[early rough draft] GCI: Don't evaluate free const items with impossible predicates

[fmease]

trafficstars

[fmease]

@bors2 try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

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

[rust-bors[bot]]

:hourglass: Trying commit 74ec3eab50aabb67fe2fd90b2dcee9855fd26b1b with merge 4151b9aaad261468f4260336981f34de2f05df15…

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Build completed unsuccessfully in 0:01:15
  local time: Tue Jun 10 12:32:22 UTC 2025
  network time: Tue, 10 Jun 2025 12:32:23 GMT
##[error]Process completed with exit code 1.
Post job cleanup.

[rust-bors[bot]]

:sunny: Try build successful (CI) Build commit: 4151b9aaad261468f4260336981f34de2f05df15 (4151b9aaad261468f4260336981f34de2f05df15)

[rust-timer]

Queued 4151b9aaad261468f4260336981f34de2f05df15 with parent 40daf23eeb711dadf140b2536e67e3ff4c999196, future comparison URL. There are currently 4 preceding artifacts in the queue. It will probably take at least ~5.9 hours until the benchmark run finishes.

[rust-timer]

Finished benchmarking commit (4151b9aaad261468f4260336981f34de2f05df15): comparison URL.

Overall result: no relevant changes - no action needed

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

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

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results (primary -5.1%, secondary -2.1%)

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

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.5%	[3.5%, 3.5%]	1
Improvements ✅ (primary)	-5.1%	[-9.4%, -3.0%]	6
Improvements ✅ (secondary)	-2.3%	[-4.3%, -1.1%]	21
All ❌✅ (primary)	-5.1%	[-9.4%, -3.0%]	6

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 753.145s -> 753.291s (0.02%) Artifact size: 372.18 MiB -> 372.22 MiB (0.01%)

[fmease]

Mono collector now uses instantiate_and_check_impossible_predicates which filters out predicates with early-bound regions contrary to impossible_predicates, so might have a mismatch in behavior between mono collection, reachability analysis and typeck which seems problematic but I haven't thought about it any further (does IACIP assume erased lifetimes?).

Despite that, imma recheck perf cuz I removed the predicates.is_empty() "micro opt". @bors2 try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

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

[rust-bors[bot]]

:hourglass: Trying commit 380088d922ec3713f9e685d246e2cc0ac9a616b0 with merge 10bc814a261100b40f7fa5feaa6a079876607337…

To cancel the try build, run the command @bors2 try cancel.

[rust-bors[bot]]

:sunny: Try build successful (CI) Build commit: 10bc814a261100b40f7fa5feaa6a079876607337 (10bc814a261100b40f7fa5feaa6a079876607337, parent: e4b9d0141fdd210fcceebd2b67f7be113401c461)

[rust-timer]

Queued 10bc814a261100b40f7fa5feaa6a079876607337 with parent e4b9d0141fdd210fcceebd2b67f7be113401c461, future comparison URL. There is currently 1 preceding artifact in the queue. It will probably take at least ~1.9 hours until the benchmark run finishes.

[rust-timer]

Finished benchmarking commit (10bc814a261100b40f7fa5feaa6a079876607337): comparison URL.

Overall result: ❌ regressions - please read the text below

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@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)	1.1%	[0.3%, 1.6%]	12
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.1%	[0.3%, 1.6%]	12

Max RSS (memory usage)

Results (secondary -2.4%)

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

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.4%	[-4.1%, -1.4%]	11
All ❌✅ (primary)	-	-	0

Cycles

Results (secondary -4.4%)

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

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-4.4%	[-4.5%, -4.4%]	2
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 690.402s -> 688.347s (-0.30%) Artifact size: 372.03 MiB -> 371.86 MiB (-0.04%)

[fmease]

@bors2 try parent=last @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

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

[rust-bors[bot]]

:hourglass: Trying commit 0e9126c9235e334793be63d50c961ae20c7702ed with merge cea506b6d4e9d59bbdaea6b74051c551246bff6d…

To cancel the try build, run the command @bors2 try cancel.

[rust-bors[bot]]

:sunny: Try build successful (CI) Build commit: cea506b6d4e9d59bbdaea6b74051c551246bff6d (cea506b6d4e9d59bbdaea6b74051c551246bff6d, parent: e4b9d0141fdd210fcceebd2b67f7be113401c461)

[rust-timer]

Queued cea506b6d4e9d59bbdaea6b74051c551246bff6d with parent e4b9d0141fdd210fcceebd2b67f7be113401c461, future comparison URL. There is currently 1 preceding artifact in the queue. It will probably take at least ~2.5 hours until the benchmark run finishes.

[rust-timer]

Finished benchmarking commit (cea506b6d4e9d59bbdaea6b74051c551246bff6d): comparison URL.

Overall result: ❌ regressions - please read the text below

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

@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)	0.7%	[0.3%, 1.0%]	8
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.7%	[0.3%, 1.0%]	8

Max RSS (memory usage)

Results (primary 2.3%)

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

	mean	range	count
Regressions ❌ (primary)	2.3%	[1.7%, 2.9%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.3%	[1.7%, 2.9%]	2

Cycles

Results (secondary -3.6%)

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

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.6%	[-4.1%, -3.0%]	2
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 690.402s -> 687.107s (-0.48%) Artifact size: 372.03 MiB -> 371.92 MiB (-0.03%)

[bors]

:umbrella: The latest upstream changes (presumably #142893) made this pull request unmergeable. Please resolve the merge conflicts.

[fmease]

PR #142893 (which conflicted with this PR / made it unmergeable) heavily affected perf. Thus I'm now retrying if this PR is still sensitive.

@bors2 try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

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

[rust-bors[bot]]

:hourglass: Trying commit 8d3bc941dc8a6c3716401e20ae06b2862ea427cd with merge 41283df7b958f7c986dcf1d3920b6896ab276564…

To cancel the try build, run the command @bors2 try cancel.

[rust-bors[bot]]

:sunny: Try build successful (CI) Build commit: 41283df7b958f7c986dcf1d3920b6896ab276564 (41283df7b958f7c986dcf1d3920b6896ab276564, parent: b94bd12401d26ccf1c3b04ceb4e950b0ff7c8d29)

[rust-timer]

Queued 41283df7b958f7c986dcf1d3920b6896ab276564 with parent b94bd12401d26ccf1c3b04ceb4e950b0ff7c8d29, future comparison URL. There are currently 11 preceding artifacts in the queue. It will probably take at least ~12.0 hours until the benchmark run finishes.

[rust-timer]

Finished benchmarking commit (41283df7b958f7c986dcf1d3920b6896ab276564): comparison URL.

Overall result: no relevant changes - no action needed

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

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

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results (primary 0.4%)

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

	mean	range	count
Regressions ❌ (primary)	2.0%	[1.5%, 2.4%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.8%	[-2.8%, -2.8%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.4%	[-2.8%, 2.4%]	3

Cycles

Results (primary -1.5%, secondary 8.2%)

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

	mean	range	count
Regressions ❌ (primary)	2.3%	[2.3%, 2.3%]	1
Regressions ❌ (secondary)	8.2%	[0.7%, 13.3%]	10
Improvements ✅ (primary)	-2.7%	[-5.1%, -1.0%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-1.5%	[-5.1%, 2.3%]	4

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 462.452s -> 460.902s (-0.34%) Artifact size: 372.20 MiB -> 372.15 MiB (-0.01%)

[rustbot]

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri, @RalfJung, @oli-obk, @lcnr

[fmease]

@rustbot review

[bors]

:umbrella: The latest upstream changes (presumably #144377) made this pull request unmergeable. Please resolve the merge conflicts.

[fmease]

semver concerns etc etc (voiced by Boxy) @rustbot author