[libre-riscv-dev] [Bug 44] IEEE754 FPU inverse-sqrt

[Hendrik Boom]

On Sat, May 11, 2019 at 09:44:15AM +0000, bugzilla-daemon at libre-riscv.org wrote:
> http://bugs.libre-riscv.org/show_bug.cgi?id=44
> 
> --- Comment #17 from Jacob Lifshay <programmerjake at gmail.com> ---
> (In reply to Luke Kenneth Casson Leighton from comment #16)
> > (In reply to Jacob Lifshay from comment #15)
> > > (In reply to Luke Kenneth Casson Leighton from comment #14)
> > > > looking at the diagram from ep08-21.pdf on page 36 (figure 3.15)
> > > > 
> > > > * q[j+1] in radix 2 is a 2-bit signed binary number, -1 0 or +1
> > > >   (top of p35), in binary -1 = 0b10, 0 = 0b00, 1 = 0b01
> > > shouldn't that be -1 = 0b11 assuming it's in 2s complement?
> > 
> > err... the paper does say -1, 0 or +1 (as does Tanako), this will need
> > to be checked.
> yeah, it is -1, 0, or 1. I had meant that -1 in 2s complement is 0b11, not
> 0b10.

Could it be one's complemet?  Does anyone still use that for anything?

-- hendrik