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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Hi James,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Thanks for your response. You are correct that matching the two intrinsic is trivial.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">My worry is regarding the query for cost calculation for specific SAD instructions<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">such as ‘psad’ (X86) or ‘usad’ (ARM) in Loop Vectorizer.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">In case of absd/hadd, we have to query the cost separately for both intrinsics and the<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">returned cost may be bigger than actual cost of ‘psad’ or ‘usad’ instruction.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">And hence vectorizer may decide not to generate these intrinsic at all.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I am not sure if my ‘worry’ is valid here, thoughts?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Shahid<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> James Molloy [mailto:james@jamesmolloy.co.uk]
<br>
<b>Sent:</b> Monday, May 04, 2015 11:44 AM<br>
<b>To:</b> Shahid, Asghar-ahmad; llvmdev@cs.uiuc.edu<br>
<b>Subject:</b> Re: [LLVMdev] [RFC][PATCH] Adding absd/hadd/sad intrinsics<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hi Asghar-Ahmed,<br>
<br>
I saw your last ping - sorry, I'm away on vacation and back on Wednesday. <br>
<br>
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.
<br>
<br>
Given that those two intrinsics are fairly trivial to match , I don't see the need to have two different canonical forms.<br>
<br>
James<o:p></o:p></p>
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<p class="MsoNormal">On Mon, 4 May 2015 at 07:55, Shahid, Asghar-ahmad <<a href="mailto:Asghar-ahmad.Shahid@amd.com">Asghar-ahmad.Shahid@amd.com</a>> wrote:<o:p></o:p></p>
<p class="MsoNormal">Hi Devs,<br>
<br>
Pinging..., as didn't get any response yet. Or shall I assume it is acceptable to all?<br>
<br>
Regards,<br>
Shahid<br>
<br>
> -----Original Message-----<br>
> From: <a href="mailto:llvmdev-bounces@cs.uiuc.edu" target="_blank">llvmdev-bounces@cs.uiuc.edu</a> [mailto:<a href="mailto:llvmdev-bounces@cs.uiuc.edu" target="_blank">llvmdev-bounces@cs.uiuc.edu</a>]<br>
> On Behalf Of Shahid, Asghar-ahmad<br>
> Sent: Friday, May 01, 2015 10:29 PM<br>
> To: <a href="mailto:llvmdev@cs.uiuc.edu" target="_blank">llvmdev@cs.uiuc.edu</a><br>
> Subject: [LLVMdev] [RFC][PATCH] Adding absd/hadd/sad intrinsics<br>
><br>
> Hi All,<br>
><br>
> I would like to introduce intrinsics to generate efficient codes for 'absolute<br>
> differences', 'horizontal add'<br>
> and 'sum of absolute differences' Idioms used by user programs.<br>
><br>
> Identifying these idioms at lower level (Codegen) is complex. These idioms<br>
> can be identified in LV/SLP and vectorized using above intrinsics to generate<br>
> better code.<br>
><br>
> Proposal:<br>
> 1. Add intrinsics for 'absolute differences', 'horizontal add' and 'sum of<br>
> absolute differences' having variants of Fixed / floating point data types and<br>
> signed/unsigned operations.<br>
> 2. Recognize these idioms at loop vectorizer or SLP and replace with<br>
> corresponding intrinsics based on the target's Backend support.<br>
><br>
> Having these intrinsic will also help in cost modeling for these idioms which is<br>
> complex down the lane.<br>
><br>
> Pls find attached a patch regarding this which is incomplete & dirty at this<br>
> moment, however, it may help in this discussion.<br>
><br>
> Regards,<br>
> Shahid<br>
><br>
<br>
<br>
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