Re: R: R: About hardfloat in ppc

["罗勇刚(Yonggang Luo)" <luoyonggang@gmail.com>]

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Question, in hard-float, if we don't want to read the fp register.
for example: If we wanna compute c = a + b in fp32
if c = a + b In hard float
and if b1 = c - a in hard float
if b1 != b at bitwise level, the we se the inexat to 1, otherwsie
we set inexat bit to 0? are this valid?

we can also do it for a * b, a - b, a / b.


On Thu, Apr 30, 2020 at 2:25 AM Alex Bennée <alex.bennee@linaro.org> wrote:

>
> Dino Papararo <skizzato73@msn.com> writes:
>
> > Hi Alex,
> <snip>
> >
> > I leave to you TCG's experts how it works and how to implement it, I'm
> > only tryng to explain a possible fast way to go (if ever possible) 😊
>
> This is all a theoretical discussion unless someone cares enough to
> improve the situation. While I have an interest in improving TCG
> performance I'm afraid there are many more easier wins before tackling a
> target specific hack for which I'm not familiar. No doubt this thread
> will be referred to next time someone wants something done about it.
>
> > ..Large majority of software don't check for exceptions at all and if
> > I really want to pursue max precision I'll go for a software
> > multiprecision library like GMP or MPFR Libraries.
>
> However for QEMU we regard failure to correctly emulate the architecture
> as a bug - we don't code to common software patterns because there is
> plenty of software out there that doesn't follow it.
>
> > So the hardfloats 'should' be set as first choice and only if
> > instruction requires precision/error check process it in softfloats.
>
> Sure but someone will have to do the work to support that.
>
> --
> Alex Bennée
>


-- 
         此致
礼
罗勇刚
Yours
    sincerely,
Yonggang Luo

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