ref: 8294be6e7c9032e3c472018b53154d5b4faec00c
dir: /os/pc/fpsave.s/
TEXT FPsave(SB), 1, $0 /* save FPU environment without waiting */ MOVL fpu+0(FP), AX FSTENV 0(AX) RET TEXT FPrestore(SB), 1, $0 /* restore FPU environment without waiting */ MOVL fpu+0(FP), AX FLDENV 0(AX) RET