Let me wikipedia that for you :-) Like people mentioned already, gcc predates LLVM by quite some years, ie. Wikipedia mentions March 22, 1987 for gcc, while LLVM's initial release was 2003.
A big difference between the 2 is also the license. GCC uses the GPL while LLVM uses Apache License, hence the projects don't share code.
A big difference between the 2 is also the license. GCC uses the GPL while LLVM uses Apache License, hence the projects don't share code.