ref: 83246e296ea433b65b9d295b5e08fedd39ff1ab7
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