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

[Xinliang David Li via llvm-commits]

yes -- let's do that in this patch.

David

On Tue, Jan 12, 2016 at 11:29 AM, Cong Hou <congh at google.com> wrote:
> 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
>> >> >
>> >> >
>> >> >
>> >
>> >
>
>