[LLVMdev] Problems with optimizations and va_arg intrinsic

[Rinaldini Julien]

Hi all, 

I am currently writing an obfuscation pass (on LLVM 3.3 code base) that works at IR level and that implement procedures fusion. For this, I am heavily
relying on the va_arg intrinsic. My code is functional when compiled with no optimization (-O0), but I experience strange behavior 
when compiling with -O2 or -O3. I am currently using the libgmp and OpenSSL libraries test suites.

I know that clang is *not* relying on the va_arg intrinsic, but implements itself this set of function, hence my question: is the va_arg intrinsic
something we can trust to work with, or not? 

Thank you for any input on this topic !

Cheers, 

Rinaldini Julien