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Fix determinism of compiled modules (#3229)

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* Fix determinism of compiled modules

Currently wasmtime's compilation artifacts are not deterministic due to
the usage of `HashMap` during serialization which has randomized order
of its elements. This commit fixes that by switching to a sorted
`BTreeMap` for various maps. A test is also added to ensure determinism.

If in the future the performance of `BTreeMap` is not as good as
`HashMap` for some of these cases we can implement a fancier
`serialize_with`-style solution where we sort keys during serialization,
but only during serialization and otherwise use a `HashMap`.

* fix lightbeam
This commit is contained in:
Alex Crichton
2021-08-23 17:08:19 -05:00
committed by GitHub
parent eb21ae149a
commit f3977f1d97
7 changed files with 63 additions and 20 deletions
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10
crates/environ/src/module.rs
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@@ -3,7 +3,7 @@
use crate::{EntityRef, PrimaryMap, Tunables};
use indexmap::IndexMap;
use serde::{Deserialize, Serialize};
use std::collections::{HashMap, HashSet};
use std::collections::{BTreeMap, BTreeSet};
use std::convert::TryFrom;
use std::sync::Arc;
use wasmtime_types::*;
@@ -349,17 +349,17 @@ pub struct Module {
pub passive_elements: Vec<Box<[FuncIndex]>>,
/// The map from passive element index (element segment index space) to index in `passive_elements`.
pub passive_elements_map: HashMap<ElemIndex, usize>,
pub passive_elements_map: BTreeMap<ElemIndex, usize>,
/// WebAssembly passive data segments.
#[serde(with = "passive_data_serde")]
pub passive_data: Vec<Arc<[u8]>>,
/// The map from passive data index (data segment index space) to index in `passive_data`.
pub passive_data_map: HashMap<DataIndex, usize>,
pub passive_data_map: BTreeMap<DataIndex, usize>,
/// WebAssembly function names.
pub func_names: HashMap<FuncIndex, String>,
pub func_names: BTreeMap<FuncIndex, String>,
/// Types declared in the wasm module.
pub types: PrimaryMap<TypeIndex, ModuleType>,
@@ -396,7 +396,7 @@ pub struct Module {
/// The set of defined functions within this module which are located in
/// element segments.
pub possibly_exported_funcs: HashSet<DefinedFuncIndex>,
pub possibly_exported_funcs: BTreeSet<DefinedFuncIndex>,
}
/// Initialization routines for creating an instance, encompassing imports,