[cfe-dev] How to report bug when compiler hangs

[Steven Peters via cfe-dev]

Thanks for the idea. It looks like another infinite loop in DAG Combine
(like r206873
<http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20140421/213744.html>
and D26605 <https://reviews.llvm.org/D26605>) when I compile that file with
-O2 and for the core2 target cpu. Is there any advice on introspecting
SelectionDAG? I'm not sure how to identify which part of the source code is
triggering the infinite loop.

example stacktrace:
~~~
(lldb) thread backtrace all
* thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
  * frame #0: 0x00000001079c39d1
clang`llvm::SelectionDAG::Combine(llvm::CombineLevel, llvm::AAResults&,
llvm::CodeGenOpt::Level) + 1441
    frame #1: 0x00000001079c242e
clang`llvm::SelectionDAGISel::CodeGenAndEmitDAG() + 974
    frame #2: 0x000000010790f726
clang`llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) +
6118
    frame #3: 0x0000000107907846
clang`llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&)
+ 998
    frame #4: 0x000000010829cd54 clang`(anonymous
namespace)::X86DAGToDAGISel::runOnMachineFunction(llvm::MachineFunction&) +
20
    frame #5: 0x000000010790590d
clang`llvm::MachineFunctionPass::runOnFunction(llvm::Function&) + 125
    frame #6: 0x00000001078c2562
clang`llvm::FPPassManager::runOnFunction(llvm::Function&) + 498
    frame #7: 0x00000001078eb943
clang`llvm::FPPassManager::runOnModule(llvm::Module&) + 67
    frame #8: 0x00000001078c67f5
clang`llvm::legacy::PassManagerImpl::run(llvm::Module&) + 693
    frame #9: 0x000000010789e09c
clang`clang::EmitBackendOutput(clang::DiagnosticsEngine&,
clang::HeaderSearchOptions const&, clang::CodeGenOptions const&,
clang::TargetOptions const&, clang::LangOptions const&, llvm::DataLayout
const&, llvm::Module*, clang::BackendAction,
std::__1::unique_ptr<llvm::raw_pwrite_stream,
std::__1::default_delete<llvm::raw_pwrite_stream> >) + 2700
    frame #10: 0x000000010786f00a
clang`clang::BackendConsumer::HandleTranslationUnit(clang::ASTContext&) +
410
    frame #11: 0x000000010754b249 clang`clang::ParseAST(clang::Sema&, bool,
bool) + 249
    frame #12: 0x00000001075482bc clang`clang::FrontendAction::Execute() +
44
    frame #13: 0x00000001074fe666
clang`clang::CompilerInstance::ExecuteAction(clang::FrontendAction&) + 294
    frame #14: 0x00000001074fc7b9
clang`clang::ExecuteCompilerInvocation(clang::CompilerInstance*) + 2329
    frame #15: 0x00000001074c6974 clang`cc1_main(llvm::ArrayRef<char
const*>, char const*, void*) + 1492
    frame #16: 0x00000001074c24ac clang`main + 13820
    frame #17: 0x00007fff6206b145 libdyld.dylib`start + 1
    frame #18: 0x00007fff6206b145 libdyld.dylib`start + 1
~~~

Regards,
Steve

On Fri, Sep 29, 2017 at 12:57 AM, Csaba Raduly <rcsaba at gmail.com> wrote:

> Hi Steven,
>
> If the compiler hangs, try to attach the debugger (gdb --pid). You
> should be able to get a stack trace, which would carry more
> information.
>
> On Thu, Sep 28, 2017 at 10:03 PM, Steven Peters via cfe-dev
> <cfe-dev at lists.llvm.org> wrote:
> > Hello,
> >
> > I've been digging into a compilation problem using the version of clang
> > distrubuted with XCode 9 on macOS High Sierra. I narrowed the problem
> down
> > to the transition from `-O1` to `-O2` for a target cpu of core2, and
> then I
> > further narrowed it down to the `-vectorize-loops` option for clang. The
> > challenge is that this problem manifests with clang failing to
> terminate. I
> > don't know if it's a deadlock or getting stuck in an infinite loop, but I
> > didn't see any guidance in the support documents about how to submit a
> bug
> > report in a case like this.
> >
> > Current discussion of the compilation failure:
> > https://github.com/bulletphysics/bullet3/issues/1347
> >
> > ~~~
> > $ cc --version
> > Apple LLVM version 9.0.0 (clang-900.0.37)
> > Target: x86_64-apple-darwin17.0.0
> > Thread model: posix
> > InstalledDir: /Library/Developer/CommandLineTools/usr/bin
> > ~~~
> >
> > Thanks for your time.
> >
> > Regards,
> > Steve Peters
> >
> >
> > _______________________________________________
> > cfe-dev mailing list
> > cfe-dev at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
> >
>
>
>
> --
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> Torvalds
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