1 //! Intrinsics and other functions that the miri engine executes without
2 //! looking at their MIR. Intrinsics/functions supported here are shared by CTFE
5 use std::convert::TryFrom;
7 use rustc_hir::def_id::DefId;
8 use rustc_middle::mir::{
10 interpret::{ConstValue, GlobalId, InterpResult, PointerArithmetic, Scalar},
14 use rustc_middle::ty::layout::LayoutOf as _;
15 use rustc_middle::ty::subst::SubstsRef;
16 use rustc_middle::ty::{Ty, TyCtxt};
17 use rustc_span::symbol::{sym, Symbol};
18 use rustc_target::abi::{Abi, Align, Primitive, Size};
21 util::ensure_monomorphic_enough, CheckInAllocMsg, ImmTy, InterpCx, Machine, OpTy, PlaceTy,
28 fn numeric_intrinsic<Prov>(name: Symbol, bits: u128, kind: Primitive) -> Scalar<Prov> {
29 let size = match kind {
30 Primitive::Int(integer, _) => integer.size(),
31 _ => bug!("invalid `{}` argument: {:?}", name, bits),
33 let extra = 128 - u128::from(size.bits());
34 let bits_out = match name {
35 sym::ctpop => u128::from(bits.count_ones()),
36 sym::ctlz => u128::from(bits.leading_zeros()) - extra,
37 sym::cttz => u128::from((bits << extra).trailing_zeros()) - extra,
38 sym::bswap => (bits << extra).swap_bytes(),
39 sym::bitreverse => (bits << extra).reverse_bits(),
40 _ => bug!("not a numeric intrinsic: {}", name),
42 Scalar::from_uint(bits_out, size)
45 /// The logic for all nullary intrinsics is implemented here. These intrinsics don't get evaluated
46 /// inside an `InterpCx` and instead have their value computed directly from rustc internal info.
47 pub(crate) fn eval_nullary_intrinsic<'tcx>(
49 param_env: ty::ParamEnv<'tcx>,
51 substs: SubstsRef<'tcx>,
52 ) -> InterpResult<'tcx, ConstValue<'tcx>> {
53 let tp_ty = substs.type_at(0);
54 let name = tcx.item_name(def_id);
57 ensure_monomorphic_enough(tcx, tp_ty)?;
58 let alloc = type_name::alloc_type_name(tcx, tp_ty);
59 ConstValue::Slice { data: alloc, start: 0, end: alloc.inner().len() }
62 ensure_monomorphic_enough(tcx, tp_ty)?;
63 ConstValue::from_bool(tp_ty.needs_drop(tcx, param_env))
65 sym::pref_align_of => {
66 // Correctly handles non-monomorphic calls, so there is no need for ensure_monomorphic_enough.
67 let layout = tcx.layout_of(param_env.and(tp_ty)).map_err(|e| err_inval!(Layout(e)))?;
68 ConstValue::from_machine_usize(layout.align.pref.bytes(), &tcx)
71 ensure_monomorphic_enough(tcx, tp_ty)?;
72 ConstValue::from_u64(tcx.type_id_hash(tp_ty))
74 sym::variant_count => match tp_ty.kind() {
75 // Correctly handles non-monomorphic calls, so there is no need for ensure_monomorphic_enough.
76 ty::Adt(ref adt, _) => {
77 ConstValue::from_machine_usize(adt.variants().len() as u64, &tcx)
84 | ty::Infer(_) => throw_inval!(TooGeneric),
100 | ty::Generator(_, _, _)
101 | ty::GeneratorWitness(_)
104 | ty::Error(_) => ConstValue::from_machine_usize(0u64, &tcx),
106 other => bug!("`{}` is not a zero arg intrinsic", other),
110 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
111 /// Returns `true` if emulation happened.
112 /// Here we implement the intrinsics that are common to all Miri instances; individual machines can add their own
113 /// intrinsic handling.
114 pub fn emulate_intrinsic(
116 instance: ty::Instance<'tcx>,
117 args: &[OpTy<'tcx, M::Provenance>],
118 dest: &PlaceTy<'tcx, M::Provenance>,
119 ret: Option<mir::BasicBlock>,
120 ) -> InterpResult<'tcx, bool> {
121 let substs = instance.substs;
122 let intrinsic_name = self.tcx.item_name(instance.def_id());
124 // First handle intrinsics without return place.
125 let ret = match ret {
126 None => match intrinsic_name {
127 sym::transmute => throw_ub_format!("transmuting to uninhabited type"),
128 sym::abort => M::abort(self, "the program aborted execution".to_owned())?,
129 // Unsupported diverging intrinsic.
130 _ => return Ok(false),
135 match intrinsic_name {
136 sym::caller_location => {
137 let span = self.find_closest_untracked_caller_location();
138 let location = self.alloc_caller_location_for_span(span);
139 self.write_immediate(location.to_ref(self), dest)?;
142 sym::min_align_of_val | sym::size_of_val => {
143 // Avoid `deref_operand` -- this is not a deref, the ptr does not have to be
145 let place = self.ref_to_mplace(&self.read_immediate(&args[0])?)?;
146 let (size, align) = self
147 .size_and_align_of_mplace(&place)?
148 .ok_or_else(|| err_unsup_format!("`extern type` does not have known layout"))?;
150 let result = match intrinsic_name {
151 sym::min_align_of_val => align.bytes(),
152 sym::size_of_val => size.bytes(),
156 self.write_scalar(Scalar::from_machine_usize(result, self), dest)?;
163 | sym::variant_count => {
164 let gid = GlobalId { instance, promoted: None };
165 let ty = match intrinsic_name {
166 sym::pref_align_of | sym::variant_count => self.tcx.types.usize,
167 sym::needs_drop => self.tcx.types.bool,
168 sym::type_id => self.tcx.types.u64,
169 sym::type_name => self.tcx.mk_static_str(),
173 self.tcx.const_eval_global_id(self.param_env, gid, Some(self.tcx.span))?;
174 let val = self.const_val_to_op(val, ty, Some(dest.layout))?;
175 self.copy_op(&val, dest, /*allow_transmute*/ false)?;
184 | sym::bitreverse => {
185 let ty = substs.type_at(0);
186 let layout_of = self.layout_of(ty)?;
187 let val = self.read_scalar(&args[0])?.check_init()?;
188 let bits = val.to_bits(layout_of.size)?;
189 let kind = match layout_of.abi {
190 Abi::Scalar(scalar) => scalar.primitive(),
193 "{} called on invalid type {:?}",
198 let (nonzero, intrinsic_name) = match intrinsic_name {
199 sym::cttz_nonzero => (true, sym::cttz),
200 sym::ctlz_nonzero => (true, sym::ctlz),
201 other => (false, other),
203 if nonzero && bits == 0 {
204 throw_ub_format!("`{}_nonzero` called on 0", intrinsic_name);
206 let out_val = numeric_intrinsic(intrinsic_name, bits, kind);
207 self.write_scalar(out_val, dest)?;
209 sym::add_with_overflow | sym::sub_with_overflow | sym::mul_with_overflow => {
210 let lhs = self.read_immediate(&args[0])?;
211 let rhs = self.read_immediate(&args[1])?;
212 let bin_op = match intrinsic_name {
213 sym::add_with_overflow => BinOp::Add,
214 sym::sub_with_overflow => BinOp::Sub,
215 sym::mul_with_overflow => BinOp::Mul,
218 self.binop_with_overflow(
219 bin_op, /*force_overflow_checks*/ true, &lhs, &rhs, dest,
222 sym::saturating_add | sym::saturating_sub => {
223 let l = self.read_immediate(&args[0])?;
224 let r = self.read_immediate(&args[1])?;
225 let val = self.saturating_arith(
226 if intrinsic_name == sym::saturating_add { BinOp::Add } else { BinOp::Sub },
230 self.write_scalar(val, dest)?;
232 sym::discriminant_value => {
233 let place = self.deref_operand(&args[0])?;
234 let discr_val = self.read_discriminant(&place.into())?.0;
235 self.write_scalar(discr_val, dest)?;
243 | sym::unchecked_rem => {
244 let l = self.read_immediate(&args[0])?;
245 let r = self.read_immediate(&args[1])?;
246 let bin_op = match intrinsic_name {
247 sym::unchecked_shl => BinOp::Shl,
248 sym::unchecked_shr => BinOp::Shr,
249 sym::unchecked_add => BinOp::Add,
250 sym::unchecked_sub => BinOp::Sub,
251 sym::unchecked_mul => BinOp::Mul,
252 sym::unchecked_div => BinOp::Div,
253 sym::unchecked_rem => BinOp::Rem,
256 let (val, overflowed, _ty) = self.overflowing_binary_op(bin_op, &l, &r)?;
258 let layout = self.layout_of(substs.type_at(0))?;
259 let r_val = r.to_scalar()?.to_bits(layout.size)?;
260 if let sym::unchecked_shl | sym::unchecked_shr = intrinsic_name {
261 throw_ub_format!("overflowing shift by {} in `{}`", r_val, intrinsic_name);
263 throw_ub_format!("overflow executing `{}`", intrinsic_name);
266 self.write_scalar(val, dest)?;
268 sym::rotate_left | sym::rotate_right => {
269 // rotate_left: (X << (S % BW)) | (X >> ((BW - S) % BW))
270 // rotate_right: (X << ((BW - S) % BW)) | (X >> (S % BW))
271 let layout = self.layout_of(substs.type_at(0))?;
272 let val = self.read_scalar(&args[0])?.check_init()?;
273 let val_bits = val.to_bits(layout.size)?;
274 let raw_shift = self.read_scalar(&args[1])?.check_init()?;
275 let raw_shift_bits = raw_shift.to_bits(layout.size)?;
276 let width_bits = u128::from(layout.size.bits());
277 let shift_bits = raw_shift_bits % width_bits;
278 let inv_shift_bits = (width_bits - shift_bits) % width_bits;
279 let result_bits = if intrinsic_name == sym::rotate_left {
280 (val_bits << shift_bits) | (val_bits >> inv_shift_bits)
282 (val_bits >> shift_bits) | (val_bits << inv_shift_bits)
284 let truncated_bits = self.truncate(result_bits, layout);
285 let result = Scalar::from_uint(truncated_bits, layout.size);
286 self.write_scalar(result, dest)?;
289 self.copy_intrinsic(&args[0], &args[1], &args[2], /*nonoverlapping*/ false)?;
291 sym::write_bytes => {
292 self.write_bytes_intrinsic(&args[0], &args[1], &args[2])?;
295 let ptr = self.read_pointer(&args[0])?;
296 let offset_count = self.read_scalar(&args[1])?.to_machine_isize(self)?;
297 let pointee_ty = substs.type_at(0);
299 let offset_ptr = self.ptr_offset_inbounds(ptr, pointee_ty, offset_count)?;
300 self.write_pointer(offset_ptr, dest)?;
302 sym::arith_offset => {
303 let ptr = self.read_pointer(&args[0])?;
304 let offset_count = self.read_scalar(&args[1])?.to_machine_isize(self)?;
305 let pointee_ty = substs.type_at(0);
307 let pointee_size = i64::try_from(self.layout_of(pointee_ty)?.size.bytes()).unwrap();
308 let offset_bytes = offset_count.wrapping_mul(pointee_size);
309 let offset_ptr = ptr.wrapping_signed_offset(offset_bytes, self);
310 self.write_pointer(offset_ptr, dest)?;
312 sym::ptr_offset_from | sym::ptr_offset_from_unsigned => {
313 let a = self.read_pointer(&args[0])?;
314 let b = self.read_pointer(&args[1])?;
316 let usize_layout = self.layout_of(self.tcx.types.usize)?;
317 let isize_layout = self.layout_of(self.tcx.types.isize)?;
319 // Get offsets for both that are at least relative to the same base.
320 let (a_offset, b_offset) =
321 match (self.ptr_try_get_alloc_id(a), self.ptr_try_get_alloc_id(b)) {
322 (Err(a), Err(b)) => {
323 // Neither poiner points to an allocation.
324 // If these are inequal or null, this *will* fail the deref check below.
327 (Err(_), _) | (_, Err(_)) => {
328 // We managed to find a valid allocation for one pointer, but not the other.
329 // That means they are definitely not pointing to the same allocation.
331 "`{}` called on pointers into different allocations",
335 (Ok((a_alloc_id, a_offset, _)), Ok((b_alloc_id, b_offset, _))) => {
336 // Found allocation for both. They must be into the same allocation.
337 if a_alloc_id != b_alloc_id {
339 "`{}` called on pointers into different allocations",
343 // Use these offsets for distance calculation.
344 (a_offset.bytes(), b_offset.bytes())
350 // Addresses are unsigned, so this is a `usize` computation. We have to do the
351 // overflow check separately anyway.
352 let (val, overflowed, _ty) = {
353 let a_offset = ImmTy::from_uint(a_offset, usize_layout);
354 let b_offset = ImmTy::from_uint(b_offset, usize_layout);
355 self.overflowing_binary_op(BinOp::Sub, &a_offset, &b_offset)?
359 if intrinsic_name == sym::ptr_offset_from_unsigned {
361 "`{}` called when first pointer has smaller offset than second: {} < {}",
367 // The signed form of the intrinsic allows this. If we interpret the
368 // difference as isize, we'll get the proper signed difference. If that
369 // seems *positive*, they were more than isize::MAX apart.
370 let dist = val.to_machine_isize(self)?;
373 "`{}` called when first pointer is too far before second",
380 let dist = val.to_machine_isize(self)?;
381 // If converting to isize produced a *negative* result, we had an overflow
382 // because they were more than isize::MAX apart.
385 "`{}` called when first pointer is too far ahead of second",
393 // Check that the range between them is dereferenceable ("in-bounds or one past the
394 // end of the same allocation"). This is like the check in ptr_offset_inbounds.
395 let min_ptr = if dist >= 0 { b } else { a };
396 self.check_ptr_access_align(
398 Size::from_bytes(dist.unsigned_abs()),
400 CheckInAllocMsg::OffsetFromTest,
403 // Perform division by size to compute return value.
404 let ret_layout = if intrinsic_name == sym::ptr_offset_from_unsigned {
405 assert!(0 <= dist && dist <= self.machine_isize_max());
408 assert!(self.machine_isize_min() <= dist && dist <= self.machine_isize_max());
411 let pointee_layout = self.layout_of(substs.type_at(0))?;
412 // If ret_layout is unsigned, we checked that so is the distance, so we are good.
413 let val = ImmTy::from_int(dist, ret_layout);
414 let size = ImmTy::from_int(pointee_layout.size.bytes(), ret_layout);
415 self.exact_div(&val, &size, dest)?;
419 self.copy_op(&args[0], dest, /*allow_transmute*/ true)?;
421 sym::assert_inhabited | sym::assert_zero_valid | sym::assert_uninit_valid => {
422 let ty = instance.substs.type_at(0);
423 let layout = self.layout_of(ty)?;
425 // For *all* intrinsics we first check `is_uninhabited` to give a more specific
427 if layout.abi.is_uninhabited() {
428 // The run-time intrinsic panics just to get a good backtrace; here we abort
429 // since there is no problem showing a backtrace even for aborts.
433 "aborted execution: attempted to instantiate uninhabited type `{}`",
439 if intrinsic_name == sym::assert_zero_valid {
440 let should_panic = !self.tcx.permits_zero_init(layout);
446 "aborted execution: attempted to zero-initialize type `{}`, which is invalid",
453 if intrinsic_name == sym::assert_uninit_valid {
454 let should_panic = !self.tcx.permits_uninit_init(layout);
460 "aborted execution: attempted to leave type `{}` uninitialized, which is invalid",
467 sym::simd_insert => {
468 let index = u64::from(self.read_scalar(&args[1])?.to_u32()?);
470 let (input, input_len) = self.operand_to_simd(&args[0])?;
471 let (dest, dest_len) = self.place_to_simd(dest)?;
472 assert_eq!(input_len, dest_len, "Return vector length must match input length");
475 "Index `{}` must be in bounds of vector with length {}`",
480 for i in 0..dest_len {
481 let place = self.mplace_index(&dest, i)?;
482 let value = if i == index {
485 self.mplace_index(&input, i)?.into()
487 self.copy_op(&value, &place.into(), /*allow_transmute*/ false)?;
490 sym::simd_extract => {
491 let index = u64::from(self.read_scalar(&args[1])?.to_u32()?);
492 let (input, input_len) = self.operand_to_simd(&args[0])?;
495 "index `{}` must be in bounds of vector with length `{}`",
500 &self.mplace_index(&input, index)?.into(),
502 /*allow_transmute*/ false,
505 sym::likely | sym::unlikely | sym::black_box => {
506 // These just return their argument
507 self.copy_op(&args[0], dest, /*allow_transmute*/ false)?;
510 let cond = self.read_scalar(&args[0])?.check_init()?.to_bool()?;
512 throw_ub_format!("`assume` intrinsic called with `false`");
516 let result = self.raw_eq_intrinsic(&args[0], &args[1])?;
517 self.write_scalar(result, dest)?;
520 sym::vtable_size => {
521 let ptr = self.read_pointer(&args[0])?;
522 let (size, _align) = self.get_vtable_size_and_align(ptr)?;
523 self.write_scalar(Scalar::from_machine_usize(size.bytes(), self), dest)?;
525 sym::vtable_align => {
526 let ptr = self.read_pointer(&args[0])?;
527 let (_size, align) = self.get_vtable_size_and_align(ptr)?;
528 self.write_scalar(Scalar::from_machine_usize(align.bytes(), self), dest)?;
531 _ => return Ok(false),
534 trace!("{:?}", self.dump_place(**dest));
535 self.go_to_block(ret);
541 a: &ImmTy<'tcx, M::Provenance>,
542 b: &ImmTy<'tcx, M::Provenance>,
543 dest: &PlaceTy<'tcx, M::Provenance>,
544 ) -> InterpResult<'tcx> {
545 // Performs an exact division, resulting in undefined behavior where
546 // `x % y != 0` or `y == 0` or `x == T::MIN && y == -1`.
547 // First, check x % y != 0 (or if that computation overflows).
548 let (res, overflow, _ty) = self.overflowing_binary_op(BinOp::Rem, &a, &b)?;
549 assert!(!overflow); // All overflow is UB, so this should never return on overflow.
550 if res.assert_bits(a.layout.size) != 0 {
551 throw_ub_format!("exact_div: {} cannot be divided by {} without remainder", a, b)
553 // `Rem` says this is all right, so we can let `Div` do its job.
554 self.binop_ignore_overflow(BinOp::Div, &a, &b, dest)
557 pub fn saturating_arith(
560 l: &ImmTy<'tcx, M::Provenance>,
561 r: &ImmTy<'tcx, M::Provenance>,
562 ) -> InterpResult<'tcx, Scalar<M::Provenance>> {
563 assert!(matches!(mir_op, BinOp::Add | BinOp::Sub));
564 let (val, overflowed, _ty) = self.overflowing_binary_op(mir_op, l, r)?;
566 let size = l.layout.size;
567 let num_bits = size.bits();
568 if l.layout.abi.is_signed() {
569 // For signed ints the saturated value depends on the sign of the first
570 // term since the sign of the second term can be inferred from this and
571 // the fact that the operation has overflowed (if either is 0 no
572 // overflow can occur)
573 let first_term: u128 = l.to_scalar()?.to_bits(l.layout.size)?;
574 let first_term_positive = first_term & (1 << (num_bits - 1)) == 0;
575 if first_term_positive {
576 // Negative overflow not possible since the positive first term
577 // can only increase an (in range) negative term for addition
578 // or corresponding negated positive term for subtraction
579 Scalar::from_int(size.signed_int_max(), size)
581 // Positive overflow not possible for similar reason
583 Scalar::from_int(size.signed_int_min(), size)
587 if matches!(mir_op, BinOp::Add) {
589 Scalar::from_uint(size.unsigned_int_max(), size)
592 Scalar::from_uint(0u128, size)
600 /// Offsets a pointer by some multiple of its type, returning an error if the pointer leaves its
601 /// allocation. For integer pointers, we consider each of them their own tiny allocation of size
602 /// 0, so offset-by-0 (and only 0) is okay -- except that null cannot be offset by _any_ value.
603 pub fn ptr_offset_inbounds(
605 ptr: Pointer<Option<M::Provenance>>,
606 pointee_ty: Ty<'tcx>,
608 ) -> InterpResult<'tcx, Pointer<Option<M::Provenance>>> {
609 // We cannot overflow i64 as a type's size must be <= isize::MAX.
610 let pointee_size = i64::try_from(self.layout_of(pointee_ty)?.size.bytes()).unwrap();
611 // The computed offset, in bytes, must not overflow an isize.
612 // `checked_mul` enforces a too small bound, but no actual allocation can be big enough for
613 // the difference to be noticeable.
615 offset_count.checked_mul(pointee_size).ok_or(err_ub!(PointerArithOverflow))?;
616 // The offset being in bounds cannot rely on "wrapping around" the address space.
617 // So, first rule out overflows in the pointer arithmetic.
618 let offset_ptr = ptr.signed_offset(offset_bytes, self)?;
619 // ptr and offset_ptr must be in bounds of the same allocated object. This means all of the
620 // memory between these pointers must be accessible. Note that we do not require the
621 // pointers to be properly aligned (unlike a read/write operation).
622 let min_ptr = if offset_bytes >= 0 { ptr } else { offset_ptr };
623 // This call handles checking for integer/null pointers.
624 self.check_ptr_access_align(
626 Size::from_bytes(offset_bytes.unsigned_abs()),
628 CheckInAllocMsg::PointerArithmeticTest,
633 /// Copy `count*size_of::<T>()` many bytes from `*src` to `*dst`.
634 pub(crate) fn copy_intrinsic(
636 src: &OpTy<'tcx, <M as Machine<'mir, 'tcx>>::Provenance>,
637 dst: &OpTy<'tcx, <M as Machine<'mir, 'tcx>>::Provenance>,
638 count: &OpTy<'tcx, <M as Machine<'mir, 'tcx>>::Provenance>,
639 nonoverlapping: bool,
640 ) -> InterpResult<'tcx> {
641 let count = self.read_scalar(&count)?.to_machine_usize(self)?;
642 let layout = self.layout_of(src.layout.ty.builtin_deref(true).unwrap().ty)?;
643 let (size, align) = (layout.size, layout.align.abi);
644 // `checked_mul` enforces a too small bound (the correct one would probably be machine_isize_max),
645 // but no actual allocation can be big enough for the difference to be noticeable.
646 let size = size.checked_mul(count, self).ok_or_else(|| {
648 "overflow computing total size of `{}`",
649 if nonoverlapping { "copy_nonoverlapping" } else { "copy" }
653 let src = self.read_pointer(&src)?;
654 let dst = self.read_pointer(&dst)?;
656 self.mem_copy(src, align, dst, align, size, nonoverlapping)
659 pub(crate) fn write_bytes_intrinsic(
661 dst: &OpTy<'tcx, <M as Machine<'mir, 'tcx>>::Provenance>,
662 byte: &OpTy<'tcx, <M as Machine<'mir, 'tcx>>::Provenance>,
663 count: &OpTy<'tcx, <M as Machine<'mir, 'tcx>>::Provenance>,
664 ) -> InterpResult<'tcx> {
665 let layout = self.layout_of(dst.layout.ty.builtin_deref(true).unwrap().ty)?;
667 let dst = self.read_pointer(&dst)?;
668 let byte = self.read_scalar(&byte)?.to_u8()?;
669 let count = self.read_scalar(&count)?.to_machine_usize(self)?;
671 // `checked_mul` enforces a too small bound (the correct one would probably be machine_isize_max),
672 // but no actual allocation can be big enough for the difference to be noticeable.
675 .checked_mul(count, self)
676 .ok_or_else(|| err_ub_format!("overflow computing total size of `write_bytes`"))?;
678 let bytes = std::iter::repeat(byte).take(len.bytes_usize());
679 self.write_bytes_ptr(dst, bytes)
682 pub(crate) fn raw_eq_intrinsic(
684 lhs: &OpTy<'tcx, <M as Machine<'mir, 'tcx>>::Provenance>,
685 rhs: &OpTy<'tcx, <M as Machine<'mir, 'tcx>>::Provenance>,
686 ) -> InterpResult<'tcx, Scalar<M::Provenance>> {
687 let layout = self.layout_of(lhs.layout.ty.builtin_deref(true).unwrap().ty)?;
688 assert!(!layout.is_unsized());
690 let lhs = self.read_pointer(lhs)?;
691 let rhs = self.read_pointer(rhs)?;
692 let lhs_bytes = self.read_bytes_ptr(lhs, layout.size)?;
693 let rhs_bytes = self.read_bytes_ptr(rhs, layout.size)?;
694 Ok(Scalar::from_bool(lhs_bytes == rhs_bytes))