[ewjordan]

This happens in JVM languages as well. Most optimizing compilers will do things differently depending on what happens elsewhere in a function, even if it's "dead code" (and especially if it's dead code that the compiler is too stupid to realize is dead).

Granted this usually only affects runtime speed, but in some circumstances things can get worse (multithreaded programs are particularly susceptible to such optimizations, especially if they're not written correctly - yes, the real problem may be that you've written your code wrong, but there are very real situations where the presence of dead code can change the optimization path taken enough so that it either works or doesn't, which is a very real effect).

And that's even before we take into account compiler bugs, which just make things worse.