Strange compiler crash on a custom rustc target

[Amjad50]

Hello.

I thought of opening an issue, since this may not be issue from this crate?, but its still strange that no other rust project had this issue (from my testing yet).

I'm developing an OS, and have forked rust and added a custom target x86_64-unknown-emerald.

I'm testing several rust programs, and then I was trying to compile a project that uses this library.

Trying to compile this crate alone also gives the same issue.

For some reason, rustc would crash with SIGILL: illegal instruction.

After digging a bit with debugger, looks like its crashing at llvm::X86TargetLowering::LowerOperation [clone .cold].
Not sure what's [clone .cold], but its different from the normal function, looks very small in assembly.

Here is a gdb backtrace:

#0  0x00007ffff0cdabfc in llvm::X86TargetLowering::LowerOperation(llvm::SDValue, llvm::SelectionDAG&) const [clone .cold] ()
   from /home/user/Development/OS/rust_os/extern/toolchain/bin/../lib/librustc_driver-d0b93258ef84166d.so
#1  0x00007ffff345982f in llvm::TargetLowering::LowerOperationWrapper(llvm::SDNode*, llvm::SmallVectorImpl<llvm::SDValue>&, llvm::SelectionDAG&) const ()
   from /home/user/Development/OS/rust_os/extern/toolchain/bin/../lib/librustc_driver-d0b93258ef84166d.so
#2  0x00007ffff3a26736 in llvm::DAGTypeLegalizer::CustomLowerNode(llvm::SDNode*, llvm::EVT, bool) ()
   from /home/user/Development/OS/rust_os/extern/toolchain/bin/../lib/librustc_driver-d0b93258ef84166d.so
#3  0x00007ffff3a544d6 in llvm::DAGTypeLegalizer::SplitVectorOperand(llvm::SDNode*, unsigned int) ()
   from /home/user/Development/OS/rust_os/extern/toolchain/bin/../lib/librustc_driver-d0b93258ef84166d.so
#4  0x00007ffff3a26e1d in llvm::DAGTypeLegalizer::run() () from /home/user/Development/OS/rust_os/extern/toolchain/bin/../lib/librustc_driver-d0b93258ef84166d.so
#5  0x00007ffff3a27569 in llvm::SelectionDAG::LegalizeTypes() () from /home/user/Development/OS/rust_os/extern/toolchain/bin/../lib/librustc_driver-d0b93258ef84166d.so
#6  0x00007ffff3519890 in llvm::SelectionDAGISel::CodeGenAndEmitDAG() [clone .localalias] ()
   from /home/user/Development/OS/rust_os/extern/toolchain/bin/../lib/librustc_driver-d0b93258ef84166d.so
#7  0x00007ffff351c33f in llvm::SelectionDAGISel::SelectAllBasicBlocks(llvm::Function const&) [clone .localalias] ()
   from /home/user/Development/OS/rust_os/extern/toolchain/bin/../lib/librustc_driver-d0b93258ef84166d.so
#8  0x00007ffff351e8e1 in llvm::SelectionDAGISel::runOnMachineFunction(llvm::MachineFunction&) [clone .part.0] ()
   from /home/user/Development/OS/rust_os/extern/toolchain/bin/../lib/librustc_driver-d0b93258ef84166d.so
#9  0x00007ffff3096630 in (anonymous namespace)::X86DAGToDAGISel::runOnMachineFunction(llvm::MachineFunction&) ()
   from /home/user/Development/OS/rust_os/extern/toolchain/bin/../lib/librustc_driver-d0b93258ef84166d.so
#10 0x00007ffff1d46a32 in llvm::MachineFunctionPass::runOnFunction(llvm::Function&) [clone .part.0] ()
   from /home/user/Development/OS/rust_os/extern/toolchain/bin/../lib/librustc_driver-d0b93258ef84166d.so
#11 0x00007ffff2dbeb41 in llvm::FPPassManager::runOnFunction(llvm::Function&) [clone .localalias] ()
   from /home/user/Development/OS/rust_os/extern/toolchain/bin/../lib/librustc_driver-d0b93258ef84166d.so
#12 0x00007ffff2dbee8c in llvm::FPPassManager::runOnModule(llvm::Module&) [clone .localalias] ()
   from /home/user/Development/OS/rust_os/extern/toolchain/bin/../lib/librustc_driver-d0b93258ef84166d.so
#13 0x00007ffff2dbf82e in llvm::legacy::PassManagerImpl::run(llvm::Module&) [clone .localalias] ()
   from /home/user/Development/OS/rust_os/extern/toolchain/bin/../lib/librustc_driver-d0b93258ef84166d.so
#14 0x00007ffff13e435c in LLVMRustWriteOutputFile () from /home/user/Development/OS/rust_os/extern/toolchain/bin/../lib/librustc_driver-d0b93258ef84166d.so
#15 0x00007ffff137613a in rustc_codegen_llvm::back::write::write_output_file ()
   from /home/user/Development/OS/rust_os/extern/toolchain/bin/../lib/librustc_driver-d0b93258ef84166d.so
#16 0x00007ffff137a6cd in rustc_codegen_llvm::back::write::codegen (
...trimmed...

Note that using check works fine.

Not sure if this where we can discuss this. But would love to get some pointers if this is a known issue.

Thanks

[BurntSushi]

No idea sorry. This looks like more of a question for someone who works on the compiler, not for library authors. :)

[Amjad50]

Thanks for the quick response, I guess you are right. I'll investigate more on that.

Would this be valid issue for the rustc repo?

[Amjad50]

Nvm about reporting to rustc, I found the cause. Its from first_non_ascii_byte, using first_non_ascii_byte_sse2 crashes the system.

Fixed here: #177