| //! 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 syntax_pos::symbol::{sym, Symbol}; |
| use syntax_pos::Span; |
| use rustc::ty; |
| use rustc::ty::layout::{LayoutOf, Primitive, Size}; |
| use rustc::ty::subst::SubstsRef; |
| use rustc::hir::def_id::DefId; |
| use rustc::ty::TyCtxt; |
| use rustc::mir::{ |
| self, BinOp, |
| interpret::{InterpResult, Scalar, GlobalId, ConstValue} |
| }; |
| |
| use super::{ |
| Machine, PlaceTy, OpTy, InterpCx, ImmTy, |
| }; |
| |
| 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 - size.bits() as u128; |
| let bits_out = match name { |
| sym::ctpop => bits.count_ones() as u128, |
| sym::ctlz => bits.leading_zeros() as u128 - extra, |
| sym::cttz => (bits << extra).trailing_zeros() as u128 - 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, &'tcx ty::Const<'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); |
| tcx.mk_const(ty::Const { |
| val: ty::ConstKind::Value(ConstValue::Slice { |
| data: alloc, |
| start: 0, |
| end: alloc.len(), |
| }), |
| ty: tcx.mk_static_str(), |
| }) |
| }, |
| sym::needs_drop => ty::Const::from_bool(tcx, 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!(), |
| }; |
| ty::Const::from_usize(tcx, n) |
| }, |
| sym::type_id => ty::Const::from_bits( |
| tcx, |
| tcx.type_id_hash(tp_ty).into(), |
| param_env.and(tcx.types.u64), |
| ), |
| other => bug!("`{}` is not a zero arg intrinsic", other), |
| }) |
| } |
| |
| impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> { |
| /// Returns `true` if emulation happened. |
| pub fn emulate_intrinsic( |
| &mut self, |
| span: Span, |
| 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()); |
| |
| // We currently do not handle any intrinsics that are *allowed* to diverge, |
| // but `transmute` could lack a return place in case of UB. |
| let (dest, ret) = match ret { |
| Some(p) => p, |
| None => match intrinsic_name { |
| sym::transmute => throw_ub!(Unreachable), |
| _ => return Ok(false), |
| } |
| }; |
| |
| // Keep the patterns in this match ordered the same as the list in |
| // `src/librustc/ty/constness.rs` |
| match intrinsic_name { |
| sym::caller_location => { |
| let span = self.find_closest_untracked_caller_location().unwrap_or(span); |
| 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 => { |
| let gid = GlobalId { |
| instance, |
| promoted: None, |
| }; |
| let val = self.tcx.const_eval(self.param_env.and(gid))?; |
| let val = self.eval_const_to_op(val, None)?; |
| 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 { |
| ty::layout::Abi::Scalar(ref scalar) => scalar.value, |
| _ => throw_unsup!(TypeNotPrimitive(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_value() >> (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::unchecked_shl | sym::unchecked_shr => { |
| 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, |
| _ => 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)?; |
| throw_ub_format!("Overflowing shift by {} in `{}`", r_val, 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 = layout.size.bits() as u128; |
| 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::ptr_offset_from => { |
| let isize_layout = self.layout_of(self.tcx.types.isize)?; |
| 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_int(0, isize_layout.size), 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 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.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_field(dest, i)?; |
| let value = if i == index { |
| elem |
| } else { |
| self.operand_field(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.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_field(args[0], index)?, dest)?; |
| } |
| _ => return Ok(false), |
| } |
| |
| self.dump_place(*dest); |
| self.go_to_block(ret); |
| Ok(true) |
| } |
| |
| /// "Intercept" a function call to a panic-related function |
| /// because we have something special to do for it. |
| /// Returns `true` if an intercept happened. |
| pub fn hook_panic_fn( |
| &mut self, |
| instance: ty::Instance<'tcx>, |
| args: &[OpTy<'tcx, M::PointerTag>], |
| _ret: Option<(PlaceTy<'tcx, M::PointerTag>, mir::BasicBlock)>, |
| ) -> InterpResult<'tcx, bool> { |
| let def_id = instance.def_id(); |
| if Some(def_id) == self.tcx.lang_items().panic_fn() { |
| // &'static str, &core::panic::Location { &'static str, u32, u32 } |
| assert!(args.len() == 2); |
| |
| let msg_place = self.deref_operand(args[0])?; |
| let msg = Symbol::intern(self.read_str(msg_place)?); |
| |
| let location = self.deref_operand(args[1])?; |
| let (file, line, col) = ( |
| self.mplace_field(location, 0)?, |
| self.mplace_field(location, 1)?, |
| self.mplace_field(location, 2)?, |
| ); |
| |
| let file_place = self.deref_operand(file.into())?; |
| let file = Symbol::intern(self.read_str(file_place)?); |
| let line = self.read_scalar(line.into())?.to_u32()?; |
| let col = self.read_scalar(col.into())?.to_u32()?; |
| throw_panic!(Panic { msg, file, line, col }) |
| } else if Some(def_id) == self.tcx.lang_items().begin_panic_fn() { |
| assert!(args.len() == 2); |
| // &'static str, &(&'static str, u32, u32) |
| let msg = args[0]; |
| let place = self.deref_operand(args[1])?; |
| let (file, line, col) = ( |
| self.mplace_field(place, 0)?, |
| self.mplace_field(place, 1)?, |
| self.mplace_field(place, 2)?, |
| ); |
| |
| let msg_place = self.deref_operand(msg.into())?; |
| let msg = Symbol::intern(self.read_str(msg_place)?); |
| let file_place = self.deref_operand(file.into())?; |
| let file = Symbol::intern(self.read_str(file_place)?); |
| let line = self.read_scalar(line.into())?.to_u32()?; |
| let col = self.read_scalar(col.into())?.to_u32()?; |
| throw_panic!(Panic { msg, file, line, col }) |
| } else { |
| return Ok(false); |
| } |
| } |
| |
| 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_value() && y == -1`. |
| // First, check x % y != 0. |
| if self.binary_op(BinOp::Rem, a, b)?.to_bits()? != 0 { |
| // Then, check if `b` is -1, which is the "min_value / -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, |
| ) |
| } |
| } |
| self.binop_ignore_overflow(BinOp::Div, a, b, dest) |
| } |
| } |
