#include
int main(){
std::cout << “hello\n”;
return 0;
}
After generating llvm bitcode using the following command:
$ clang++ -c -emit-llvm -O -Xclang -disable-llvm-passes a.cpp
the bitcode has the following function with define.
__cxx_global_var_init
main
_ZStlsISt11char_traitsIcEERSt13basic_ostreamIcT_ES5_PKc
_ZNSt9basic_iosIcSt11char_traitsIcEE8setstateESt12_Ios_Iostate
_ZNSt11char_traitsIcE6lengthEPKc ZStorSt12_Ios_IostateS
_ZNKSt9basic_iosIcSt11char_traitsIcEE7rdstateEv
_GLOBAL__sub_I_a.cpp
In a pass, I want to know what are the functions defined by the user e.g ‘main’ and what are not e.g. other than ‘main’.
Actually I want to run some analysis pass only on the user defined functions but not on the library functions. Is there any boolean method that can tell which is a library function and which is not?
LLVM’s analysis infrastructure is mostly intended for optimizations, which should apply to any code equally - I don’t believe there’s any bit that tracks which functions came from system libraries or not.
In general it isn’t possible I believe, however if you are tolerant to false positives / false negatives you can compile with debug information (-g or -gline-tables-only) and figure it out.
Obviously after inlining this becomes more murky (user code can get inlined into library code, and vice-versa).
Perhaps you can check where a function is defined and treat all functions defined in a file passed to the compiler as user defined and all other as system defined. Not sure if that's good enough for you.
I’d imagine you can tweak clang’s CodeGen to add a Metadata node to all llvm::Functions clang emits that basically says whether or not the code appeared in a system header. SourceManager::isInSystemHeader should help you figure out what’s where. You’ll probably need special handling for generated code, like __cxx_global_var_init
I offer no guarantees about the LLVM community accepting this patch, though
To Mehdi’s point, inlining can make things materially more difficult.
