[llvm-bugs] [Bug 48346] New: linker segfaults when using -shared on AMDGPU kernel

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=48346

            Bug ID: 48346
           Summary: linker segfaults when using -shared on AMDGPU kernel
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: release blocker
          Priority: P
         Component: Backend: AMDGPU
          Assignee: unassignedbugs at nondot.org
          Reporter: fwinter at jlab.org
                CC: llvm-bugs at lists.llvm.org

When linking a module containing a really trivial function with ld.lld I get:

$ ld.lld -shared module.o -o module.so

ld.lld: /home/users/coe0193/llvm-project/lld/ELF/Arch/AMDGPU.cpp:48: virtual
uint32_t {anonymous}::AMDGPU::calcEFlags() const: Assertion
`!objectFiles.empty()' failed.
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash
backtrace.
Stack dump:
0.      Program arguments:
/home/users/coe0193/install/llvm-trunk-x86-amdgpu-debug/bin/ld.lld -shared
module_empty.o -o module_empty.so
 #0 0x0000155552e30eed llvm::sys::PrintStackTrace(llvm::raw_ostream&, int)
/home/users/coe0193/llvm-project/llvm/lib/Support/Unix/Signals.inc:563:22
 #1 0x0000155552e30fa4 PrintStackTraceSignalHandler(void*)
/home/users/coe0193/llvm-project/llvm/lib/Support/Unix/Signals.inc:630:1
 #2 0x0000155552e2efa6 llvm::sys::RunSignalHandlers()
/home/users/coe0193/llvm-project/llvm/lib/Support/Signals.cpp:71:20
 #3 0x0000155552e30934 SignalHandler(int)
/home/users/coe0193/llvm-project/llvm/lib/Support/Unix/Signals.inc:405:1
 #4 0x000015555511ddd0 __restore_rt (/lib64/libpthread.so.0+0x12dd0)
 #5 0x0000155551d6170f raise (/lib64/libc.so.6+0x3770f)
 #6 0x0000155551d4bb25 abort (/lib64/libc.so.6+0x21b25)
 #7 0x0000155551d4b9f9 _nl_load_domain.cold.0 (/lib64/libc.so.6+0x219f9)
 #8 0x0000155551d59cc6 (/lib64/libc.so.6+0x2fcc6)
 #9 0x000015555476b887 (anonymous namespace)::AMDGPU::calcEFlags() const
/home/users/coe0193/llvm-project/lld/ELF/Arch/AMDGPU.cpp:49:41
#10 0x00001555547cc335 void
lld::elf::LinkerDriver::link<llvm::object::ELFType<(llvm::support::endianness)1,
true> >(llvm::opt::InputArgList&)
/home/users/coe0193/llvm-project/lld/ELF/Driver.cpp:2209:3
#11 0x00001555547b1ed2 lld::elf::LinkerDriver::main(llvm::ArrayRef<char
const*>) /home/users/coe0193/llvm-project/lld/ELF/Driver.cpp:558:7
#12 0x00001555547ae1ad lld::elf::link(llvm::ArrayRef<char const*>, bool,
llvm::raw_ostream&, llvm::raw_ostream&)
/home/users/coe0193/llvm-project/lld/ELF/Driver.cpp:125:3
#13 0x000000000040810a lldMain(int, char const**, llvm::raw_ostream&,
llvm::raw_ostream&, bool)
/home/users/coe0193/llvm-project/lld/tools/lld/lld.cpp:153:12
#14 0x0000000000408581 main
/home/users/coe0193/llvm-project/lld/tools/lld/lld.cpp:211:19
#15 0x0000155551d4d6a3 __libc_start_main (/lib64/libc.so.6+0x236a3)
#16 0x00000000004073ee _start
(/home/users/coe0193/install/llvm-trunk-x86-amdgpu-debug/bin/ld.lld+0x4073ee)
Aborted (core dumped)


This bug is present in LLVM 11 release as well as in LLVM 12 current trunk (as
of Nov. 30th 2020).

On Linux I built llvm-project with 

cmake ../llvm-project/llvm \
        -DCMAKE_INSTALL_PREFIX="$HOME/install/llvm-trunk-x86-amdgpu-debug" \
        -DLLVM_ENABLE_PROJECTS="clang;lld" \
        -DCMAKE_BUILD_TYPE="Debug" \
        -DBUILD_SHARED_LIBS=ON \
        -DCMAKE_CXX_COMPILER=g++ \
        -DCMAKE_C_COMPILER=gcc \
        -DLLVM_TARGETS_TO_BUILD="X86;AMDGPU"


To provoke the bug I created a small module written in LLVM IR containing a
simple AMDGPU kernel function, like

module.ll:

define amdgpu_kernel void @test() {
entry:
  ret void
}


Then I compile this module with

$ clang -target amdgcn-amd-amdhsa -mcpu=gfx908 module.ll -o module.o

And try to link a shared library for it:

$ ld.lld -shared module.o -o module.so

This crashes the linker with the above back trace.

Please help!

Frank

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