_layout) as i128;
 200                 // We need a special check for overflowing remainder:
 201                 // "int_min % -1" overflows and returns 0, but after casting things to a larger int
 202                 // type it does *not* overflow nor give an unrepresentable result!
 203                 if bin_op == Rem {
 204                     if r == -1 && l == (1 << (size.bits() - 1)) {
 205                         return Ok((Scalar::from_int(0, size), true, left_layout.ty));
 206                     }
 207                 }
 208                 let l = self.sign_extend(l, left_layout) as i128;
 209
 210                 let (result, oflo) = op(l, r);
 211                 // This may be out-of-bounds for the result type, so we have to truncate ourselves.
 212                 // If that truncation loses any information, we have an overflow.
 213                 let result = result as u128;
 214                 let truncated = self.truncate(result, left_layout);
 215                 return Ok((
 216                     Scalar::from_uint(truncated, size),
 217                     oflo || self.sign_extend(truncated, left_layout) != result,
 218                     left_layout.ty,
 219                 ));
 220             }
 221         }
 222
 223         let (val, ty) = match bin_op {
 224             Eq => (Scalar::from_bool(l == r), self.tcx.types.bool),
 225             Ne => (Scalar::from_bool(l != r), self.tcx.types.bool),
 226
 227             Lt => (Scalar::from_bool(l < r), self.tcx.types.bool),
 228             Le => (Scalar::from_bool(l <= r), self.tcx.types.bool),
 229             Gt => (Scalar::from_bool(l > r), self.tcx.types.bool),
 230             Ge => (Scalar::from_bool(l >= r), self.tcx.types.bool),
 231
 232             BitOr => (Scalar::from_uint(l | r, size), left_layout.ty),
 233             BitAnd => (Scalar::from_uint(l & r, size), left_layout.ty),
 234             BitXor => (Scalar::from_uint(l ^ r, size), left_layout.ty),
 235
 236             Add | Sub | Mul | Rem | Div => {
 237                 assert!(!left_layout.abi.is_signed());
 238                 let op: fn(u128, u128) -> (u128, bool) = match bin_op {
 239                     Add => u128::overflowing_add,
 240                     Sub => u128::overflowing_sub,
 241                     Mul => u128::overflowing_mul,
 242                     Div if r == 0 => throw_ub!(DivisionByZero),
 243                     Rem if r == 0 => throw_ub!(RemainderByZero),
 244                     Div => u128::overflowing_div,
 245                     Rem => u128::overflowing_rem,
 246                     _ => bug!(),
 247                 };
 248                 let (result, oflo) = op(l, r);
 249                 // Truncate to target type.
 250                 // If that truncation loses any information, we have an overflow.
 251                 let truncated = self.truncate(result, left_layout);
 252                 return Ok((
 253                     Scalar::from_uint(truncated, size),
 254                     oflo || truncated != result,
 255                     left_layout.ty,
 256                 ));
 257             }
 258
 259             _ => span_bug!(
 260                 self.cur_span(),
 261                 "invalid binary op {:?}: {:?}, {:?} (both {:?})",
 262                 bin_op,
 263                 l,
 264                 r,
 265                 right_layout.ty,
 266             ),
 267         };
 268
 269         Ok((val, false, ty))
 270     }
 271
 272     /// Returns the result of the specified operation, whether it overflowed, and
 273     /// the result type.
 274     pub fn overflowing_binary_op(
 275         &self,
 276         bin_op: mir::BinOp,
 277         left: &ImmTy<'tcx, M::PointerTag>,
 278         right: &ImmTy<'tcx, M::PointerTag>,
 279     ) -> InterpResult<'tcx, (Scalar<M::PointerTag>, bool, Ty<'tcx>)> {
 280         trace!(
 281             "Running binary op {:?}: {:?} ({:?}), {:?} ({:?})",
 282             bin_op,
 283             *left,
 284             left.layout.ty,
 285             *right,
 286             right.layout.ty
 287         );
 288
 289         match left.layout.ty.kind() {
 290             ty::Char => {
 291                 assert_eq!(left.layout.ty, right.layout.ty);
 292                 let left = left.to_scalar()?;
 293                 let right = right.to_scalar()?;
 294                 Ok(self.binary_char_op(bin_op, left.to_char()?, right.to_char()?))
 295             }
 296             ty::Bool => {
 297                 assert_eq!(left.layout.ty, right.layout.ty);
 298                 let left = left.to_scalar()?;
 299                 let right = right.to_scalar()?;
 300                 Ok(self.binary_bool_op(bin_op, left.to_bool()?, right.to_bool()?))
 301             }
 302             ty::Float(fty) => {
 303                 assert_eq!(left.layout.ty, right.layout.ty);
 304                 let ty = left.layout.ty;
 305                 let left = left.to_scalar()?;
 306                 let right = right.to_scalar()?;
 307                 Ok(match fty {
 308                     FloatTy::F32 => {
 309                         self.binary_float_op(bin_op, ty, left.to_f32()?, right.to_f32()?)
 310                     }
 311                     FloatTy::F64 => {
 312                         self.binary_float_op(bin_op, ty, left.to_f64()?, right.to_f64()?)
 313                     }
 314                 })
 315             }
 316             _ if left.layout.ty.is_integral() => {
 317                 // the RHS type can be different, e.g. for shifts -- but it has to be integral, too
 318                 assert!(
 319                     right.layout.ty.is_integral(),
 320                     "Unexpected types for BinOp: {:?} {:?} {:?}",
 321                     left.layout.ty,
 322                     bin_op,
 323                     right.layout.ty
 324                 );
 325
 326                 let l = left.to_scalar()?.to_bits(left.layout.size)?;
 327                 let r = right.to_scalar()?.to_bits(right.layout.size)?;
 328                 self.binary_int_op(bin_op, l, left.layout, r, right.layout)
 329             }
 330             _ if left.layout.ty.is_any_ptr() => {
 331                 // The RHS type must be the same *or an integer type* (for `Offset`).
 332                 assert!(
 333                     right.layout.ty == left.layout.ty || right.layout.ty.is_integral(),
 334                     "Unexpected types for BinOp: {:?} {:?} {:?}",
 335                     left.layout.ty,
 336                     bin_op,
 337                     right.layout.ty
 338                 );
 339
 340                 M::binary_ptr_op(self, bin_op, left, right)
 341             }
 342             _ => span_bug!(
 343                 self.cur_span(),
 344                 "Invalid MIR: bad LHS type for binop: {:?}",
 345                 left.layout.ty
 346             ),
 347         }
 348     }
 349
 350     /// Typed version of `overflowing_binary_op`, returning an `ImmTy`. Also ignores overflows.
 351     #[inline]
 352     pub fn binary_op(
 353         &self,
 354         bin_op: mir::BinOp,
 355         left: &ImmTy<'tcx, M::PointerTag>,
 356         right: &ImmTy<'tcx, M::PointerTag>,
 357     ) -> InterpResult<'tcx, ImmTy<'tcx, M::PointerTag>> {
 358         let (val, _overflow, ty) = self.overflowing_binary_op(bin_op, left, right)?;
 359         Ok(ImmTy::from_scalar(val, self.layout_of(ty)?))
 360     }
 361
 362     /// Returns the result of the specified operation, whether it overflowed, and
 363     /// the result type.
 364     pub fn overflowing_unary_op(
 365         &self,
 366         un_op: mir::UnOp,
 367         val: &ImmTy<'tcx, M::PointerTag>,
 368     ) -> InterpResult<'tcx, (Scalar<M::PointerTag>, bool, Ty<'tcx>)> {
 369         use rustc_middle::mir::UnOp::*;
 370
 371         let layout = val.layout;
 372         let val = val.to_scalar()?;
 373         trace!("Running unary op {:?}: {:?} ({:?})", un_op, val, layout.ty);
 374
 375         match layout.ty.kind() {
 376             ty::Bool => {
 377                 let val = val.to_bool()?;
 378                 let res = match un_op {
 379                     Not => !val,
 380                     _ => span_bug!(self.cur_span(), "Invalid bool op {:?}", un_op),
 381                 };
 382                 Ok((Scalar::from_bool(res), false, self.tcx.types.bool))
 383             }
 384             ty::Float(fty) => {
 385                 let res = match (un_op, fty) {
 386                     (Neg, FloatTy::F32) => Scalar::from_f32(-val.to_f32()?),
 387                     (Neg, FloatTy::F64) => Scalar::from_f64(-val.to_f64()?),
 388                     _ => span_bug!(self.cur_span(), "Invalid float op {:?}", un_op),
 389                 };
 390                 Ok((res, false, layout.ty))
 391             }
 392             _ => {
 393                 assert!(layout.ty.is_integral());
 394                 let val = val.to_bits(layout.size)?;
 395                 let (res, overflow) = match un_op {
 396                     Not => (self.truncate(!val, layout), false), // bitwise negation, then truncate
 397                     Neg => {
 398                         // arithmetic negation
 399                         assert!(layout.abi.is_signed());
 400                         let val = self.sign_extend(val, layout) as i128;
 401                         let (res, overflow) = val.overflowing_neg();
 402                         let res = res as u128;
 403                         // Truncate to target type.
 404                         // If that truncation loses any information, we have an overflow.
 405                         let truncated = self.truncate(res, layout);
 406                         (truncated, overflow || self.sign_extend(truncated, layout) != res)
 407                     }
 408                 };
 409                 Ok((Scalar::from_uint(res, layout.size), overflow, layout.ty))
 410             }
 411         }
 412     }
 413
 414     pub fn unary_op(
 415         &self,
 416         un_op: mir::UnOp,
 417         val: &ImmTy<'tcx, M::PointerTag>,
 418     ) -> InterpResult<'tcx, ImmTy<'tcx, M::PointerTag>> {
 419         let (val, _overflow, ty) = self.overflowing_unary_op(un_op, val)?;
 420         Ok(ImmTy::from_scalar(val, self.layout_of(ty)?))
 421     }
 422 }