Noncopyable types aren't really "POD", but the bit is still useful to track
whether a noncopyable type has a no-op destroy operation, so rename the
existing bit to be more specific within IRGen's implementation.
Don't rename it in the runtime or Builtin names yet, since doing so will
require a naming transition for compatibility.
- Witness method calls are done via @llvm.type.checked.load instrinsic call with a type identifier
- Type id of a witness method is the requirement's mangled name
- Witness tables get !type markers that list offsets and type ids of all methods in the wtable
- Added -enable-llvm-wme to enable Witness Method Elimination
- Added IR test and execution test
This is essentially a long-belated follow-up to Arnold's #12606.
The key observation here is that the enum-tag-single-payload witnesses
are strictly more powerful than the XI witnesses: you can simulate
the XI witnesses by using an extra case count that's <= the XI count.
Of course the result is less efficient than the XI witnesses, but
that's less important than overall code size, and we can work on
fast-paths for that.
The extra inhabitant count is stored in a 32-bit field (always present)
following the ValueWitnessFlags, which now occupy a fixed 32 bits.
This inflates non-XI VWTs on 32-bit targets by a word, but the net effect
on XI VWTs is to shrink them by two words, which is likely to be the
more important change. Also, being able to access the XI count directly
should be a nice win.
When accessing the associated type witness metadata for a resilient
protocol, compute the index based on the difference between the
associated type’s descriptor and the protocol requirement base descriptor
to determine the offset into the witness table.
And update the existential container's initializeWithTake implementation
in the runtime. After only allowing bitwise takable values in the
inline buffer we can use memcpy to move existential container values.
rdar://31414907
SR-343
So far single payload enums were implemented in terms of runtime functions which
internally emitted several calls to value witnesses.
This commit adds value witnesses to get and store the enum tag side stepping the
need for witness calls as this information is statically available in many cases
/// int (*getEnumTagSinglePayload)(const T* enum, UINT_TYPE emptyCases)
/// Given an instance of valid single payload enum with a payload of this
/// witness table's type (e.g Optional<ThisType>) , get the tag of the enum.
/// void (*storeEnumTagSinglePayload)(T* enum, INT_TYPE whichCase,
/// UINT_TYPE emptyCases)
/// Given uninitialized memory for an instance of a single payload enum with a
/// payload of this witness table's type (e.g Optional<ThisType>), store the
/// tag.
A simple 'for element in array' loop in generic code operating on a
ContigousArray of Int is ~25% faster on arm64.
rdar://31408033
Adds the runtime implementation for copy-on-write existentials. This support is
enabled if SWIFT_RUNTIME_ENABLE_COW_EXISTENTIALS is defined. Focus is on
correctness -- not performance yet.
Don't use allocate/deallocate/projectBuffer witnesses for globals in cow
existential mode.
Use SWIFT_RUNTIME_ENABLE_COW_EXISTENTIALS configuration to set the default for
SILOptions.
This includes an IRGen fix to use the right projection in
emitMetatypeOfOpaqueExistential if SWIFT_RUNTIME_ENABLE_COW_EXISTENTIALS is set.
Use unknownRetain instead of native retain in dynamicCastToExistential.
Allocate buffers for local generic/resilient values on the stack. alloc_stack
instructions in the entry block are translated using a dynamic alloca
instruction with variables size. All other alloc_stack instructions in addition
use llvm's stacksave/restore instrinsics to reset the stack (they could be
executed multiple times and with varying sizes).
Use them to generate value witnesses when the type has dynamic packing.
Regularize the interface for calling value witnesses.
Not a huge difference yet, although we do re-use local type data
a little more effectively now.
Resilient enums are manipulated as opaque values.
Clients are still allowed to assume physical case indices and case
payload types for now -- we might add a level of indirection here,
which would require designing a new case dispatch mechanism.
Resilient enums are never constructed directly, only by calling
case constructor functions. Case constructors already get emitted,
however they're [transparent] -- this will change in a subsequent
patch.
We could save on code size by emitting an InjectEnumTag value
witness function that can construct any case given a physical case
number, rather than emitting constructors for each case, but for
now going through case constructor functions will suffice.
Don't project every value witness from the metadata every time we need one; this wastes code size in a way LLVM can't really optimize since it doesn't know the metadata is immutable. The code size wins on the standard library are disappointingly small (stdlib only shrinks by 4KB), but this makes generic IR a lot more compact and easier to read.
Swift SVN r28095
We've had a rash of bugs due to inconsistencies between how IRGen and the runtime think types are laid out. Add a '-verify-type-layout' mode to the frontend that causes IRGen to emit a bunch of code that compares its static assumptions against what the runtime value witness does.
Swift SVN r24918
initializeBufferWithTakeOfBuffer value witness.
Attempt to use initializeBufferWithTakeOfBuffer in
some appropriate places.
There are some changes enabled by this which are
coming in a follow-up patch.
Swift SVN r20741
Add Builtin.destroyArray, .copyArray, .takeArrayFrontToBack, and .takeArrayBackToFront, which perform bulk destroy/copy/take operations using memcpy/memmove, a loop, or a generic value witness.
Swift SVN r17009
If a single-payload union doesn't use up all of its payload's extra inhabitants, it can claim the remaining ones as its own. While we're here, specialize the extra inhabitants implementation for no-payload unions to generously (and more efficiently) give out all integer values within its storage type above the largest discriminator as extra inhabitants, instead of relying entirely on the spare bits mask.
Swift SVN r8470
The value witnesses are always available through type metadata (through an extra indirection). Saving that indirection costs 16 words (and growing!) in every witness table, and when we start instantiating conformances for generic instances, would require us to instantiate practically every generic witness table. Removing the value witnesses from the protocol witness table means we will only need to instantiate witness tables when associated types are dependent on the conforming type's type variables.
This is an ABI break, but should have no user-visible functional change.
Swift SVN r6651
Use the new swift_dynamicCastIndirect runtime functions to implement casts from opaque archetype and existential types to concrete types.
Swift SVN r5684
Provide a lowering for the DeinitExistential instruction to deallocate the buffer in an existential container with an uninitialized value, using its deallocateBuffer witness.
Swift SVN r5623
storage in a flags word in the value witness table. Pack the
alignment into only 16 bits of this word. Optimize tuple value
witnesses based on whether they're POD and inline.
Swift SVN r5138
To be able to get the dynamic type of a generic value, the 'typeof' operation needs to be part of the value witness for the type. Add 'typeof' to the value witness table layout, and in the runtime, provide standard typeof witnesses for static, Swift class, and ObjC class values.
Swift SVN r5013
