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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'>Hi Chris,<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'>Function is currently 108 bytes large. Could
4 more bytes really be an issue? Actually 2 should suffice. While I understand
that some applications value storage more than anything, many applications
value compilation time very highly. getIntrinsicID is called all over the place
(isIntrinsic uses it as well), and every single time it checks the function
name. To me that sounds a lot more dramatic than 2 bytes…<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'>Anyway, using SubclassData could work. It’s
already being used for the calling convention, which has values ranging from 0
to 68 (fitting in 7 bits), while intrinsic ID’s would take 9 bits. So
that would only just work. However, the calling convention enums could be
reordered to only take 3 bits.<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 was wondering whether it would make
sense to have an IntrinsicFunction class, derived from Function. This way only
the IntrinsicFunction would have an intrinsicID field. I noticed that Function
already has virtual methods so getIntrinsicID could be another virtual method
without adding any real overhead. For Function it would simply return 0 while
for IntrinsicFunction it returns the intrinsicID field that was initialized in
the constructor.<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'>Cheers,<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'>Nicolas<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>
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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'> Chris Lattner
[mailto:clattner@apple.com] <br>
<b><span style='font-weight:bold'>Sent:</span></b> Saturday, 17 October, 2009
22:54<br>
<b><span style='font-weight:bold'>To:</span></b> Nicolas Capens<br>
<b><span style='font-weight:bold'>Cc:</span></b> '<st1:PersonName w:st="on">LLVM
Developers Mailing List</st1:PersonName>'<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [LLVMdev]
getIntrinsicID() optimization</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><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 Oct 16, 2009, at 5:50 AM, Nicolas Capens wrote:<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>
<br>
<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt;
font-family:Calibri'>Hi all,<o:p></o:p></span></font></p>
<u1:p></u1:p></div>
<div><u1:p>
<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt;
font-family:Calibri'> <o:p></o:p></span></font></p>
</u1:p></div>
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<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt;
font-family:Calibri'>While profiling I discovered that the
Function::getIntrinsicID() method is called a lot, and every time it uses
string comparison to recompute the ID number. As far as I know the name of an
intrinsic function doesn’t change, so the ID could be determined just
once at Function construction time.<o:p></o:p></span></font></p>
<u1:p></u1:p></div>
<div><u1:p>
<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt;
font-family:Calibri'> <o:p></o:p></span></font></p>
</u1:p></div>
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<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt;
font-family:Calibri'>I’ve attached a patch that does this and it appears
to work for the code I tested it with. Could anyone look at potential caveats
and if there are none commit it?<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'>Hi Nicolas,<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'>Sorry for the delay. I don't think that this is the right way to
go. Making Function larger is an extremely expensive thing to do.
There are use cases in LLVM where apps load large modules lazily and
stream in functions on demand. The way this works currently is that the
function objects are created eagerly, but their bodies are lazy.
Increasing hte size of function can substantially penalize these cases.<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'>Also, as Jeffrey points out, it is not safe with setName().<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'>However, this would be a great thing to have. Instead of adding a
new field, is there space in the "SubClassData" field in Value?<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'>-Chris<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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