FCMP and the vector compares no longer flush denormal operands under FPCR.FZ: rt_fpcr_sync keeps MXCSR.DAZ equal to
FPCR.FZ, and x86 compares under DAZ read a denormal as a zero of its sign, as ARM does under FZ. The directed RMode
check of FN(op) and FN(vop) moved into the result check's branch, and min/max skip it, since they do not round.
Hot lifted functions shrink by about 10% of their x86 instructions; the town camera-pan bench (1080p, two runs each)
goes from 10.25 to 9.78 ms per frame. simd.py (60000 encodings), lift.py and func.py report 0 failures.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The FP helpers compared c->fpcr with a cached copy before every operation to resync MXCSR lazily. MXCSR now
follows FPCR.FZ at once: MSR FPCR calls rt_fpcr_sync, and so do rt_call (thread, fiber and host entry into guest
code), fiber resume (FIBER_FLAG_FLOAT_SWITCH fibers keep their own MXCSR) and the differential test harness per
case. op and vop only test FPCR.RMode for the slow path, and their redo check is one ordered-not-equal compare of
|r| with the smallest normal, the same NaN-or-smallest-normal set as before.
Hot guest code shrinks by about a quarter (132 functions holding half the guest cycles, 1.4.3); fight frame time
moves 1-3%, inside the run-to-run spread. lift, simd, func, atomic and flags_check pass on 1.4.3; simd.py fails
without the harness sync.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
