Perf: Toom-3 for Fp6 in R1CS

[yelhousni]

Description

For cubic extensions use Toom-3 in R1CS and Karatsuba in SCS.

Type of change

• New feature (non-breaking change which adds functionality)

How has this been tested?

• Equality check between Karatsuba and Toom-3 variants + equality with gnark-crypto.

How has this been benchmarked?

A single pairing on:

• BLS12-377 (native):
  old: 13,289 R1CS
  new: 12,588 R1CS

• BN254 (emulated):
  old: 973,423 R1CS
  new: 972,708 R1CS

• BLS12-381 (emulated):
  old: 1,436,626 R1CS
  new: 1,429,646 R1CS

Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I did not modify files generated from templates
• golangci-lint does not output errors locally
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[ivokub]

LGTM!