Fix mono reachability with no-op landing pads

[amirHdev]

the landing pad filtering used regular MIR successors when the initial traversal used monomorphized one
fixes #159980

[rustbot]

r? @davidtwco

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The reviewer was selected based on:

• Owners of files modified in this PR: compiler
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[davidtwco]

@bors r+ rollup

[rust-bors]

📌 Commit ffd19d0 has been approved by davidtwco

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 10. This pull request will be tested once the tree is reopened.

Reason for tree closure: manually handling queue due to backlog

[JonathanBrouwer]

@rust-timer build a3989e1

[rust-timer]

Finished benchmarking commit (a3989e1): comparison URL.

Overall result: ❌✅ regressions and improvements - 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 rustc-perf
@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)	0.2%	[0.2%, 0.3%]	5
Regressions ❌ (secondary)	2.5%	[0.1%, 8.5%]	19
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.1%]	4
All ❌✅ (primary)	0.2%	[0.2%, 0.3%]	5

Max RSS (memory usage)

Results (primary 0.9%, secondary 17.1%)

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

	mean	range	count
Regressions ❌ (primary)	0.9%	[0.9%, 0.9%]	1
Regressions ❌ (secondary)	24.7%	[0.8%, 30.1%]	13
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.9%	[-6.1%, -0.6%]	5
All ❌✅ (primary)	0.9%	[0.9%, 0.9%]	1

Cycles

Results (primary 1.5%, secondary 8.5%)

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

	mean	range	count
Regressions ❌ (primary)	1.5%	[0.5%, 2.9%]	9
Regressions ❌ (secondary)	10.8%	[0.5%, 31.7%]	28
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.9%	[-14.0%, -0.6%]	5
All ❌✅ (primary)	1.5%	[0.5%, 2.9%]	9

Binary size

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

Bootstrap: 489.825s -> 491.238s (0.29%)
Artifact size: 391.14 MiB -> 393.43 MiB (0.59%)

[JonathanBrouwer]

Something funky is going on, all PRs in the rollup have this same result