We may want to use optimized ErrorType representations that don't naturally "become" NSErrors, such as tagged-pointer representations of small error enums, or a tagged function pointer to a deferred error type constructor. Rename the runtime function to something a bit more descriptive of its real purpose, not its implementation.
Swift SVN r27209
We define two new library functions _knownForceBridgeFromObjectiveC/_knownConditionallyBridgeFromObjectiveC, similar to _forceBridgeFromObjectiveC/_conditionallyBridgeFromObjectiveC. The main difference is that they require their arguments to conform to _BridgedToObjectiveC and _BridgedToObjectiveC. _ObjectiveCType accordingly. With this change, it is now possible to invoke the _BridgedToObjectiveC._forceBridgeFromObjectiveC witness directly, without going via the inefficient swift_bridgeNonVerbatimFromObjectiveC.
So now, for a cast O -> S, if it can be statically proven that an ObjC type O is bridgeable to a Swift type S implementing the _BridgedToObjectiveC protocol (i.e. O is the class (or its subclass) defined by the S._ObjectiveCType alias), we can generate a code to invoke the newly defined library function _knownForceBridgeFromObjectiveC/_knownConditionallyBridgeFromObjectiveC instead of _forceBridgeFromObjectiveC/_conditionallyBridgeFromObjectiveC.
After inlining, this will end-up invoking S._forceBridgeFromObjectiveC directly instead of invoking a more general, but less effective swift_bridgeNonVerbatimFromObjectiveC, which always performs conformance checks at runtime, even if conformances are known statically. As a result, no conformance checks are performed at run-time if conformances are known statically.
The client code making use of these new APIs and the tests are coming in the subsequent commits.
The naming of the two new helper library functions was discussed with Dmitri.
This is part of the bridging casts optimization effort. And it is specifically useful for e.g. rdar://19081345.
Swift SVN r27100
The problem here was that the _preconditionImplicitlyUnwrappedOptionalHasValue
compiler intrinsic was taking the optional/IUO argument as inout as a performance
optimization, but DI would reject it (in narrow cases, in inits) because the inout
argument looks like a mutation.
We could rework this to take it as an @in argument or something, but it is better
to just define this problem away: the precondition doesn't actually care about the
optional, it is just testing its presence, which SILGen does all the time. Have
SILGen open code the switch_enum and just have the stdlib provide a simpler
_diagnoseUnexpectedNilOptional() to produce the error message.
This avoids the problem completely and produces slightly better -O0 codegen.
Swift SVN r25254
Eliminate the intermediate top_level_code function. Now that SIL is expressive enough to express a "main" function, there's no reason for it, and this eliminates a bunch of mystery code in IRGen to thunk from main to top_level_code by reaching for hardcoded symbol names. Demystify the special code for setting up C_ARGC and C_ARGV by having SILGen look for a transparent "_didEnterMain" hook in the stdlib and emit a call to it.
Swift SVN r22525
This avoids a pointless copy every time an array literal is written, and will let us retire the horrible "alloc_array" instruction and globs of broken IRGen code. Implements rdar://problem/16386862, and probably fixes a bunch of bugs related to alloc_array brokenness.
Swift SVN r22289
This is essentially NFC, but the protocols we were calling into are
changing in a way that makes it hard to use the witnesses directly
from the type checker.
Swift SVN r20933
This means that we'll get deferred checking of array and dictionary
downcasts when writing "arr as Derived[]",
"(dict as? Dictionary<DerivedKey, DerivedValue>)!", etc, when the
collection can do so.
This is both a general optimization and also staging for
<rdar://problem/17319154>.
Swift SVN r18975
