[LLVMdev] LLVM GC

[Trevor Elliott]

Hi,

I've been implementing a compiler that targets LLVM, and was looking
into using the shadow-stack gc strategy.  Currently, I build the runtime
with clang (using -emit-llvm), and then link that with the LLVM bitcode
output from my compiler using llvm-ld.

This works fine without the gc strategy annotations and use of the
llvm.gcroot intrinsic, but adding them causes some odd behavior: the
resulting bitcode will generate a large stack trace from lli (appended
at the end of this message), and the resulting native assembly,
generated with llc, will never update my llvm_gc_root_chain global.

Interestingly, if I build my runtime with g++, or clang without
-emit-llvm, and link everything together after generating native
assembly from the output of my compiler, it works.  The stack roots get
registered, and the llvm_gc_root_chain global gets updated.

Is linking in the runtime as an LLVM bitcode object something that I
should expect to work, or does it make more sense to build the runtime
for the target, and not try to emit LLVM bitcode programs from my compiler?

Thanks!

--trevor


0  libLLVM-2.8.so  0x0000003cc36eee9f
1  libLLVM-2.8.so  0x0000003cc36ef99a
2  libpthread.so.0 0x0000003cc200f4a0
3  libLLVM-2.8.so  0x0000003cc33360dd
llvm::StructType::StructType(llvm::LLVMContext&, std::vector<llvm::Type
const*, std::allocator<llvm::Type const*> > const&, bool) + 237
4  libLLVM-2.8.so  0x0000003cc3337c95
llvm::StructType::get(llvm::LLVMContext&, std::vector<llvm::Type const*,
std::allocator<llvm::Type const*> > const&, bool) + 533
5  libLLVM-2.8.so  0x0000003cc3242d58
6  libLLVM-2.8.so  0x0000003cc318f09e
7  libLLVM-2.8.so  0x0000003cc3330628
llvm::FPPassManager::runOnFunction(llvm::Function&) + 424
8  libLLVM-2.8.so  0x0000003cc33307cb
llvm::FunctionPassManagerImpl::run(llvm::Function&) + 91
9  libLLVM-2.8.so  0x0000003cc33309bd
llvm::FunctionPassManager::run(llvm::Function&) + 173
10 libLLVM-2.8.so  0x0000003cc33e8647
llvm::JIT::jitTheFunction(llvm::Function*, llvm::MutexGuard const&) + 39
11 libLLVM-2.8.so  0x0000003cc33e8a2f
llvm::JIT::runJITOnFunctionUnlocked(llvm::Function*, llvm::MutexGuard
const&) + 15
12 libLLVM-2.8.so  0x0000003cc33e8cde
llvm::JIT::getPointerToFunction(llvm::Function*) + 606
13 libLLVM-2.8.so  0x0000003cc33ea253
llvm::JIT::runFunction(llvm::Function*, std::vector<llvm::GenericValue,
std::allocator<llvm::GenericValue> > const&) + 67
14 libLLVM-2.8.so  0x0000003cc336ad4a
llvm::ExecutionEngine::runFunctionAsMain(llvm::Function*,
std::vector<std::string, std::allocator<std::string> > const&, char
const* const*) + 1130
15 lli             0x0000000000404cd6 main + 2054
16 libc.so.6       0x0000003cc1c1ec5d __libc_start_main + 253
17 lli             0x0000000000403689
Stack dump:
0.	Program arguments: lli test.bc
1.	Running pass 'Lower Garbage Collection Instructions' on function '@main'
zsh: segmentation fault (core dumped)  ./test

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