[llvm-dev] how to add my own passes to LTO pass

[y liu via llvm-dev]

  Thanks for your help.

Eli Friedman <efriedma at quicinc.com> 于2020年4月24日周五 上午2:59写道：

> It should be possible to dynamically load legacy pass manager plugins into
> lld on trunk.  Pass “-mllvm=-load=plugin.so” to lld (“-fuse-ld=lld
> -Wl,-mllvm=-load=plugin.so” to clang) for a plugin with an appropriate
> RegisterStandardPasses, and it should be called.
>
>
>
> Dynamically loading pass plugins into gold is still in progress. (See
> https://reviews.llvm.org/D77704.)
>
>
>
> It’s also possible to statically link both legacy pass manager and new
> pass manager LTO pass plugins into LLVM; that should work for both gold and
> lld without any command-line flags at runtime.
>
>
>
> llvm/examples/Bye/ is a very simple pass plugin which supports running
> during LTO; it should serve as a reasonable template if you’re having
> trouble getting started.  It support both the legacy pass manager and the
> new pass manager; new pass manager isn’t enabled by default, so you can
> ignore the getByePluginInfo() etc. if you’re not interested in that.
>
>
>
> There’s a little documentation for pass plugins at
> http://llvm.org/docs/WritingAnLLVMPass.html#building-pass-plugins ; the
> documentation could probably use some work.
>
>
>
> Note that all of this is only working on trunk; 10.0 doesn’t have the
> changes in question.
>
>
>
> -Eli
>
>
>
> *From:* Teresa Johnson <tejohnson at google.com>
> *Sent:* Thursday, April 23, 2020 10:16 AM
> *To:* y liu <ly820nha at gmail.com>; Eli Friedman <efriedma at quicinc.com>
> *Cc:* llvm-dev <llvm-dev at lists.llvm.org>
> *Subject:* [EXT] Re: [llvm-dev] how to add my own passes to LTO pass
>
>
>
> cc-ed llvm-dev back so others can hopefully help. I don't load passes via
> plugins so this is outside my area of expertise. But I have seen some
> recent patches fly by that are working on this.
>
>
>
> I saw from an earlier question you posted that you are using gold. There
> is a patch under development/review to get pass plugins to work for LTO
> through gold. See https://reviews.llvm.org/D77704.
>
>
>
> Eli (added) was working on adding support as well, here are a couple of
> patches he recently landed for this in LTO and lld:
>
> https://reviews.llvm.org/D75879 (lld)
>
> https://reviews.llvm.org/D76866 (LTO)
>
>
>
> I'm not completely sure what the status is at this point though. Eli is
> probably the best person to answer.
>
>
>
> Teresa
>
>
>
> On Wed, Apr 22, 2020 at 7:50 PM y liu <ly820nha at gmail.com> wrote:
>
> I‘m using LLVM 10, and register my pass by following code:
>
> char MyModulePass::ID = 0;
>
> static RegisterPass<MyModulePass> X("MyModule", "MyModule pass");
>
> static void registerMyModulePass(const PassManagerBuilder &,
>
>                          legacy::PassManagerBase &PM) {
>
>   PM.add(new MyModulePass());
>
> }
>
> static RegisterStandardPasses
>
>   RegisterMyPass(PassManagerBuilder::EP_FullLinkTimeOptimizationLast,
>
>                  registerMyModulePass);
>
> MyModulePass reles on helper.c.
>
> I want to use it for optimization after the link is compelte.
>
> Now, I compile it manually with opt.
>
> For example:
>
>
>
> Target: fun1.c fun2.c fun3.c main.c
> Pass: Mypass.so
> Dependency: helper.c
>
>
> fun1.c fun2.c fun3.c main.c ---> target.bc
>                    helper.c ---> helper.o
>
> target.bc helper.o ---> target-link.bc ----> opt Mypass.so  --->
> target-opt.bc ---> target
>
>
>
> I want to achieve my goals by LTO.
>
>
>
> Teresa Johnson <tejohnson at google.com>于2020年4月22日 周三23:11写道：
>
>
>
>
>
> On Wed, Apr 22, 2020 at 5:12 AM y liu via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
> Hi,
>
> I have a module pass and I hope to use it to optimize a real-world program.
>
> I need LTO，and I have got LTO plugin.
>
>
>
> Do you mean the LLVM gold plugin (relevant when doing LTO links with gold
> or gnu ld), or are you trying to load your new pass via a pass plugin?
>
>  Yes, it’s gold plugin, I need it to link .bc and .o files. I want to
> optimize the target after linking.
>
> But How can I add my passes to LTO Pass. I can't find solution.
>
> What should I do?
>
>
>
> This depends on whether you are trying to add via a pass plugin
> dynamically via the command line (I believe the support for this is work in
> progress), or by manually modifying the pass pipeline within LLVM.
>
> Have you implemented as an old pass manager pass (the current default) or
> the new pass manager or both?
>
> Is it an LTO specific pass, or do you also want to run for non-LTO
> optimizing compiles (most optimizing passes should run in all cases).
>
>
>
> Assuming the latter, and also assuming you are using the default old pass
> manager, you would want to look at the following places in
> PassManagerBuilder.cpp:
>
>
>
> regular (full) LTO: PassManagerBuilder::addLTOOptimizationPasses
>
>
>
> ThinLTO: PassManagerBuilder::populateModulePassManager, which is used both
> by the pre-LTO compile and by the LTO linking ThinLTO compiles. If you want
> to insert your pass for both, just put it in the relevant place in this
> file, if you want to only do during the LTO link portion of the ThinLTO
> compile, then guard it with a check for "PerformThinLTO".
>
>
>
> For the new pass manager, it would be added to PassBuilder.cpp (that is
> structured a bit differently so let me know and I can point you in the
> right direction). If you are planning to send upstream it should be
> supported by both pass managers.
>
>
>
> HTH,
>
> Teresa
>
>
>
> _______________________________________________
>
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
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>
>
>
>
>
>
> --
>
> Teresa Johnson |
>
>  Software Engineer |
>
>  tejohnson at google.com |
>
>
>
>
> --
>
> Teresa Johnson |
>
>  Software Engineer |
>
>  tejohnson at google.com |
>
>
>
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