From: Eric Lin <tesheng@andestech.com>
To: Paul Walmsley <paul.walmsley@sifive.com>
Cc: "dslin1010@gmail.com" <dslin1010@gmail.com>,
"Alan Quey-Liang Kao(高魁良)" <alankao@andestech.com>,
"palmer@sifive.com" <palmer@sifive.com>,
"Rick Jian-Zhi Chen(陳建志)" <rick@andestech.com>,
"K.C. Kuen-Chern Lin(林坤成)" <kclin@andestech.com>,
"linux-riscv@lists.infradead.org"
<linux-riscv@lists.infradead.org>,
"jimw@sifive.com" <jimw@sifive.com>
Subject: Re: About __udivdi3
Date: Tue, 6 Aug 2019 10:59:25 +0800 [thread overview]
Message-ID: <20190806025925.GA18995@andestech.com> (raw)
In-Reply-To: <alpine.DEB.2.21.9999.1908051911290.13971@viisi.sifive.com>
Hi Paul,
On Tue, Aug 06, 2019 at 10:13:40AM +0800, Paul Walmsley wrote:
> On Tue, 6 Aug 2019, Eric Lin wrote:
>
> > Cc: mailing list
> > On Mon, Aug 05, 2019 at 01:58:56PM +0800, Eric Lin wrote:
> > > Hi Palmer/Paul,
> > >
> > > Recently I encounter a problem that the output from __udivdi3 is wrong.
> > > The compiler will generate __udivdi3 library call when doing 64-bit
> > > over 64-bit division on 32-bit platform.
> > >
> > > It seems __udivdi3 only supports 64-bit platform.
> > > Do you have any comments? Thanks.
>
> It sounds like you're describing a potential issue with gcc, rather than
> the kernel. If that's so, then the gcc mailing list(s) would be a better
> place to discuss this: https://gcc.gnu.org/lists.html
>
>
> - Paul
Sorry, maybe I didn't describe it clearly.
When doing 64-bit over 64-bit division on 32-bit platform, the gcc will
link the __udivdi3 function in arch/riscv/lib/udivdi3.S, but the output
is wrong because the function is designed for RV64 ABI only.
I've tried to modify the arch/riscv/Makefile to make it link libgcc's
__udivdi3 library. The output is correct after using the libgcc's __udivdi3.
So, I don't think the __udivdi3 in arch/riscv/lib can support 64-bit
over 64-bit division on 32-bit platform.
Best Regards,
Eric
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next prev parent reply other threads:[~2019-08-06 2:59 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20190805055844.GE4292@andestech.com>
2019-08-06 1:37 ` About __udivdi3 Eric Lin
2019-08-06 2:13 ` Paul Walmsley
2019-08-06 2:59 ` Eric Lin [this message]
2019-08-06 3:01 ` Jim Wilson
2019-08-06 3:45 ` Nicolas Pitre
2019-08-06 8:31 ` Christoph Hellwig
2019-08-06 15:08 ` Palmer Dabbelt
2019-08-06 17:53 ` Paul Walmsley
2019-08-06 17:59 ` Palmer Dabbelt
2019-08-06 18:37 ` Nicolas Pitre
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