<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
<p><br>
</p>
3/3/2020 12:48 AM, Greg Clayton via llvm-dev пишет:<br>
<blockquote type="cite"
cite="mid:445D4E5F-A0FD-4E35-9DDA-E6CA45385907@gmail.com">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<br class="">
<div><br class="">
<blockquote type="cite" class="">
<div class="">On Feb 28, 2020, at 11:25 PM, Fangrui Song via
llvm-dev <<a href="mailto:llvm-dev@lists.llvm.org"
class="" moz-do-not-send="true">llvm-dev@lists.llvm.org</a>>
wrote:</div>
<br class="Apple-interchange-newline">
<div class=""><span style="caret-color: rgb(0, 0, 0);
font-family: Menlo-Regular; font-size: 12px; font-style:
normal; font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none; float: none; display: inline
!important;" class="">On 2020-02-28, Greg Clayton via
llvm-dev wrote:</span><br style="caret-color: rgb(0, 0,
0); font-family: Menlo-Regular; font-size: 12px;
font-style: normal; font-variant-caps: normal;
font-weight: normal; letter-spacing: normal; text-align:
start; text-indent: 0px; text-transform: none;
white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; text-decoration: none;"
class="">
<blockquote type="cite" style="font-family: Menlo-Regular;
font-size: 12px; font-style: normal; font-variant-caps:
normal; font-weight: normal; letter-spacing: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-size-adjust: auto;
-webkit-text-stroke-width: 0px; text-decoration: none;"
class="">I am looking to create a tool that can add Apple
or DWARF5 accelerator tables to fully linked executables
that contain DWARF. This will help us benchmark how much
accelerator tables can improve the debugging experience as
debuggers don't need to manually index all of the debug
info during debugging.<br class="">
</blockquote>
<span style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none; float: none; display: inline
!important;" class="">Is it for ELF, Mach-O, wasm, COFF,
or any of the combinations?</span><br style="caret-color:
rgb(0, 0, 0); font-family: Menlo-Regular; font-size: 12px;
font-style: normal; font-variant-caps: normal;
font-weight: normal; letter-spacing: normal; text-align:
start; text-indent: 0px; text-transform: none;
white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; text-decoration: none;"
class="">
</div>
</blockquote>
<div><br class="">
</div>
Yes, for any object files that LLVM currently supports. But I am
looking to support ELF first as MachO already has these tables
available since dsymutil already creates either Apple or DWARF
accelerator tables. COFF and Wasm can come later.</div>
<div><br class="">
<blockquote type="cite" class="">
<div class=""><br style="caret-color: rgb(0, 0, 0);
font-family: Menlo-Regular; font-size: 12px; font-style:
normal; font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;" class="">
<blockquote type="cite" style="font-family: Menlo-Regular;
font-size: 12px; font-style: normal; font-variant-caps:
normal; font-weight: normal; letter-spacing: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-size-adjust: auto;
-webkit-text-stroke-width: 0px; text-decoration: none;"
class="">Looking at how accelerator tables are currently
emitted, they seem to be built up as DWARF is being
created or linked, and then emitted using a subclass of
DWARFEmitter. The only subclass if this right now that I
see is one in dsymutil which ends up emitting everything
using an AsmPrinter by eventually emitAppleAccelTable(...)
from llvm/include/llvm/CodeGen/AccelTable.h.<br class="">
<br class="">
I spoke briefly with Shoaib on this subject and he
suggested adding code to llvm-objcopy. I briefly looked
through the code and from what I can tell, llvm-objcopy
doesn't seem to have any DWARF abilities other than
compressing DWARF sections. If we do add functionality to
llvm-objcopy, are we ok pulling in DebugInfoDWARF and the
LLVM object model? AFAICT the code for this tools has its
own object file layer which doesn't match the full layer
inside of LLVM (llvm::ObjectFile and DWARFContext). Also,
no AsmPrinter objects are used in this codebase either.<br
class="">
</blockquote>
<br style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;" class="">
<span style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none; float: none; display: inline
!important;" class="">llvm-objcopy supports various ad-hoc
binary manipulation features where each feature does a
very</span><br style="caret-color: rgb(0, 0, 0);
font-family: Menlo-Regular; font-size: 12px; font-style:
normal; font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;" class="">
<span style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none; float: none; display: inline
!important;" class="">simple task. Neither llvm-objcopy
nor GNU objcopy knows DWARF. --strip-debug,</span><br
style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;" class="">
<span style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none; float: none; display: inline
!important;" class="">--compress-debug-sections,
--add-gnu-debuglink and --only-keep-debug have "debug" in
their names but</span><br style="caret-color: rgb(0, 0,
0); font-family: Menlo-Regular; font-size: 12px;
font-style: normal; font-variant-caps: normal;
font-weight: normal; letter-spacing: normal; text-align:
start; text-indent: 0px; text-transform: none;
white-space: normal; word-spacing: 0px;
-webkit-text-stroke-width: 0px; text-decoration: none;"
class="">
<span style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none; float: none; display: inline
!important;" class="">these features don't need to parse
DWARF. (GNU objcopy has a --debugging but that only works
for</span><br style="caret-color: rgb(0, 0, 0);
font-family: Menlo-Regular; font-size: 12px; font-style:
normal; font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;" class="">
<span style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none; float: none; display: inline
!important;" class="">a.out and coff, not elf).</span><br
style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;" class="">
<br style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;" class="">
<span style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none; float: none; display: inline
!important;" class="">Do we have a more suitable tool for
such debugging functionality? dsymutil for ELF?</span><br
style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;" class="">
</div>
</blockquote>
<div><br class="">
</div>
<div>dsymutil is such a tool, but it uses the llvm::ObjectFile
layer and the llvm targets, so if you open a file that
contains "armv7" architecture and the ARM target hasn't been
built into your bistro, it will fail to open this binary with
an error that says:</div>
<div><br class="">
</div>
<div>No available targets are compatible with triple
"arm-unknown-unknown"</div>
<div class=""><br class="">
</div>
<div class="">I ran into this with a recent gsym patch that is
trying to fix the buildbots for testing, but it fails when the
ARM targets are not enabled and I try to load the DWARF from
an object file:</div>
<div class=""><br class="">
</div>
<div class=""><a
href="http://lab.llvm.org:8011/builders/llvm-clang-lld-x86_64-scei-ps4-ubuntu-fast/builds/63473/steps/test-check-all/logs/stdio"
class="" moz-do-not-send="true">http://lab.llvm.org:8011/builders/llvm-clang-lld-x86_64-scei-ps4-ubuntu-fast/builds/63473/steps/test-check-all/logs/stdio</a></div>
<div class=""><br class="">
</div>
<div class="">And this is part of the reason for this email. I
would love to not require llvm-gsymutil to require all LLVM
targets to be there. DebugInfoDWARF doesn't need the targets,
it just needs to know address byte size and endianness and it
can parse the debug info in the DWARF.</div>
<div class=""><br class="">
</div>
</div>
</blockquote>
<p>Hi Greg, dsymutil code was recently refactored so that it`s
linking part was moved into lib/DWARFLinker library.</p>
<p>As an advantage, it allows making DWARFLinker to not depend on
ObjectFile : <a class="moz-txt-link-freetext" href="https://reviews.llvm.org/D75029">https://reviews.llvm.org/D75029</a> .<br>
</p>
<p>It might make sense that your tool uses DWARFLinker
library(probably extending it with new functionality) to work with
DWARF.<br>
</p>
<p>Alexey.<br>
</p>
<blockquote type="cite"
cite="mid:445D4E5F-A0FD-4E35-9DDA-E6CA45385907@gmail.com">
<div>
<div class="">So my main question stands: do we want all tools
that must manipulate DWARF to require the llvm::ObjectFile
layer and all of the targets to be enabled just so that the
object files can be parsed, or do we want to make lighter
layer available, akin to what llvm-objcopy has, so more tools
can take advantage of this lighter weight layer.</div>
<br class="">
<blockquote type="cite" class="">
<div class=""><br style="caret-color: rgb(0, 0, 0);
font-family: Menlo-Regular; font-size: 12px; font-style:
normal; font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;" class="">
<blockquote type="cite" style="font-family: Menlo-Regular;
font-size: 12px; font-style: normal; font-variant-caps:
normal; font-weight: normal; letter-spacing: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-size-adjust: auto;
-webkit-text-stroke-width: 0px; text-decoration: none;"
class="">Looking at lld sources, is seems to use the
DebugInfoDWARF library to some extent already. Not sure if
this tool uses the standard LLVM object model or has all
of its own emitters. Does lld use AsmPrinter at all? I
don't see any mention of it in there.<br class="">
</blockquote>
<br style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;" class="">
<span style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none; float: none; display: inline
!important;" class="">--gdb-index and diagnostics (line
tables) use DebugInfoDWARF. I have a plan to implement
.debug_names, which is similar to --gdb-index.</span><br
style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;" class="">
</div>
</blockquote>
<div><br class="">
</div>
<div>That is great, and we will share code for this of course
between the tool I write and the modifications to lld. Does
lld use the llvm::ObjectFile layer? or does it have its own
lighter weight layer?</div>
</div>
</blockquote>
<blockquote type="cite"
cite="mid:445D4E5F-A0FD-4E35-9DDA-E6CA45385907@gmail.com">
<div>
<blockquote type="cite" class="">
<div class=""><br style="caret-color: rgb(0, 0, 0);
font-family: Menlo-Regular; font-size: 12px; font-style:
normal; font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;" class="">
<blockquote type="cite" style="font-family: Menlo-Regular;
font-size: 12px; font-style: normal; font-variant-caps:
normal; font-weight: normal; letter-spacing: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-size-adjust: auto;
-webkit-text-stroke-width: 0px; text-decoration: none;"
class="">dsymutil has a --update feature which seems to
load all of the DWARF and pretend to link it all the while
generating the new accelerator table data, but I fear
using this would pull it way too much code (AsmPrinter,
all targets required to load all object files types, the
standard llvm object file model (not the lld or
llvm-objcopy versions), targets, etc).<br class="">
<br class="">
My initial thoughts are:<br class="">
1 - load a DWARFContext and iterate through the DWARF and
build accelerator table data<br class="">
2 - create the sections for the accelerator tables and
either keep in memory or save to disk<br class="">
3 - call functions to add the newly created sections to
the binary<br class="">
<br class="">
#1 should be easy as long as I can use a DWARFContext from
DebugInfoDWARF.<br class="">
#2 might need to be re-implemented using something other
than an AsmPrinter?<br class="">
#3 can use llvm-objcopy code if needed since it can add
sections?<br class="">
<br class="">
Any advice on how this can or should be implemented would
be appreciated from anyone with experience.<br class="">
<br class="">
Greg Clayton<br class="">
<br class="">
</blockquote>
<br style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;" class="">
<blockquote type="cite" style="font-family: Menlo-Regular;
font-size: 12px; font-style: normal; font-variant-caps:
normal; font-weight: normal; letter-spacing: normal;
orphans: auto; text-align: start; text-indent: 0px;
text-transform: none; white-space: normal; widows: auto;
word-spacing: 0px; -webkit-text-size-adjust: auto;
-webkit-text-stroke-width: 0px; text-decoration: none;"
class="">_______________________________________________<br
class="">
LLVM Developers mailing list<br class="">
<a href="mailto:llvm-dev@lists.llvm.org" class=""
moz-do-not-send="true">llvm-dev@lists.llvm.org</a><br
class="">
<a
href="https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev"
class="" moz-do-not-send="true">https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a><br
class="">
</blockquote>
<br style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;" class="">
<span style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none; float: none; display: inline
!important;" class="">_______________________________________________</span><br
style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;" class="">
<span style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none; float: none; display: inline
!important;" class="">LLVM Developers mailing list</span><br
style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;" class="">
<a href="mailto:llvm-dev@lists.llvm.org" style="font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; orphans: auto; text-align: start;
text-indent: 0px; text-transform: none; white-space:
normal; widows: auto; word-spacing: 0px;
-webkit-text-size-adjust: auto; -webkit-text-stroke-width:
0px;" class="" moz-do-not-send="true">llvm-dev@lists.llvm.org</a><br
style="caret-color: rgb(0, 0, 0); font-family:
Menlo-Regular; font-size: 12px; font-style: normal;
font-variant-caps: normal; font-weight: normal;
letter-spacing: normal; text-align: start; text-indent:
0px; text-transform: none; white-space: normal;
word-spacing: 0px; -webkit-text-stroke-width: 0px;
text-decoration: none;" class="">
<a
href="https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev"
style="font-family: Menlo-Regular; font-size: 12px;
font-style: normal; font-variant-caps: normal;
font-weight: normal; letter-spacing: normal; orphans:
auto; text-align: start; text-indent: 0px; text-transform:
none; white-space: normal; widows: auto; word-spacing:
0px; -webkit-text-size-adjust: auto;
-webkit-text-stroke-width: 0px;" class=""
moz-do-not-send="true">https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a></div>
</blockquote>
</div>
<br class="">
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<pre class="moz-quote-pre" wrap="">_______________________________________________
LLVM Developers mailing list
<a class="moz-txt-link-abbreviated" href="mailto:llvm-dev@lists.llvm.org">llvm-dev@lists.llvm.org</a>
<a class="moz-txt-link-freetext" href="https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev">https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev</a>
</pre>
</blockquote>
</body>
</html>