The condition variable is in scope in the loop increment, so we need to
emit the jump destination from wthin the scope of the condition
variable.
For GCC compatibility (and compatibility with real-world 'FOR_EACH'
macros), 'continue' is permitted in a statement expression within the
condition of a for loop, though, so there are two cases here:
* If the for loop has no condition variable, we can emit the jump
destination before emitting the condition.
* If the for loop has a condition variable, we must defer emitting the
jump destination until after emitting the variable. We diagnose a
'continue' appearing in the initializer of the condition variable,
because it would jump past the initializer into the scope of that
variable.
Reviewed By: rjmccall
Differential Revision: https://reviews.llvm.org/D98816
Benjamin Kramer