bjoernager/rust
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Tweak CGU sorting in a couple of places.

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In `base.rs`, tweak how the CGU size interleaving works. Since #113777,
it's much more common to have multiple CGUs with identical sizes. With
the existing code these same-sized items ended up in the
opposite-to-desired order due to the stable sorting. The code now starts
with a reverse sort (like is done in `partitioning.rs`) which gives the
behaviour we want. This doesn't matter much for perf, but makes profiles
in `samply` look more like what we expect.

In `partitioning.rs`, we can use `sort_by_key` instead of
`sort_by_cached_key` because `CGU::size_estimate()` is cheap. (There is
an identical CGU sort earlier in that function that already uses
`sort_by_key`.)
This commit is contained in:
Nicholas Nethercote 2023-07-20 09:52:26 +10:00
parent 0d6a9b2bf7
commit 8c31219d5c
2 changed files with 4 additions and 3 deletions
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2
compiler/rustc_monomorphize/src/partitioning.rs
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@ -394,7 +394,7 @@ fn merge_codegen_units<'tcx>(
&& codegen_units.iter().any(|cgu| cgu.size_estimate() < NON_INCR_MIN_CGU_SIZE)
{
// Sort small cgus to the back.
codegen_units.sort_by_cached_key(|cgu| cmp::Reverse(cgu.size_estimate()));
codegen_units.sort_by_key(|cgu| cmp::Reverse(cgu.size_estimate()));
let mut smallest = codegen_units.pop().unwrap();
let second_smallest = codegen_units.last_mut().unwrap();