[region-isolation] Add support for *_existential_box instructions.

NOTE: I am just adding coverage that we support these instructions. One can only
use this with Error today and Error is always Sendable. So this is just going
for completeness.

Author: gottesmm

lib/SILOptimizer/Mandatory/TransferNonSendable.cpp

@@ -2434,11 +2434,22 @@ CONSTANT_TRANSLATION(CondBranchInst, TerminatorPhi)
 CONSTANT_TRANSLATION(CheckedCastBranchInst, TerminatorPhi)
 CONSTANT_TRANSLATION(DynamicMethodBranchInst, TerminatorPhi)
 
+//===---
+// Existential Box
+//
+
+// NOTE: Today these can only be used with Errors. Since Error is a sub-protocol
+// of Sendable, we actually do not have any way to truly test them. These are
+// just hypothetical assignments so we are complete.
+CONSTANT_TRANSLATION(AllocExistentialBoxInst, AssignFresh)
+CONSTANT_TRANSLATION(ProjectExistentialBoxInst, Assign)
+CONSTANT_TRANSLATION(OpenExistentialBoxValueInst, Assign)
+CONSTANT_TRANSLATION(DeallocExistentialBoxInst, Ignored)
+
 //===---
 // Unhandled Instructions
 //
 
-CONSTANT_TRANSLATION(AllocExistentialBoxInst, Unhandled)
 CONSTANT_TRANSLATION(IndexRawPointerInst, Unhandled)
 CONSTANT_TRANSLATION(UncheckedTrivialBitCastInst, Unhandled)
 CONSTANT_TRANSLATION(UncheckedBitwiseCastInst, Unhandled)
@@ -2460,7 +2471,6 @@ CONSTANT_TRANSLATION(StrongCopyUnmanagedValueInst, Unhandled)
 CONSTANT_TRANSLATION(DropDeinitInst, Unhandled)
 CONSTANT_TRANSLATION(IsUniqueInst, Unhandled)
 CONSTANT_TRANSLATION(LoadUnownedInst, Unhandled)
-CONSTANT_TRANSLATION(ProjectExistentialBoxInst, Unhandled)
 CONSTANT_TRANSLATION(ValueMetatypeInst, Unhandled)
 CONSTANT_TRANSLATION(ExistentialMetatypeInst, Unhandled)
 CONSTANT_TRANSLATION(VectorInst, Unhandled)
@@ -2472,7 +2482,6 @@ CONSTANT_TRANSLATION(InitExistentialValueInst, Unhandled)
 CONSTANT_TRANSLATION(InitExistentialMetatypeInst, Unhandled)
 CONSTANT_TRANSLATION(OpenExistentialMetatypeInst, Unhandled)
 CONSTANT_TRANSLATION(OpenExistentialValueInst, Unhandled)
-CONSTANT_TRANSLATION(OpenExistentialBoxValueInst, Unhandled)
 CONSTANT_TRANSLATION(OpenPackElementInst, Unhandled)
 CONSTANT_TRANSLATION(PackLengthInst, Unhandled)
 CONSTANT_TRANSLATION(DynamicPackIndexInst, Unhandled)
@@ -2494,7 +2503,6 @@ CONSTANT_TRANSLATION(DeallocPackInst, Unhandled)
 CONSTANT_TRANSLATION(DeallocStackRefInst, Unhandled)
 CONSTANT_TRANSLATION(DeallocRefInst, Unhandled)
 CONSTANT_TRANSLATION(DeallocPartialRefInst, Unhandled)
-CONSTANT_TRANSLATION(DeallocExistentialBoxInst, Unhandled)
 CONSTANT_TRANSLATION(UnmanagedRetainValueInst, Unhandled)
 CONSTANT_TRANSLATION(UnmanagedReleaseValueInst, Unhandled)
 CONSTANT_TRANSLATION(UnmanagedAutoreleaseValueInst, Unhandled)

test/Concurrency/transfernonsendable_instruction_matching.sil

@@ -442,4 +442,38 @@ sil [ossa] @mark_dependence_test_base_is_a_require : $@convention(thin) @async (
 
   %9999 = tuple ()
   return %9999 : $()
-}
+}
+
+// NOTE: Since Error is Sendable, this just validates that we handle the
+// instruction and don't crash.
+sil [ossa] @alloc_existential_box_test : $@convention(thin) @async <T : Error> (@in T) -> @owned any Error {
+bb0(%inError : $*T):
+  %b = alloc_existential_box $Error, $T
+  %p = project_existential_box $T in %b : $Error
+  copy_addr [take] %inError to [init] %p : $*T
+
+  %4 = function_ref @transferIndirect : $@convention(thin) @async <τ_0_0> (@in_guaranteed τ_0_0) -> ()
+  apply [caller_isolation=nonisolated] [callee_isolation=global_actor] %4<T>(%p) : $@convention(thin) @async <τ_0_0> (@in_guaranteed τ_0_0) -> ()
+
+  return %b : $Error
+}
+
+sil [ossa] @alloc_existential_box_test_2 : $@convention(thin) @async <T : Error> (@in T) -> () {
+bb0(%inError : $*T):
+  %b = alloc_existential_box $Error, $T
+  %p = project_existential_box $T in %b : $Error
+  copy_addr [take] %inError to [init] %p : $*T
+
+  %bb = begin_borrow %b : $Error
+  %addr = open_existential_box %bb : $any Error to $*@opened("169A6848-B636-11EC-83C4-D0817AD59B9D", any Error) Self
+
+  %4 = function_ref @transferIndirect : $@convention(thin) @async <τ_0_0> (@in_guaranteed τ_0_0) -> ()
+  apply [caller_isolation=nonisolated] [callee_isolation=global_actor] %4<@opened("169A6848-B636-11EC-83C4-D0817AD59B9D", any Error) Self>(%addr) : $@convention(thin) @async <τ_0_0> (@in_guaranteed τ_0_0) -> ()
+  end_borrow %bb : $Error
+
+  destroy_addr %p : $*T
+  dealloc_existential_box %b : $Error, $T
+
+  %9999 = tuple ()
+  return %9999 : $()
+}