Use optimized overflow operation everywhere

[celinval]

Description of changes:

This is related to the performance degradation we are seeing in the toolchain upgrade: #2293

Resolved issues:

Towards #1483. There are a few remaining instances of add_overflow and mul_overflow in intrinsics.rs.

Related RFC:

Optional #ISSUE-NUMBER.

Call-outs:

This PR has a side effect of removing redundant checks inserted by CBMC for checked arithmetic operations.

Testing:

• How is this change tested? Existing tests and manual tests with my other branch where I'm doing the upgrade

• Is this a refactor change? yes

Checklist

• Each commit message has a non-empty body, explaining why the change was made
• Methods or procedures are documented
• Regression or unit tests are included, or existing tests cover the modified code
• My PR is restricted to a single feature or bugfix

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

[celinval]

It looks like the performance is not always better... :(

[celinval]

I do wonder if this proof is also somewhat unstable. I noticed that in my other PR (#2407) that had minimum changes to the model, there was also a performance degradation of 47% for the same test.

[tautschnig]

I'd like to ask for an explanation as to why the no-longer-failing checks are ok.

[zhassan-aws]

This has been on my to-do list for too long. Thanks for taking care of it @celinval!

You should add in the PR description "Towards #1483". There are a few remaining instances of add_overflow and mul_overflow in intrinsics.rs (and possibly elsewhere).

[celinval]

I'd like to ask for an explanation as to why the no-longer-failing checks are ok.

That's fair! My bad, I should've added an explanation before. I added it as part of an answer to one of your question and addressed the issue in the call-out section. In a nutshell, the arithmetic check that was being added by CBMC was redundant.