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Auto merge of #92278 - Aaron1011:fix-fingerprint-caching, r=michaelwoerister

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Ensure that `Fingerprint` caching respects hashing configuration

Fixes #92266

In some `HashStable` impls, we use a cache to avoid re-computing
the same `Fingerprint` from the same structure (e.g. an `AdtDef`).
However, the `StableHashingContext` used can be configured to
perform hashing in different ways (e.g. skipping `Span`s). This
configuration information is not included in the cache key,
which will cause an incorrect `Fingerprint` to be used if
we hash the same structure with different `StableHashingContext`
settings.

To fix this, the configuration settings of `StableHashingContext`
are split out into a separate `HashingControls` struct. This
struct is used as part of the cache key, ensuring that our caches
always produce the correct result for the given settings.

With this in place, we now turn off `Span` hashing during the
entire process of computing the hash included in legacy symbols.
This current has no effect, but will matter when a future PR
starts hashing more `Span`s that we currently skip.
This commit is contained in:
bors
2022-01-10 00:26:07 +00:00
parent 092e1c9d23 4ca275add0
commit d63a8d965e
9 changed files with 120 additions and 48 deletions
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6
compiler/rustc_middle/src/ty/adt.rs
View File

@@ -4,6 +4,7 @@ use crate::ty::util::{Discr, IntTypeExt};
use rustc_data_structures::captures::Captures;
use rustc_data_structures::fingerprint::Fingerprint;
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::stable_hasher::HashingControls;
use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
use rustc_errors::ErrorReported;
use rustc_hir as hir;
@@ -136,12 +137,13 @@ impl Hash for AdtDef {
impl<'a> HashStable<StableHashingContext<'a>> for AdtDef {
fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
thread_local! {
static CACHE: RefCell<FxHashMap<usize, Fingerprint>> = Default::default();
static CACHE: RefCell<FxHashMap<(usize, HashingControls), Fingerprint>> = Default::default();
}
let hash: Fingerprint = CACHE.with(|cache| {
let addr = self as *const AdtDef as usize;
*cache.borrow_mut().entry(addr).or_insert_with(|| {
let hashing_controls = hcx.hashing_controls();
*cache.borrow_mut().entry((addr, hashing_controls)).or_insert_with(|| {
let ty::AdtDef { did, ref variants, ref flags, ref repr } = *self;
let mut hasher = StableHasher::new();

5
compiler/rustc_middle/src/ty/impls_ty.rs
View File

@@ -6,6 +6,7 @@ use crate::mir;
use crate::ty;
use rustc_data_structures::fingerprint::Fingerprint;
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::stable_hasher::HashingControls;
use rustc_data_structures::stable_hasher::{HashStable, StableHasher, ToStableHashKey};
use rustc_query_system::ich::StableHashingContext;
use std::cell::RefCell;
@@ -17,12 +18,12 @@ where
{
fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
thread_local! {
static CACHE: RefCell<FxHashMap<(usize, usize), Fingerprint>> =
static CACHE: RefCell<FxHashMap<(usize, usize, HashingControls), Fingerprint>> =
RefCell::new(Default::default());
}
let hash = CACHE.with(|cache| {
let key = (self.as_ptr() as usize, self.len());
let key = (self.as_ptr() as usize, self.len(), hcx.hashing_controls());
if let Some(&hash) = cache.borrow().get(&key) {
return hash;
}