[LLVMdev] Fw: LLVM GC
Trevor Elliott
trevor at galois.com
Mon Jan 17 13:01:55 PST 2011
Hi Everyone,
I've built a minimal test that exposes the problem that I'm encountering
[1]. The Makefile that it includes has two targets of interest,
test-llvm and test.
The test-llvm target will compile a c++ main using "clang -emit-llvm
-c", and link it with an llvm-assembly program that uses the
shadow-stack gc strategy. The asm_main function will allocate 32 bytes
using malloc, and then register that as a gc root, using the llvm.gcroot
intrinsic. It will then print the value of the llvm_gc_root_chain
global, and exit.
The test target will build the c++ main using "clang -c" producing
native code, then use llc and as to produce a native object from the
asm-main.bc bitcode file. It then links everything together using clang
to produce a native executable called test.
The test-llvm target will produce the stack trace that I attached in a
previous message, while the test target produces a program that will
output a non-nil value for the llvm_gc_root_chain when run.
Disassembling test.bc using llvm-dis shows that everything has been
inlined into the @main function, though I'm not sure if this is actually
a problem.
Is there a reason that the test-llvm target isn't working? I was under
the impression that the shadow-stack gc strategy was available when
using lli, though there certainly could be something wrong with the way
I'm putting all of the constituents together.
Thanks,
--trevor
[1] http://www.internetofdeath.com/~moltar/gc.tar.gz
On 01/16/2011 10:51 PM, Trevor Elliott wrote:
> Hi Sam,
>
> I've not actually gotten to the linking process with my runtime, as I've
> compiled it with clang -emit-llvm -c, and then archived it with llvm-ar
> and llvm-ranlib. I'm also not producing a GC plugin, as I'm using the
> builtin "shadow-stack" strategy.
>
> My current build process looks like this:
>
> 1. build the compiler
> 2. build the runtime using clang -emit-llvm -c
> 3. generate an archive from the runtime .bc files using llvm-ar and
> llvm-ranlib
> 3. compile a program with the compiler, producing a .bc file
> 4. link the program and runtime together using llvm-ld
> 5. run the program with lli
>
> This all works fine until step 5 when the stack trace gets generated.
> The function that it complains about, @main, is the main function from
> my runtime. When disassembled with llvm-dis, it doesn't have a gc
> attribute on the declaration. Should it still be getting processed by
> the "shadow-stack" strategy?
>
> Thanks!
>
> --trevor
>
>
> On 01/14/2011 05:33 PM, Samuel Crow wrote:
>> Forgot to CC the list.
>>
>>
>> ----- Forwarded Message ----
>>> From: Samuel Crow <samuraileumas at yahoo.com>
>>> To: Trevor Elliott <trevor at galois.com>
>>> Sent: Fri, January 14, 2011 7:33:15 PM
>>> Subject: Re: [LLVMdev] LLVM GC
>>>
>>> Hi Trevor,
>>>
>>> Are you linking with LibStdC++ or LibC++? That is a requirement for running
>>> code that has been compiled from C++ to bitcode.
>>>
>>> Hope this helps,
>>>
>>> --Sam Crow
>>>
>>>
>>> ----- Original Message ----
>>>> From: Trevor Elliott <trevor at galois.com>
>>>> To: llvmdev at cs.uiuc.edu
>>>> Sent: Fri, January 14, 2011 7:17:30 PM
>>>> Subject: [LLVMdev] LLVM GC
>>>>
>>>> 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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>
>
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