From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
To: Libre-RISCV General Development <libre-riscv-dev@lists.libre-riscv.org>
Subject: Re: [libre-riscv-dev] div pipe
Date: Mon, 20 Jul 2020 02:38:28 +0100
Message-ID: <CAPweEDzzY9OXscMQSh1HM26AtM+43PJpCa0RS44y+MmErFr8sw@mail.gmail.com> (raw)
In-Reply-To: <CAC2bXD4ipWkR=1Z2hX+=HvMbDwtinhvC7CWgG6GFEsu57j1-Eg@mail.gmail.com>
On Monday, July 20, 2020, Jacob Lifshay <programmerjake@gmail.com> wrote:
>
> effectively what's happening is the code is treating the compare_?hs
> signals as if the binary value N means the fraction N/2^(3*fract_width)
> (essentially fixed-point numbers), so changing the bit width of N without
> adjusting the fract_width means there are too few integer bits and too many
> fractional bits.
ahh i remember. that took a while to get right when connecting to fpdiv.
> additionally, some of the shifts and bit sliced will have
> to be adjusted to get the right bits.
>
> >
> > no reversion should be needed.
> >
>
> except that, last I checked DivPipeCore doesn't correctly do divisions when
> configured to only support UDivRem, since that's when it enables the broken
> code adjustments.
yuk. hmm a way to "cheat" there: tell it that it can handle sqrt as well,
temporarily :)
that at least provides a functional codepath. inefficient but functional.
l.
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Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-18 22:18 [libre-riscv-dev] lots of stuff broken Luke Kenneth Casson Leighton
2020-07-19 6:55 ` Jacob Lifshay
2020-07-19 10:46 ` Luke Kenneth Casson Leighton
2020-07-19 21:11 ` Luke Kenneth Casson Leighton
2020-07-19 21:27 ` [libre-riscv-dev] div pipe Jacob Lifshay
2020-07-19 22:07 ` Luke Kenneth Casson Leighton
2020-07-20 0:32 ` Jacob Lifshay
2020-07-20 1:38 ` Luke Kenneth Casson Leighton [this message]
2020-07-20 2:06 ` Jacob Lifshay
2020-07-20 2:13 ` Luke Kenneth Casson Leighton
2020-07-20 3:21 ` Jacob Lifshay
2020-07-20 10:31 ` Luke Kenneth Casson Leighton
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