__builtin_smulll_overflow usage results in undefined symbol

[Ryan Cumming]

This simple nonsense program:

int main(int argc, char *argv[])
{
 long long result;
 return __builtin_smulll_overflow(argc, 5, &result);
}

Will result in the following:
ryan@ubuntu32:~/Code/test$ clang++ main.cpp -o main
/tmp/main-10feb1.o: In function `main':
main.cpp:(.text+0x46): undefined reference to `__mulodi4'
clang: error: linker command failed with exit code 1 (use -v to see invocation)

This can be manually fixed up by explicitly linking against compiler-rt:
clang++ main.cpp /usr/lib/clang/3.5.0/lib/linux/libclang_rt.builtins-i386.a -o main

This only occurs on 32bit

$ lsb_release -rd
Description: Ubuntu 14.10
Release: 14.10

$ apt-cache policy clang++-3.5
libclang-3.5-dev:
  Installed: (none)
  Candidate: 1:3.5-4ubuntu2
  Version table:
     1:3.5-4ubuntu2 0
        500 http://archive.ubuntu.com/ubuntu/ utopic/main i386 Packages
clang-3.5-doc:
  Installed: (none)
  Candidate: 1:3.5-4ubuntu2
  Version table:
     1:3.5-4ubuntu2 0
        500 http://archive.ubuntu.com/ubuntu/ utopic/universe i386 Packages
clang-3.5:
  Installed: 1:3.5-4ubuntu2
  Candidate: 1:3.5-4ubuntu2
  Version table:
 *** 1:3.5-4ubuntu2 0
        500 http://archive.ubuntu.com/ubuntu/ utopic/universe i386 Packages
        100 /var/lib/dpkg/status
python-clang-3.5:
  Installed: (none)
  Candidate: 1:3.5-4ubuntu2
  Version table:
     1:3.5-4ubuntu2 0
        500 http://archive.ubuntu.com/ubuntu/ utopic/universe i386 Packages
clang-3.5-examples:
  Installed: (none)
  Candidate: 1:3.5-4ubuntu2
  Version table:
     1:3.5-4ubuntu2 0
        500 http://archive.ubuntu.com/ubuntu/ utopic/universe i386 Packages

$ apt-cache policy llvm-3.5
llvm-3.5:
  Installed: 1:3.5-4ubuntu2
  Candidate: 1:3.5-4ubuntu2
  Version table:
 *** 1:3.5-4ubuntu2 0
        500 http://archive.ubuntu.com/ubuntu/ utopic/main i386 Packages
        100 /var/lib/dpkg/status