Encode span parent in the inlined representation.

[cjgillot]

Follow-up to #84373 attempting to store SpanData::parent in the inline Span implementation.

[rust-highfive]

r? @michaelwoerister

(rust-highfive has picked a reviewer for you, use r? to override)

[michaelwoerister]

r? @JohnTitor (randomly picked someone from wg-diagnostics, feel free to re-assign)

[michaelwoerister]

Sorry, wrong PR :)

r? @michaelwoerister

[michaelwoerister]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[bors]

⌛ Trying commit fb97675ade329b7a5b6d4802f8e4a16f255ff286 with merge a13e5e0fd686d901e52bfc27198f084a6e09f3d7...

[bors]

☀️ Try build successful - checks-actions
Build commit: a13e5e0fd686d901e52bfc27198f084a6e09f3d7 (a13e5e0fd686d901e52bfc27198f084a6e09f3d7)

[rust-timer]

Queued a13e5e0fd686d901e52bfc27198f084a6e09f3d7 with parent ec9a1bd, future comparison URL.

[rust-timer]

Finished benchmarking commit (a13e5e0fd686d901e52bfc27198f084a6e09f3d7): comparison url.

Summary: This change led to small relevant regressions 😿 in compiler performance.

• Small regression in instruction counts (up to 0.6% on incr-unchanged builds of tuple-stress)

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR led to changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf +perf-regression

[michaelwoerister]

Is this PR still active? It does not seem to give the performance improvements we hoped for.

[JohnCSimon]

@cjgillot - ping from triage:

Is this PR still active? It does not seem to give the performance improvements we hoped for.