chore: Add mem2reg_simple pass

[jfecher]

Description

Problem

Resolves #9838

Summary

Adds a new ssa pass mem2reg_simple based on https://bernsteinbear.com/assets/img/bebenita-ssa.pdf which itself is a summary of https://link.springer.com/content/pdf/10.1007/3-540-46423-9_8.pdf.

The algorithm is roughly:

1. Create a block parameter for every possible variable in every possible block
2. Figure out the value of each variable at the end of each block, forward that as a jmp argument to the next block
3. For every block parameter, if the values passed to it from every jmp is the same, it can be removed and mapped to that value.

Or, again but in more detail:

1. Pre-process our CFG to ensure that for each node with multiple predecessors, each of its predecessors will have only one successor - the original node. This is a work-around since we do not support block arguments on jmpif terminators.
2. Collect every applicable variable to be optimized in the function. An applicable variable is a allocate instruction which is only used in the address field of store or load instructions - e.g. the address itself is never used in a first-class manner. Note that this excludes any variable that may be aliased, used in an array, function, etc.
3. For each variable, add block arguments to every block that is dominated by the variable's declaration block.
4. For each block, calculate:
   4.a. the value of each parameter at the start of the block (which will always just be the block argument)
   4.b. the value of each parameter at the end of the block (follow all the stores), optimizing out intermediate loads.
5. Go through each block, adding the ending value of each variable as a terminator argument to pass to the next blocks.
6. Go through each block's parameters. For each parameter, if the value of the jmp argument of all predecessor blocks is equal, the block parameter can be removed and we can map its value to the jmp value.

Additional Context

It turns out adding more block arguments to most blocks breaks a lot of things. Although by a lot of things it mostly just breaks unrolling in quite a few different ways. The process cfg mini pass also breaks unrolling's ability to identify all blocks in a loop, so that also had to be adjusted.

User Documentation

Check one:

• No user documentation needed.
• Changes in docs/ included in this PR.
• [For Experimental Features] Changes in docs/ to be submitted in a separate PR.

PR Checklist

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'ACVM Benchmarks'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: deca2cd	Previous: dbdfe6f	Ratio
perfectly_parallel_batch_inversion_opcodes	2790371 ns/iter (± 2019)	2262655 ns/iter (± 1808)	1.23

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CC: @TomAFrench

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Test Suite Duration'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: 8a72a40	Previous: 0db6c97	Ratio
test_report_zkpassport_noir-ecdsa_	2 s	1 s	2
test_report_zkpassport_noir_rsa_	1 s	0 s	+∞

This comment was automatically generated by workflow using github-action-benchmark.

CC: @TomAFrench

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Compilation Time'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: 8a72a40	Previous: 0db6c97	Ratio
rollup-tx-base-private	27.72 s	19.12 s	1.45
rollup-tx-base-public	131.8 s	80.78 s	1.63

This comment was automatically generated by workflow using github-action-benchmark.

CC: @TomAFrench

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Execution Time'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: deca2cd	Previous: dbdfe6f	Ratio
rollup-root	0.005 s	0.004 s	1.25

This comment was automatically generated by workflow using github-action-benchmark.

CC: @TomAFrench

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Opcode count'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.10.

Benchmark suite	Current: 8a72a40	Previous: 0db6c97	Ratio
rollup-tx-merge	1504 opcodes	1304 opcodes	1.15

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CC: @TomAFrench

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Execution Memory'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: 8a72a40	Previous: 0db6c97	Ratio
rollup-checkpoint-root-single-block	2140 MB	1760 MB	1.22
rollup-checkpoint-root	2140 MB	1760 MB	1.22

This comment was automatically generated by workflow using github-action-benchmark.

CC: @TomAFrench

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Brillig Execution Time'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: 8a72a40	Previous: 0db6c97	Ratio
rollup-tx-merge	0.002 s	0.001 s	2

This comment was automatically generated by workflow using github-action-benchmark.

CC: @TomAFrench