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Rollup merge of #119591 - Enselic:DestinationPropagation-stable, r=cjgillot

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rustc_mir_transform: Make DestinationPropagation stable for queries

By using `FxIndexMap` instead of `FxHashMap`, so that the order of visiting of locals is deterministic.

We also need to bless
`copy_propagation_arg.foo.DestinationPropagation.panic*.diff`. Do not review the diff of the diff. Instead look at the diff files before and after this commit. Both before and after this commit, 3 statements are replaced with nop. It's just that due to change in ordering, different statements are replaced. But the net result is the same. In other words, compare this diff (before fix):
* 090d5eac72/tests/mir-opt/dest-prop/copy_propagation_arg.foo.DestinationPropagation.panic-unwind.diff

With this diff (after fix):
* f603babd63/tests/mir-opt/dest-prop/copy_propagation_arg.foo.DestinationPropagation.panic-unwind.diff

and you can see that both before and after the fix, we replace 3 statements with `nop`s.

I find it _slightly_ surprising that the test this PR affects did not previously fail spuriously due to the indeterminism of `FxHashMap`, but I guess in can be explained with the predictability of small `FxHashMap`s with `usize` (`Local`) keys, or something along those lines.

This should fix [this](https://github.com/rust-lang/rust/pull/119252#discussion_r1436101791) comment, but I wanted to make a separate PR for this fix for a simpler development and review process.

Part of https://github.com/rust-lang/rust/issues/84447 which is E-help-wanted.

r? `@cjgillot` who is reviewer for the highly related PR https://github.com/rust-lang/rust/pull/119252.
This commit is contained in:
Matthias Krüger 2024-01-06 16:07:47 +01:00 • committed by GitHub
commit 909f2b63a3
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compiler/rustc_data_structures/src/fx.rs
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@ -7,6 +7,7 @@ pub type StdEntry<'a, K, V> = std::collections::hash_map::Entry<'a, K, V>;
pub type FxIndexMap<K, V> = indexmap::IndexMap<K, V, BuildHasherDefault<FxHasher>>;
pub type FxIndexSet<V> = indexmap::IndexSet<V, BuildHasherDefault<FxHasher>>;
pub type IndexEntry<'a, K, V> = indexmap::map::Entry<'a, K, V>;
pub type IndexOccupiedEntry<'a, K, V> = indexmap::map::OccupiedEntry<'a, K, V>;
#[macro_export]
macro_rules! define_id_collections {