Introduce compiler-rt and add bitwise `and`, `or`, `xor` polyfills

[wzmuda]

Summary

Introduce compiler runtime module. Add relevant CI changes and update the PR template to reflect that we should also format the Cairo code.

Start implementing ALU. Add the top-level module and submodules for and, or and xor operations. Add relevant readmes.

Implemented polyfills:

and

Implements bitwise and operation.

API

• __llvm_and_bool_bool(lhs: u128, rhs: u128) -> u128
• __llvm_and_i8_i8(lhs: u128, rhs: u128) -> u128
• __llvm_and_i16_i16(lhs: u128, rhs: u128) -> u128
• __llvm_and_i32_i32(lhs: u128, rhs: u128) -> u128
• __llvm_and_i64_i64(lhs: u128, rhs: u128) -> u128
• __llvm_and_i128_i128(lhs: u128, rhs: u128) -> u128

or

Implements bitwise or operation.

API

• __llvm_or_bool_bool(lhs: u128, rhs: u128) -> u128
• __llvm_or_i8_i8(lhs: u128, rhs: u128) -> u128
• __llvm_or_i16_i16(lhs: u128, rhs: u128) -> u128
• __llvm_or_i32_i32(lhs: u128, rhs: u128) -> u128
• __llvm_or_i64_i64(lhs: u128, rhs: u128) -> u128
• __llvm_or_i128_i128(lhs: u128, rhs: u128) -> u128

xor

Implements bitwise xor operation.

API

• __llvm_xor_bool_bool(lhs: u128, rhs: u128) -> u128
• __llvm_xor_i8_i8(lhs: u128, rhs: u128) -> u128
• __llvm_xor_i16_i16(lhs: u128, rhs: u128) -> u128
• __llvm_xor_i32_i32(lhs: u128, rhs: u128) -> u128
• __llvm_xor_i64_i64(lhs: u128, rhs: u128) -> u128
• __llvm_xor_i128_i128(lhs: u128, rhs: u128) -> u128

Other PRs for issue #38 will follow.

Details

• Are we sure about using u128 instead of felts?
• Does my testing approach make sense? I generated all these cases with Python.
• Apart from code please rate the overall code organization.

Checklist

• [x] Code is formatted by Rustfmt or scarb fmt.
• [x] Documentation has been updated if necessary.

[wzmuda]

One thing I want to see is documentation of the structure and why this structure is chosen.

Sure, where would be a good place for this? Dedicated README.md in the compiler_rt directory perhaps? That would be a central point for everybody who starts reading/modifying the runtime and would display nicely on github.