The other part of rdar://problem/21444126. This is a little trickier since SIL doesn't track uses of witness tables in a principled way. Track uses in SILGen by putting a "SILGenBuilder" wrapper in front of SILBuilder, which marks conformances from apply, existential erasure, and metatype lookup instructions as used, so we can avoid emitting shared Clang importer witnesses when they aren't needed.
Swift SVN r29544
This change permits SILGen to make smarter decisions about
block placement by keeping related blocks together instead
of always inserting to the end to the function. The
flipside is that SILGen needs to be somewhat careful to
create blocks in the right order. Counter-intuitively,
that order is the reverse of the order in which the blocks
should be laid out, since blocks created later will be
inserted before blocks created earlier. Note, however,
that this produces the right results for recursive
emission.
To that end, adjust a couple of places in SILGen to
create blocks in properly nested order.
All of the block-order differences in the tests seem
to be desirable; several of them even had confused
comments wondering how on earth a block got injected
where it did.
Also, fix the implementation of SILBuilder::moveBlockTo,
and fix a latent bug in epilogue emission where epilogBB
was erased from its parent (deleting it) and then
queried multiple times (!).
Swift SVN r26428
llvm::Optional lives in "llvm/ADT/Optional.h". Like Clang, we can get
Optional in the 'swift' namespace by including "swift/Basic/LLVM.h".
We're now fully switched over to llvm::Optional!
Swift SVN r22477
Allow IfStmts and WhileStmts to have as their condition either an expression, as usual, or a pattern binding introduced by 'var' or 'let', which will conditionally bind to the value inside an optional. Unlike normal pattern bindings, these bindings require an in-line initializer, which will be required to be Optional type. Parse variable bindings in this position, and type-check them by requiring an Optional on the right-hand side and unwrapping it to form the pattern type. Extend SILGen's lowering of if and while statements to handle conditionally binding variables.
Swift SVN r13146
