Krell v2.1

Krell v2.1 — the optimization release.

Thirteen optimization work packages over the v2.0 compiler: a parse hot loop with zero stack traffic, recurrence lowering, back-edge phi coalescing in the register allocator, and a loop vectorizer with map, copy, dot-product and widening-reduction classes (the widening reduction in scalar, word-at-a-time SWAR form). No language changes; the differential battery passes 4,546 cases with 0 failures on each lane (x86_64 native, AArch64, RISC-V, LLVM).

Performance against C (gcc 13.3, -O2) on the twelve KRELLPROOF kernels — geometric mean of per-kernel speedups, timings recorded only where checksums agree across every implementation (recorded run, 2026-11-03, AMD EPYC 9D25):

• x86_64 native: 1.58x excluding fib (58% faster than C), 4.20x across all twelve
• LLVM lane: 1.59x excluding fib (59% faster than C), 4.56x across all twelve

fib is quoted both ways: its recurrence lowering runs it in 25.3 ns native / 10.0 ns LLVM against 4,901,152 ns for C -O2.

Full record, kernels, C references and methodology: https://github.com/nightwarelabz/krellproof