linux-kernel - Re: [PATCH 3/5] lib: Add umoddi3 and udivmoddi4 of GCC library routines

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Message-ID: <CA+ZOyaiJv-NZWk3ec_3zhRTSn7G-NGgyaiPTXOmuWfTWD7KSJw@mail.gmail.com>
Date:   Tue, 25 Sep 2018 10:19:55 +0800
From:   Zong Li <zongbox@...il.com>
To:     hch@...radead.org
Cc:     palmer@...ive.com, aou@...s.berkeley.edu, vincentc@...estech.com,
        zong@...estech.com, linux-riscv@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] lib: Add umoddi3 and udivmoddi4 of GCC library routines

Christoph Hellwig <hch@...radead.org> 於 2018年9月21日 週五 下午3:00寫道：
>
> On Tue, Sep 18, 2018 at 05:19:15PM +0800, Zong Li wrote:
> > Add umoddi3 and udivmoddi4 support for 32-bit.
>
> This probably wants a better explanation of why you need them.
>
> > index 0000000..69f2d36
> > --- /dev/null
> > +++ b/lib/udivmoddi4.c
> > @@ -0,0 +1,291 @@
> > +// SPDX-License-Identifier: GPL-2.0
>
> Who wrote this code, where does it come from?

The RV32 need the umoddi3 to do modulo when the operands are long long
type, like other libraries implementation such as ucmpdi2, lshrdi3 and
so on. I encounter the undefined reference 'umoddi3' when I use the in
house dma driver, although it is in house driver, but I think that
umoddi3 is a common function for RV32. The udivmoddi4 and umoddi3 are
copies from libgcc in gcc. There are other functions use the
udivmoddi4 in libgcc, so I separate the umoddi3 and udivmoddi4 for
flexible extension in the future.