ref: b548687a8ed1d0a159c9d3f3f921d93bbb56908e
dir: /os/pc64/fpsave.s/
TEXT FPsave(SB), 1, $0 /* save FPU environment without waiting */ MOVQ RARG, AX FSTENV 0(AX) RET TEXT FPrestore(SB), 1, $0 /* restore FPU environment without waiting */ MOVQ RARG, AX FLDENV 0(AX) RET