introduce a common superclass, SILNode.
This is in preparation for allowing instructions to have multiple
results. It is also a somewhat more elegant representation for
instructions that have zero results. Instructions that are known
to have exactly one result inherit from a class, SingleValueInstruction,
that subclasses both ValueBase and SILInstruction. Some care must be
taken when working with SILNode pointers and testing for equality;
please see the comment on SILNode for more information.
A number of SIL passes needed to be updated in order to handle this
new distinction between SIL values and SIL instructions.
Note that the SIL parser is now stricter about not trying to assign
a result value from an instruction (like 'return' or 'strong_retain')
that does not produce any.
Remove the include of SILInstruction.h in a couple places since it is
not necessary and forces more recompilation than necessary when edits
are made to SILInstruction.h.
Swift SVN r32091
Due to inreased use of llvm::make_range in LLVM headers and ADL for
types defined in the swift namespace, some of the LLVM headers started
to trigger ambiguity errors between llvm::make_range and
swift::make_range.
Swift SVN r29700
