A type (mostly classes) can be attributed with `@_semantics("arc.immortal")`.
ARC operations on values of such types are eliminated.
This is useful for the bridged SIL objects in the swift compiler sources.
Instead of doing the type casts and/or conformance lookup on the swift side, do it on the C++ side.
It makes a significant performance difference because `Operand.value` is a time critical function
The instance type of a metatype instruction is not necessarily a legal lowered SIL Type.
Lower the type before converting it to a SILType.
rdar://105502403
This instruction can be inserted by Onone optimizations as a replacement for deleted instructions to
ensure that it's possible to single step on its location.
- SILPackType carries whether the elements are stored directly
in the pack, which we're not currently using in the lowering,
but it's probably something we'll want in the final ABI.
Having this also makes it clear that we're doing the right
thing with substitution and element lowering. I also toyed
with making this a scalar type, which made it necessary in
various places, although eventually I pulled back to the
design where we always use packs as addresses.
- Pack boundaries are a core ABI concept, so the lowering has
to wrap parameter pack expansions up as packs. There are huge
unimplemented holes here where the abstraction pattern will
need to tell us how many elements to gather into the pack,
but a naive approach is good enough to get things off the
ground.
- Pack conventions are related to the existing parameter and
result conventions, but they're different on enough grounds
that they deserve to be separated.
Previously, SILFunction_getSelfArgumentIndex was directly using the
function type rather than interacting with the function convention.
Here, it is made to interact with the convention.
* In `ApplySite`: `argumentOperands` and `isCalleeOperand`
* In `ArgumentConvention`: `isIndirect`, `isIndirectIn` and `isGuaranteed`
* In `Function`: `isDefinition`, `numParameterArguments`, `numArguments`, `getArgumentConvention`, `effectAttribute`
* In `Type`: `isFunction` and `isCalleeConsumedFunction`
* In `Instruction`: `hasUnspecifiedSideEffects`
* New bridged instructions: `EndApplyInst` and `AbortApplyInst`
* `LoadInst.ownership`
* `BeginAccessInst.isStatic`
* make the `Allocation` protocol a `SingleValueInstruction` (instead of `AnyObject`)
* add `DynamicFunctionRefInst` and `PreviousDynamicFunctionRefInst`
* add a common base class to all function-referencing instructions: `FunctionRefBaseInst`
* add `KeyPathInst`
* add `IndexAddrInst.base` and `IndexAddrInst.index` getters
* add `Instruction.visitReferencedFunctions` to visit all functions which are referenced by an instruction
