2018-10-26 04:31:20 -05:00
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use std::cell::RefCell;
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2018-10-16 11:01:50 -05:00
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2018-11-05 09:05:17 -06:00
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use rustc::ty::{self, layout::Size};
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2018-11-09 03:53:28 -06:00
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use rustc::hir::{Mutability, MutMutable, MutImmutable};
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2018-10-16 11:01:50 -05:00
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2018-11-01 02:55:03 -05:00
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use crate::{
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2018-11-09 03:53:28 -06:00
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EvalResult, EvalErrorKind, MiriEvalContext, HelpersEvalContextExt,
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2018-11-12 01:54:12 -06:00
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MemoryKind, MiriMemoryKind, RangeMap, AllocId, Allocation, AllocationExtra,
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2018-11-07 07:56:25 -06:00
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Pointer, MemPlace, Scalar, Immediate, ImmTy, PlaceTy, MPlaceTy,
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2018-10-16 11:01:50 -05:00
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};
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2018-10-16 04:21:38 -05:00
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pub type Timestamp = u64;
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2018-11-05 09:05:17 -06:00
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/// Information about which kind of borrow was used to create the reference this is tagged
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/// with.
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2018-10-16 04:21:38 -05:00
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#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
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pub enum Borrow {
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2018-11-05 09:05:17 -06:00
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/// A unique (mutable) reference.
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Uniq(Timestamp),
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/// A shared reference. This is also used by raw pointers, which do not track details
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/// of how or when they were created, hence the timestamp is optional.
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/// Shr(Some(_)) does NOT mean that the destination of this reference is frozen;
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/// that depends on the type! Only those parts outside of an `UnsafeCell` are actually
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/// frozen.
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Shr(Option<Timestamp>),
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2018-10-16 04:21:38 -05:00
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}
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2018-10-16 11:01:50 -05:00
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impl Borrow {
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#[inline(always)]
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2018-11-09 03:53:28 -06:00
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pub fn is_shared(self) -> bool {
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2018-10-24 04:39:31 -05:00
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match self {
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2018-11-05 09:05:17 -06:00
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Borrow::Shr(_) => true,
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_ => false,
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}
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}
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#[inline(always)]
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2018-11-09 03:53:28 -06:00
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pub fn is_unique(self) -> bool {
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match self {
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Borrow::Uniq(_) => true,
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2018-10-16 11:01:50 -05:00
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_ => false,
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}
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}
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}
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2018-10-30 10:46:28 -05:00
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impl Default for Borrow {
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fn default() -> Self {
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Borrow::Shr(None)
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}
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}
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2018-11-05 09:05:17 -06:00
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/// An item in the per-location borrow stack
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2018-10-16 04:21:38 -05:00
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#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
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pub enum BorStackItem {
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2018-11-05 09:05:17 -06:00
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/// Indicates the unique reference that may mutate.
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Uniq(Timestamp),
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/// Indicates that the location has been shared. Used for raw pointers, but
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/// also for shared references. The latter *additionally* get frozen
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/// when there is no `UnsafeCell`.
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Shr,
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2018-10-17 08:15:53 -05:00
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/// A barrier, tracking the function it belongs to by its index on the call stack
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#[allow(dead_code)] // for future use
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FnBarrier(usize)
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}
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2018-10-30 10:46:28 -05:00
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impl BorStackItem {
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#[inline(always)]
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pub fn is_fn_barrier(self) -> bool {
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match self {
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BorStackItem::FnBarrier(_) => true,
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_ => false,
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}
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2018-10-16 04:21:38 -05:00
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}
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}
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2018-10-16 11:01:50 -05:00
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2018-11-05 09:05:17 -06:00
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/// Extra per-location state
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#[derive(Clone, Debug)]
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pub struct Stack {
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borrows: Vec<BorStackItem>, // used as a stack; never empty
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frozen_since: Option<Timestamp>, // virtual frozen "item" on top of the stack
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}
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impl Default for Stack {
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fn default() -> Self {
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Stack {
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borrows: vec![BorStackItem::Shr],
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frozen_since: None,
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}
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}
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}
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impl Stack {
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#[inline(always)]
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pub fn is_frozen(&self) -> bool {
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self.frozen_since.is_some()
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}
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}
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2018-11-09 03:53:28 -06:00
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/// What kind of reference is being used?
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2018-10-19 09:07:40 -05:00
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#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
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pub enum RefKind {
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/// &mut
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Unique,
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/// & without interior mutability
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Frozen,
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/// * (raw pointer) or & to `UnsafeCell`
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Raw,
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}
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2018-10-16 11:01:50 -05:00
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/// Extra global machine state
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#[derive(Clone, Debug)]
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pub struct State {
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clock: Timestamp
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2018-10-16 11:01:50 -05:00
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}
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impl State {
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pub fn new() -> State {
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2018-10-26 04:31:20 -05:00
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State { clock: 0 }
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2018-10-16 11:01:50 -05:00
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}
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2018-11-09 03:53:28 -06:00
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fn increment_clock(&mut self) -> Timestamp {
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let val = self.clock;
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self.clock = val + 1;
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val
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}
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2018-10-16 11:01:50 -05:00
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}
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/// Extra per-allocation state
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#[derive(Clone, Debug, Default)]
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pub struct Stacks {
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2018-10-26 04:31:20 -05:00
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// Even reading memory can have effects on the stack, so we need a `RefCell` here.
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2018-10-16 11:01:50 -05:00
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stacks: RefCell<RangeMap<Stack>>,
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}
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2018-11-09 03:53:28 -06:00
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/// Core per-location operations: deref, access, create.
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/// We need to make at least the following things true:
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///
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/// U1: After creating a Uniq, it is at the top (+unfrozen).
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/// U2: If the top is Uniq (+unfrozen), accesses must be through that Uniq or pop it.
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/// U3: If an access (deref sufficient?) happens with a Uniq, it requires the Uniq to be in the stack.
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///
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/// F1: After creating a &, the parts outside `UnsafeCell` are frozen.
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/// F2: If a write access happens, it unfreezes.
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/// F3: If an access (well, a deref) happens with an & outside `UnsafeCell`, it requires the location to still be frozen.
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impl<'tcx> Stack {
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/// Deref `bor`: Check if the location is frozen and the tag in the stack.
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/// This dos *not* constitute an access! "Deref" refers to the `*` operator
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/// in Rust, and includs cases like `&*x` or `(*x).foo` where no or only part
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/// of the memory actually gets accessed. Also we cannot know if we are
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/// going to read or write.
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/// Returns the index of the item we matched, `None` if it was the frozen one.
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/// `kind` indicates which kind of reference is being dereferenced.
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fn deref(&self, bor: Borrow, kind: RefKind) -> Result<Option<usize>, String> {
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// Checks related to freezing
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match bor {
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Borrow::Shr(Some(bor_t)) if kind == RefKind::Frozen => {
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// We need the location to be frozen. This ensures F3.
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let frozen = self.frozen_since.map_or(false, |itm_t| itm_t <= bor_t);
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return if frozen { Ok(None) } else {
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Err(format!("Location is not frozen long enough"))
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2018-11-05 09:05:17 -06:00
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}
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}
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2018-11-09 03:53:28 -06:00
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Borrow::Shr(_) if self.frozen_since.is_some() => {
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return Ok(None) // Shared deref to frozen location, looking good
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}
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_ => {} // Not sufficient, go on looking.
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2018-11-05 09:05:17 -06:00
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}
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2018-11-09 03:53:28 -06:00
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// If we got here, we have to look for our item in the stack.
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for (idx, &itm) in self.borrows.iter().enumerate().rev() {
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match (itm, bor) {
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2018-11-09 03:53:28 -06:00
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(BorStackItem::FnBarrier(_), _) => break,
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2018-11-05 09:05:17 -06:00
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(BorStackItem::Uniq(itm_t), Borrow::Uniq(bor_t)) if itm_t == bor_t => {
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2018-11-09 03:53:28 -06:00
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// Found matching unique item. This satisfies U3.
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return Ok(Some(idx))
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2018-10-16 11:01:50 -05:00
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}
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2018-11-05 09:05:17 -06:00
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(BorStackItem::Shr, Borrow::Shr(_)) => {
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// Found matching shared/raw item.
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return Ok(Some(idx))
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}
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// Go on looking.
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_ => {}
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2018-10-16 11:01:50 -05:00
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}
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}
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2018-11-09 03:53:28 -06:00
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// If we got here, we did not find our item. We have to error to satisfy U3.
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Err(format!(
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"Borrow being dereferenced ({:?}) does not exist on the stack, or is guarded by a barrier",
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bor
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))
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2018-10-23 08:59:50 -05:00
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}
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2018-11-09 03:53:28 -06:00
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/// Perform an actual memory access using `bor`. We do not know any types here
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/// or whether things should be frozen, but we *do* know if this is reading
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/// or writing.
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fn access(&mut self, bor: Borrow, is_write: bool) -> EvalResult<'tcx> {
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// Check if we can match the frozen "item".
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// Not possible on writes!
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2018-11-05 09:05:17 -06:00
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if self.is_frozen() {
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2018-11-09 03:53:28 -06:00
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if !is_write {
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// When we are frozen, we just accept all reads. No harm in this.
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// The deref already checked that `Uniq` items are in the stack, and that
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// the location is frozen if it should be.
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return Ok(());
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}
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trace!("access: Unfreezing");
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2018-11-05 09:05:17 -06:00
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}
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2018-11-09 03:53:28 -06:00
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// Unfreeze on writes. This ensures F2.
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2018-11-05 09:05:17 -06:00
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self.frozen_since = None;
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2018-11-09 03:53:28 -06:00
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// Pop the stack until we have something matching.
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while let Some(&itm) = self.borrows.last() {
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match (itm, bor) {
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(BorStackItem::FnBarrier(_), _) => break,
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(BorStackItem::Uniq(itm_t), Borrow::Uniq(bor_t)) if itm_t == bor_t => {
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// Found matching unique item.
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return Ok(())
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}
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(BorStackItem::Shr, _) if !is_write => {
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// When reading, everything can use a shared item!
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// We do not want to do this when writing: Writing to an `&mut`
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// should reaffirm its exclusivity (i.e., make sure it is
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// on top of the stack).
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return Ok(())
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}
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(BorStackItem::Shr, Borrow::Shr(_)) => {
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// Found matching shared item.
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return Ok(())
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}
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_ => {
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// Pop this. This ensures U2.
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let itm = self.borrows.pop().unwrap();
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trace!("access: Popping {:?}", itm);
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}
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}
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2018-10-23 08:59:50 -05:00
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}
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2018-11-09 03:53:28 -06:00
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// If we got here, we did not find our item.
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err!(MachineError(format!(
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"Borrow being accessed ({:?}) does not exist on the stack, or is guarded by a barrier",
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bor
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)))
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2018-10-16 11:01:50 -05:00
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}
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2018-11-05 09:05:17 -06:00
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/// Initiate `bor`; mostly this means pushing.
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2018-10-29 13:48:43 -05:00
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/// This operation cannot fail; it is up to the caller to ensure that the precondition
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2018-11-07 09:56:25 -06:00
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/// is met: We cannot push `Uniq` onto frozen stacks.
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2018-11-09 03:53:28 -06:00
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/// `kind` indicates which kind of reference is being created.
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fn create(&mut self, bor: Borrow, kind: RefKind) {
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// First, push the item. We do this even if we will later freeze, because we
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// will allow mutation of shared data at the expense of unfreezing.
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2018-11-13 10:05:47 -06:00
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if self.frozen_since.is_some() {
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// A frozen location, this should be impossible!
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bug!("We should never try pushing to a frozen stack");
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}
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// First, push.
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let itm = match bor {
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Borrow::Uniq(t) => BorStackItem::Uniq(t),
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Borrow::Shr(_) => BorStackItem::Shr,
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};
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if *self.borrows.last().unwrap() == itm {
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assert!(bor.is_shared());
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trace!("create: Sharing a shared location is a NOP");
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2018-11-05 09:05:17 -06:00
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} else {
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2018-11-13 10:05:47 -06:00
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// This ensures U1.
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trace!("create: Pushing {:?}", itm);
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self.borrows.push(itm);
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}
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// Then, maybe freeze. This is part 2 of ensuring F1.
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if kind == RefKind::Frozen {
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let bor_t = match bor {
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Borrow::Shr(Some(t)) => t,
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_ => bug!("Creating illegal borrow {:?} for frozen ref", bor),
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2018-11-05 09:05:17 -06:00
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};
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2018-11-13 10:05:47 -06:00
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trace!("create: Freezing");
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self.frozen_since = Some(bor_t);
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2018-10-16 11:01:50 -05:00
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}
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}
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}
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2018-11-09 03:53:28 -06:00
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/// Higher-level per-location operations: deref, access, reborrow.
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2018-10-17 08:15:53 -05:00
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impl<'tcx> Stacks {
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2018-11-09 03:53:28 -06:00
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/// Check that this stack is fine with being dereferenced
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fn deref(
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2018-10-17 08:15:53 -05:00
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&self,
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ptr: Pointer<Borrow>,
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size: Size,
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2018-11-09 03:53:28 -06:00
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kind: RefKind,
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2018-10-17 08:15:53 -05:00
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) -> EvalResult<'tcx> {
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2018-11-09 03:53:28 -06:00
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trace!("deref for tag {:?} as {:?}: {:?}, size {}",
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ptr.tag, kind, ptr, size.bytes());
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2018-10-17 08:15:53 -05:00
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let mut stacks = self.stacks.borrow_mut();
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2018-11-09 03:53:28 -06:00
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// We need `iter_mut` because `iter` would skip gaps!
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2018-10-17 08:15:53 -05:00
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for stack in stacks.iter_mut(ptr.offset, size) {
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2018-11-09 03:53:28 -06:00
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stack.deref(ptr.tag, kind).map_err(EvalErrorKind::MachineError)?;
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2018-10-17 08:15:53 -05:00
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}
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2018-11-05 09:05:17 -06:00
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Ok(())
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|
}
|
2018-10-17 08:15:53 -05:00
|
|
|
|
2018-11-09 03:53:28 -06:00
|
|
|
/// `ptr` got used, reflect that in the stack.
|
|
|
|
fn access(
|
2018-11-05 09:05:17 -06:00
|
|
|
&self,
|
|
|
|
ptr: Pointer<Borrow>,
|
|
|
|
size: Size,
|
2018-11-09 03:53:28 -06:00
|
|
|
is_write: bool,
|
|
|
|
) -> EvalResult<'tcx> {
|
|
|
|
trace!("{} access of tag {:?}: {:?}, size {}",
|
|
|
|
if is_write { "read" } else { "write" },
|
2018-11-07 09:56:25 -06:00
|
|
|
ptr.tag, ptr, size.bytes());
|
2018-11-05 09:05:17 -06:00
|
|
|
let mut stacks = self.stacks.borrow_mut();
|
|
|
|
for stack in stacks.iter_mut(ptr.offset, size) {
|
2018-11-09 03:53:28 -06:00
|
|
|
stack.access(ptr.tag, is_write)?;
|
2018-11-05 09:05:17 -06:00
|
|
|
}
|
2018-11-09 03:53:28 -06:00
|
|
|
Ok(())
|
2018-10-17 08:15:53 -05:00
|
|
|
}
|
2018-10-22 11:01:32 -05:00
|
|
|
|
2018-11-09 03:53:28 -06:00
|
|
|
/// Reborrow the given pointer to the new tag for the given kind of reference.
|
|
|
|
fn reborrow(
|
2018-11-05 09:05:17 -06:00
|
|
|
&self,
|
|
|
|
ptr: Pointer<Borrow>,
|
|
|
|
size: Size,
|
2018-11-09 03:53:28 -06:00
|
|
|
new_bor: Borrow,
|
|
|
|
new_kind: RefKind,
|
2018-11-05 09:05:17 -06:00
|
|
|
) -> EvalResult<'tcx> {
|
2018-11-16 01:40:00 -06:00
|
|
|
assert_eq!(new_bor.is_unique(), new_kind == RefKind::Unique);
|
2018-11-09 03:53:28 -06:00
|
|
|
trace!("reborrow for tag {:?} to {:?} as {:?}: {:?}, size {}",
|
|
|
|
ptr.tag, new_bor, new_kind, ptr, size.bytes());
|
2018-11-05 09:05:17 -06:00
|
|
|
let mut stacks = self.stacks.borrow_mut();
|
|
|
|
for stack in stacks.iter_mut(ptr.offset, size) {
|
2018-11-09 03:53:28 -06:00
|
|
|
// Access source `ptr`, create new ref.
|
|
|
|
let ptr_idx = stack.deref(ptr.tag, new_kind).map_err(EvalErrorKind::MachineError)?;
|
2018-11-13 06:39:03 -06:00
|
|
|
// If we can deref the new tag already, and if that tag lives higher on
|
|
|
|
// the stack than the one we come from, just use that.
|
|
|
|
// IOW, we check if `new_bor` *already* is "derived from" `ptr.tag`.
|
|
|
|
// This also checks frozenness, if required.
|
2018-11-13 07:49:04 -06:00
|
|
|
let bor_redundant = match (ptr_idx, stack.deref(new_bor, new_kind)) {
|
2018-11-13 06:39:03 -06:00
|
|
|
// If the new borrow works with the frozen item, or else if it lives
|
|
|
|
// above the old one in the stack, our job here is done.
|
|
|
|
(_, Ok(None)) => true,
|
|
|
|
(Some(ptr_idx), Ok(Some(new_idx))) if new_idx >= ptr_idx => true,
|
|
|
|
// Otherwise we need to create a new borrow.
|
|
|
|
_ => false,
|
|
|
|
};
|
2018-11-13 07:49:04 -06:00
|
|
|
if bor_redundant {
|
2018-11-13 06:39:03 -06:00
|
|
|
assert!(new_bor.is_shared(), "A unique reborrow can never be redundant");
|
2018-11-13 07:49:04 -06:00
|
|
|
trace!("reborrow is redundant");
|
2018-11-13 06:39:03 -06:00
|
|
|
continue;
|
2018-11-07 09:56:25 -06:00
|
|
|
}
|
2018-11-13 06:39:03 -06:00
|
|
|
// We need to do some actual work.
|
2018-11-09 03:53:28 -06:00
|
|
|
stack.access(ptr.tag, new_kind == RefKind::Unique)?;
|
|
|
|
stack.create(new_bor, new_kind);
|
2018-11-05 09:05:17 -06:00
|
|
|
}
|
|
|
|
Ok(())
|
|
|
|
}
|
|
|
|
}
|
|
|
|
|
|
|
|
/// Hooks and glue
|
2018-11-12 01:54:12 -06:00
|
|
|
impl AllocationExtra<Borrow> for Stacks {
|
2018-10-29 13:48:43 -05:00
|
|
|
#[inline(always)]
|
2018-11-12 01:54:12 -06:00
|
|
|
fn memory_read<'tcx>(
|
|
|
|
alloc: &Allocation<Borrow, Stacks>,
|
2018-10-29 13:48:43 -05:00
|
|
|
ptr: Pointer<Borrow>,
|
|
|
|
size: Size,
|
|
|
|
) -> EvalResult<'tcx> {
|
2018-11-09 03:53:28 -06:00
|
|
|
alloc.extra.access(ptr, size, /*is_write*/false)
|
2018-10-29 13:48:43 -05:00
|
|
|
}
|
|
|
|
|
|
|
|
#[inline(always)]
|
2018-11-12 01:54:12 -06:00
|
|
|
fn memory_written<'tcx>(
|
|
|
|
alloc: &mut Allocation<Borrow, Stacks>,
|
2018-10-29 13:48:43 -05:00
|
|
|
ptr: Pointer<Borrow>,
|
|
|
|
size: Size,
|
|
|
|
) -> EvalResult<'tcx> {
|
2018-11-09 03:53:28 -06:00
|
|
|
alloc.extra.access(ptr, size, /*is_write*/true)
|
2018-10-29 13:48:43 -05:00
|
|
|
}
|
|
|
|
|
2018-11-12 01:54:12 -06:00
|
|
|
#[inline(always)]
|
2018-11-14 09:03:38 -06:00
|
|
|
fn memory_deallocated<'tcx>(
|
|
|
|
alloc: &mut Allocation<Borrow, Stacks>,
|
2018-10-29 13:48:43 -05:00
|
|
|
ptr: Pointer<Borrow>,
|
|
|
|
size: Size,
|
|
|
|
) -> EvalResult<'tcx> {
|
|
|
|
// This is like mutating
|
2018-11-09 03:53:28 -06:00
|
|
|
alloc.extra.access(ptr, size, /*is_write*/true)
|
2018-10-29 13:48:43 -05:00
|
|
|
// FIXME: Error out of there are any barriers?
|
|
|
|
}
|
2018-11-14 09:03:38 -06:00
|
|
|
}
|
2018-10-29 13:48:43 -05:00
|
|
|
|
2018-11-14 09:03:38 -06:00
|
|
|
impl<'tcx> Stacks {
|
2018-11-05 09:05:17 -06:00
|
|
|
/// Pushes the first item to the stacks.
|
|
|
|
pub fn first_item(
|
2018-10-22 11:01:32 -05:00
|
|
|
&mut self,
|
2018-11-05 09:05:17 -06:00
|
|
|
itm: BorStackItem,
|
2018-10-22 11:01:32 -05:00
|
|
|
size: Size
|
|
|
|
) {
|
2018-11-05 09:05:17 -06:00
|
|
|
assert!(!itm.is_fn_barrier());
|
2018-10-22 11:01:32 -05:00
|
|
|
for stack in self.stacks.get_mut().iter_mut(Size::ZERO, size) {
|
2018-11-05 09:05:17 -06:00
|
|
|
assert!(stack.borrows.len() == 1);
|
|
|
|
assert_eq!(stack.borrows.pop().unwrap(), BorStackItem::Shr);
|
|
|
|
stack.borrows.push(itm);
|
2018-10-22 11:01:32 -05:00
|
|
|
}
|
|
|
|
}
|
2018-10-17 08:15:53 -05:00
|
|
|
}
|
|
|
|
|
2018-11-05 09:05:17 -06:00
|
|
|
|
|
|
|
|
2018-10-16 11:01:50 -05:00
|
|
|
pub trait EvalContextExt<'tcx> {
|
|
|
|
fn tag_dereference(
|
|
|
|
&self,
|
2018-11-05 09:05:17 -06:00
|
|
|
place: MPlaceTy<'tcx, Borrow>,
|
2018-10-18 09:59:08 -05:00
|
|
|
size: Size,
|
2018-11-09 03:53:28 -06:00
|
|
|
mutability: Option<Mutability>,
|
2018-10-16 11:01:50 -05:00
|
|
|
) -> EvalResult<'tcx, Borrow>;
|
2018-10-22 11:01:32 -05:00
|
|
|
|
|
|
|
fn tag_new_allocation(
|
|
|
|
&mut self,
|
|
|
|
id: AllocId,
|
|
|
|
kind: MemoryKind<MiriMemoryKind>,
|
|
|
|
) -> Borrow;
|
2018-10-24 10:17:44 -05:00
|
|
|
|
2018-11-07 07:56:25 -06:00
|
|
|
/// Retag an indidual pointer, returning the retagged version.
|
2018-11-09 03:53:28 -06:00
|
|
|
fn reborrow(
|
2018-11-07 07:56:25 -06:00
|
|
|
&mut self,
|
|
|
|
ptr: ImmTy<'tcx, Borrow>,
|
2018-11-09 03:53:28 -06:00
|
|
|
mutbl: Mutability,
|
2018-11-07 07:56:25 -06:00
|
|
|
) -> EvalResult<'tcx, Immediate<Borrow>>;
|
|
|
|
|
2018-10-24 10:17:44 -05:00
|
|
|
fn retag(
|
|
|
|
&mut self,
|
|
|
|
fn_entry: bool,
|
|
|
|
place: PlaceTy<'tcx, Borrow>
|
|
|
|
) -> EvalResult<'tcx>;
|
2018-10-16 11:01:50 -05:00
|
|
|
|
2018-11-07 07:56:25 -06:00
|
|
|
fn escape_to_raw(
|
2018-10-26 04:31:20 -05:00
|
|
|
&mut self,
|
2018-11-05 09:05:17 -06:00
|
|
|
place: MPlaceTy<'tcx, Borrow>,
|
2018-10-26 04:31:20 -05:00
|
|
|
size: Size,
|
2018-11-07 07:56:25 -06:00
|
|
|
) -> EvalResult<'tcx>;
|
|
|
|
}
|
2018-10-16 11:01:50 -05:00
|
|
|
|
2018-11-07 07:56:25 -06:00
|
|
|
impl<'a, 'mir, 'tcx> EvalContextExt<'tcx> for MiriEvalContext<'a, 'mir, 'tcx> {
|
2018-11-07 09:56:25 -06:00
|
|
|
fn tag_new_allocation(
|
|
|
|
&mut self,
|
|
|
|
id: AllocId,
|
|
|
|
kind: MemoryKind<MiriMemoryKind>,
|
|
|
|
) -> Borrow {
|
|
|
|
let time = match kind {
|
|
|
|
MemoryKind::Stack => {
|
|
|
|
// New unique borrow. This `Uniq` is not accessible by the program,
|
|
|
|
// so it will only ever be used when using the local directly (i.e.,
|
|
|
|
// not through a pointer). IOW, whenever we directly use a local this will pop
|
|
|
|
// everything else off the stack, invalidating all previous pointers
|
|
|
|
// and, in particular, *all* raw pointers. This subsumes the explicit
|
|
|
|
// `reset` which the blog post [1] says to perform when accessing a local.
|
|
|
|
//
|
|
|
|
// [1] https://www.ralfj.de/blog/2018/08/07/stacked-borrows.html
|
|
|
|
self.machine.stacked_borrows.increment_clock()
|
|
|
|
}
|
|
|
|
_ => {
|
|
|
|
// Nothing to do for everything else
|
|
|
|
return Borrow::default()
|
|
|
|
}
|
|
|
|
};
|
|
|
|
// Make this the active borrow for this allocation
|
|
|
|
let alloc = self.memory_mut().get_mut(id).expect("This is a new allocation, it must still exist");
|
|
|
|
let size = Size::from_bytes(alloc.bytes.len() as u64);
|
|
|
|
alloc.extra.first_item(BorStackItem::Uniq(time), size);
|
|
|
|
Borrow::Uniq(time)
|
|
|
|
}
|
|
|
|
|
2018-11-09 03:53:28 -06:00
|
|
|
/// Called for value-to-place conversion. `mutability` is `None` for raw pointers.
|
2018-10-19 09:07:40 -05:00
|
|
|
///
|
|
|
|
/// Note that this does NOT mean that all this memory will actually get accessed/referenced!
|
|
|
|
/// We could be in the middle of `&(*var).1`.
|
2018-10-16 11:01:50 -05:00
|
|
|
fn tag_dereference(
|
|
|
|
&self,
|
2018-11-05 09:05:17 -06:00
|
|
|
place: MPlaceTy<'tcx, Borrow>,
|
2018-10-18 09:59:08 -05:00
|
|
|
size: Size,
|
2018-11-09 03:53:28 -06:00
|
|
|
mutability: Option<Mutability>,
|
2018-10-16 11:01:50 -05:00
|
|
|
) -> EvalResult<'tcx, Borrow> {
|
2018-11-09 03:53:28 -06:00
|
|
|
trace!("tag_dereference: Accessing {} reference for {:?} (pointee {})",
|
|
|
|
if let Some(mutability) = mutability { format!("{:?}", mutability) } else { format!("raw") },
|
|
|
|
place.ptr, place.layout.ty);
|
2018-11-07 07:56:25 -06:00
|
|
|
let ptr = place.ptr.to_ptr()?;
|
2018-10-19 09:07:40 -05:00
|
|
|
// In principle we should not have to do anything here. However, with transmutes involved,
|
2018-11-09 03:53:28 -06:00
|
|
|
// it can happen that the tag of `ptr` does not actually match `mutability`, and we
|
2018-10-19 09:07:40 -05:00
|
|
|
// should adjust for that.
|
|
|
|
// Notably, the compiler can introduce such transmutes by optimizing away `&[mut]*`.
|
|
|
|
// That can transmute a raw ptr to a (shared/mut) ref, and a mut ref to a shared one.
|
2018-11-09 03:53:28 -06:00
|
|
|
match (mutability, ptr.tag) {
|
|
|
|
(None, _) => {
|
2018-11-07 09:56:25 -06:00
|
|
|
// Don't use the tag, this is a raw access! They should happen tagless.
|
2018-11-09 03:53:28 -06:00
|
|
|
// This is needed for `*mut` to make any sense: Writes *do* enforce the
|
|
|
|
// `Uniq` tag to be up top, but we must make sure raw writes do not do that.
|
2018-11-07 09:56:25 -06:00
|
|
|
// This does mean, however, that `&*foo` is *not* a NOP *if* `foo` is a raw ptr.
|
2018-10-22 11:01:32 -05:00
|
|
|
// Also don't do any further validation, this is raw after all.
|
2018-11-05 09:05:17 -06:00
|
|
|
return Ok(Borrow::default());
|
2018-10-22 11:01:32 -05:00
|
|
|
}
|
2018-11-09 03:53:28 -06:00
|
|
|
(Some(MutMutable), Borrow::Uniq(_)) |
|
|
|
|
(Some(MutImmutable), Borrow::Shr(_)) => {
|
2018-10-19 09:07:40 -05:00
|
|
|
// Expected combinations. Nothing to do.
|
|
|
|
}
|
2018-11-09 03:53:28 -06:00
|
|
|
(Some(MutMutable), Borrow::Shr(None)) => {
|
2018-11-12 09:18:02 -06:00
|
|
|
// Raw transmuted to mut ref. This is something real unsafe code does.
|
|
|
|
// We cannot reborrow here because we do not want to mutate state on a deref.
|
2018-10-19 09:07:40 -05:00
|
|
|
}
|
2018-11-09 03:53:28 -06:00
|
|
|
(Some(MutImmutable), Borrow::Uniq(_)) => {
|
2018-11-03 05:42:38 -05:00
|
|
|
// A mut got transmuted to shr. Can happen even from compiler transformations:
|
|
|
|
// `&*x` gets optimized to `x` even when `x` is a `&mut`.
|
2018-10-19 09:07:40 -05:00
|
|
|
}
|
2018-11-09 03:53:28 -06:00
|
|
|
(Some(MutMutable), Borrow::Shr(Some(_))) => {
|
2018-11-05 09:05:17 -06:00
|
|
|
// This is just invalid: A shr got transmuted to a mut.
|
2018-10-19 09:07:40 -05:00
|
|
|
// If we ever allow this, we have to consider what we do when a turn a
|
|
|
|
// `Raw`-tagged `&mut` into a raw pointer pointing to a frozen location.
|
|
|
|
// We probably do not want to allow that, but we have to allow
|
|
|
|
// turning a `Raw`-tagged `&` into a raw ptr to a frozen location.
|
|
|
|
return err!(MachineError(format!("Encountered mutable reference with frozen tag {:?}", ptr.tag)))
|
|
|
|
}
|
|
|
|
}
|
2018-11-05 09:05:17 -06:00
|
|
|
|
2018-11-07 09:56:25 -06:00
|
|
|
// Get the allocation
|
2018-10-19 12:51:41 -05:00
|
|
|
self.memory().check_bounds(ptr, size, false)?;
|
|
|
|
let alloc = self.memory().get(ptr.alloc_id).expect("We checked that the ptr is fine!");
|
2018-11-07 09:56:25 -06:00
|
|
|
// If we got here, we do some checking, *but* we leave the tag unchanged.
|
|
|
|
if let Borrow::Shr(Some(_)) = ptr.tag {
|
2018-11-09 03:53:28 -06:00
|
|
|
assert_eq!(mutability, Some(MutImmutable));
|
2018-11-07 09:56:25 -06:00
|
|
|
// We need a frozen-sensitive check
|
|
|
|
self.visit_freeze_sensitive(place, size, |cur_ptr, size, frozen| {
|
2018-11-09 03:53:28 -06:00
|
|
|
let kind = if frozen { RefKind::Frozen } else { RefKind::Raw };
|
|
|
|
alloc.extra.deref(cur_ptr, size, kind)
|
2018-11-05 09:05:17 -06:00
|
|
|
})?;
|
2018-11-07 09:56:25 -06:00
|
|
|
} else {
|
|
|
|
// Just treat this as one big chunk
|
2018-11-09 03:53:28 -06:00
|
|
|
let kind = if mutability == Some(MutMutable) { RefKind::Unique } else { RefKind::Raw };
|
|
|
|
alloc.extra.deref(ptr, size, kind)?;
|
2018-10-19 09:07:40 -05:00
|
|
|
}
|
2018-11-05 09:05:17 -06:00
|
|
|
|
|
|
|
// All is good, and do not change the tag
|
2018-10-19 09:07:40 -05:00
|
|
|
Ok(ptr.tag)
|
2018-10-16 11:01:50 -05:00
|
|
|
}
|
2018-10-22 11:01:32 -05:00
|
|
|
|
2018-11-07 09:56:25 -06:00
|
|
|
/// The given place may henceforth be accessed through raw pointers.
|
|
|
|
fn escape_to_raw(
|
2018-10-22 11:01:32 -05:00
|
|
|
&mut self,
|
2018-11-07 09:56:25 -06:00
|
|
|
place: MPlaceTy<'tcx, Borrow>,
|
|
|
|
size: Size,
|
|
|
|
) -> EvalResult<'tcx> {
|
2018-11-09 03:53:28 -06:00
|
|
|
trace!("escape_to_raw: {:?} is now accessible by raw pointers", *place);
|
2018-11-07 09:56:25 -06:00
|
|
|
// Get the allocation
|
2018-11-09 03:53:28 -06:00
|
|
|
let ptr = place.ptr.to_ptr()?;
|
2018-11-07 09:56:25 -06:00
|
|
|
self.memory().check_bounds(ptr, size, false)?; // `ptr_dereference` wouldn't do any checks if this is a raw ptr
|
|
|
|
let alloc = self.memory().get(ptr.alloc_id).expect("We checked that the ptr is fine!");
|
|
|
|
// Re-borrow to raw. This is a NOP for shared borrows, but we do not know the borrow
|
|
|
|
// type here and that's also okay. Freezing does not matter here.
|
2018-11-09 03:53:28 -06:00
|
|
|
alloc.extra.reborrow(ptr, size, Borrow::default(), RefKind::Raw)
|
2018-10-22 11:01:32 -05:00
|
|
|
}
|
2018-10-24 10:17:44 -05:00
|
|
|
|
2018-11-09 03:53:28 -06:00
|
|
|
fn reborrow(
|
2018-11-07 07:56:25 -06:00
|
|
|
&mut self,
|
|
|
|
val: ImmTy<'tcx, Borrow>,
|
2018-11-09 03:53:28 -06:00
|
|
|
mutbl: Mutability,
|
2018-11-07 07:56:25 -06:00
|
|
|
) -> EvalResult<'tcx, Immediate<Borrow>> {
|
|
|
|
// We want a place for where the ptr *points to*, so we get one.
|
|
|
|
let place = self.ref_to_mplace(val)?;
|
|
|
|
let size = self.size_and_align_of_mplace(place)?
|
|
|
|
.map(|(size, _)| size)
|
|
|
|
.unwrap_or_else(|| place.layout.size);
|
|
|
|
if size == Size::ZERO {
|
|
|
|
// Nothing to do for ZSTs.
|
|
|
|
return Ok(*val);
|
|
|
|
}
|
|
|
|
|
|
|
|
// Prepare to re-borrow this place.
|
|
|
|
let ptr = place.ptr.to_ptr()?;
|
|
|
|
let time = self.machine.stacked_borrows.increment_clock();
|
|
|
|
let new_bor = match mutbl {
|
2018-11-09 03:53:28 -06:00
|
|
|
MutMutable => Borrow::Uniq(time),
|
|
|
|
MutImmutable => Borrow::Shr(Some(time)),
|
2018-11-07 07:56:25 -06:00
|
|
|
};
|
2018-11-09 03:53:28 -06:00
|
|
|
trace!("reborrow: Creating new {:?} reference for {:?} (pointee {}): {:?}",
|
2018-11-07 07:56:25 -06:00
|
|
|
mutbl, ptr, place.layout.ty, new_bor);
|
|
|
|
|
2018-11-09 03:53:28 -06:00
|
|
|
// Get the allocation. It might not be mutable, so we cannot use `get_mut`.
|
|
|
|
self.memory().check_bounds(ptr, size, false)?;
|
2018-11-07 07:56:25 -06:00
|
|
|
let alloc = self.memory().get(ptr.alloc_id).expect("We checked that the ptr is fine!");
|
2018-11-09 03:53:28 -06:00
|
|
|
// Update the stacks.
|
|
|
|
if mutbl == MutImmutable {
|
|
|
|
// Shared reference. We need a frozen-sensitive reborrow.
|
|
|
|
self.visit_freeze_sensitive(place, size, |cur_ptr, size, frozen| {
|
|
|
|
let kind = if frozen { RefKind::Frozen } else { RefKind::Raw };
|
|
|
|
alloc.extra.reborrow(cur_ptr, size, new_bor, kind)
|
2018-11-07 07:56:25 -06:00
|
|
|
})?;
|
2018-11-07 09:56:25 -06:00
|
|
|
} else {
|
2018-11-09 03:53:28 -06:00
|
|
|
// Mutable reference. Just treat this as one big chunk.
|
|
|
|
alloc.extra.reborrow(ptr, size, new_bor, RefKind::Unique)?;
|
2018-11-07 07:56:25 -06:00
|
|
|
}
|
|
|
|
|
2018-11-07 09:56:25 -06:00
|
|
|
// Return new ptr
|
2018-11-09 03:53:28 -06:00
|
|
|
let new_ptr = Pointer::new_with_tag(ptr.alloc_id, ptr.offset, new_bor);
|
2018-11-07 09:56:25 -06:00
|
|
|
let new_place = MemPlace { ptr: Scalar::Ptr(new_ptr), ..*place };
|
2018-11-07 07:56:25 -06:00
|
|
|
Ok(new_place.to_ref())
|
|
|
|
}
|
|
|
|
|
2018-10-24 10:17:44 -05:00
|
|
|
fn retag(
|
|
|
|
&mut self,
|
|
|
|
_fn_entry: bool,
|
2018-10-26 04:31:20 -05:00
|
|
|
place: PlaceTy<'tcx, Borrow>
|
2018-10-24 10:17:44 -05:00
|
|
|
) -> EvalResult<'tcx> {
|
2018-10-26 04:31:20 -05:00
|
|
|
// For now, we only retag if the toplevel type is a reference.
|
|
|
|
// TODO: Recurse into structs and enums, sharing code with validation.
|
2018-11-07 07:56:25 -06:00
|
|
|
// TODO: Honor `fn_entry`.
|
2018-10-26 04:31:20 -05:00
|
|
|
let mutbl = match place.layout.ty.sty {
|
|
|
|
ty::Ref(_, _, mutbl) => mutbl, // go ahead
|
2018-11-07 07:56:25 -06:00
|
|
|
_ => return Ok(()), // do nothing, for now
|
2018-10-26 04:31:20 -05:00
|
|
|
};
|
2018-11-07 07:56:25 -06:00
|
|
|
// Retag the pointer and write it back.
|
2018-11-05 01:51:55 -06:00
|
|
|
let val = self.read_immediate(self.place_to_op(place)?)?;
|
2018-11-09 03:53:28 -06:00
|
|
|
let val = self.reborrow(val, mutbl)?;
|
2018-11-05 01:51:55 -06:00
|
|
|
self.write_immediate(val, place)?;
|
2018-10-24 10:17:44 -05:00
|
|
|
Ok(())
|
|
|
|
}
|
2018-10-16 11:01:50 -05:00
|
|
|
}
|