This allows Swift code to implement a fast path via a protocol type
check as follows:
if let existentialVal = genericVal as? SomeProtocol {
// do something fast.
}
Fixes <rdar://problem/46322928> Failure to devirtualize a protocol
method applied to an opened existential blocks implemention of
DataProtocol.
Note: the approach of devirtualization via backward pattern matching
is fundamentally wrong and will never be fully general. It should be a
forward type propagation.
Also: add an additional DeadObjectElimination pass in the low level pipeline because
redundant load elimination (which runs before) can turn an object into a dead object.
We run GlobalOpt multiple times in the pass pipeline but in some cases object outlining shouldn't be done too early.
Having it done in a separate pass enables to run it independently from GlobalOpt.
Also: add an additional DeadObjectElimination pass in the low level pipeline because
redundant load elimination (which runs before) can turn an object into a dead object.
We run GlobalOpt multiple times in the pass pipeline but in some cases object outlining shouldn't be done too early.
Having it done in a separate pass enables to run it independently from GlobalOpt.
Mainly this is done for array literals.
This new optimization creates a statically initialized global variable which is the allocated object.
The alloc_ref instruction is replaced by a global_value instruction.
This optimization can give significant performance improvements for large array literals.
This reverts commit 1b3d29a163, reversing
changes made to b32424953e.
We're seeing a handful of issues from turning on inlining of generics,
so I'm reverting to unblock the bots.
