498 lines
22 KiB
Rust
498 lines
22 KiB
Rust
//! Intrinsics and other functions that the miri engine executes without
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//! looking at their MIR. Intrinsics/functions supported here are shared by CTFE
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//! and miri.
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use std::convert::TryFrom;
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use rustc_hir::def_id::DefId;
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use rustc_middle::mir::{
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self,
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interpret::{uabs, ConstValue, GlobalId, InterpResult, Scalar},
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BinOp,
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};
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use rustc_middle::ty;
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use rustc_middle::ty::subst::SubstsRef;
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use rustc_middle::ty::{Ty, TyCtxt};
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use rustc_span::symbol::{sym, Symbol};
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use rustc_target::abi::{Abi, LayoutOf as _, Primitive, Size};
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use super::{
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util::ensure_monomorphic_enough, CheckInAllocMsg, ImmTy, InterpCx, Machine, OpTy, PlaceTy,
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};
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mod caller_location;
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mod type_name;
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fn numeric_intrinsic<'tcx, Tag>(
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name: Symbol,
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bits: u128,
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kind: Primitive,
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) -> InterpResult<'tcx, Scalar<Tag>> {
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let size = match kind {
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Primitive::Int(integer, _) => integer.size(),
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_ => bug!("invalid `{}` argument: {:?}", name, bits),
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};
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let extra = 128 - u128::from(size.bits());
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let bits_out = match name {
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sym::ctpop => u128::from(bits.count_ones()),
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sym::ctlz => u128::from(bits.leading_zeros()) - extra,
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sym::cttz => u128::from((bits << extra).trailing_zeros()) - extra,
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sym::bswap => (bits << extra).swap_bytes(),
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sym::bitreverse => (bits << extra).reverse_bits(),
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_ => bug!("not a numeric intrinsic: {}", name),
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};
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Ok(Scalar::from_uint(bits_out, size))
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}
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/// The logic for all nullary intrinsics is implemented here. These intrinsics don't get evaluated
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/// inside an `InterpCx` and instead have their value computed directly from rustc internal info.
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crate fn eval_nullary_intrinsic<'tcx>(
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tcx: TyCtxt<'tcx>,
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param_env: ty::ParamEnv<'tcx>,
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def_id: DefId,
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substs: SubstsRef<'tcx>,
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) -> InterpResult<'tcx, ConstValue<'tcx>> {
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let tp_ty = substs.type_at(0);
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let name = tcx.item_name(def_id);
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Ok(match name {
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sym::type_name => {
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ensure_monomorphic_enough(tcx, tp_ty)?;
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let alloc = type_name::alloc_type_name(tcx, tp_ty);
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ConstValue::Slice { data: alloc, start: 0, end: alloc.len() }
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}
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sym::needs_drop => ConstValue::from_bool(tp_ty.needs_drop(tcx, param_env)),
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sym::size_of | sym::min_align_of | sym::pref_align_of => {
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let layout = tcx.layout_of(param_env.and(tp_ty)).map_err(|e| err_inval!(Layout(e)))?;
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let n = match name {
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sym::pref_align_of => layout.align.pref.bytes(),
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sym::min_align_of => layout.align.abi.bytes(),
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sym::size_of => layout.size.bytes(),
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_ => bug!(),
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};
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ConstValue::from_machine_usize(n, &tcx)
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}
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sym::type_id => {
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ensure_monomorphic_enough(tcx, tp_ty)?;
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ConstValue::from_u64(tcx.type_id_hash(tp_ty))
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}
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sym::variant_count => {
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if let ty::Adt(ref adt, _) = tp_ty.kind() {
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ConstValue::from_machine_usize(adt.variants.len() as u64, &tcx)
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} else {
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ConstValue::from_machine_usize(0u64, &tcx)
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}
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}
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other => bug!("`{}` is not a zero arg intrinsic", other),
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})
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}
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impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
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/// Returns `true` if emulation happened.
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/// Here we implement the intrinsics that are common to all Miri instances; individual machines can add their own
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/// intrinsic handling.
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pub fn emulate_intrinsic(
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&mut self,
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instance: ty::Instance<'tcx>,
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args: &[OpTy<'tcx, M::PointerTag>],
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ret: Option<(PlaceTy<'tcx, M::PointerTag>, mir::BasicBlock)>,
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) -> InterpResult<'tcx, bool> {
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let substs = instance.substs;
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let intrinsic_name = self.tcx.item_name(instance.def_id());
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// First handle intrinsics without return place.
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let (dest, ret) = match ret {
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None => match intrinsic_name {
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sym::transmute => throw_ub_format!("transmuting to uninhabited type"),
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sym::unreachable => throw_ub!(Unreachable),
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sym::abort => M::abort(self)?,
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// Unsupported diverging intrinsic.
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_ => return Ok(false),
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},
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Some(p) => p,
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};
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// Keep the patterns in this match ordered the same as the list in
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// `src/librustc_middle/ty/constness.rs`
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match intrinsic_name {
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sym::caller_location => {
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let span = self.find_closest_untracked_caller_location();
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let location = self.alloc_caller_location_for_span(span);
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self.write_scalar(location.ptr, dest)?;
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}
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sym::min_align_of_val | sym::size_of_val => {
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let place = self.deref_operand(args[0])?;
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let (size, align) = self
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.size_and_align_of(place.meta, place.layout)?
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.ok_or_else(|| err_unsup_format!("`extern type` does not have known layout"))?;
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let result = match intrinsic_name {
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sym::min_align_of_val => align.bytes(),
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sym::size_of_val => size.bytes(),
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_ => bug!(),
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};
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self.write_scalar(Scalar::from_machine_usize(result, self), dest)?;
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}
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sym::min_align_of
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| sym::pref_align_of
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| sym::needs_drop
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| sym::size_of
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| sym::type_id
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| sym::type_name
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| sym::variant_count => {
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let gid = GlobalId { instance, promoted: None };
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let ty = match intrinsic_name {
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sym::min_align_of | sym::pref_align_of | sym::size_of | sym::variant_count => {
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self.tcx.types.usize
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}
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sym::needs_drop => self.tcx.types.bool,
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sym::type_id => self.tcx.types.u64,
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sym::type_name => self.tcx.mk_static_str(),
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_ => bug!("already checked for nullary intrinsics"),
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};
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let val = self.const_eval(gid, ty)?;
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self.copy_op(val, dest)?;
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}
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sym::ctpop
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| sym::cttz
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| sym::cttz_nonzero
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| sym::ctlz
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| sym::ctlz_nonzero
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| sym::bswap
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| sym::bitreverse => {
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let ty = substs.type_at(0);
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let layout_of = self.layout_of(ty)?;
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let val = self.read_scalar(args[0])?.check_init()?;
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let bits = self.force_bits(val, layout_of.size)?;
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let kind = match layout_of.abi {
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Abi::Scalar(ref scalar) => scalar.value,
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_ => span_bug!(
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self.cur_span(),
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"{} called on invalid type {:?}",
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intrinsic_name,
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ty
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),
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};
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let (nonzero, intrinsic_name) = match intrinsic_name {
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sym::cttz_nonzero => (true, sym::cttz),
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sym::ctlz_nonzero => (true, sym::ctlz),
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other => (false, other),
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};
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if nonzero && bits == 0 {
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throw_ub_format!("`{}_nonzero` called on 0", intrinsic_name);
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}
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let out_val = numeric_intrinsic(intrinsic_name, bits, kind)?;
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self.write_scalar(out_val, dest)?;
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}
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sym::wrapping_add
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| sym::wrapping_sub
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| sym::wrapping_mul
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| sym::add_with_overflow
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| sym::sub_with_overflow
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| sym::mul_with_overflow => {
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let lhs = self.read_immediate(args[0])?;
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let rhs = self.read_immediate(args[1])?;
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let (bin_op, ignore_overflow) = match intrinsic_name {
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sym::wrapping_add => (BinOp::Add, true),
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sym::wrapping_sub => (BinOp::Sub, true),
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sym::wrapping_mul => (BinOp::Mul, true),
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sym::add_with_overflow => (BinOp::Add, false),
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sym::sub_with_overflow => (BinOp::Sub, false),
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sym::mul_with_overflow => (BinOp::Mul, false),
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_ => bug!("Already checked for int ops"),
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};
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if ignore_overflow {
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self.binop_ignore_overflow(bin_op, lhs, rhs, dest)?;
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} else {
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self.binop_with_overflow(bin_op, lhs, rhs, dest)?;
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}
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}
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sym::saturating_add | sym::saturating_sub => {
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let l = self.read_immediate(args[0])?;
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let r = self.read_immediate(args[1])?;
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let is_add = intrinsic_name == sym::saturating_add;
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let (val, overflowed, _ty) =
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self.overflowing_binary_op(if is_add { BinOp::Add } else { BinOp::Sub }, l, r)?;
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let val = if overflowed {
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let num_bits = l.layout.size.bits();
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if l.layout.abi.is_signed() {
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// For signed ints the saturated value depends on the sign of the first
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// term since the sign of the second term can be inferred from this and
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// the fact that the operation has overflowed (if either is 0 no
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// overflow can occur)
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let first_term: u128 = self.force_bits(l.to_scalar()?, l.layout.size)?;
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let first_term_positive = first_term & (1 << (num_bits - 1)) == 0;
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if first_term_positive {
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// Negative overflow not possible since the positive first term
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// can only increase an (in range) negative term for addition
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// or corresponding negated positive term for subtraction
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Scalar::from_uint(
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(1u128 << (num_bits - 1)) - 1, // max positive
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Size::from_bits(num_bits),
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)
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} else {
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// Positive overflow not possible for similar reason
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// max negative
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Scalar::from_uint(1u128 << (num_bits - 1), Size::from_bits(num_bits))
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}
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} else {
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// unsigned
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if is_add {
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// max unsigned
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Scalar::from_uint(
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u128::MAX >> (128 - num_bits),
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Size::from_bits(num_bits),
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)
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} else {
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// underflow to 0
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Scalar::from_uint(0u128, Size::from_bits(num_bits))
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}
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}
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} else {
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val
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};
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self.write_scalar(val, dest)?;
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}
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sym::discriminant_value => {
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let place = self.deref_operand(args[0])?;
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let discr_val = self.read_discriminant(place.into())?.0;
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self.write_scalar(discr_val, dest)?;
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}
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sym::unchecked_shl
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| sym::unchecked_shr
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| sym::unchecked_add
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| sym::unchecked_sub
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| sym::unchecked_mul
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| sym::unchecked_div
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| sym::unchecked_rem => {
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let l = self.read_immediate(args[0])?;
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let r = self.read_immediate(args[1])?;
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let bin_op = match intrinsic_name {
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sym::unchecked_shl => BinOp::Shl,
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sym::unchecked_shr => BinOp::Shr,
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sym::unchecked_add => BinOp::Add,
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sym::unchecked_sub => BinOp::Sub,
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sym::unchecked_mul => BinOp::Mul,
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sym::unchecked_div => BinOp::Div,
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sym::unchecked_rem => BinOp::Rem,
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_ => bug!("Already checked for int ops"),
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};
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let (val, overflowed, _ty) = self.overflowing_binary_op(bin_op, l, r)?;
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if overflowed {
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let layout = self.layout_of(substs.type_at(0))?;
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let r_val = self.force_bits(r.to_scalar()?, layout.size)?;
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if let sym::unchecked_shl | sym::unchecked_shr = intrinsic_name {
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throw_ub_format!("overflowing shift by {} in `{}`", r_val, intrinsic_name);
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} else {
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throw_ub_format!("overflow executing `{}`", intrinsic_name);
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}
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}
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self.write_scalar(val, dest)?;
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}
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sym::rotate_left | sym::rotate_right => {
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// rotate_left: (X << (S % BW)) | (X >> ((BW - S) % BW))
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// rotate_right: (X << ((BW - S) % BW)) | (X >> (S % BW))
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let layout = self.layout_of(substs.type_at(0))?;
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let val = self.read_scalar(args[0])?.check_init()?;
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let val_bits = self.force_bits(val, layout.size)?;
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let raw_shift = self.read_scalar(args[1])?.check_init()?;
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let raw_shift_bits = self.force_bits(raw_shift, layout.size)?;
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let width_bits = u128::from(layout.size.bits());
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let shift_bits = raw_shift_bits % width_bits;
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let inv_shift_bits = (width_bits - shift_bits) % width_bits;
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let result_bits = if intrinsic_name == sym::rotate_left {
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(val_bits << shift_bits) | (val_bits >> inv_shift_bits)
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} else {
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(val_bits >> shift_bits) | (val_bits << inv_shift_bits)
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};
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let truncated_bits = self.truncate(result_bits, layout);
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let result = Scalar::from_uint(truncated_bits, layout.size);
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self.write_scalar(result, dest)?;
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}
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sym::offset => {
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let ptr = self.read_scalar(args[0])?.check_init()?;
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let offset_count = self.read_scalar(args[1])?.to_machine_isize(self)?;
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let pointee_ty = substs.type_at(0);
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let offset_ptr = self.ptr_offset_inbounds(ptr, pointee_ty, offset_count)?;
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self.write_scalar(offset_ptr, dest)?;
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}
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sym::arith_offset => {
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let ptr = self.read_scalar(args[0])?.check_init()?;
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let offset_count = self.read_scalar(args[1])?.to_machine_isize(self)?;
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let pointee_ty = substs.type_at(0);
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let pointee_size = i64::try_from(self.layout_of(pointee_ty)?.size.bytes()).unwrap();
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let offset_bytes = offset_count.wrapping_mul(pointee_size);
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let offset_ptr = ptr.ptr_wrapping_signed_offset(offset_bytes, self);
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self.write_scalar(offset_ptr, dest)?;
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}
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sym::ptr_offset_from => {
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let a = self.read_immediate(args[0])?.to_scalar()?;
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let b = self.read_immediate(args[1])?.to_scalar()?;
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// Special case: if both scalars are *equal integers*
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// and not NULL, we pretend there is an allocation of size 0 right there,
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// and their offset is 0. (There's never a valid object at NULL, making it an
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// exception from the exception.)
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// This is the dual to the special exception for offset-by-0
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// in the inbounds pointer offset operation (see the Miri code, `src/operator.rs`).
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//
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// Control flow is weird because we cannot early-return (to reach the
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// `go_to_block` at the end).
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let done = if a.is_bits() && b.is_bits() {
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let a = a.to_machine_usize(self)?;
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let b = b.to_machine_usize(self)?;
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if a == b && a != 0 {
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self.write_scalar(Scalar::from_machine_isize(0, self), dest)?;
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true
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} else {
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false
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}
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} else {
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false
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};
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if !done {
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// General case: we need two pointers.
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let a = self.force_ptr(a)?;
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let b = self.force_ptr(b)?;
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if a.alloc_id != b.alloc_id {
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throw_ub_format!(
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"ptr_offset_from cannot compute offset of pointers into different \
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allocations.",
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);
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}
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let usize_layout = self.layout_of(self.tcx.types.usize)?;
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let isize_layout = self.layout_of(self.tcx.types.isize)?;
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let a_offset = ImmTy::from_uint(a.offset.bytes(), usize_layout);
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let b_offset = ImmTy::from_uint(b.offset.bytes(), usize_layout);
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let (val, _overflowed, _ty) =
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self.overflowing_binary_op(BinOp::Sub, a_offset, b_offset)?;
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let pointee_layout = self.layout_of(substs.type_at(0))?;
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let val = ImmTy::from_scalar(val, isize_layout);
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let size = ImmTy::from_int(pointee_layout.size.bytes(), isize_layout);
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self.exact_div(val, size, dest)?;
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}
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}
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sym::transmute => {
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self.copy_op_transmute(args[0], dest)?;
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}
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sym::simd_insert => {
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let index = u64::from(self.read_scalar(args[1])?.to_u32()?);
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let elem = args[2];
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let input = args[0];
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let (len, e_ty) = input.layout.ty.simd_size_and_type(*self.tcx);
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assert!(
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index < len,
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"Index `{}` must be in bounds of vector type `{}`: `[0, {})`",
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index,
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e_ty,
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len
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);
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assert_eq!(
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input.layout, dest.layout,
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"Return type `{}` must match vector type `{}`",
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dest.layout.ty, input.layout.ty
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);
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assert_eq!(
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elem.layout.ty, e_ty,
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"Scalar element type `{}` must match vector element type `{}`",
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elem.layout.ty, e_ty
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);
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for i in 0..len {
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let place = self.place_index(dest, i)?;
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let value = if i == index { elem } else { self.operand_index(input, i)? };
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self.copy_op(value, place)?;
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}
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}
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sym::simd_extract => {
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let index = u64::from(self.read_scalar(args[1])?.to_u32()?);
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let (len, e_ty) = args[0].layout.ty.simd_size_and_type(*self.tcx);
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assert!(
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index < len,
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"index `{}` is out-of-bounds of vector type `{}` with length `{}`",
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index,
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e_ty,
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len
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);
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assert_eq!(
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e_ty, dest.layout.ty,
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"Return type `{}` must match vector element type `{}`",
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dest.layout.ty, e_ty
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);
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self.copy_op(self.operand_index(args[0], index)?, dest)?;
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}
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sym::likely | sym::unlikely => {
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// These just return their argument
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self.copy_op(args[0], dest)?;
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}
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_ => return Ok(false),
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}
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trace!("{:?}", self.dump_place(*dest));
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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)
|
|
}
|
|
}
|