swift234

SIL: Introduce the dynamic_method_br instruction.

The dynamic_method_br instruction branches depending on whether a
particular object can accept a given message, as determined at
runtime. If the object can accept the message, it branches to the
first basic block, providing the uncurried method as the BB
argument. If the object cannot accept the message, it branches to the
second basic block. Either way, the result is packaged up into an
optional type and passed along to the continuation block, which
provides the optional result.

Note that this instruction is restricted to lookup of Objective-C
methods.

Documentation and IR generation (via -respondsToSelector) to
follow. Review greatly appreciated!



Swift SVN r8065