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<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>Hi Jim,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
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 lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>The MCJIT with changed
RuntimeDyLd passes most of ExecutionEngine tests on Mac OS, except of 3 tests: stubs.ll,
test-common-symbols.ll and test-global.ll.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>And I will work to ensure
that these three tests are also passed.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>Please look
01-RuntimeDyLd-02.patch of the previous letter, can I commit it?<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
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 lang=EN-US
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 lang=EN-US
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 lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>Regards,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>Danil<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
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 lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<div>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center tabindex=-1>
</span></font></div>
<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'> Kaylor, Andrew
[mailto:andrew.kaylor@intel.com] <br>
<b><span style='font-weight:bold'>Sent:</span></b> Saturday, February 18, 2012
5:41 AM<br>
<b><span style='font-weight:bold'>To:</span></b> Danil Malyshev; <st1:PersonName
w:st="on">llvm-commits@cs.uiuc.edu</st1:PersonName><br>
<b><span style='font-weight:bold'>Cc:</span></b> Jim Grosbach<br>
<b><span style='font-weight:bold'>Subject:</span></b> RE: RuntimeDyLd new
features</span></font><o:p></o:p></p>
</div>
<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=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>Hi Danil,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>I’d like to
make clear that if Jim is OK with the impact of your patch on MachO JIT loading
then I’d be happy for you to proceed with your patch, incorporating my
comments below, and we will withdraw our previous uncommitted patch and I will
merge the GDB JIT debugging integration code we have with your changes after
they have been committed.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>Thanks,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>Andy<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><o:p> </o:p></span></font></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'>
<p class=MsoNormal><b><font size=2 face=Tahoma><span lang=EN-US
style='font-size:10.0pt;font-family:Tahoma;font-weight:bold'>From:</span></font></b><font
size=2 face=Tahoma><span lang=EN-US style='font-size:10.0pt;font-family:Tahoma'>
llvm-commits-bounces@cs.uiuc.edu [mailto:llvm-commits-bounces@cs.uiuc.edu] <b><span
style='font-weight:bold'>On Behalf Of </span></b>Kaylor, Andrew<br>
<b><span style='font-weight:bold'>Sent:</span></b> Tuesday, February 14, 2012
4:53 PM<br>
<b><span style='font-weight:bold'>To:</span></b> Danil Malyshev; <st1:PersonName
w:st="on">llvm-commits@cs.uiuc.edu</st1:PersonName><br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [llvm-commits]
RuntimeDyLd new features<o:p></o:p></span></font></p>
</div>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-US
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>Hi Danil,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>I've been working
with your patch also. Mostly, it looks pretty good. I've been able
to layer most of our added functionality on top of it, and I have GDB
integration working and our integration tests passing. There are a few
issues I'd like to bring up, however.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>The first thing I
saw with your patch is that I had problems loading images that were generated
with debug information included. In particular, applying relocations to
debug sections using the actual addresses of the debug sections causes
problems. This is really a small issue because, as you mentioned, debug
sections don't need to be loaded. I worked around this problem by adding
a new member function to SectionRef to query whether or not the section is
required for execution. This is fairly trivial for ELF.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>A related problem is
that your code does not properly handle sections which are only represented by
a header in the ELF image (that is, SHT_NOBITS sections) or sections which need
to be zero-initialized. I worked around these problems using the existing
isBSS() member in SectionRef, but it would probably be better to split these
two concepts.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>Similarly, your code
does not handle symbols which are marked as relative to the SHN_COMMON
section. Fixing this is a bit more complicated. I think we can
probably build a table of these symbols in the RuntimeDyldImpl class by adding
a new member to SectionRef, but we'll need deeper access to the format-specific
classes to update the symbol addresses. I'm working on an implementation
of this for ELF.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>The code which loads
the sections is currently assuming pointer-sized alignment for all
sections. I ran into a case using floating point numbers where 16-byte
alignment was required. This is a fairly simple fix as the alignment
value is accessible through SectionRef.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>I think it would be
worthwhile adding an function to SectionRef to query whether or not a section
contains code rather than the current algorithmic method you are using.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>In a few places you
are using uintptr_t or uint8_t* in places that will restrict cross-architecture
JITing. The TargetAddr in the SectionEntry structure is an example that comes
to mind.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>The distinction
between code and data for memory allocation will be important going
forward. I think it would be better to fix the existing bug that to
disable the specific allocations.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>In
RuntimeDyld::loadObject, in the "parse and process relocations loop"
"SectionID == 0" is used to identify sections that need to be looked
up, but zero is a valid SectionID. For that section, it goes into the
lookup for every relocation.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>I'm continuing to
work on integrating our code, including some that hasn't yet been submitted to
the list for review, with your changes. I need to go over what I've done
with the rest of my co-workers, but I wanted to give you a progress update now.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'>-Andy<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><o:p> </o:p></span></font></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'>
<p class=MsoNormal><b><font size=2 face=Tahoma><span lang=EN-US
style='font-size:10.0pt;font-family:Tahoma;font-weight:bold'>From:</span></font></b><font
size=2 face=Tahoma><span lang=EN-US style='font-size:10.0pt;font-family:Tahoma'>
Danil Malyshev [mailto:dmalyshev@accesssoftek.com] <br>
<b><span style='font-weight:bold'>Sent:</span></b> Tuesday, February 14, 2012
10:30 AM<br>
<b><span style='font-weight:bold'>To:</span></b> Kaylor, Andrew; <st1:PersonName
w:st="on">llvm-commits@cs.uiuc.edu</st1:PersonName><br>
<b><span style='font-weight:bold'>Cc:</span></b> Jim Grosbach<br>
<b><span style='font-weight:bold'>Subject:</span></b> RE: RuntimeDyLd new
features<o:p></o:p></span></font></p>
</div>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-US
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>Hi Andrew,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
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 lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>Thank you for the
detailed explanation.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>I have carefully studied
your patch and DyldELFObject.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>A gdb support is very
important and it's actually a big step for MCJIT. I like your patch, its
loadObject() looks faster than my. But I see one big conceptual problem.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
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 lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>The RuntimeDyLd was
developed as a linker, which is able to prepare data for running on another platform.
The RuntimeDyldMachO largely implements it.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>In the RuntimeDyldELF you
went the other way. Now it is very far from remote execution. And even if the
object file will be emitted with RTDyldMemoryManager, it is not a good idea:
(1) remote execution doesn't need many parts of object file, such as debugging
information, headers, section table and etc, (2) some sections is code and must
has execution permit, some sections is data without execution permit, so the
best way is use a different methods for emits different type of sections.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>If your patch will be
committed, we obtain a RuntimeDyldMachO and RuntimeDyldELF, which different
principles and a different results. And most likely, for ELF will never be
fully realization for remote execution.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
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 lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>I think another ways will
be better, just for instance, two possible solutions:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>1. Always emits the
sections required to execution with a RTDyldMemoryManager. Resolve relocation
in these sections. And if the isDebugging flag is set, then in addition, DyldELFObject::rebaseObject
make his job, except that for the sections stored by the RTDyldMemoryManager
write the correct address.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>2. Check the debug flag
at first, before load object file. If it set, just use your realization of
loadObject, otherwise - use normal way with RTDyldMemoryManager.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
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 lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>Both alternatives have
their shortcomings, perhaps you find another solution. Also, I would be glad to
hear that Jim thinks about it.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>Now I trying to merge
your patch with my.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
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 lang=EN-US
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 lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>Regards,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'>Danil<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span lang=EN-US
style='font-size:10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<div>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center>
</span></font></div>
<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'> Kaylor, Andrew
[mailto:andrew.kaylor@intel.com] <br>
<b><span style='font-weight:bold'>Sent:</span></b> Thursday, February 09, 2012
4:56 AM<br>
<b><span style='font-weight:bold'>To:</span></b> Danil Malyshev; <st1:PersonName
w:st="on">llvm-commits@cs.uiuc.edu</st1:PersonName><br>
<b><span style='font-weight:bold'>Subject:</span></b> RE: RuntimeDyLd new
features</span></font><o:p></o:p></p>
</div>
<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=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'>Hi Danil,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'>Thanks for your
efforts in this area. As Eli Bendersky mentioned, we have a patch out for
review in this area also. I'm hopeful that we can find a convergence
between our code, your code and the code that Jim Grosbach has put in place.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'>Unfortunately, we have
been submitting our code in small chunks for ease of review and to keep things
stable, and it may not be obvious from what we've put out for review what our
intentions were or our intended solutions to the problems that were left
open. I'd like to take this opportunity to discuss the direction we we're
heading and see how it might align with what you and Jim have done.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'>Let me first explain
what we have done, and then I'll offer specific comments on your code and
possible next steps.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'>We have had two
primary goals: (1) to get MCJIT generated code to work correctly on Intel
architecture and help pave the way for other implementations and (2) enable
source-level debugging of JITed code with GDB. This second goal seems to
be dropping from view, but it places a few constraints on the eventual
implementation. We've had GDB integration working, BTW.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'>In order to get GDB to
handle JITed code, we need to register an ELF object image through an interface
GDB defines. As you might expect, GDB has some peculiar expectations for
what this ELF object image should look like. In particular, we need to
set a flag in the ELF header and update the sh_addr members in the section
headers to reflect the address where the section contents reside in memory.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'>Our most recent patch
(<a
href="http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20120130/135997.html">http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20120130/135997.html</a>,
not yet committed) begins by copying the entire ELF image emitted by the MC
code generator into an executable buffer. This was intended as a
temporary step toward our eventual solution. It enabled us to perform
relocations in-place on the object and execute functions in place (thus
eliminating an extra copy that was previously being done). We were in the
process of implementing a smarter section-based approach, but Jim Grosbach was
implementing a similar approach in parallel and our submission ended up
appearing out of step in this regard.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'>So that's our
background. Now, returning to your patch....<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'>I like the idea of
combining as much common code as possible into the RuntimeDyldImpl class.
I'm interested to hear from users of the MachO loader if your implementation
has lost any of the specialization that they need. I think it's a promising
approach. There are some ELF-specific details that we will need to have
incorporated to re-enable GDB integration, but I expect that we'll be able to
find a way to work that in with a few well-placed overloaded function calls.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'>I have some
reservations about the use of the basic ObjectFile interface, which has some
serious limitations. We've been working toward exposing the ELFObjectFile
template for use in the runtime loading process (as well as other unrelated
uses). It may be that this is something that can be generalized enough to
fit with your approach. My main concern in this regard is that we need to
be able to update specific entries in the ELF image, as described above.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'>A related issue is
that section loading can be refined with some ELF-specific details. Some
sections need to have memory allocated for their contents. Other sections
can be left in place in the originally generated image. There is a good
bit of unnecessary copying going on in the existing implementation, and I'm not
clear to what extent your patch addresses that. Before the object is
loaded, it is copied into a new buffer and then the contents of each section
are copied again as we go. What I'd like is for the runtime loaders to
use the buffer into which the object is originally generated and only make
copies where it is strictly necessary. This isn't necessarily something
you need to do for your work to be acceptable, but I mention it as a likely
next step.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'>Over the next few days
I intend to apply your patch locally and try to merge our work into it.
I'll provide additional feedback as I get a better feel for what you've done.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=black face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:black'>-Andy</span></font><font
size=2 color="#1f497d" face=Calibri><span lang=EN-US style='font-size:11.0pt;
font-family:Calibri;color:#1F497D'><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color="#1f497d" face=Calibri><span lang=EN-US
style='font-size:11.0pt;font-family:Calibri;color:#1F497D'><o:p> </o:p></span></font></p>
<div>
<div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'>
<p class=MsoNormal><b><font size=2 face=Tahoma><span lang=EN-US
style='font-size:10.0pt;font-family:Tahoma;font-weight:bold'>From:</span></font></b><font
size=2 face=Tahoma><span lang=EN-US style='font-size:10.0pt;font-family:Tahoma'>
llvm-commits-bounces@cs.uiuc.edu [mailto:llvm-commits-bounces@cs.uiuc.edu] <b><span
style='font-weight:bold'>On Behalf Of </span></b>Danil Malyshev<br>
<b><span style='font-weight:bold'>Sent:</span></b> Tuesday, February 07, 2012
12:24 PM<br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName w:st="on">llvm-commits@cs.uiuc.edu</st1:PersonName><br>
<b><span style='font-weight:bold'>Subject:</span></b> [llvm-commits]
RuntimeDyLd new features<o:p></o:p></span></font></p>
</div>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span lang=EN-US
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'>Hello everyone,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'>Please review the RuntimeDyLd-01.patch.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'>This patch makes the following changes:<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'>1. The main works will made in the RuntimeDyLdImpl
with uses the ObjectFile class. RuntimeDyLdMachO and RuntimeDyLdELF now only
parses relocations and resolve it. This is allows to make improvements of the
RuntimeDyLd more easily. In addition the support for COFF can be easily added.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'>2. Added ARM relocations to RuntimeDyLdELF.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'>3. Added support for stub functions for the ARM,
allowing to do a <st1:City w:st="on"><st1:place w:st="on">long branch</st1:place></st1:City>.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'>4. Added support for external functions that are not
loaded from the object files, but can be loaded from external libraries. Now
MCJIT can correctly execute the code containing the printf, putc, and etc.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'> <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'>5. The sections emitted instead functions, thanks Jim
Grosbach. MemoryManager.startFunctionBody() and MemoryManager.endFunctionBody()
have been removed.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'>6. MCJITMemoryManager.allocateDataSection() and
MCJITMemoryManager. allocateCodeSection() used JMM->allocateSpace() instead
of JMM->allocateCodeSection() and JMM->allocateDataSection(), because I
got an error: "Cannot allocate an allocated block!" with object file
contains more than one code or data sections.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'>7. Fixed ELF::R_X86_64_PC32 relocation for the case
when RealOffset is negative value.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'>8. Added new testing folder: ExecutionEngine/MCJIT
because mcjit tests can be running only for x86 and arm and it's can be
filtered with dg.exp.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'>Tested in Ubuntu x86_64, Ubuntu armv7 and MacOS 64.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'>Thank you,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span lang=EN-US style='font-size:
10.0pt;font-family:Arial'>Danil<o:p></o:p></span></font></p>
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