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<div class=Section1>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>>If you are using a non-C ABI, then you may not need to do the
promotion at all. However, if you do need to do the ….</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Our port is for C language, however, on an
8-bit platform priorities shift a little bit.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Really the natural size of int must be 8
bit, however, 8 bit is too small for most calculations so we have to choose 16,
but there is no 16-bit register available. And that is where the whole problem starts
because promoting the return of char to int becomes too expensive; so we don’t
want to do it.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Being able to turn the promotion off is
going to solve our problem, but currently there is no hook for that in target
specific classes. </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Ali.</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </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'>
llvmdev-bounces@cs.uiuc.edu [mailto:llvmdev-bounces@cs.uiuc.edu] <b><span
style='font-weight:bold'>On Behalf Of </span></b>Evan Cheng<br>
<b><span style='font-weight:bold'>Sent:</span></b> Thursday, May 15, 2008 11:11
AM<br>
<b><span style='font-weight:bold'>To:</span></b> LLVM Developers Mailing List<br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [LLVMdev] Troubling
promotion of return value to Integer ...</span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> </span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> </span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>On May 14, 2008, at 10:43 AM, <a
href="mailto:Alireza.Moshtaghi@microchip.com">Alireza.Moshtaghi@microchip.com</a>
wrote:</span></font></p>
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12.0pt'><br>
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<p class=MsoNormal><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>In this thread
I’m trying to merge two email threads into one, because both discuss the
same problem that’s troubling us and I would like to reach a conclusion
on what would be the best approach.</span></font></p>
</div>
<div>
<p class=MsoNormal><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>To minimize the
size of this thread I only mention the subject of the other two threads:</span></font></p>
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<p class=MsoNormal style='text-indent:-24.0pt'><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:black'>(1)</span></font><font size=1 color=black><span style='font-size:
7.0pt;color:black'> <span class=apple-converted-space> </span></span></font><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt;font-family:
"Courier New";color:black'>[LLVMdev] Integer promotion of return node operand
(initiated by Sachin)</span></font></p>
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<div>
<p class=MsoNormal style='text-indent:-24.0pt'><font size=2 color=black
face="Courier New"><span style='font-size:10.0pt;font-family:"Courier New";
color:black'>(2)</span></font><font size=1 color=black><span style='font-size:
7.0pt;color:black'> <span class=apple-converted-space> </span></span></font><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt;font-family:
"Courier New";color:black'>[LLVMdev] trouble with 32-bit promotion of return
value (initiated by myself)</span></font></p>
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<p class=MsoNormal><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:black'> </span></font></p>
<div>
<p class=MsoNormal><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>To summarize:</span></font></p>
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<div>
<p class=MsoNormal><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>Evan has replied
to thread (1) and suggested to add a calling convention and check for it in
visitRet</span></font></p>
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<div>
<p class=MsoNormal><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>Dan replied to
thread (2) and suggested to add a new field to the TargetLowering class, and
then let each target specify the minimum integer type to promote return types
to</span></font></p>
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<p class=MsoNormal><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:black'> </span></font></p>
<div>
<p class=MsoNormal><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>Either way, I
think we all agree that the root of the problem is the FIXME in
SelectionDAGLowering::visitRet()</span></font></p>
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<p class=MsoNormal><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:black'> </span></font></p>
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<p class=MsoNormal><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>But what is the
preferred method?</span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> </span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Both. :-)</span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> </span></font></p>
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<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>If you are using a non-C ABI, then you may not need to do the promotion
at all. However, if you do need to do the promotion, you need to know the type
of "int". It's not entirely clear to me what is the best way to
accomplish. To me, I don't think TargetLowering is the right place to add the
hook. How about TargetData.h ? There is a getIntPtrType(), perhaps we need
a getIntType()?</span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> </span></font></p>
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<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Evan</span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
<br>
</span></font></p>
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style='font-size:10.0pt;font-family:"Courier New";color:black'> </span></font></p>
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<p class=MsoNormal><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>Thanks</span></font></p>
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<div>
<p class=MsoNormal><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt;font-family:"Courier New";color:black'>Ali</span></font></p>
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<p class=MsoNormal><font size=1 color=black face=Helvetica><span
style='font-size:9.0pt;font-family:Helvetica;color:black'>_______________________________________________<br>
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href="http://llvm.cs.uiuc.edu">http://llvm.cs.uiuc.edu</a><br>
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