diff options
Diffstat (limited to 'compiler/rustc_const_eval/src/interpret/operator.rs')
| -rw-r--r-- | compiler/rustc_const_eval/src/interpret/operator.rs | 463 |
1 files changed, 463 insertions, 0 deletions
diff --git a/compiler/rustc_const_eval/src/interpret/operator.rs b/compiler/rustc_const_eval/src/interpret/operator.rs new file mode 100644 index 000000000..f9912d706 --- /dev/null +++ b/compiler/rustc_const_eval/src/interpret/operator.rs @@ -0,0 +1,463 @@ +use std::convert::TryFrom; + +use rustc_apfloat::Float; +use rustc_middle::mir; +use rustc_middle::mir::interpret::{InterpResult, Scalar}; +use rustc_middle::ty::layout::{LayoutOf, TyAndLayout}; +use rustc_middle::ty::{self, FloatTy, Ty}; +use rustc_target::abi::Abi; + +use super::{ImmTy, Immediate, InterpCx, Machine, PlaceTy}; + +impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { + /// Applies the binary operation `op` to the two operands and writes a tuple of the result + /// and a boolean signifying the potential overflow to the destination. + /// + /// `force_overflow_checks` indicates whether overflow checks should be done even when + /// `tcx.sess.overflow_checks()` is `false`. + pub fn binop_with_overflow( + &mut self, + op: mir::BinOp, + force_overflow_checks: bool, + left: &ImmTy<'tcx, M::Provenance>, + right: &ImmTy<'tcx, M::Provenance>, + dest: &PlaceTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx> { + let (val, overflowed, ty) = self.overflowing_binary_op(op, &left, &right)?; + debug_assert_eq!( + self.tcx.intern_tup(&[ty, self.tcx.types.bool]), + dest.layout.ty, + "type mismatch for result of {:?}", + op, + ); + // As per https://github.com/rust-lang/rust/pull/98738, we always return `false` in the 2nd + // component when overflow checking is disabled. + let overflowed = + overflowed && (force_overflow_checks || M::checked_binop_checks_overflow(self)); + // Write the result to `dest`. + if let Abi::ScalarPair(..) = dest.layout.abi { + // We can use the optimized path and avoid `place_field` (which might do + // `force_allocation`). + let pair = Immediate::ScalarPair(val.into(), Scalar::from_bool(overflowed).into()); + self.write_immediate(pair, dest)?; + } else { + assert!(self.tcx.sess.opts.unstable_opts.randomize_layout); + // With randomized layout, `(int, bool)` might cease to be a `ScalarPair`, so we have to + // do a component-wise write here. This code path is slower than the above because + // `place_field` will have to `force_allocate` locals here. + let val_field = self.place_field(&dest, 0)?; + self.write_scalar(val, &val_field)?; + let overflowed_field = self.place_field(&dest, 1)?; + self.write_scalar(Scalar::from_bool(overflowed), &overflowed_field)?; + } + Ok(()) + } + + /// Applies the binary operation `op` to the arguments and writes the result to the + /// destination. + pub fn binop_ignore_overflow( + &mut self, + op: mir::BinOp, + left: &ImmTy<'tcx, M::Provenance>, + right: &ImmTy<'tcx, M::Provenance>, + dest: &PlaceTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx> { + let (val, _overflowed, ty) = self.overflowing_binary_op(op, left, right)?; + assert_eq!(ty, dest.layout.ty, "type mismatch for result of {:?}", op); + self.write_scalar(val, dest) + } +} + +impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { + fn binary_char_op( + &self, + bin_op: mir::BinOp, + l: char, + r: char, + ) -> (Scalar<M::Provenance>, bool, Ty<'tcx>) { + use rustc_middle::mir::BinOp::*; + + let res = match bin_op { + Eq => l == r, + Ne => l != r, + Lt => l < r, + Le => l <= r, + Gt => l > r, + Ge => l >= r, + _ => span_bug!(self.cur_span(), "Invalid operation on char: {:?}", bin_op), + }; + (Scalar::from_bool(res), false, self.tcx.types.bool) + } + + fn binary_bool_op( + &self, + bin_op: mir::BinOp, + l: bool, + r: bool, + ) -> (Scalar<M::Provenance>, bool, Ty<'tcx>) { + use rustc_middle::mir::BinOp::*; + + let res = match bin_op { + Eq => l == r, + Ne => l != r, + Lt => l < r, + Le => l <= r, + Gt => l > r, + Ge => l >= r, + BitAnd => l & r, + BitOr => l | r, + BitXor => l ^ r, + _ => span_bug!(self.cur_span(), "Invalid operation on bool: {:?}", bin_op), + }; + (Scalar::from_bool(res), false, self.tcx.types.bool) + } + + fn binary_float_op<F: Float + Into<Scalar<M::Provenance>>>( + &self, + bin_op: mir::BinOp, + ty: Ty<'tcx>, + l: F, + r: F, + ) -> (Scalar<M::Provenance>, bool, Ty<'tcx>) { + use rustc_middle::mir::BinOp::*; + + let (val, ty) = match bin_op { + Eq => (Scalar::from_bool(l == r), self.tcx.types.bool), + Ne => (Scalar::from_bool(l != r), self.tcx.types.bool), + Lt => (Scalar::from_bool(l < r), self.tcx.types.bool), + Le => (Scalar::from_bool(l <= r), self.tcx.types.bool), + Gt => (Scalar::from_bool(l > r), self.tcx.types.bool), + Ge => (Scalar::from_bool(l >= r), self.tcx.types.bool), + Add => ((l + r).value.into(), ty), + Sub => ((l - r).value.into(), ty), + Mul => ((l * r).value.into(), ty), + Div => ((l / r).value.into(), ty), + Rem => ((l % r).value.into(), ty), + _ => span_bug!(self.cur_span(), "invalid float op: `{:?}`", bin_op), + }; + (val, false, ty) + } + + fn binary_int_op( + &self, + bin_op: mir::BinOp, + // passing in raw bits + l: u128, + left_layout: TyAndLayout<'tcx>, + r: u128, + right_layout: TyAndLayout<'tcx>, + ) -> InterpResult<'tcx, (Scalar<M::Provenance>, bool, Ty<'tcx>)> { + use rustc_middle::mir::BinOp::*; + + // Shift ops can have an RHS with a different numeric type. + if bin_op == Shl || bin_op == Shr { + let size = u128::from(left_layout.size.bits()); + // Even if `r` is signed, we treat it as if it was unsigned (i.e., we use its + // zero-extended form). This matches the codegen backend: + // <https://github.com/rust-lang/rust/blob/c274e4969f058b1c644243181ece9f829efa7594/compiler/rustc_codegen_ssa/src/base.rs#L315-L317>. + // The overflow check is also ignorant to the sign: + // <https://github.com/rust-lang/rust/blob/c274e4969f058b1c644243181ece9f829efa7594/compiler/rustc_codegen_ssa/src/mir/rvalue.rs#L728>. + // This would behave rather strangely if we had integer types of size 256: a shift by + // -1i8 would actually shift by 255, but that would *not* be considered overflowing. A + // shift by -1i16 though would be considered overflowing. If we had integers of size + // 512, then a shift by -1i8 would even produce a different result than one by -1i16: + // the first shifts by 255, the latter by u16::MAX % 512 = 511. Lucky enough, our + // integers are maximally 128bits wide, so negative shifts *always* overflow and we have + // consistent results for the same value represented at different bit widths. + assert!(size <= 128); + let overflow = r >= size; + // The shift offset is implicitly masked to the type size, to make sure this operation + // is always defined. This is the one MIR operator that does *not* directly map to a + // single LLVM operation. See + // <https://github.com/rust-lang/rust/blob/c274e4969f058b1c644243181ece9f829efa7594/compiler/rustc_codegen_ssa/src/common.rs#L131-L158> + // for the corresponding truncation in our codegen backends. + let r = r % size; + let r = u32::try_from(r).unwrap(); // we masked so this will always fit + let result = if left_layout.abi.is_signed() { + let l = self.sign_extend(l, left_layout) as i128; + let result = match bin_op { + Shl => l.checked_shl(r).unwrap(), + Shr => l.checked_shr(r).unwrap(), + _ => bug!(), + }; + result as u128 + } else { + match bin_op { + Shl => l.checked_shl(r).unwrap(), + Shr => l.checked_shr(r).unwrap(), + _ => bug!(), + } + }; + let truncated = self.truncate(result, left_layout); + return Ok((Scalar::from_uint(truncated, left_layout.size), overflow, left_layout.ty)); + } + + // For the remaining ops, the types must be the same on both sides + if left_layout.ty != right_layout.ty { + span_bug!( + self.cur_span(), + "invalid asymmetric binary op {:?}: {:?} ({:?}), {:?} ({:?})", + bin_op, + l, + left_layout.ty, + r, + right_layout.ty, + ) + } + + let size = left_layout.size; + + // Operations that need special treatment for signed integers + if left_layout.abi.is_signed() { + let op: Option<fn(&i128, &i128) -> bool> = match bin_op { + Lt => Some(i128::lt), + Le => Some(i128::le), + Gt => Some(i128::gt), + Ge => Some(i128::ge), + _ => None, + }; + if let Some(op) = op { + let l = self.sign_extend(l, left_layout) as i128; + let r = self.sign_extend(r, right_layout) as i128; + return Ok((Scalar::from_bool(op(&l, &r)), false, self.tcx.types.bool)); + } + let op: Option<fn(i128, i128) -> (i128, bool)> = match bin_op { + Div if r == 0 => throw_ub!(DivisionByZero), + Rem if r == 0 => throw_ub!(RemainderByZero), + Div => Some(i128::overflowing_div), + Rem => Some(i128::overflowing_rem), + Add => Some(i128::overflowing_add), + Sub => Some(i128::overflowing_sub), + Mul => Some(i128::overflowing_mul), + _ => None, + }; + if let Some(op) = op { + let l = self.sign_extend(l, left_layout) as i128; + let r = self.sign_extend(r, right_layout) as i128; + + // We need a special check for overflowing Rem and Div since they are *UB* + // on overflow, which can happen with "int_min $OP -1". + if matches!(bin_op, Rem | Div) { + if l == size.signed_int_min() && r == -1 { + if bin_op == Rem { + throw_ub!(RemainderOverflow) + } else { + throw_ub!(DivisionOverflow) + } + } + } + + let (result, oflo) = op(l, r); + // This may be out-of-bounds for the result type, so we have to truncate ourselves. + // If that truncation loses any information, we have an overflow. + let result = result as u128; + let truncated = self.truncate(result, left_layout); + return Ok(( + Scalar::from_uint(truncated, size), + oflo || self.sign_extend(truncated, left_layout) != result, + left_layout.ty, + )); + } + } + + let (val, ty) = match bin_op { + Eq => (Scalar::from_bool(l == r), self.tcx.types.bool), + Ne => (Scalar::from_bool(l != r), self.tcx.types.bool), + + Lt => (Scalar::from_bool(l < r), self.tcx.types.bool), + Le => (Scalar::from_bool(l <= r), self.tcx.types.bool), + Gt => (Scalar::from_bool(l > r), self.tcx.types.bool), + Ge => (Scalar::from_bool(l >= r), self.tcx.types.bool), + + BitOr => (Scalar::from_uint(l | r, size), left_layout.ty), + BitAnd => (Scalar::from_uint(l & r, size), left_layout.ty), + BitXor => (Scalar::from_uint(l ^ r, size), left_layout.ty), + + Add | Sub | Mul | Rem | Div => { + assert!(!left_layout.abi.is_signed()); + let op: fn(u128, u128) -> (u128, bool) = match bin_op { + Add => u128::overflowing_add, + Sub => u128::overflowing_sub, + Mul => u128::overflowing_mul, + Div if r == 0 => throw_ub!(DivisionByZero), + Rem if r == 0 => throw_ub!(RemainderByZero), + Div => u128::overflowing_div, + Rem => u128::overflowing_rem, + _ => bug!(), + }; + let (result, oflo) = op(l, r); + // Truncate to target type. + // If that truncation loses any information, we have an overflow. + let truncated = self.truncate(result, left_layout); + return Ok(( + Scalar::from_uint(truncated, size), + oflo || truncated != result, + left_layout.ty, + )); + } + + _ => span_bug!( + self.cur_span(), + "invalid binary op {:?}: {:?}, {:?} (both {:?})", + bin_op, + l, + r, + right_layout.ty, + ), + }; + + Ok((val, false, ty)) + } + + /// Returns the result of the specified operation, whether it overflowed, and + /// the result type. + pub fn overflowing_binary_op( + &self, + bin_op: mir::BinOp, + left: &ImmTy<'tcx, M::Provenance>, + right: &ImmTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx, (Scalar<M::Provenance>, bool, Ty<'tcx>)> { + trace!( + "Running binary op {:?}: {:?} ({:?}), {:?} ({:?})", + bin_op, + *left, + left.layout.ty, + *right, + right.layout.ty + ); + + match left.layout.ty.kind() { + ty::Char => { + assert_eq!(left.layout.ty, right.layout.ty); + let left = left.to_scalar()?; + let right = right.to_scalar()?; + Ok(self.binary_char_op(bin_op, left.to_char()?, right.to_char()?)) + } + ty::Bool => { + assert_eq!(left.layout.ty, right.layout.ty); + let left = left.to_scalar()?; + let right = right.to_scalar()?; + Ok(self.binary_bool_op(bin_op, left.to_bool()?, right.to_bool()?)) + } + ty::Float(fty) => { + assert_eq!(left.layout.ty, right.layout.ty); + let ty = left.layout.ty; + let left = left.to_scalar()?; + let right = right.to_scalar()?; + Ok(match fty { + FloatTy::F32 => { + self.binary_float_op(bin_op, ty, left.to_f32()?, right.to_f32()?) + } + FloatTy::F64 => { + self.binary_float_op(bin_op, ty, left.to_f64()?, right.to_f64()?) + } + }) + } + _ if left.layout.ty.is_integral() => { + // the RHS type can be different, e.g. for shifts -- but it has to be integral, too + assert!( + right.layout.ty.is_integral(), + "Unexpected types for BinOp: {:?} {:?} {:?}", + left.layout.ty, + bin_op, + right.layout.ty + ); + + let l = left.to_scalar()?.to_bits(left.layout.size)?; + let r = right.to_scalar()?.to_bits(right.layout.size)?; + self.binary_int_op(bin_op, l, left.layout, r, right.layout) + } + _ if left.layout.ty.is_any_ptr() => { + // The RHS type must be a `pointer` *or an integer type* (for `Offset`). + // (Even when both sides are pointers, their type might differ, see issue #91636) + assert!( + right.layout.ty.is_any_ptr() || right.layout.ty.is_integral(), + "Unexpected types for BinOp: {:?} {:?} {:?}", + left.layout.ty, + bin_op, + right.layout.ty + ); + + M::binary_ptr_op(self, bin_op, left, right) + } + _ => span_bug!( + self.cur_span(), + "Invalid MIR: bad LHS type for binop: {:?}", + left.layout.ty + ), + } + } + + /// Typed version of `overflowing_binary_op`, returning an `ImmTy`. Also ignores overflows. + #[inline] + pub fn binary_op( + &self, + bin_op: mir::BinOp, + left: &ImmTy<'tcx, M::Provenance>, + right: &ImmTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx, ImmTy<'tcx, M::Provenance>> { + let (val, _overflow, ty) = self.overflowing_binary_op(bin_op, left, right)?; + Ok(ImmTy::from_scalar(val, self.layout_of(ty)?)) + } + + /// Returns the result of the specified operation, whether it overflowed, and + /// the result type. + pub fn overflowing_unary_op( + &self, + un_op: mir::UnOp, + val: &ImmTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx, (Scalar<M::Provenance>, bool, Ty<'tcx>)> { + use rustc_middle::mir::UnOp::*; + + let layout = val.layout; + let val = val.to_scalar()?; + trace!("Running unary op {:?}: {:?} ({:?})", un_op, val, layout.ty); + + match layout.ty.kind() { + ty::Bool => { + let val = val.to_bool()?; + let res = match un_op { + Not => !val, + _ => span_bug!(self.cur_span(), "Invalid bool op {:?}", un_op), + }; + Ok((Scalar::from_bool(res), false, self.tcx.types.bool)) + } + ty::Float(fty) => { + let res = match (un_op, fty) { + (Neg, FloatTy::F32) => Scalar::from_f32(-val.to_f32()?), + (Neg, FloatTy::F64) => Scalar::from_f64(-val.to_f64()?), + _ => span_bug!(self.cur_span(), "Invalid float op {:?}", un_op), + }; + Ok((res, false, layout.ty)) + } + _ => { + assert!(layout.ty.is_integral()); + let val = val.to_bits(layout.size)?; + let (res, overflow) = match un_op { + Not => (self.truncate(!val, layout), false), // bitwise negation, then truncate + Neg => { + // arithmetic negation + assert!(layout.abi.is_signed()); + let val = self.sign_extend(val, layout) as i128; + let (res, overflow) = val.overflowing_neg(); + let res = res as u128; + // Truncate to target type. + // If that truncation loses any information, we have an overflow. + let truncated = self.truncate(res, layout); + (truncated, overflow || self.sign_extend(truncated, layout) != res) + } + }; + Ok((Scalar::from_uint(res, layout.size), overflow, layout.ty)) + } + } + } + + pub fn unary_op( + &self, + un_op: mir::UnOp, + val: &ImmTy<'tcx, M::Provenance>, + ) -> InterpResult<'tcx, ImmTy<'tcx, M::Provenance>> { + let (val, _overflow, ty) = self.overflowing_unary_op(un_op, val)?; + Ok(ImmTy::from_scalar(val, self.layout_of(ty)?)) + } +} |