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<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:navy">Attached is a small patch to allow users of the PBQP allocator to optionally insert a custom pass. I believe it can be usefull to other
users of the pbqp.<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:navy">I used it to undo some of the coalescer work, and make sure that I have different virtual registers, inserting a copy if necessary, to
build a pair.<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:navy"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:navy">I noticed an unexpected --- to me at least --- behaviour of the allocator.<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:navy">I have some instructions using 2 pairs of registers, say “mpra R_x, R_x+1, R_y, R_y+1”, and setting the pairing constraints R_x -> R_x+1
and R_y -> R_y+1 could silently produce wrong code like “mpra %R0, %R2, %R1, %R3”. I add to explicitly add another constraint to describe that y must differ from x, x-1 and x+1 to make the allocator build valid pairs, i.e “mpra %R0, %R1, %R2, %R3”. Is there
anything I missed ?<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:navy"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:navy">Now, 99% of my users’ codebase is compiling.
</span></font><font size="2" color="navy" face="Wingdings"><span style="font-size:10.0pt;font-family:Wingdings;color:navy">J</span></font><font size="2" color="navy" face="Arial"><span style="font-size:10.0pt;font-family:Arial;
color:navy"><o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Arial"><span style="font-size:
10.0pt;font-family:Arial;color:navy">The last issue I have is an assert during regalloc in LiveIntervalAnalysis : “attempt to spill already spilled interval!”, and I do not
know where to start looking. Any hint would be welcome.<o:p></o:p></span></font></p>
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<p class="MsoNormal"><font size="2" color="navy" face="Courier New"><span style="font-size:10.0pt;font-family:"Courier New";color:navy"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Courier New"><span style="font-size:10.0pt;font-family:"Courier New";color:navy">Regards,<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Courier New"><span style="font-size:10.0pt;font-family:"Courier New";color:navy">--
<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2" color="navy" face="Courier New"><span style="font-size:10.0pt;font-family:"Courier New";color:navy">Arnaud de Grandmaison
<o:p></o:p></span></font></p>
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<p class="MsoNormal"><b><font size="2" face="Tahoma"><span style="font-size:10.0pt;
font-family:Tahoma;font-weight:bold">From:</span></font></b><font size="2" face="Tahoma"><span style="font-size:10.0pt;font-family:Tahoma"> Lang Hames [mailto:lhames@gmail.com]
<br>
<b><span style="font-weight:bold">Sent:</span></b> Tuesday, June 07, 2011 11:20 AM<br>
<b><span style="font-weight:bold">To:</span></b> Arnaud Allard de Grandmaison<br>
<b><span style="font-weight:bold">Cc:</span></b> Jakob Stoklund Olesen; Peter Lawrence; llvmdev@cs.uiuc.edu<br>
<b><span style="font-weight:bold">Subject:</span></b> Re: [LLVMdev] PBQP & register pairing</span></font><o:p></o:p></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:
12.0pt"><o:p> </o:p></span></font></p>
<p class="MsoNormal" style="margin-bottom:12.0pt"><font size="3" face="Times New Roman"><span style="font-size:12.0pt">Hi Arnaud,<o:p></o:p></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:
12.0pt">That sounds great. I look forward to seeing a patch.<o:p></o:p></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:
12.0pt"><o:p> </o:p></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:
12.0pt">You may also look forward to big performance improvements in the PBQP allocator: I'm working on updates which will improve compile speeds and massively reduce memory
use.<o:p></o:p></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:
12.0pt"><o:p> </o:p></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:
12.0pt">Regards,<o:p></o:p></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:
12.0pt">Lang.<o:p></o:p></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:
12.0pt"><o:p> </o:p></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:
12.0pt">On Tue, Jun 7, 2011 at 7:02 PM, Arnaud Allard de Grandmaison <<a href="mailto:Arnaud.AllardDeGrandMaison@dibcom.com">Arnaud.AllardDeGrandMaison@dibcom.com</a>> wrote:<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:
12.0pt"><br>
I also considered this approach, but did not want to dive in the constraint handling for now.<br>
<br>
The PBQP path seemed easier at first sight --- and was easy to setup. And I always wanted to give a try to the pbqp :)<br>
<br>
I will add the hook to the pbqp and propose a patch if this looks clean enough.<br>
<br>
Thanks,<br>
--<br>
Arnaud de Grandmaison<o:p></o:p></span></font></p>
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<p class="MsoNormal"><font size="3" face="Times New Roman"><span style="font-size:
12.0pt"><br>
-----Original Message-----<br>
From: Jakob Stoklund Olesen [mailto:<a href="mailto:stoklund@2pi.dk">stoklund@2pi.dk</a>]<o:p></o:p></span></font></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><font size="3" face="Times New Roman"><span style="font-size:12.0pt">Sent: Monday, June 06, 2011 9:28 PM<br>
To: Peter Lawrence<br>
Cc: Arnaud Allard de Grandmaison; <a href="mailto:llvmdev@cs.uiuc.edu">llvmdev@cs.uiuc.edu</a><br>
Subject: Re: [LLVMdev] PBQP & register pairing<br>
<br>
<o:p></o:p></span></font></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><font size="3" face="Times New Roman"><span style="font-size:12.0pt">On Jun 6, 2011, at 12:14 PM, Peter Lawrence wrote:<br>
<br>
> Arnaud,<br>
> another way to look at it, if the description of your register sets includes "pairs",<br>
> is that your assembly language syntax for MPQD is redundant, operand-2 is the second<br>
> half of the register-pair in operand-0, so an alternative is to let llvm think this is a two<br>
> operand instruction (one of them being a pair) rather than a three operand instruction.<br>
><br>
> even if you are not currently defining pairs in your register definitions, it might be less work<br>
> to do that than to write and add an extra new pass. Many many target machines have some<br>
> notion of register pairs, so it should not be too hard to find examples of how to do this.<br>
<br>
ARM's QQ and QQQQ register classes are examples.<br>
<br>
It is currently a bit tedious to specify these constraints; cleaning that up is on my todo list.<br>
<br>
/jakob<br>
<br>
<o:p></o:p></span></font></p>
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