a08152d576
When the machine code was generated the JIT retains a lock to the global values
so they don't go out of sync. In the cases of circular references like:
int g();
int f() {g();}
int g() {f();}
we cannot count on the removal order to get rid of the uses. We need to use the
replaceAllUsesWith. This is however tricky because the JIT already generated the
code for f and g and it doesn't make sense to replace anything with anything else.
Thus in order to support that we need to hack one of the JIT callbacks which
prevents the replace of values of already emitted code.