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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Hi Seb,<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’m going to reiterate – Clang can decide when it
wants to optimise away a variable. You asked for that behaviour when you
specified –O2. You can’t expect deterministically the same
behaviour on both x86 and x86-64 platforms – the procedure call standards
are different and different decisions go in to deciding how to optimise.<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'>You can’t expect debug information for an optimised build
to fully track that of the source because by definition the source is being
modified to optimise.<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'>Cheers,<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'>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>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'>
<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> Seb [mailto:babslachem@gmail.com] <br>
<b>Sent:</b> 07 March 2012 13:37<br>
<b>To:</b> James Molloy<br>
<b>Cc:</b> llvmdev@cs.uiuc.edu<br>
<b>Subject:</b> Re: [LLVMdev] Problem with x86 32-bit debug information ?<o:p></o:p></span></p>
</div>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-bottom:12.0pt'>Hi James,<br>
<br>
clang is able to generate correct debug informations for 64-bit target at -O2.
My feeling, given some other experiments I've done, is that debug
information generated for x86 32-bit might be broken for parameters as long as
they are not 'homed' in the code (local copy to an automatic variable). It
seems that when llvm.declare is turned into a llvm.value for parameter there is
something incorrect with respect to parameters debug informations that is
generated by clang/llvm. I just would like confirmation of this.<br>
<br>
Thanks for your answer<br>
Best Regards<br>
Seb<o:p></o:p></p>
<div>
<p class=MsoNormal>2012/3/7 James Molloy <<a
href="mailto:james.molloy@arm.com">james.molloy@arm.com</a>><o:p></o:p></p>
<div>
<div>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Hi
Seb,</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Clang
cannot generate debug information for something that it has optimised away. You
should reduce the optimisation level.</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>In
general debug information is only really accurate at –O0.</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Cheers,</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> </span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>James</span><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><span
style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'> </span><o:p></o:p></p>
<div style='border:none;border-top:solid windowtext 1.0pt;padding:3.0pt 0cm 0cm 0cm;
border-color:-moz-use-text-color -moz-use-text-color'>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><b><span
lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> <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>]
<b>On Behalf Of </b>Seb<br>
<b>Sent:</b> 07 March 2012 13:17<br>
<b>To:</b> <a href="mailto:llvmdev@cs.uiuc.edu" target="_blank">llvmdev@cs.uiuc.edu</a><br>
<b>Subject:</b> [LLVMdev] Problem with x86 32-bit debug information ?</span><o:p></o:p></p>
</div>
<div>
<div>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;margin-bottom:12.0pt'>Hi all,<br>
<br>
I'm using trunk version of LLVM/CLANG.<br>
When I compile attached files on my 64-bit Ubuntu 10.04 LTS system as follows:<br>
<br>
clang -O2 -g check.c main.c -o check64<br>
<br>
When I do gdb check64 and set a breakpoint to the check routine and executes to
the breakpoint, I've got:<br>
<br>
Breakpoint 1, check (result=0x601110, expect=0x601020, n=53) at check.c:7<br>
7 {<br>
<br>
As you can see I can inspect 'n' value.<br>
<br>
Now if I compile for x86 32-bit as follows:<br>
<br>
clang -m32 -O2 -g check.c main.c -o check32<br>
<br>
When I do gdb check32 and set a breakpoint to the check routine and executes to
the breakpoint, I've got:<br>
<br>
Breakpoint 1, check (result=<value optimized out>, <br>
expect=<value optimized out>, n=0) at check.c:7<br>
7 {<br>
<br>
As you can see I can NOT inspect 'n' value. Is there a way to inforce even at
-O2 clang to generate debug informations so that I can inspect 'n' value ?<br>
Or is it a BUG from clang for x86 32-bit ?<br>
Thanks for your answers.<br>
Best Regards<br>
Seb<o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
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