fix(ssa): Validate signed mul overflow

[vezenovm]

Description

Problem*

Resolves #8088

Builds upon #8765.

Summary*

This adds validation similar to #8706, except for signed multiplication. The semantics for which are seen here. We could be more strict with these checks by checking this code gen as well:

self.check_signed_overflow(result, lhs, rhs, operator, bit_size, location);
self.insert_safe_cast(result, result_type, location)

However, for now I have chosen to simply check up to the truncate point to simplify our "state machine". We also mainly want to guarantee that we have truncated the result of an operation appropriately so that someone cannot code gen an overflow.

Additional Context

Documentation*

Check one:

• No documentation needed.
• Documentation included in this PR.
• [For Experimental Features] Documentation 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: d1dd840	Previous: 9d44ab7	Ratio
perfectly_parallel_batch_inversion_opcodes	3564172 ns/iter (± 1987)	2778522 ns/iter (± 7503)	1.28

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

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: a9d8f3c	Previous: 9d44ab7	Ratio
test_report_zkpassport_noir_rsa_	3 s	2 s	1.50

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: fd50edb	Previous: c2cedd4	Ratio
rollup-merge	0.004 s	0.003 s	1.33

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

CC: @TomAFrench

[asterite]

Why is this gone? (maybe it's already done somewhere else and this was redundant?)

[vezenovm]

It was redundant. It was being done in FunctionBuilder::finish

[asterite]

Looks good! Would a test for mul followed by truncate but not by any cast be worth having?

[asterite]

Looks good?

Argh, I meant to type "!" instead of "?" 😅

[vezenovm]

Would a test for mul followed by truncate but not by any cast be worth having?

Yes, I will add one.

[vezenovm]

Added a test for a mul followed by a truncate with no cast. I also added a test that a lone truncate compiles:

        acir(inline) pure fn main f0 {
          b0(v0: i16):
            v1 = truncate v0 to 8 bits, max_bit_size: 8
            return v1
        }