Merge pull request #84528 from rjmccall/async-let-runtime-realism

Model async let begin/finish as builtins in SIL

include/swift/Runtime/RuntimeFunctions.def

@@ -2549,27 +2549,6 @@ FUNCTION(DistributedActorInitializeRemote,
          EFFECT(RuntimeEffect::Concurrency),
          UNKNOWN_MEMEFFECTS)
 
-/// void swift_asyncLet_start(
-///     AsyncLet *alet,
-///     TaskOptionRecord *options,
-///     const Metadata *futureResultType,
-///     void *closureEntryPoint,
-///     HeapObject *closureContext
-/// );
-FUNCTION(AsyncLetStart,
-         _Concurrency, swift_asyncLet_start, SwiftCC,
-         ConcurrencyAvailability,
-         RETURNS(VoidTy),
-         ARGS(SwiftAsyncLetPtrTy,         // AsyncLet*
-              SwiftTaskOptionRecordPtrTy, // options
-              TypeMetadataPtrTy,          // futureResultType
-              Int8PtrTy,                  // closureEntry
-              OpaquePtrTy                 // closureContext
-         ),
-         ATTRS(NoUnwind),
-         EFFECT(RuntimeEffect::Concurrency),
-         MEMEFFECTS(ArgMemOnly))
-
 /// void swift_asyncLet_begin(
 ///     AsyncLet *alet,
 ///     TaskOptionRecord *options,
@@ -2593,15 +2572,27 @@ FUNCTION(AsyncLetBegin,
          EFFECT(RuntimeEffect::Concurrency),
          MEMEFFECTS(ArgMemOnly))
 
-// void swift_asyncLet_end(AsyncLet *alet);
-FUNCTION(EndAsyncLet,
-         _Concurrency, swift_asyncLet_end, SwiftCC,
+/// void swift_asyncLet_finish(
+///     AsyncLet *alet,
+///     TaskOptionRecord *options,
+///     const Metadata *futureResultType,
+///     void *closureEntryPoint,
+///     HeapObject *closureContext,
+///     void *resultBuffer
+/// );
+FUNCTION(AsyncLetFinish,
+         _Concurrency, swift_asyncLet_finish, SwiftAsyncCC,
          ConcurrencyAvailability,
          RETURNS(VoidTy),
-         ARGS(SwiftAsyncLetPtrTy),
+         ARGS(SwiftContextPtrTy,          // current context
+              SwiftAsyncLetPtrTy,         // AsyncLet*
+              Int8PtrTy,                  // resultBuffer
+              TaskContinuationFunctionPtrTy, // continuation
+              SwiftContextPtrTy           // temp context
+         ),
          ATTRS(NoUnwind),
          EFFECT(RuntimeEffect::Concurrency),
-         UNKNOWN_MEMEFFECTS)
+         MEMEFFECTS(ArgMemOnly))
 
 /// void swift_task_run_inline(
 ///     OpaqueValue *result,