| //! Intrinsics and other functions that the miri engine executes without |
| //! looking at their MIR. Intrinsics/functions supported here are shared by CTFE |
| //! and miri. |
| |
| use std::convert::TryFrom; |
| |
| use rustc_hir::def_id::DefId; |
| use rustc_middle::mir::{ |
| self, |
| interpret::{uabs, ConstValue, GlobalId, InterpResult, Scalar}, |
| BinOp, |
| }; |
| use rustc_middle::ty; |
| use rustc_middle::ty::subst::SubstsRef; |
| use rustc_middle::ty::{Ty, TyCtxt}; |
| use rustc_span::symbol::{sym, Symbol}; |
| use rustc_target::abi::{Abi, LayoutOf as _, Primitive, Size}; |
| |
| use super::{CheckInAllocMsg, ImmTy, InterpCx, Machine, OpTy, PlaceTy}; |
| |
| mod caller_location; |
| mod type_name; |
| |
| fn numeric_intrinsic<'tcx, Tag>( |
| name: Symbol, |
| bits: u128, |
| kind: Primitive, |
| ) -> InterpResult<'tcx, Scalar<Tag>> { |
| let size = match kind { |
| Primitive::Int(integer, _) => integer.size(), |
| _ => bug!("invalid `{}` argument: {:?}", name, bits), |
| }; |
| let extra = 128 - u128::from(size.bits()); |
| let bits_out = match name { |
| sym::ctpop => u128::from(bits.count_ones()), |
| sym::ctlz => u128::from(bits.leading_zeros()) - extra, |
| sym::cttz => u128::from((bits << extra).trailing_zeros()) - extra, |
| sym::bswap => (bits << extra).swap_bytes(), |
| sym::bitreverse => (bits << extra).reverse_bits(), |
| _ => bug!("not a numeric intrinsic: {}", name), |
| }; |
| Ok(Scalar::from_uint(bits_out, size)) |
| } |
| |
| /// The logic for all nullary intrinsics is implemented here. These intrinsics don't get evaluated |
| /// inside an `InterpCx` and instead have their value computed directly from rustc internal info. |
| crate fn eval_nullary_intrinsic<'tcx>( |
| tcx: TyCtxt<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| def_id: DefId, |
| substs: SubstsRef<'tcx>, |
| ) -> InterpResult<'tcx, ConstValue<'tcx>> { |
| let tp_ty = substs.type_at(0); |
| let name = tcx.item_name(def_id); |
| Ok(match name { |
| sym::type_name => { |
| let alloc = type_name::alloc_type_name(tcx, tp_ty); |
| ConstValue::Slice { data: alloc, start: 0, end: alloc.len() } |
| } |
| sym::needs_drop => ConstValue::from_bool(tp_ty.needs_drop(tcx, param_env)), |
| sym::size_of | sym::min_align_of | sym::pref_align_of => { |
| let layout = tcx.layout_of(param_env.and(tp_ty)).map_err(|e| err_inval!(Layout(e)))?; |
| let n = match name { |
| sym::pref_align_of => layout.align.pref.bytes(), |
| sym::min_align_of => layout.align.abi.bytes(), |
| sym::size_of => layout.size.bytes(), |
| _ => bug!(), |
| }; |
| ConstValue::from_machine_usize(n, &tcx) |
| } |
| sym::type_id => ConstValue::from_u64(tcx.type_id_hash(tp_ty)), |
| sym::variant_count => { |
| if let ty::Adt(ref adt, _) = tp_ty.kind { |
| ConstValue::from_machine_usize(adt.variants.len() as u64, &tcx) |
| } else { |
| ConstValue::from_machine_usize(0u64, &tcx) |
| } |
| } |
| other => bug!("`{}` is not a zero arg intrinsic", other), |
| }) |
| } |
| |
| impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { |
| /// Returns `true` if emulation happened. |
| pub fn emulate_intrinsic( |
| &mut self, |
| instance: ty::Instance<'tcx>, |
| args: &[OpTy<'tcx, M::PointerTag>], |
| ret: Option<(PlaceTy<'tcx, M::PointerTag>, mir::BasicBlock)>, |
| ) -> InterpResult<'tcx, bool> { |
| let substs = instance.substs; |
| let intrinsic_name = self.tcx.item_name(instance.def_id()); |
| |
| // First handle intrinsics without return place. |
| let (dest, ret) = match ret { |
| None => match intrinsic_name { |
| sym::transmute => throw_ub_format!("transmuting to uninhabited type"), |
| sym::abort => M::abort(self)?, |
| // Unsupported diverging intrinsic. |
| _ => return Ok(false), |
| }, |
| Some(p) => p, |
| }; |
| |
| // Keep the patterns in this match ordered the same as the list in |
| // `src/librustc_middle/ty/constness.rs` |
| match intrinsic_name { |
| sym::caller_location => { |
| let span = self.find_closest_untracked_caller_location(); |
| let location = self.alloc_caller_location_for_span(span); |
| self.write_scalar(location.ptr, dest)?; |
| } |
| |
| sym::min_align_of |
| | sym::pref_align_of |
| | sym::needs_drop |
| | sym::size_of |
| | sym::type_id |
| | sym::type_name |
| | sym::variant_count => { |
| let gid = GlobalId { instance, promoted: None }; |
| let ty = match intrinsic_name { |
| sym::min_align_of | sym::pref_align_of | sym::size_of | sym::variant_count => { |
| self.tcx.types.usize |
| } |
| sym::needs_drop => self.tcx.types.bool, |
| sym::type_id => self.tcx.types.u64, |
| sym::type_name => self.tcx.mk_static_str(), |
| _ => bug!("already checked for nullary intrinsics"), |
| }; |
| let val = self.const_eval(gid, ty)?; |
| self.copy_op(val, dest)?; |
| } |
| |
| sym::ctpop |
| | sym::cttz |
| | sym::cttz_nonzero |
| | sym::ctlz |
| | sym::ctlz_nonzero |
| | sym::bswap |
| | sym::bitreverse => { |
| let ty = substs.type_at(0); |
| let layout_of = self.layout_of(ty)?; |
| let val = self.read_scalar(args[0])?.not_undef()?; |
| let bits = self.force_bits(val, layout_of.size)?; |
| let kind = match layout_of.abi { |
| Abi::Scalar(ref scalar) => scalar.value, |
| _ => span_bug!( |
| self.cur_span(), |
| "{} called on invalid type {:?}", |
| intrinsic_name, |
| ty |
| ), |
| }; |
| let (nonzero, intrinsic_name) = match intrinsic_name { |
| sym::cttz_nonzero => (true, sym::cttz), |
| sym::ctlz_nonzero => (true, sym::ctlz), |
| other => (false, other), |
| }; |
| if nonzero && bits == 0 { |
| throw_ub_format!("`{}_nonzero` called on 0", intrinsic_name); |
| } |
| let out_val = numeric_intrinsic(intrinsic_name, bits, kind)?; |
| self.write_scalar(out_val, dest)?; |
| } |
| sym::wrapping_add |
| | sym::wrapping_sub |
| | sym::wrapping_mul |
| | sym::add_with_overflow |
| | sym::sub_with_overflow |
| | sym::mul_with_overflow => { |
| let lhs = self.read_immediate(args[0])?; |
| let rhs = self.read_immediate(args[1])?; |
| let (bin_op, ignore_overflow) = match intrinsic_name { |
| sym::wrapping_add => (BinOp::Add, true), |
| sym::wrapping_sub => (BinOp::Sub, true), |
| sym::wrapping_mul => (BinOp::Mul, true), |
| sym::add_with_overflow => (BinOp::Add, false), |
| sym::sub_with_overflow => (BinOp::Sub, false), |
| sym::mul_with_overflow => (BinOp::Mul, false), |
| _ => bug!("Already checked for int ops"), |
| }; |
| if ignore_overflow { |
| self.binop_ignore_overflow(bin_op, lhs, rhs, dest)?; |
| } else { |
| self.binop_with_overflow(bin_op, lhs, rhs, dest)?; |
| } |
| } |
| sym::saturating_add | sym::saturating_sub => { |
| let l = self.read_immediate(args[0])?; |
| let r = self.read_immediate(args[1])?; |
| let is_add = intrinsic_name == sym::saturating_add; |
| let (val, overflowed, _ty) = |
| self.overflowing_binary_op(if is_add { BinOp::Add } else { BinOp::Sub }, l, r)?; |
| let val = if overflowed { |
| let num_bits = l.layout.size.bits(); |
| if l.layout.abi.is_signed() { |
| // For signed ints the saturated value depends on the sign of the first |
| // term since the sign of the second term can be inferred from this and |
| // the fact that the operation has overflowed (if either is 0 no |
| // overflow can occur) |
| let first_term: u128 = self.force_bits(l.to_scalar()?, l.layout.size)?; |
| let first_term_positive = first_term & (1 << (num_bits - 1)) == 0; |
| if first_term_positive { |
| // Negative overflow not possible since the positive first term |
| // can only increase an (in range) negative term for addition |
| // or corresponding negated positive term for subtraction |
| Scalar::from_uint( |
| (1u128 << (num_bits - 1)) - 1, // max positive |
| Size::from_bits(num_bits), |
| ) |
| } else { |
| // Positive overflow not possible for similar reason |
| // max negative |
| Scalar::from_uint(1u128 << (num_bits - 1), Size::from_bits(num_bits)) |
| } |
| } else { |
| // unsigned |
| if is_add { |
| // max unsigned |
| Scalar::from_uint( |
| u128::MAX >> (128 - num_bits), |
| Size::from_bits(num_bits), |
| ) |
| } else { |
| // underflow to 0 |
| Scalar::from_uint(0u128, Size::from_bits(num_bits)) |
| } |
| } |
| } else { |
| val |
| }; |
| self.write_scalar(val, dest)?; |
| } |
| sym::discriminant_value => { |
| let place = self.deref_operand(args[0])?; |
| let discr_val = self.read_discriminant(place.into())?.0; |
| self.write_scalar(discr_val, dest)?; |
| } |
| sym::unchecked_shl |
| | sym::unchecked_shr |
| | sym::unchecked_add |
| | sym::unchecked_sub |
| | sym::unchecked_mul |
| | sym::unchecked_div |
| | sym::unchecked_rem => { |
| let l = self.read_immediate(args[0])?; |
| let r = self.read_immediate(args[1])?; |
| let bin_op = match intrinsic_name { |
| sym::unchecked_shl => BinOp::Shl, |
| sym::unchecked_shr => BinOp::Shr, |
| sym::unchecked_add => BinOp::Add, |
| sym::unchecked_sub => BinOp::Sub, |
| sym::unchecked_mul => BinOp::Mul, |
| sym::unchecked_div => BinOp::Div, |
| sym::unchecked_rem => BinOp::Rem, |
| _ => bug!("Already checked for int ops"), |
| }; |
| let (val, overflowed, _ty) = self.overflowing_binary_op(bin_op, l, r)?; |
| if overflowed { |
| let layout = self.layout_of(substs.type_at(0))?; |
| let r_val = self.force_bits(r.to_scalar()?, layout.size)?; |
| if let sym::unchecked_shl | sym::unchecked_shr = intrinsic_name { |
| throw_ub_format!("overflowing shift by {} in `{}`", r_val, intrinsic_name); |
| } else { |
| throw_ub_format!("overflow executing `{}`", intrinsic_name); |
| } |
| } |
| self.write_scalar(val, dest)?; |
| } |
| sym::rotate_left | sym::rotate_right => { |
| // rotate_left: (X << (S % BW)) | (X >> ((BW - S) % BW)) |
| // rotate_right: (X << ((BW - S) % BW)) | (X >> (S % BW)) |
| let layout = self.layout_of(substs.type_at(0))?; |
| let val = self.read_scalar(args[0])?.not_undef()?; |
| let val_bits = self.force_bits(val, layout.size)?; |
| let raw_shift = self.read_scalar(args[1])?.not_undef()?; |
| let raw_shift_bits = self.force_bits(raw_shift, layout.size)?; |
| let width_bits = u128::from(layout.size.bits()); |
| let shift_bits = raw_shift_bits % width_bits; |
| let inv_shift_bits = (width_bits - shift_bits) % width_bits; |
| let result_bits = if intrinsic_name == sym::rotate_left { |
| (val_bits << shift_bits) | (val_bits >> inv_shift_bits) |
| } else { |
| (val_bits >> shift_bits) | (val_bits << inv_shift_bits) |
| }; |
| let truncated_bits = self.truncate(result_bits, layout); |
| let result = Scalar::from_uint(truncated_bits, layout.size); |
| self.write_scalar(result, dest)?; |
| } |
| sym::offset => { |
| let ptr = self.read_scalar(args[0])?.not_undef()?; |
| let offset_count = self.read_scalar(args[1])?.to_machine_isize(self)?; |
| let pointee_ty = substs.type_at(0); |
| |
| let offset_ptr = self.ptr_offset_inbounds(ptr, pointee_ty, offset_count)?; |
| self.write_scalar(offset_ptr, dest)?; |
| } |
| sym::arith_offset => { |
| let ptr = self.read_scalar(args[0])?.not_undef()?; |
| let offset_count = self.read_scalar(args[1])?.to_machine_isize(self)?; |
| let pointee_ty = substs.type_at(0); |
| |
| let pointee_size = i64::try_from(self.layout_of(pointee_ty)?.size.bytes()).unwrap(); |
| let offset_bytes = offset_count.wrapping_mul(pointee_size); |
| let offset_ptr = ptr.ptr_wrapping_signed_offset(offset_bytes, self); |
| self.write_scalar(offset_ptr, dest)?; |
| } |
| sym::ptr_guaranteed_eq | sym::ptr_guaranteed_ne => { |
| // FIXME: return `true` for at least some comparisons where we can reliably |
| // determine the result of runtime (in)equality tests at compile-time. |
| self.write_scalar(Scalar::from_bool(false), dest)?; |
| } |
| sym::ptr_offset_from => { |
| let a = self.read_immediate(args[0])?.to_scalar()?; |
| let b = self.read_immediate(args[1])?.to_scalar()?; |
| |
| // Special case: if both scalars are *equal integers* |
| // and not NULL, we pretend there is an allocation of size 0 right there, |
| // and their offset is 0. (There's never a valid object at NULL, making it an |
| // exception from the exception.) |
| // This is the dual to the special exception for offset-by-0 |
| // in the inbounds pointer offset operation (see the Miri code, `src/operator.rs`). |
| // |
| // Control flow is weird because we cannot early-return (to reach the |
| // `go_to_block` at the end). |
| let done = if a.is_bits() && b.is_bits() { |
| let a = a.to_machine_usize(self)?; |
| let b = b.to_machine_usize(self)?; |
| if a == b && a != 0 { |
| self.write_scalar(Scalar::from_machine_isize(0, self), dest)?; |
| true |
| } else { |
| false |
| } |
| } else { |
| false |
| }; |
| |
| if !done { |
| // General case: we need two pointers. |
| let a = self.force_ptr(a)?; |
| let b = self.force_ptr(b)?; |
| if a.alloc_id != b.alloc_id { |
| throw_ub_format!( |
| "ptr_offset_from cannot compute offset of pointers into different \ |
| allocations.", |
| ); |
| } |
| let usize_layout = self.layout_of(self.tcx.types.usize)?; |
| let isize_layout = self.layout_of(self.tcx.types.isize)?; |
| let a_offset = ImmTy::from_uint(a.offset.bytes(), usize_layout); |
| let b_offset = ImmTy::from_uint(b.offset.bytes(), usize_layout); |
| let (val, _overflowed, _ty) = |
| self.overflowing_binary_op(BinOp::Sub, a_offset, b_offset)?; |
| let pointee_layout = self.layout_of(substs.type_at(0))?; |
| let val = ImmTy::from_scalar(val, isize_layout); |
| let size = ImmTy::from_int(pointee_layout.size.bytes(), isize_layout); |
| self.exact_div(val, size, dest)?; |
| } |
| } |
| |
| sym::transmute => { |
| self.copy_op_transmute(args[0], dest)?; |
| } |
| sym::simd_insert => { |
| let index = u64::from(self.read_scalar(args[1])?.to_u32()?); |
| let elem = args[2]; |
| let input = args[0]; |
| let (len, e_ty) = input.layout.ty.simd_size_and_type(*self.tcx); |
| assert!( |
| index < len, |
| "Index `{}` must be in bounds of vector type `{}`: `[0, {})`", |
| index, |
| e_ty, |
| len |
| ); |
| assert_eq!( |
| input.layout, dest.layout, |
| "Return type `{}` must match vector type `{}`", |
| dest.layout.ty, input.layout.ty |
| ); |
| assert_eq!( |
| elem.layout.ty, e_ty, |
| "Scalar element type `{}` must match vector element type `{}`", |
| elem.layout.ty, e_ty |
| ); |
| |
| for i in 0..len { |
| let place = self.place_index(dest, i)?; |
| let value = if i == index { elem } else { self.operand_index(input, i)? }; |
| self.copy_op(value, place)?; |
| } |
| } |
| sym::simd_extract => { |
| let index = u64::from(self.read_scalar(args[1])?.to_u32()?); |
| let (len, e_ty) = args[0].layout.ty.simd_size_and_type(*self.tcx); |
| assert!( |
| index < len, |
| "index `{}` is out-of-bounds of vector type `{}` with length `{}`", |
| index, |
| e_ty, |
| len |
| ); |
| assert_eq!( |
| e_ty, dest.layout.ty, |
| "Return type `{}` must match vector element type `{}`", |
| dest.layout.ty, e_ty |
| ); |
| self.copy_op(self.operand_index(args[0], index)?, dest)?; |
| } |
| sym::likely | sym::unlikely => { |
| // These just return their argument |
| self.copy_op(args[0], dest)?; |
| } |
| // FIXME(#73156): Handle source code coverage in const eval |
| sym::count_code_region |
| | sym::coverage_counter_add |
| | sym::coverage_counter_subtract |
| | sym::coverage_unreachable => (), |
| _ => return Ok(false), |
| } |
| |
| self.dump_place(*dest); |
| self.go_to_block(ret); |
| Ok(true) |
| } |
| |
| pub fn exact_div( |
| &mut self, |
| a: ImmTy<'tcx, M::PointerTag>, |
| b: ImmTy<'tcx, M::PointerTag>, |
| dest: PlaceTy<'tcx, M::PointerTag>, |
| ) -> InterpResult<'tcx> { |
| // Performs an exact division, resulting in undefined behavior where |
| // `x % y != 0` or `y == 0` or `x == T::MIN && y == -1`. |
| // First, check x % y != 0 (or if that computation overflows). |
| let (res, overflow, _ty) = self.overflowing_binary_op(BinOp::Rem, a, b)?; |
| if overflow || res.assert_bits(a.layout.size) != 0 { |
| // Then, check if `b` is -1, which is the "MIN / -1" case. |
| let minus1 = Scalar::from_int(-1, dest.layout.size); |
| let b_scalar = b.to_scalar().unwrap(); |
| if b_scalar == minus1 { |
| throw_ub_format!("exact_div: result of dividing MIN by -1 cannot be represented") |
| } else { |
| throw_ub_format!("exact_div: {} cannot be divided by {} without remainder", a, b,) |
| } |
| } |
| // `Rem` says this is all right, so we can let `Div` do its job. |
| self.binop_ignore_overflow(BinOp::Div, a, b, dest) |
| } |
| |
| /// Offsets a pointer by some multiple of its type, returning an error if the pointer leaves its |
| /// allocation. For integer pointers, we consider each of them their own tiny allocation of size |
| /// 0, so offset-by-0 (and only 0) is okay -- except that NULL cannot be offset by _any_ value. |
| pub fn ptr_offset_inbounds( |
| &self, |
| ptr: Scalar<M::PointerTag>, |
| pointee_ty: Ty<'tcx>, |
| offset_count: i64, |
| ) -> InterpResult<'tcx, Scalar<M::PointerTag>> { |
| // We cannot overflow i64 as a type's size must be <= isize::MAX. |
| let pointee_size = i64::try_from(self.layout_of(pointee_ty)?.size.bytes()).unwrap(); |
| // The computed offset, in bytes, cannot overflow an isize. |
| let offset_bytes = |
| offset_count.checked_mul(pointee_size).ok_or(err_ub!(PointerArithOverflow))?; |
| // The offset being in bounds cannot rely on "wrapping around" the address space. |
| // So, first rule out overflows in the pointer arithmetic. |
| let offset_ptr = ptr.ptr_signed_offset(offset_bytes, self)?; |
| // ptr and offset_ptr must be in bounds of the same allocated object. This means all of the |
| // memory between these pointers must be accessible. Note that we do not require the |
| // pointers to be properly aligned (unlike a read/write operation). |
| let min_ptr = if offset_bytes >= 0 { ptr } else { offset_ptr }; |
| let size: u64 = uabs(offset_bytes); |
| // This call handles checking for integer/NULL pointers. |
| self.memory.check_ptr_access_align( |
| min_ptr, |
| Size::from_bytes(size), |
| None, |
| CheckInAllocMsg::InboundsTest, |
| )?; |
| Ok(offset_ptr) |
| } |
| } |
