fp-hw-survey capture: x86-64 baseline (Intel + AMD)

[MikeGrier]

Capture native FP behavior on x86-64 (one Intel and one AMD part) with crates/fp-hw-survey. This anchors the cross-architecture divergence axis (x86-64 ↔ AArch64): fmax/fmin NaN handling, float→int saturation, flush-to-zero edges.

Steps

cargo build --release -p fp-hw-survey
./target/release/fp-hw-survey info        # confirm CPU brand + features (sse2/sse4.1/avx/fma/avx512f)
./target/release/fp-hw-survey selftest    # must pass
./target/release/fp-hw-survey capture --label <intel-xeon|amd-zen4>-<os>

What to attach to this issue

• The info output (CPU brand + detected features).
• The selftest result (must be clean — capture refuses to write otherwise).
• The one-line NDJSON header from the capture (durable provenance: cpu / os / features / date).
• The capture-*.ndjson file itself (attachment or link).

Notes

• The x86-64 oracle covers the SSE-mappable subset only (arithmetic, fmax/fmin, fsqrt, fma, f32↔f64, truncating signed float→int, signed int→float); ops with no scalar SSE form are skipped. MXCSR status bits are translated into the AArch64 FPSR layout so flags compare directly across arches.
• x86-64 self-test caveat: the x86 asm was authored on an arm64 host; eyeball the first real-hardware selftest output before trusting the capture.

Part of the FP hardware survey fleet-capture campaign.