For those (like me) who didn’t know,
-fgcse Performs a global common subexpression elimination pass. This pass also performs global constant and copy propagation.
So your simple code must have global common subexpressions (whatever they are) for the optimizer to eliminate any duplication.
That said, gcc says the last option in the command-line overrides any previous options. Have you checked the command-line that invoked gcc to see if ogcse came before or after o0?
