Fix issues and Update toolchain 10-26

[jaisnan]

Resolves issues caused by

1. rename Generator to Coroutine rust-lang/rust#116958
2. Rollup of 6 pull requests rust-lang/rust#117103

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 and MIT licenses.

[celinval]

Looks good! Thanks Jai

[adpaco-aws]

Despite this looking like a simple renaming, there is a performance regression in the hashset/check_insert_two_concrete benchmark. Comparing runs with the latest run in main:

	This PR	Latest in main	Difference
number_program_steps	33199	28927	+4272
number_vccs	3310	2859	+451
solver_runtime	48.81328	12.15361	+301.636%
symex_runtime	31.2295	28.7472	+8.635%
verification_time	88.96327	48.72418	+82.585%

@zhassan-aws @tautschnig have you seen this benchmark fail lately? Do you have any suggestions?

[jaisnan]

@adpaco-aws, the second issue rust-lang/rust#117103 required very minor refactoring, which is contained in this commit dce6524. It's possible that this could be causing the performance regression.

[celinval]

Hi @jaisnan, can you compare the MIR emitted before and after the toolchain upgrade (Instruction here)?

My guess is that the performance impact doesn't have anything to do with the conflict resolutions but more with an underlying change to the compiler.

[jaisnan]

I ran kani on the check_insert_two_concrete example with the command RUSTFLAGS="--emit mir" /home/ubuntu/kani/scripts/kani src/lib.rs --harness check_insert_two_concrete before and after the toolchain update.

My findings were:

1. There is no difference in the MIRs generated by Kani in the two cases. I used diff to compare the two files and found no difference in the two MIRs.
2. However, the symtabs for the two cases have a pretty big difference. The symtab for the case after the update is larger.
3. Even locally, the performance seems to have regressed.

Before:

---snip---
Check 2220: std::ptr::swap_nonoverlapping_simple_untyped::<u8>.unwind.0
	 - Status: SUCCESS
	 - Description: "unwinding assertion loop 0"
	 - Location: ../../../../.rustup/toolchains/nightly-2023-10-20-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ptr/mod.rs:977:5 in function std::ptr::swap_nonoverlapping_simple_untyped::<u8>

SUMMARY:
 ** 0 of 2221 failed (73 unreachable)

VERIFICATION:- SUCCESSFUL
Verification Time: 39.018295s

Complete - 1 successfully verified harnesses, 0 failures, 1 total.

After:

---snip---
Check 2315: std::ptr::swap_nonoverlapping_simple_untyped::<u8>.unwind.0
	 - Status: SUCCESS
	 - Description: "unwinding assertion loop 0"
	 - Location: ../../../../.rustup/toolchains/nightly-2023-10-26-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ptr/mod.rs:977:5 in function std::ptr::swap_nonoverlapping_simple_untyped::<u8>

SUMMARY:
 ** 0 of 2316 failed (76 unreachable)

VERIFICATION:- SUCCESSFUL
Verification Time: 53.54866s

[adpaco-aws]

We agreed to merge the PR and continue the investigation in a separate issue. @jaisnan do you mind opening that?