Arnold Schwaighofer d51053b003 Add convert_escape_to_noescape instruction for converting escaping to noescape functions ...

@noescape function types will eventually be trivial. A
convert_escape_to_noescape instruction does not take ownership of its
operand. It is a projection to the trivial value carried by the closure
-- both context and implementation function viewed as a trivial value.

A safe SIL program must ensure that the object that the project value is based
on is live beyond the last use of the trivial value. This will be
achieve by means of making the lifetimes dependent.

For example:

  %e = partial_apply [callee_guaranteed] %f(%z) : $@convention(thin) (Builtin.Int64) -> ()
  %n = convert_escape_to_noescape %e : $@callee_guaranteed () -> () to $@noescape @callee_guaranteed () -> ()
  %n2 = mark_dependence %n : $@noescape @callee_guaranteed () -> () on %e : $@callee_guaranteed () -> ()
  %f2 = function_ref @use : $@convention(thin) (@noescape @callee_guaranteed () -> ()) -> ()
  apply %f2(%n2) : $@convention(thin) (@noescape @callee_guaranteed () -> ()) -> ()
  release_value %e : $@callee_guaranteed () -> ()

Note: This is not yet actually used.

Part of:
SR-5441
rdar://36116691

2018-02-06 18:01:23 -08:00

90 KiB

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