[PATCH] D65222: [IPSCCP] Add assertion to surface cases where we zap returns with overdefined users.

Fri Jul 26 08:10:26 PDT 2019

peter.smith added a comment.

A couple of our CI jobs have found this assertion triggering. The first is when compiling the linux kernel using allmodconfig. The second is on this reduced example using LTO:

  // test1.cpp
  // clang --target=armv7a-linux-gnueabihf test1.cpp -O2 -flto -fuse-ld=lld
  struct b {
    double a;
  };
  void d();
  short e(b) {
    try {
      d();
    } catch (short) {
    }
  }
  int g() {
    b f;
    try {
      e(f);
    } catch (short) {
    }
  }
  int main() {
    try {
      try {
        g();
      } catch (char) {
      }
    } catch (char) {
    }
  }

Results in:

  ld.lld: /work/llvm/src/llvm/lib/Transforms/Scalar/SCCP.cpp:1940: void findReturnsToZap(llvm::Function &, SmallVector<llvm::ReturnInst *, 8> &, (anonymous namespace)::SCCPSolver &): Assertion `all_of(F.users(), [&Solver](User *U) { if (isa<Instruction>(U) && !Solver.isBlockExecutable(cast<Instruction>(U)->getParent())) return false; if (U->getType()->isStructTy()) { return all_of( Solver.getStructLatticeValueFor(U), [](const LatticeVal &LV) { return !LV.isOverdefined(); }); } return !Solver.getLatticeValueFor(U).isOverdefined(); }) && "We can only zap functions where all live users have a concrete value"' failed.
  Stack dump:
  0.      Program arguments: /work/llvm/build/bin/ld.lld -EL -z relro -X --hash-style=gnu --eh-frame-hdr -m armelf_linux_eabi -dynamic-linker /lib/ld-linux-armhf.so.3 -o a.out /usr/lib/gcc-cross/arm-linux-gnueabihf/7.3.0/../../../../arm-linux-gnueabihf/lib/../lib/crt1.o /usr/lib/gcc-cross/arm-linux-gnueabihf/7.3.0/../../../../arm-linux-gnueabihf/lib/../lib/crti.o /usr/lib/gcc-cross/arm-linux-gnueabihf/7.3.0/crtbegin.o -L/usr/lib/gcc-cross/arm-linux-gnueabihf/7.3.0 -L/usr/lib/gcc-cross/arm-linux-gnueabihf/7.3.0/../../../../arm-linux-gnueabihf/lib/../lib -L/usr/lib/gcc-cross/arm-linux-gnueabihf/7.3.0/../../../../lib -L/work/llvm/build/bin/../lib -L/lib/../lib -L/usr/lib/../lib -L/usr/lib/arm-linux-gnueabihf/../../lib -L/usr/lib/gcc-cross/arm-linux-gnueabihf/7.3.0/../../../../arm-linux-gnueabihf/lib -L/usr/lib/gcc-cross/arm-linux-gnueabihf/7.3.0/../../.. -L/work/llvm/build/bin/../lib -L/lib -L/usr/lib -plugin /work/llvm/build/bin/../lib/LLVMgold.so -plugin-opt=mcpu=generic -plugin-opt=O2 /tmp/test1-87b8ab.o -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/lib/gcc-cross/arm-linux-gnueabihf/7.3.0/crtend.o /usr/lib/gcc-cross/arm-linux-gnueabihf/7.3.0/../../../../arm-linux-gnueabihf/lib/../lib/crtn.o 
  1.      Running pass 'Interprocedural Sparse Conditional Constant Propagation' on module 'ld-temp.o'.
   #0 0x0000000001bdc184 PrintStackTraceSignalHandler(void*) (/work/llvm/build/bin/ld.lld+0x1bdc184)
   #1 0x0000000001bd9eee llvm::sys::RunSignalHandlers() (/work/llvm/build/bin/ld.lld+0x1bd9eee)
   #2 0x0000000001bdc718 SignalHandler(int) (/work/llvm/build/bin/ld.lld+0x1bdc718)
   #3 0x00007feade941890 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x12890)
   #4 0x00007feadd029e97 raise /build/glibc-OTsEL5/glibc-2.27/signal/../sysdeps/unix/sysv/linux/raise.c:51:0
   #5 0x00007feadd02b801 abort /build/glibc-OTsEL5/glibc-2.27/stdlib/abort.c:81:0
   #6 0x00007feadd01b39a __assert_fail_base /build/glibc-OTsEL5/glibc-2.27/assert/assert.c:89:0
   #7 0x00007feadd01b412 (/lib/x86_64-linux-gnu/libc.so.6+0x30412)
   #8 0x0000000003884f75 (/work/llvm/build/bin/ld.lld+0x3884f75)
   #9 0x00000000038819ef llvm::runIPSCCP(llvm::Module&, llvm::DataLayout const&, llvm::TargetLibraryInfo const*, llvm::function_ref<llvm::AnalysisResultsForFn (llvm::Function&)>) (/work/llvm/build/bin/ld.lld+0x38819ef)
  #10 0x000000000366acec (anonymous namespace)::IPSCCPLegacyPass::runOnModule(llvm::Module&) (/work/llvm/build/bin/ld.lld+0x366acec)
  #11 0x000000000408b76d llvm::legacy::PassManagerImpl::run(llvm::Module&) (/work/llvm/build/bin/ld.lld+0x408b76d)
  #12 0x00000000031b4d6b (anonymous namespace)::opt(llvm::lto::Config&, llvm::TargetMachine*, unsigned int, llvm::Module&, bool, llvm::ModuleSummaryIndex*, llvm::ModuleSummaryIndex const*) (/work/llvm/build/bin/ld.lld+0x31b4d6b)
  #13 0x00000000031b38e6 llvm::lto::backend(llvm::lto::Config&, std::function<std::unique_ptr<llvm::lto::NativeObjectStream, std::default_delete<llvm::lto::NativeObjectStream> > (unsigned int)>, unsigned int, std::unique_ptr<llvm::Module, std::default_delete<llvm::Module> >, llvm::ModuleSummaryIndex&) (/work/llvm/build/bin/ld.lld+0x31b38e6)
  #14 0x00000000031a91bb llvm::lto::LTO::runRegularLTO(std::function<std::unique_ptr<llvm::lto::NativeObjectStream, std::default_delete<llvm::lto::NativeObjectStream> > (unsigned int)>) (/work/llvm/build/bin/ld.lld+0x31a91bb)
  #15 0x00000000031a8b71 llvm::lto::LTO::run(std::function<std::unique_ptr<llvm::lto::NativeObjectStream, std::default_delete<llvm::lto::NativeObjectStream> > (unsigned int)>, std::function<std::function<std::unique_ptr<llvm::lto::NativeObjectStream, std::default_delete<llvm::lto::NativeObjectStream> > (unsigned int)> (unsigned int, llvm::StringRef)>) (/work/llvm/build/bin/ld.lld+0x31a8b71)
  #16 0x0000000001d2cfa0 lld::elf::BitcodeCompiler::compile() (/work/llvm/build/bin/ld.lld+0x1d2cfa0)
  #17 0x0000000001cb2226 void lld::elf::LinkerDriver::compileBitcodeFiles<llvm::object::ELFType<(llvm::support::endianness)1, false> >() (/work/llvm/build/bin/ld.lld+0x1cb2226)
  #18 0x0000000001ca678a void lld::elf::LinkerDriver::link<llvm::object::ELFType<(llvm::support::endianness)1, false> >(llvm::opt::InputArgList&) (/work/llvm/build/bin/ld.lld+0x1ca678a)
  #19 0x0000000001c9ebb4 lld::elf::LinkerDriver::main(llvm::ArrayRef<char const*>) (/work/llvm/build/bin/ld.lld+0x1c9ebb4)
  #20 0x0000000001c9d0f7 lld::elf::link(llvm::ArrayRef<char const*>, bool, llvm::raw_ostream&) (/work/llvm/build/bin/ld.lld+0x1c9d0f7)
  #21 0x0000000001b7d838 main (/work/llvm/build/bin/ld.lld+0x1b7d838)
  #22 0x00007feadd00cb97 __libc_start_main /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:344:0
  #23 0x0000000001b7d02a _start (/work/llvm/build/bin/ld.lld+0x1b7d02a)
  clang-10: error: unable to execute command: Aborted (core dumped)
  clang-10: error: linker command failed due to signal (use -v to see invocation)

I do have a mail from our CI system with a series of reproducible steps that can clone and checkout revisions of LLVM and Linux that can cross-compile the linux kernel for aarch64 on an x86_64 linux machine that I'll forward on to you. I also have the preprocessed source of kernel/signal.c that failed that I'll include in the mail but I can also probably add to a PR if I compress it.

Would you be able to take a look to see if the failures are genuine bugs in clang that the assertion has uncovered or whether it is triggering by mistake?

It is

Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D65222/new/

https://reviews.llvm.org/D65222