[LLVMdev] HowToUseJIT: failed assertion on PPC/Mac OS X

[Evan Jones]

I just got the CVS version of LLVM running tonight. On my PowerBook,  
one of the examples (HowToUseJIT) has an assertion error when I try and  
run it:

Running foo: JIT.cpp:217: failed assertion `!isAlreadyCodeGenerating &&  
"Error: Recursive compilation detected!"'


However, when I compile and run the same program on x86 Linux, it runs  
fine (Running foo: Result: 11). I can run the Fibonacci example, and I  
can execute simple C programs compiled with llvm-gcc. I couldn't see  
anything that looked like a bug report for this issue in Bugzilla. I  
can't quite figure out this bug. The backtrace looks like:


#0  0x900429ac in kill ()
#1  0x9009eb1c in abort ()
#2  0x00120ec8 in __eprintf () at  
/Users/ejones/llvm/llvm/include/llvm/ADT/ilist:440
#3  0x00011ae8 in llvm::JIT::runJITOnFunction(llvm::Function*)  
(this=0x51015c0, F=0x5101010) at JIT.cpp:217
#4  0x00011da4 in llvm::JIT::getPointerToFunction(llvm::Function*)  
(this=0x51015c0, F=0x5101010) at JIT.cpp:261
#5  0x000123e4 in (anonymous  
namespace)::JITResolver::getFunctionStub(llvm::Function*)  
(this=0x70be78, F=0x5101010) at JITEmitter.cpp:184
#6  0x00012a48 in (anonymous  
namespace)::JITEmitter::getPointerToGlobal(llvm::GlobalValue*, void*,  
bool) (this=0x5101670, V=0x5101010, Reference=0x5685010,  
DoesntNeedStub=false) at JITEmitter.cpp:334
#7  0x00012ccc in (anonymous  
namespace)::JITEmitter::finishFunction(llvm::MachineFunction&)  
(this=0x5101670, F=@0x51038c0) at JITEmitter.cpp:355
#8  0x00033fec in (anonymous  
namespace)::PPC32CodeEmitter::runOnMachineFunction(llvm:: 
MachineFunction&) (this=0x5101b50, MF=@0x51038c0) at  
PPC32CodeEmitter.cpp:95
#9  0x00254a7c in  
llvm::MachineFunctionPass::runOnFunction(llvm::Function&)  
(this=0x5101b50, F=@0x51012d0) at  
/Users/ejones/llvm/llvm/include/llvm/CodeGen/MachineFunctionPass.h:38
#10 0x00415ee8 in  
llvm::PassManagerTraits<llvm::Function>::runPass(llvm::FunctionPass*,  
llvm::Function*) (P=0x5101b50, F=0x51012d0) at PassManagerT.h:706
#11 0x0040834c in  
llvm::PassManagerT<llvm::Function>::runOnUnit(llvm::Function*)  
(this=0x5101610, M=0x51012d0) at PassManagerT.h:256
#12 0x00408ad0 in  
llvm::PassManagerTraits<llvm::Function>::runOnFunction(llvm::Function&)  
(this=0x5101610, F=@0x51012d0) at PassManagerT.h:810
#13 0x000ef23c in llvm::FunctionPass::run(llvm::Function&)  
(this=0x5101610, F=@0x51012d0) at Pass.cpp:261
#14 0x000ee370 in llvm::FunctionPassManager::run(llvm::Function&)  
(this=0x51015f0, F=@0x51012d0) at Pass.cpp:108
#15 0x00011b0c in llvm::JIT::runJITOnFunction(llvm::Function*)  
(this=0x51015c0, F=0x51012d0) at JIT.cpp:221
#16 0x00011da4 in llvm::JIT::getPointerToFunction(llvm::Function*)  
(this=0x51015c0, F=0x51012d0) at JIT.cpp:261
#17 0x00010b18 in llvm::JIT::runFunction(llvm::Function*,  
std::vector<llvm::GenericValue, std::allocator<llvm::GenericValue> >  
const&) (this=0x51015c0, F=0x51012d0, ArgValues=@0xbffffb90) at  
JIT.cpp:65
#18 0x00002e8c in main () at HowToUseJIT.cpp:104


I figured the problem must be some difference between  
PPC32CodeEmitter::runOnMachineFunction and  
X86CodeEmitter::runOnMachineFunction, but the code at the beginning of  
these two functions is identical.

I'm assuming that what happens is that on X86, "DoesntNeedStub" is set,  
so JITEmitter::getPointerToGlobal calls AddCallbackAtLocation instead  
of getFunctionStub. In JITResolver::getFunctionStub, the function that  
is being resolved is "add1", and it is marked as "Linkage =  
ExternalLinkage". The code uses F->hasExternalLinkage() to decide if  
the function is external or not. This returns true, so instead of  
emitting a stub, it calls TheJIT->getPointerToFunction.

In TheJIT->getPointerToFunction, it uses F->isExternal() to decide if  
it should run the JIT or not. This returns false, so it decides to run  
the JIT, which causes the assertion.

I can "fix" it by changing JITResolver::getFunctionStub to use  
F->isExternal() instead of F->hasExternalLinkage(). However, this then  
breaks when calling *real* external functions (native code). I've  
attached a patch for this anyway, in case that makes it easier for  
someone to understand. At this point, I am completely lost and out of  
ideas. Any comments?

Thanks,

Evan Jones

-------------- next part --------------
A non-text attachment was scrubbed...
Name: JITEmitter.patch
Type: application/octet-stream
Size: 866 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20050220/288d7916/attachment.obj>
-------------- next part --------------