The only places where ReturnStatement is constructed are:
- onReturn(check_yield=true) -> not allowed in generator
- onReturn(check_yield=false) -> coming from transform_yield_break, right after creating hphp_continuation_done()
- MethodStatement, end of function call -> hphp_continuation_done() is created at end of generator in prepare_generator()
Emitter is emitting ContExit in ReturnStatements used in generators. As
can be seen from the analysis above, it's always preceded by emitting
ContDone from hphp_continuation_done(). Let's emit ContDone inside the
ReturnStatement directly and kill usage of hphp_continuation_done().
transform_yield_break() becomes a simple onReturn(check_yield=false), so
let's inline it into onYield and create ReturnStatement directly. After
this change, check_yield flag is always true and can be killed.
ContExit was also used after emitting a generator method in case the end
of method is still reachable. ContDone is added so that the generator is
properly closed. I believe this is never actually used, as MethodStatement
creates ReturnStatement at the end of method anyway.
Unhack the parser and introduce YieldExpression that emits the
equivalent set of opcodes that were emitted by bunch of
expressions/statements generated by parser before.
YieldExpression expects evaluation stack to contain just the value
being yielded, so {,List}AssignmentExpression need to evaluate RHS
first. The previous code had the same behavior.
This will let us consolidate continuation-related opcodes and make
them less tied with continuation objects.
This change is mostly for FB internal organizational reasons.
Building is not effected beyond the fact that the target now
lands in hphp/hhvm/hhvm rather than src/hhvm/hhvm.
jan