-march=x86-64-v3 kept the port and the installer to CPUs with AVX2 and FMA. --cpu v2 compiles the generated code and the runtime for SSE4.2 instead. Without FMA3 the FP lowering calls fma/fmaf, so runtime/fma.c provides correctly rounded ones (musl, MIT) that honour MXCSR's rounding mode, FTZ and DAZ; the UCRT's software fallback rounds incorrectly by up to half an ulp. simd.h's fast paths keep their assumptions.
The installer's host check asks for x86-64-v2 and selects libtotkrt.a or libtotkrt-v2.a; both release scripts build and ship the pair. The differential tests compile fma.c as well, so a --cflags=-march=x86-64-v2 run tests it.
Tested on an i7-3770K (no AVX2, FMA or BMI) with an RTX 3060 Ti, game 1.4.3: the installer ran end to end, --selftest passed and play holds 40-60 fps at 1080p. fma and fmaf matched 152,288 exact vectors over two seeds, including ties, subnormals and every rounding mode, FTZ and DAZ combination. The v3 build is unchanged: fma.c is an empty translation unit there.
Every flag-setting instruction packed N, Z, C and V into c->nzcv and every reader unpacked them. recomp/flags.py
now runs a reaching-definitions pass per function: a compare stores its operands in a local Flags F, and a reader
whose definitions are all of one kind computes its condition from them, so cmp and b.cond become one host compare.
CCMP, FCMP, MSR NZCV and ADCS write the packed form, which readers reached by several kinds also use. Calls and
returns publish nothing (AAPCS64 neither passes nor preserves NZCV); tail branches, falls into the next function and
br through rt_dispatch publish c->nzcv, since discovery can start a function inside another one. Functions with an
unresolved computed br keep flags in c->nzcv.
1.4.3 main: 492k direct and 89k packed flag reads, .text 342 -> 299 MiB. Fight bench (bench-fight2-2026-10-27b,
frames 5400-7500, uncapped) 13.15 and 13.63 ms vs 13.9 before. tests/flags_check.py checks the new helpers against
the packed ones; tests/diff/func.py no longer compares NZCV, which generated code leaves untouched.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
CHEN Feng