ref: bbe261d58359dbbcfc2f0108323f3fae688a568c
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