From: "Yangfei (Felix)" <felix.yang@huawei.com>
To: "augustine.sterling@gmail.com" <augustine.sterling@gmail.com>
Cc: "gcc-patches@gcc.gnu.org" <gcc-patches@gcc.gnu.org>,
Felix Yang <fei.yang0953@gmail.com>
Subject: Re: [PATCH] Add zero-overhead looping for xtensa backend
Date: Fri, 24 Oct 2014 06:53:00 -0000 [thread overview]
Message-ID: <DA41BE1DDCA941489001C7FBD7A8820E5554BB89@szxema507-mbx.china.huawei.com> (raw)
In-Reply-To: <CAGSvup_cpVBXLTPQdhZQeSAGnSdMCAddA1DkYh=CZdKCQjkrgw@mail.gmail.com>
Thanks for the explanation. I think I am clear about what you are thinking now.
That's an interesting question. I am not sure about reason why GCC's reload cannot handle a doloop_end insn.
I guess maybe the doloop_end pattern is special? I mean it's a branch insn in a parallel form.
>
> On Thu, Oct 23, 2014 at 11:40 PM, Yangfei (Felix) <felix.yang@huawei.com>
> wrote:
> > 1. The original xtensa port never generates "loop" instruction at all.
> > 2. A port doesn't need to implement hwloop_pattern_reg hook if it has no
> zero-cost loop instruction.
> >
> > Is that clear?
>
> We are talking in circles. I understand very well what goes on here.
>
> My point is:
>
> 1. Right now, today, GCC generates loops with branch instructions even when the
> trip count is spilled.
> 2. Branch instructions and loop instructions have identical register requirements.
>
> Therefore:
>
> 3. loop instructions should be generatable when the trip count is spilled.
next prev parent reply other threads:[~2014-10-24 6:51 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-08 16:27 Felix Yang
2014-01-08 16:49 ` Sterling Augustine
2014-01-09 15:08 ` Felix Yang
2014-01-09 23:51 ` Felix Yang
2014-01-10 3:49 ` Yangfei (Felix)
2014-01-13 17:24 ` Sterling Augustine
2014-10-09 11:04 ` Felix Yang
2014-10-10 14:01 ` Felix Yang
2014-10-11 9:32 ` [PING] [PATCH, xtensa] " Yangfei (Felix)
2014-10-13 16:09 ` [PATCH] " augustine.sterling
2014-10-13 16:30 ` Felix Yang
2014-10-14 15:43 ` Felix Yang
2014-10-15 19:51 ` augustine.sterling
2014-10-16 4:52 ` Yangfei (Felix)
2014-10-21 14:57 ` augustine.sterling
2014-10-22 2:20 ` Yangfei (Felix)
2014-10-22 5:20 ` Yangfei (Felix)
2014-10-23 17:51 ` augustine.sterling
2014-10-24 1:49 ` Yangfei (Felix)
2014-10-24 4:32 ` Yangfei (Felix)
2014-10-24 6:28 ` augustine.sterling
2014-10-24 6:33 ` Yangfei (Felix)
2014-10-24 6:40 ` augustine.sterling
2014-10-24 6:43 ` Yangfei (Felix)
2014-10-24 6:49 ` augustine.sterling
2014-10-24 6:53 ` Yangfei (Felix) [this message]
2014-10-24 7:15 ` Andrew Pinski
2014-10-28 12:24 ` Yangfei (Felix)
2014-10-30 22:02 ` augustine.sterling
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