Re: [PATCH] Look for FIR in the last FreeBSD/mips floating-point register.

["Maciej W. Rozycki" <macro@imgtec.com>]

On Mon, 12 Jun 2017, John Baldwin wrote:

> >  Well, CP1.FIR is generally expected to hold non zero; in particular in 
> > legacy MIPS processors (before CP0.Config1.FP was defined) checking for a 
> > non-zero value in CP1.FIR (bits 15:8 specifically) was the recommended way 
> > to detect the presence of FPU hardware[1].  And from MIPSr1 on there have 
> > to be floating-point formats supported reported in CP1.FIR, with D and S 
> > being mandatory, so you'll see non-zero bits at least in their positions 
> > (the W bit was only added with MIPSr2).
> 
> Ah, I had been going off of my (probably stale) copy of See Mips Run which
> only talks about comparing FIR with 0.  FreeBSD requires MIPSr3, so it should
> always see a non-zero FIR then.

 FAOD MIPSr3 (as in MIPS32r3/MIPS64r3) or MIPS III?

 I'm asking as I find it odd for anything to require MIPSr3 and not to 
handle MIPSr2 given that the main difference between the two is microMIPS 
and 2008-NaN support, both optional.

  Maciej