gcc.dg/20031102-1.c now causes some 'surprising' optimization behaviour.  It is 
essentially

int FooBar(void)
{
  ... stuff
   return 0;
}

int main(void)
{
   return FooBar();
}


What happens is  that FooBar gets inlined into main, and then ipa-icf notices 
FooBar and main have identical bodies.  It chooses to have FooBar tail call 
main, which results in a surprising  call of 'main'.   On PTX this is 
particularly unfortunate because we have to emit a single prototype for main 
with the regular argc and argv arguments (the backend gets around 'int main 
(void)' by faking the additional 2 args).  But that fails here because the tail 
call doesn't match the prototype.

Anyway, picking 'main' as the source function struck me as a poor choice, hence 
the attached patch.  It picks the second function of a congruent set, if the 
first is 'main'.  Note that even on, say x86-linux, we emit a tail call rather 
than an alias for the included testcase.

I removed the gcc_assert, as the vector indexing operator already checks the 
subscript is within range.

Alternatively I could probably just fixup the testcase to make FooBar 
uninlinable, as I suspect that might have been the original intent.

tested on x86_64-linux and ptx-none.

nathan