1. Can you show one such example where the performance is improved?

2. Can you make sure the tests are passing for you locally? You can follow .circleci/config.yml test steps to install and generate everything needed.

1). I have tested changes on:

• https://github.com/OilerNetwork/fossil/blob/master/contracts/starknet/FactsRegistry.cairo
  Its deployment to starknet-devnet (invoking command starknet deploy) takes ~31 seconds. Calculating hashes takes over half of this time. After I have subsituted the default pedersen_hash function with one implemented in cpp, the deployment time was cut to ~20 seconds.

• I have also tested on example contract from cairo docs -> https://www.cairo-lang.org/docs/hello_starknet/intro.html#your-first-contract, but since this is very small and uncomplicated contract, there are no such gains :)

2). I can confirm tests are passing on my linux 64bit machine; I have however some issues running on mac m1 (I have tried to run the tests without my changes - from freshly cloned repo on master branch, but they also fail, so I don’t think this is conected to the change)