<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On May 20, 2019, at 6:47 AM, Liming Gao <<a href="mailto:liming.gao@intel.com" class="">liming.gao@intel.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; 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="">Jordan:</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; 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: Helvetica; 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: Helvetica; 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="">-----Original Message-----<br class="">From: Justen, Jordan L<br class="">Sent: Monday, May 20, 2019 4:15 AM<br class="">To: Ard Biesheuvel <<a href="mailto:ard.biesheuvel@linaro.org" class="">ard.biesheuvel@linaro.org</a>>; Gao, Liming <<a href="mailto:liming.gao@intel.com" class="">liming.gao@intel.com</a>>; edk2-devel-groups-io <<a href="mailto:devel@edk2.groups.io" class="">devel@edk2.groups.io</a>><br class="">Subject: Re: [edk2-devel] [Patch 0/7] Add new CLANG8ELF tool chain for new LLVM/CLANG8<br class=""><br class="">On 2019-04-27 17:55:02, Liming Gao wrote:<br class=""><blockquote type="cite" class=""><blockquote type="cite" class="">-----Original Message-----<br class="">From: Ard Biesheuvel [<a href="mailto:ard.biesheuvel@linaro.org" class="">mailto:ard.biesheuvel@linaro.org</a>]<br class="">Sent: Saturday, April 27, 2019 12:33 AM<br class=""><br class=""><br class="">This series confuses me. The existing CLANGxx toolchains already use<br class="">GenFw and ELF to PE/COFF conversion, so the name CLANG8ELF is<br class="">misleading.<br class=""><br class=""></blockquote>LLVM/CLANG8.0 compiler supports to generate PE image or ELF image.<br class="">This tool chain is to generate ELF image and be converted to PE<br class="">image. I am investigating another tool chain with CLANG8.0 to<br class="">directly generate PE image. To differentiate them, I use the tool<br class="">chain name CLANG8ELF and CLANG8PE for them.<br class=""></blockquote><br class="">Assuming CLANG8ELF and CLANG8PE were functional, would both be needed?<br class="">It kind of sounds like this a half-finished investigation.<br class=""><br class=""></blockquote><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; 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="">One point is that they will generate the different debug format symbols (WinDBG or GDB).</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; 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: Helvetica; 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="">I have not done the full investigation to generate the different debug format symbols in single tool chain.</span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; 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: Helvetica; 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><br class=""></div><div><div>Liming,</div><div><br class=""></div><div>I don't know the current answer but we moved over to using clang a while back on Mac so here are some general thoughts incase they help your investigation. </div><div><br class=""></div><div>We had to take a different approach for i386 vs x86_64.:</div><div>1) i386</div><div>For i386 we used -arch i386 and compiler flags to produce the correct ABI. The thing about using -arch is the target triple defaults to your current machine, thus -arch i386 on a Mac is going to make a Mach-O object. if you use it one Linux it is going to make an ELF, on Windows a PE/COFF. To make this work we add mtoc to CCTOOLS this is a tool that converts Mach-O to PE/COFF. The PE/COFF contains a UUID for the Mach-O and the Mach-O dSYM (kind of like the PDB file) and that is what is used for debugging. You can even load the Mach-O directly into the debugger and do offline investigation of the image at its linked address. </div><div><br class=""></div><div>2) x86_64</div><div>Since the Mac uses the System V ABI we needed a cross compiler. Clang implements cross compilers via the Triple (this is the -target argument you pass to clang). We actually end up open sourcing a triple that did what we needed. </div><div><br class=""></div><div>For building on a Mac the triple is: -target x86_64-pc-win32-macho</div><div><br class=""></div><div><div> <arch><sub>-<vendor>-<sys>-<abi></div><div class=""> < x86_64 ><>-< pc >-< win32 >-< macho ></div><div class=""><br class=""></div><div class="">Examples:</div></div><div><div>arch = x86_64, i386, arm, thumb, mips, etc.</div><div>sub = for ex. on ARM: v5, v6m, v7a, v7m, etc.</div><div>vendor = pc, apple, nvidia, ibm, etc.</div><div>sys = none, linux, win32, darwin, cuda, etc.</div><div>abi = eabi, gnu, android, macho, elf, etc.</div><div class=""><br class=""></div></div>OK so they expanded the Triple to have 4 fields, so that is kind of naming fail, but they still seem to call it a triple. When we did the port "-DEFIAPI=__attribute__((ms_abi))" was not an option and that is why we ended up having to male our own triple. As far as I can tell __attribute__((ms_abi)) works correctly in the Xcode compiler. </div><div><br class=""></div><div>To make the debugging work we ended up defining a new CodeView signature [1] to the PE/COFF Debug Directory Entry. At this point the native lldb (llvm debugger) does not know how to load Mach-O DWARF from PE/COFF. We could teach it, but we have not really found a need as we ended up writing debugger scripts to load symbols and lldb can load the Mach-O image (our build system leaves them around) for offline debugging.</div><div><br class=""></div><div>In terms of PDB vs DWARF generally the compiler emits the DWARF (or PDB) data at compile time and the linker just aggregates it together. I see a blog from last April [2] talking about LLVM PDB support and it ends with "Do I hear cross-compilation?". So you might have to compile from the start for PDB or DWARF. This seems to imply you are going to need a triple to invoke a cross compiler? Also you are going to need that triple present in the clang binary, so you might be able to make a custom version of clang that supports the triples you need, but that may not be in the official binary for clang. </div><div><br class=""></div><div>Converting ELF to PE/COFF is much more straight forward than converting the debugging information so that makes sense that it could just be the backend of the linker. </div><div><br class=""></div><div>I look forward to getting the results of your investigation.</div><div><br class=""></div><div>[1] <a href="https://github.com/tianocore/edk2/blob/master/MdePkg/Include/IndustryStandard/PeImage.h#L647" class="">https://github.com/tianocore/edk2/blob/master/MdePkg/Include/IndustryStandard/PeImage.h#L647</a></div><div>[2] <a href="http://blog.llvm.org/2017/08/llvm-on-windows-now-supports-pdb-debug.html" class="">http://blog.llvm.org/2017/08/llvm-on-windows-now-supports-pdb-debug.html</a></div><div><br class=""></div><div>Thanks,</div><div><br class=""></div><div>Andrew Fish</div><div><br class=""></div><blockquote type="cite" class=""><div class=""><blockquote type="cite" style="font-family: Helvetica; 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'm guessing that if CLANG8PE produces equal or better code, then it<br class="">would be preferred.<br class=""><br class="">Therefore, shouldn't we just finish the investigation, and add a<br class="">single CLANG8 toolchain at the end? Or, maybe to reflect that it<br class="">mostly uses the LLVM tool stack we could name it LLVM8.<br class=""></blockquote><span style="caret-color: rgb(0, 0, 0); font-family: Helvetica; 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="">I also prefer single CLANG8 tool chain. I will collect more information and see whether it is possible.<span class="Apple-converted-space"> </span></span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; 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: Helvetica; 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="">Now, I would like to add this tool chain for the developer evaluation. Because I can't address all<span class="Apple-converted-space"> </span></span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; 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: Helvetica; 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="">comments now, I will remove this feature from Q2 stable tag. I will add it into edk2-staging first.<span class="Apple-converted-space"> </span></span><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; 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: Helvetica; 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><blockquote type="cite" class=""><div class=""><blockquote type="cite" style="font-family: Helvetica; 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="">-Jordan<br class=""></blockquote><br style="caret-color: rgb(0, 0, 0); font-family: Helvetica; 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: Helvetica; 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></div></blockquote></div><br class=""></body></html>
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