swift234

Rework SILGen of optional methods to work with non-@objc situations:
  - Split getSelfTypeForDynamicLookup into two pieces, and generalize it
    to work on non-loadable protocols.
  - Change dynamic_method_branch to take its argument as a protocol of any
    protocol type, instead of as something of UnownObject type.
  - Teach emitForcedDynamicMemberRef to only do its peephole optimization for
    @objc cases, since it is special behavior of objc_msgSend.
  - enhance emitDynamicPartialApply & emitDynamicMemberRefExpr to emit the
    proper project_existential instruction (not a _ref) when dealing with a
    non-classbound protocol.

Change the verifier to allow DynamicMethodBranchInst to work on non-@objc
protocol members.

This eliminates a bunch of pointless unchecked_ref_cast's in the generated
SIL for existing code, but this got squashed at IRGen time anyway, so no
real change for anything that sema permits.



Swift SVN r21519