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search_graph: strengthen provisional cache by tracking more info in the happy path#155917

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lcnr:memories-of-a-forgotten-past
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search_graph: strengthen provisional cache by tracking more info in the happy path#155917
lcnr wants to merge 2 commits intorust-lang:mainfrom
lcnr:memories-of-a-forgotten-past

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@lcnr lcnr commented Apr 28, 2026 •
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See the added inline comment, stacked on top of #155914

r? BoxyUwU

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) labels Apr 28, 2026
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rustbot commented Apr 28, 2026

BoxyUwU is currently at their maximum review capacity.
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lcnr
lcnr commented Apr 28, 2026
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Comment thread compiler/rustc_type_ir/src/search_graph/mod.rs
{
continue;
}
}
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@lcnr lcnr Apr 28, 2026 •
edited by rustbot
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this fast path meant exponential blowup in ml-kem ended up causing a hang. let's instead just track all nested goals

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@lcnr lcnr marked this pull request as draft April 28, 2026 11:42
@rustbot rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Apr 28, 2026
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lcnr commented Apr 28, 2026

@bors try @rust-timer queue

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@rustbot rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Apr 28, 2026
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rust-bors Bot pushed a commit that referenced this pull request Apr 28, 2026
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Auto merge of #155917 - lcnr:memories-of-a-forgotten-past, r=<try>
4fcc7a6 
Memories of a forgotten past
@lcnr lcnr changed the title Memories of a forgotten past search_graph: strengthen provisional cache by tracking more info in the happy path Apr 28, 2026
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@lcnr lcnr force-pushed the memories-of-a-forgotten-past branch from bf814f9 to 31ca4ac Compare April 28, 2026 12:00
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rust-bors Bot commented Apr 28, 2026

☀️ Try build successful (CI)
Build commit: 4fcc7a6 (4fcc7a6db761f82fbe08fb9c1fb17ea68c0758ca, parent: 4ddb0b7f8ecda9dbdbcbc0519c9988badbd65d1c)

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rust-timer commented Apr 28, 2026

Finished benchmarking commit (4fcc7a6): comparison URL.

Overall result: ❌ regressions - please read:

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

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

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

mean range count
Regressions ❌
(primary)		 - - 0
Regressions ❌
(secondary)		 0.7% [0.2%, 1.5%] 10
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) - - 0

Max RSS (memory usage)

Results (primary 0.7%, secondary 7.9%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

mean range count
Regressions ❌
(primary)		 4.1% [4.1%, 4.1%] 1
Regressions ❌
(secondary)		 7.9% [1.6%, 18.1%] 9
Improvements ✅
(primary)		 -2.7% [-2.7%, -2.7%] 1
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) 0.7% [-2.7%, 4.1%] 2

Cycles

Results (primary 2.0%, secondary 0.6%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

mean range count
Regressions ❌
(primary)		 2.0% [2.0%, 2.0%] 1
Regressions ❌
(secondary)		 2.1% [2.0%, 2.2%] 2
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 -2.4% [-2.4%, -2.4%] 1
All ❌✅ (primary) 2.0% [2.0%, 2.0%] 1

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 489.39s -> 485.808s (-0.73%)
Artifact size: 393.41 MiB -> 393.44 MiB (0.01%)

@rustbot rustbot added perf-regression Performance regression. and removed S-waiting-on-perf Status: Waiting on a perf run to be completed. labels Apr 28, 2026
lcnr
lcnr commented Apr 30, 2026
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Comment thread compiler/rustc_type_ir/src/search_graph/mod.rs
// - A
// - BA cycle
// - CB :x:
if let Some(result) = self.lookup_provisional_cache(input, step_kind_from_parent) {
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@lcnr lcnr Apr 30, 2026 •
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should move this below the global cache, don't think there's a good reason to do this early anymore

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actually, this is necessary for

  • ABC
  • D
    • EA
      • BC overflow
      • D cycle
    • A ❌ both the global cache and the provisional cache are applicable?

@lcnr lcnr mentioned this pull request May 1, 2026
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