llvm dev - May 2015 - [LLVMdev] [RFC][PATCH] Adding absd/hadd/sad intrinsics

Hi All,

I would like to introduce intrinsics to generate efficient codes for
'absolute differences', 'horizontal add'
and 'sum of absolute differences' Idioms used by user programs.

Identifying these idioms at lower level (Codegen) is complex. These idioms can
be identified in LV/SLP
and vectorized using above intrinsics to generate better code.

Proposal:
1. Add intrinsics for 'absolute differences', 'horizontal add'
and 'sum of absolute differences' having variants of
Fixed / floating point data types and signed/unsigned operations.
2. Recognize these idioms at loop vectorizer or SLP and replace with
corresponding intrinsics based on the target's
Backend support.

Having these intrinsic will also help in cost modeling for these idioms which is
complex down the lane.

Pls find attached a patch regarding this which is incomplete & dirty at this
moment, however, it may help in this
discussion.

Regards,
Shahid


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Hi Devs,

Pinging..., as didn't get any response yet. Or shall I assume it is
acceptable to all?

Regards,
Shahid
> -----Original Message-----
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at
cs.uiuc.edu]
> On Behalf Of Shahid, Asghar-ahmad
> Sent: Friday, May 01, 2015 10:29 PM
> To: llvmdev at cs.uiuc.edu
> Subject: [LLVMdev] [RFC][PATCH] Adding absd/hadd/sad intrinsics
> 
> Hi All,
> 
> I would like to introduce intrinsics to generate efficient codes for
'absolute
> differences', 'horizontal add'
> and 'sum of absolute differences' Idioms used by user programs.
> 
> Identifying these idioms at lower level (Codegen) is complex. These idioms
> can be identified in LV/SLP and vectorized using above intrinsics to
generate
> better code.
> 
> Proposal:
> 1. Add intrinsics for 'absolute differences', 'horizontal
add' and 'sum of
> absolute differences' having variants of Fixed / floating point data
types and
> signed/unsigned operations.
> 2. Recognize these idioms at loop vectorizer or SLP and replace with
> corresponding intrinsics based on the target's Backend support.
> 
> Having these intrinsic will also help in cost modeling for these idioms
which is
> complex down the lane.
> 
> Pls find attached a patch regarding this which is incomplete & dirty at
this
> moment, however, it may help in this discussion.
> 
> Regards,
> Shahid
>

Hi Asghar-Ahmed,

I saw your last ping - sorry, I'm away on vacation and back on Wednesday.

Generally, I'm not sure that having both absd/hadd and sad are compatible
with the discussions going on in other threads, for example my thread about
min and max.

Given that those two intrinsics are fairly trivial to match , I don't see
the need to have two different canonical forms.

James
On Mon, 4 May 2015 at 07:55, Shahid, Asghar-ahmad <
Asghar-ahmad.Shahid at amd.com> wrote:
> Hi Devs,
>
> Pinging..., as didn't get any response yet. Or shall I assume it is
> acceptable to all?
>
> Regards,
> Shahid
>
> > -----Original Message-----
> > From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at
cs.uiuc.edu]
> > On Behalf Of Shahid, Asghar-ahmad
> > Sent: Friday, May 01, 2015 10:29 PM
> > To: llvmdev at cs.uiuc.edu
> > Subject: [LLVMdev] [RFC][PATCH] Adding absd/hadd/sad intrinsics
> >
> > Hi All,
> >
> > I would like to introduce intrinsics to generate efficient codes for
> 'absolute
> > differences', 'horizontal add'
> > and 'sum of absolute differences' Idioms used by user
programs.
> >
> > Identifying these idioms at lower level (Codegen) is complex. These
> idioms
> > can be identified in LV/SLP and vectorized using above intrinsics to
> generate
> > better code.
> >
> > Proposal:
> > 1. Add intrinsics for 'absolute differences', 'horizontal
add' and 'sum
> of
> > absolute differences' having variants of Fixed / floating point
data
> types and
> > signed/unsigned operations.
> > 2. Recognize these idioms at loop vectorizer or SLP and replace with
> > corresponding intrinsics based on the target's Backend support.
> >
> > Having these intrinsic will also help in cost modeling for these
idioms
> which is
> > complex down the lane.
> >
> > Pls find attached a patch regarding this which is incomplete &
dirty at
> this
> > moment, however, it may help in this discussion.
> >
> > Regards,
> > Shahid
> >
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
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