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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2018-10-18 09:59:08 -05:00
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use rustc::hir;
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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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2018-11-05 09:05:17 -06:00
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EvalResult, 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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2018-11-05 09:05:17 -06:00
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Pointer, 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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2018-11-05 09:05:17 -06:00
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pub fn is_shr(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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2018-11-05 09:05:17 -06:00
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pub fn is_uniq(self) -> bool {
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match self {
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2018-11-05 09:05:17 -06:00
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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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2018-11-05 09:05:17 -06:00
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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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2018-10-16 04:21:38 -05:00
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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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2018-10-30 10:46:28 -05:00
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/// What kind of usage of the pointer are we talking about?
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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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2018-10-30 10:46:28 -05:00
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pub enum UsageKind {
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/// Write, or create &mut
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Write,
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/// Read, or create &
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Read,
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/// Create * (raw ptr)
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Raw,
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}
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2018-10-30 10:46:28 -05:00
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impl From<Option<hir::Mutability>> for UsageKind {
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fn from(mutbl: Option<hir::Mutability>) -> Self {
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match mutbl {
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2018-10-30 10:46:28 -05:00
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None => UsageKind::Raw,
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Some(hir::MutMutable) => UsageKind::Write,
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Some(hir::MutImmutable) => UsageKind::Read,
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2018-10-19 09:07:40 -05:00
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}
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}
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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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2018-10-26 04:31:20 -05:00
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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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}
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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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/// Core operations
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impl<'tcx> Stack {
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2018-10-19 09:07:40 -05:00
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/// Check if `bor` could be activated by unfreezing and popping.
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2018-11-05 09:23:22 -06:00
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/// `is_write` indicates whether this is being used to write (or, equivalently, to
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/// borrow as &mut).
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2018-11-05 09:05:17 -06:00
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/// Returns `Err` if the answer is "no"; otherwise the return value indicates what to
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/// do: With `Some(n)` you need to unfreeze, and then additionally pop `n` items.
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2018-11-05 09:23:22 -06:00
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fn reactivatable(&self, bor: Borrow, is_write: bool) -> Result<Option<usize>, String> {
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2018-11-05 09:05:17 -06:00
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// Check if we can match the frozen "item". Not possible on writes!
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2018-11-05 09:23:22 -06:00
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if !is_write {
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2018-11-05 09:05:17 -06:00
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// For now, we do NOT check the timestamp. That might be surprising, but
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// we cannot even notice when a location should be frozen but is not!
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// Those checks are both done in `tag_dereference`, where we have type information.
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// Either way, it is crucial that the frozen "item" matches raw pointers:
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// Reading through a raw should not unfreeze.
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match (self.frozen_since, bor) {
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(Some(_), Borrow::Shr(_)) => {
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return Ok(None)
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}
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_ => {},
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}
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}
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// See if we can find this borrow.
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for (idx, &itm) in self.borrows.iter().rev().enumerate() {
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// Check borrow and stack item for compatibility.
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match (itm, bor) {
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(BorStackItem::FnBarrier(_), _) => {
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return Err(format!("Trying to reactivate a borrow ({:?}) that lives \
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behind a barrier", bor))
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}
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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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2018-11-05 09:23:22 -06:00
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if !is_write {
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2018-11-05 09:05:17 -06:00
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// As a special case, if we are reading and since we *did* find the `Uniq`,
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// we try to pop less: We are happy with making a `Shr` or `Frz` active;
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// that one will not mind concurrent reads.
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2018-11-05 09:23:22 -06:00
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match self.reactivatable(Borrow::default(), is_write) {
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2018-11-05 09:05:17 -06:00
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// If we got something better that `idx`, use that
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Ok(None) => return Ok(None),
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Ok(Some(shr_idx)) if shr_idx <= idx => return Ok(Some(shr_idx)),
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// Otherwise just go on.
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_ => {},
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2018-10-30 09:08:18 -05:00
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}
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}
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2018-11-05 09:05:17 -06:00
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return Ok(Some(idx))
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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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2018-10-22 11:01:32 -05:00
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// Nothing to be found.
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2018-11-05 09:05:17 -06:00
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Err(format!("Borrow-to-reactivate {:?} does not exist on the stack", bor))
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2018-10-23 08:59:50 -05:00
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}
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2018-11-05 09:23:22 -06:00
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/// Reactive `bor` for this stack. `is_write` indicates whether this is being
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/// used to write (or, equivalently, to borrow as &mut).
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fn reactivate(&mut self, bor: Borrow, is_write: bool) -> EvalResult<'tcx> {
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let mut pop = match self.reactivatable(bor, is_write) {
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2018-11-05 09:05:17 -06:00
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Ok(None) => return Ok(()),
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Ok(Some(pop)) => pop,
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2018-10-23 08:59:50 -05:00
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Err(err) => return err!(MachineError(err)),
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};
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2018-11-05 09:05:17 -06:00
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// Pop what `reactivatable` told us to pop. Always unfreeze.
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if self.is_frozen() {
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trace!("reactivate: Unfreezing");
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}
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self.frozen_since = None;
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while pop > 0 {
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let itm = self.borrows.pop().unwrap();
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trace!("reactivate: Popping {:?}", itm);
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pop -= 1;
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2018-10-23 08:59:50 -05:00
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}
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Ok(())
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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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/// is met: We cannot push onto frozen stacks.
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fn initiate(&mut self, bor: Borrow) {
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2018-11-05 09:05:17 -06:00
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if let Some(_) = self.frozen_since {
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// "Pushing" a Shr or Frz on top is redundant.
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match bor {
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Borrow::Uniq(_) => bug!("Trying to create unique ref to frozen location"),
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Borrow::Shr(_) => trace!("initiate: New shared ref to frozen location is a NOP"),
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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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} else {
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// Just 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(_) if *self.borrows.last().unwrap() == BorStackItem::Shr => {
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// Optimization: Don't push a Shr onto a Shr.
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trace!("initiate: New shared ref to already shared location is a NOP");
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return
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},
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Borrow::Shr(_) => BorStackItem::Shr,
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};
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trace!("initiate: Pushing {:?}", itm);
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self.borrows.push(itm)
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}
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}
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/// Check if this location is "frozen enough".
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fn check_frozen(&self, bor_t: Timestamp) -> EvalResult<'tcx> {
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let frozen = self.frozen_since.map_or(false, |itm_t| itm_t <= bor_t);
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if !frozen {
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err!(MachineError(format!("Location is not frozen long enough")))
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} else {
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Ok(())
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}
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}
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/// Freeze this location, since `bor_t`.
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fn freeze(&mut self, bor_t: Timestamp) {
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if let Some(itm_t) = self.frozen_since {
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assert!(itm_t <= bor_t, "Trying to freeze shorter than it was frozen?");
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} else {
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trace!("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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impl State {
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2018-10-26 04:31:20 -05:00
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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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2018-10-18 09:59:08 -05:00
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val
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2018-10-16 11:01:50 -05:00
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}
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}
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2018-10-17 08:15:53 -05:00
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/// Higher-level operations
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impl<'tcx> Stacks {
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2018-11-05 09:23:22 -06:00
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/// The single most important operation: Make sure that using `ptr` is okay,
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2018-10-29 13:48:43 -05:00
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/// and if `new_bor` is present then make that the new current borrow.
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fn use_and_maybe_re_borrow(
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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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2018-10-30 10:46:28 -05:00
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usage: UsageKind,
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2018-10-29 13:48:43 -05:00
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new_bor: Option<Borrow>,
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2018-10-17 08:15:53 -05:00
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) -> EvalResult<'tcx> {
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2018-10-29 13:48:43 -05:00
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trace!("use_and_maybe_re_borrow of tag {:?} as {:?}, new {:?}: {:?}, size {}",
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2018-10-30 10:46:28 -05:00
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ptr.tag, usage, new_bor, 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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for stack in stacks.iter_mut(ptr.offset, size) {
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2018-11-05 09:23:22 -06:00
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stack.reactivate(ptr.tag, usage == UsageKind::Write)?;
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2018-10-29 13:48:43 -05:00
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if let Some(new_bor) = new_bor {
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stack.initiate(new_bor);
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2018-10-17 08:15:53 -05:00
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}
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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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}
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2018-10-17 08:15:53 -05:00
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2018-11-05 09:05:17 -06:00
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/// Freeze the given memory range.
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fn freeze(
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&self,
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ptr: Pointer<Borrow>,
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|
|
size: Size,
|
|
|
|
bor_t: Timestamp
|
|
|
|
) -> EvalResult<'tcx> {
|
|
|
|
let mut stacks = self.stacks.borrow_mut();
|
|
|
|
for stack in stacks.iter_mut(ptr.offset, size) {
|
|
|
|
stack.freeze(bor_t);
|
|
|
|
}
|
2018-10-17 08:15:53 -05:00
|
|
|
Ok(())
|
|
|
|
}
|
2018-10-22 11:01:32 -05:00
|
|
|
|
2018-11-05 09:05:17 -06:00
|
|
|
/// Check that this stack is fine with being dereferenced
|
|
|
|
fn check_deref(
|
|
|
|
&self,
|
|
|
|
ptr: Pointer<Borrow>,
|
|
|
|
size: Size,
|
|
|
|
) -> EvalResult<'tcx> {
|
|
|
|
let mut stacks = self.stacks.borrow_mut();
|
|
|
|
// We need `iter_mut` because `iter` would skip gaps!
|
|
|
|
for stack in stacks.iter_mut(ptr.offset, size) {
|
|
|
|
// Conservatively assume we will just read
|
2018-11-05 09:23:22 -06:00
|
|
|
if let Err(err) = stack.reactivatable(ptr.tag, /*is_write*/false) {
|
2018-11-05 09:05:17 -06:00
|
|
|
return err!(MachineError(format!(
|
|
|
|
"Encountered reference with non-reactivatable tag: {}",
|
|
|
|
err
|
|
|
|
)))
|
|
|
|
}
|
|
|
|
}
|
|
|
|
Ok(())
|
|
|
|
}
|
|
|
|
|
|
|
|
/// Check that this stack is appropriately frozen
|
|
|
|
fn check_frozen(
|
|
|
|
&self,
|
|
|
|
ptr: Pointer<Borrow>,
|
|
|
|
size: Size,
|
|
|
|
bor_t: Timestamp
|
|
|
|
) -> EvalResult<'tcx> {
|
|
|
|
let mut stacks = self.stacks.borrow_mut();
|
|
|
|
for stack in stacks.iter_mut(ptr.offset, size) {
|
|
|
|
stack.check_frozen(bor_t)?;
|
|
|
|
}
|
|
|
|
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> {
|
|
|
|
// Reads behave exactly like the first half of a reborrow-to-shr
|
2018-11-12 01:54:12 -06:00
|
|
|
alloc.extra.use_and_maybe_re_borrow(ptr, size, UsageKind::Read, None)
|
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> {
|
|
|
|
// Writes behave exactly like the first half of a reborrow-to-mut
|
2018-11-12 01:54:12 -06:00
|
|
|
alloc.extra.use_and_maybe_re_borrow(ptr, size, UsageKind::Write, None)
|
2018-10-29 13:48:43 -05:00
|
|
|
}
|
2018-11-12 01:54:12 -06:00
|
|
|
}
|
2018-10-29 13:48:43 -05:00
|
|
|
|
2018-11-12 01:54:12 -06:00
|
|
|
impl<'tcx> Stacks {
|
|
|
|
#[inline(always)]
|
2018-10-29 13:48:43 -05:00
|
|
|
pub fn memory_deallocated(
|
|
|
|
&mut self,
|
|
|
|
ptr: Pointer<Borrow>,
|
|
|
|
size: Size,
|
|
|
|
) -> EvalResult<'tcx> {
|
|
|
|
// This is like mutating
|
2018-10-30 10:46:28 -05:00
|
|
|
self.use_and_maybe_re_borrow(ptr, size, UsageKind::Write, None)
|
2018-10-29 13:48:43 -05:00
|
|
|
// FIXME: Error out of there are any barriers?
|
|
|
|
}
|
|
|
|
|
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_reference(
|
2018-10-26 04:31:20 -05:00
|
|
|
&mut self,
|
2018-11-05 09:05:17 -06:00
|
|
|
place: MPlaceTy<'tcx, Borrow>,
|
2018-10-16 11:01:50 -05:00
|
|
|
size: Size,
|
2018-10-30 10:46:28 -05:00
|
|
|
usage: UsageKind,
|
2018-10-16 11:01:50 -05:00
|
|
|
) -> EvalResult<'tcx, Borrow>;
|
|
|
|
|
|
|
|
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,
|
2018-10-30 10:46:28 -05:00
|
|
|
usage: UsageKind,
|
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
|
|
|
|
|
|
|
fn retag(
|
|
|
|
&mut self,
|
|
|
|
fn_entry: bool,
|
|
|
|
place: PlaceTy<'tcx, Borrow>
|
|
|
|
) -> EvalResult<'tcx>;
|
2018-10-16 11:01:50 -05:00
|
|
|
}
|
|
|
|
|
2018-11-05 09:05:17 -06:00
|
|
|
impl<'a, 'mir, 'tcx> EvalContextExt<'tcx> for MiriEvalContext<'a, 'mir, 'tcx> {
|
2018-10-26 04:31:20 -05:00
|
|
|
/// Called for place-to-value conversion.
|
|
|
|
fn tag_reference(
|
|
|
|
&mut self,
|
2018-11-05 09:05:17 -06:00
|
|
|
place: MPlaceTy<'tcx, Borrow>,
|
2018-10-26 04:31:20 -05:00
|
|
|
size: Size,
|
2018-10-30 10:46:28 -05:00
|
|
|
usage: UsageKind,
|
2018-10-26 04:31:20 -05:00
|
|
|
) -> EvalResult<'tcx, Borrow> {
|
2018-11-05 09:05:17 -06:00
|
|
|
let ptr = place.ptr.to_ptr()?;
|
2018-10-16 11:01:50 -05:00
|
|
|
let time = self.machine.stacked_borrows.increment_clock();
|
2018-10-30 10:46:28 -05:00
|
|
|
let new_bor = match usage {
|
2018-11-05 09:05:17 -06:00
|
|
|
UsageKind::Write => Borrow::Uniq(time),
|
|
|
|
UsageKind::Read => Borrow::Shr(Some(time)),
|
|
|
|
UsageKind::Raw => Borrow::Shr(None),
|
2018-10-26 04:31:20 -05:00
|
|
|
};
|
2018-11-05 09:05:17 -06:00
|
|
|
trace!("tag_reference: Creating new reference ({:?}) for {:?} (pointee {}): {:?}",
|
|
|
|
usage, ptr, place.layout.ty, new_bor);
|
2018-10-16 11:01:50 -05:00
|
|
|
|
2018-11-05 09:05:17 -06:00
|
|
|
// Update the stacks. First create the new ref as usual, then maybe freeze stuff.
|
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!");
|
2018-10-30 10:46:28 -05:00
|
|
|
alloc.extra.use_and_maybe_re_borrow(ptr, size, usage, Some(new_bor))?;
|
2018-11-05 09:05:17 -06:00
|
|
|
// Maybe freeze stuff
|
|
|
|
if let Borrow::Shr(Some(bor_t)) = new_bor {
|
|
|
|
self.visit_frozen(place, size, |frz_ptr, size| {
|
|
|
|
debug_assert_eq!(frz_ptr.alloc_id, ptr.alloc_id);
|
|
|
|
// Be frozen!
|
|
|
|
alloc.extra.freeze(frz_ptr, size, bor_t)
|
|
|
|
})?;
|
|
|
|
}
|
2018-10-16 11:01:50 -05:00
|
|
|
|
|
|
|
Ok(new_bor)
|
|
|
|
}
|
|
|
|
|
2018-10-18 09:59:08 -05:00
|
|
|
/// Called for value-to-place conversion.
|
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,
|
2018-10-30 10:46:28 -05:00
|
|
|
usage: UsageKind,
|
2018-10-16 11:01:50 -05:00
|
|
|
) -> EvalResult<'tcx, Borrow> {
|
2018-11-05 09:05:17 -06:00
|
|
|
let ptr = place.ptr.to_ptr()?;
|
|
|
|
trace!("tag_dereference: Accessing reference ({:?}) for {:?} (pointee {})",
|
|
|
|
usage, ptr, place.layout.ty);
|
2018-10-19 09:07:40 -05:00
|
|
|
// In principle we should not have to do anything here. However, with transmutes involved,
|
2018-10-30 10:46:28 -05:00
|
|
|
// it can happen that the tag of `ptr` does not actually match `usage`, 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.
|
2018-10-30 10:46:28 -05:00
|
|
|
match (usage, ptr.tag) {
|
|
|
|
(UsageKind::Raw, _) => {
|
2018-10-22 11:01:32 -05:00
|
|
|
// Don't use the tag, this is a raw access! Even if there is a tag,
|
|
|
|
// that means transmute happened and we ignore the tag.
|
|
|
|
// 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
|
|
|
}
|
2018-11-05 09:05:17 -06:00
|
|
|
(UsageKind::Write, Borrow::Uniq(_)) |
|
|
|
|
(UsageKind::Read, Borrow::Shr(_)) => {
|
2018-10-19 09:07:40 -05:00
|
|
|
// Expected combinations. Nothing to do.
|
|
|
|
}
|
2018-11-05 09:05:17 -06:00
|
|
|
(UsageKind::Write, Borrow::Shr(None)) => {
|
2018-10-22 11:01:32 -05:00
|
|
|
// Raw transmuted to mut ref. Keep this as raw access.
|
2018-10-19 09:07:40 -05:00
|
|
|
// We cannot reborrow here; there might be a raw in `&(*var).1` where
|
|
|
|
// `var` is an `&mut`. The other field of the struct might be already frozen,
|
|
|
|
// also using `var`, and that would be okay.
|
|
|
|
}
|
2018-11-05 09:05:17 -06:00
|
|
|
(UsageKind::Read, 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
|
|
|
}
|
2018-11-05 09:05:17 -06:00
|
|
|
(UsageKind::Write, Borrow::Shr(Some(_))) => {
|
|
|
|
// 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
|
|
|
|
|
|
|
// If we got here, we do some checking, *but* we leave the tag unchanged.
|
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!");
|
2018-11-05 09:05:17 -06:00
|
|
|
alloc.extra.check_deref(ptr, size)?;
|
|
|
|
// Maybe check frozen stuff
|
|
|
|
if let Borrow::Shr(Some(bor_t)) = ptr.tag {
|
|
|
|
self.visit_frozen(place, size, |frz_ptr, size| {
|
|
|
|
debug_assert_eq!(frz_ptr.alloc_id, ptr.alloc_id);
|
|
|
|
// Are you frozen?
|
|
|
|
alloc.extra.check_frozen(frz_ptr, size, bor_t)
|
|
|
|
})?;
|
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
|
|
|
|
|
|
|
fn tag_new_allocation(
|
|
|
|
&mut self,
|
|
|
|
id: AllocId,
|
|
|
|
kind: MemoryKind<MiriMemoryKind>,
|
|
|
|
) -> Borrow {
|
2018-11-05 09:05:17 -06:00
|
|
|
let time = match kind {
|
2018-10-22 11:01:32 -05:00
|
|
|
MemoryKind::Stack => {
|
2018-10-30 09:08:18 -05:00
|
|
|
// 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
|
2018-11-05 09:05:17 -06:00
|
|
|
self.machine.stacked_borrows.increment_clock()
|
2018-10-22 11:01:32 -05:00
|
|
|
}
|
|
|
|
_ => {
|
2018-11-05 09:05:17 -06:00
|
|
|
// Nothing to do for everything else
|
|
|
|
return Borrow::default()
|
2018-10-22 11:01:32 -05:00
|
|
|
}
|
|
|
|
};
|
|
|
|
// 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);
|
2018-11-05 09:05:17 -06:00
|
|
|
alloc.extra.first_item(BorStackItem::Uniq(time), size);
|
|
|
|
Borrow::Uniq(time)
|
2018-10-22 11:01:32 -05:00
|
|
|
}
|
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.
|
|
|
|
let mutbl = match place.layout.ty.sty {
|
|
|
|
ty::Ref(_, _, mutbl) => mutbl, // go ahead
|
|
|
|
_ => return Ok(()), // don't do a thing
|
|
|
|
};
|
|
|
|
// We want to reborrow the reference stored there. This will call the hooks
|
2018-10-29 13:48:43 -05:00
|
|
|
// above. First deref, which will call `tag_dereference`.
|
2018-10-26 04:31:20 -05:00
|
|
|
// (This is somewhat redundant because validation already did the same thing,
|
|
|
|
// but what can you do.)
|
2018-11-05 01:51:55 -06:00
|
|
|
let val = self.read_immediate(self.place_to_op(place)?)?;
|
2018-10-26 04:31:20 -05:00
|
|
|
let dest = self.ref_to_mplace(val)?;
|
2018-10-29 13:48:43 -05:00
|
|
|
// Now put a new ref into the old place, which will call `tag_reference`.
|
2018-10-26 04:31:20 -05:00
|
|
|
// FIXME: Honor `fn_entry`!
|
|
|
|
let val = self.create_ref(dest, Some(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
|
|
|
}
|