[PATCH] D11393: [X86] Allow X86::COND_NE_OR_P and X86::COND_NP_OR_E to be reversed.

[Cong Hou via llvm-commits]

On Tue, Jan 12, 2016 at 11:07 AM, Xinliang David Li <davidxl at google.com>
wrote:

> On Tue, Jan 12, 2016 at 11:04 AM, Cong Hou <congh at google.com> wrote:
> > On Mon, Jan 11, 2016 at 5:35 PM, Xinliang David Li <davidxl at google.com>
> > wrote:
> >>
> >> On Mon, Jan 11, 2016 at 4:59 PM, Cong Hou <congh at google.com> wrote:
> >> > congh added a comment.
> >> >
> >> > In http://reviews.llvm.org/D11393#323944, @davidxl wrote:
> >> >
> >> >> Restart discussion on this thread:
> >> >>
> >> >> For the motivating example where two conditional branches have
> >> >> different targets,
> >> >>
> >> >> jne   .BB1
> >> >>  jnp  .BB2
> >> >>  .BB1:
> >> >>  ...
> >> >>  .BB2:
> >> >>  ...
> >> >>
> >> >> Is it possible to teach AnalyzeBranch to recognize the pattern --
> with
> >> >> opcode COND_NE_OR_P ?
> >> >
> >> >
> >> > Yes, I think this is done in this patch. Or do I misunderstand what
> you
> >> > mean?
> >>
> >> The patch removes the branch condition reversing optimization in
> >> AnalyzeBranch -- is that needed? For the motivating example, no new
> >> opcode seems to be needed either ..
> >
> >
> > I think branch condition reversing optimization in AnalyzeBranch is
> > unnecessary: we will do it in block-placement anyway. And just as you
> once
> > said, it is a bad idea to modify the branch in a function called
> > AnalyzeBranch(), which seems a readonly function.
>
> Yes -- agree with that part. However I think removing transformation
> in AnalyzeBranch is an independent issue that should be done
> separately.  The main focus of this patch should be to enhance
> AnalyzeBranch to recognize more patterns.
>

OK. I can bring back the deleted part. The pattern recognition is still
done later in this function. Let me know if I am wrong.


Cong



>
> David
>
> >
> > Cong
> >
> >>
> >>
> >> David
> >>
> >> >
> >> >
> >> > http://reviews.llvm.org/D11393
> >> >
> >> >
> >> >
> >
> >
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20160112/178f7dde/attachment.html>