[Distributed] Runtime/IRGen: Allow passing substitutions to distributed accessor

Accept an optional list of substitutions which are required to form
a call to a generic distributed thunk.

Author: xedin

lib/IRGen/GenDistributed.cpp

@@ -161,6 +161,7 @@ static CanSILFunctionType getAccessorType(IRGenModule &IGM,
       {/*argumentBuffer=*/getRawPointerParameter(),
        /*argumentTypes=*/getRawPointerParameter(),
        /*resultBuffer=*/getRawPointerParameter(),
+       /*substitutions=*/getRawPointerParameter(),
        /*actor=*/targetTy->getParameters().back()},
       /*Yields=*/{},
       /*Results=*/{},
@@ -437,6 +438,8 @@ void DistributedAccessor::emit() {
   auto *argTypes = params.claimNext();
   // UnsafeRawPointer that is used to store the result.
   auto *resultBuffer = params.claimNext();
+  // UnsafeRawPointer that represents a list of substitutions
+  auto *substitutions = params.claimNext();
   // Reference to a `self` of the actor to be called.
   auto *actorSelf = params.claimNext();
 

stdlib/public/Concurrency/Actor.cpp

@@ -1723,14 +1723,16 @@ void *swift_distributed_get_generic_environment(const char *targetNameStart,
 ///    _ targetNameLength: UInt,
 ///    argumentBuffer: Builtin.RawPointer,
 ///    argumentTypes: UnsafeBufferPointer<Any.Type>,
-///    resultBuffer: Builtin.RawPointer
+///    resultBuffer: Builtin.RawPointer,
+///    substitutions: UnsafeRawPointer?
 /// ) async throws
 using TargetExecutorSignature =
     AsyncSignature<void(/*on=*/DefaultActor *,
                         /*targetName=*/const char *, /*targetNameSize=*/size_t,
                         /*argumentBuffer=*/void *,
                         /*argumentTypes=*/const Metadata *const *,
                         /*resultBuffer=*/void *,
+                        /*substitutions=*/void *,
                         /*resumeFunc=*/TaskContinuationFunction *,
                         /*callContext=*/AsyncContext *),
                    /*throws=*/true>;
@@ -1742,12 +1744,15 @@ TargetExecutorSignature::FunctionType swift_distributed_execute_target;
 /// Accessor takes:
 ///   - an async context
 ///   - an argument buffer as a raw pointer
+///   - a list of all argument types (with substitutions applied)
 ///   - a result buffer as a raw pointer
+///   - a list of substitutions
 ///   - a reference to an actor to execute method on.
 using DistributedAccessorSignature =
     AsyncSignature<void(/*argumentBuffer=*/void *,
                         /*argumentTypes=*/const Metadata *const *,
                         /*resultBuffer=*/void *,
+                        /*substitutions=*/void *,
                         /*actor=*/HeapObject *),
                    /*throws=*/true>;
 
@@ -1777,6 +1782,7 @@ void ::swift_distributed_execute_target(
     void *argumentBuffer,
     const Metadata *const *argumentTypes,
     void *resultBuffer,
+    void *substitutions,
     TaskContinuationFunction *resumeFunc,
     AsyncContext *callContext) {
   auto *accessor = findDistributedAccessor(targetNameStart, targetNameLength);
@@ -1813,5 +1819,6 @@ void ::swift_distributed_execute_target(
   accessorEntry(calleeContext,
                 argumentBuffer, argumentTypes,
                 resultBuffer,
+                substitutions,
                 actor);
 }

stdlib/public/Distributed/DistributedActorSystem.swift

@@ -307,7 +307,8 @@ extension DistributedActorSystem {
         mangledTargetName, UInt(mangledTargetName.count),
         argumentBuffer: hargs.buffer._rawValue, // TODO(distributed): pass the invocationDecoder instead, so we can decode inside IRGen directly into the argument explosion
         argumentTypes: argumentTypesBuffer.baseAddress!._rawValue,
-        resultBuffer: resultBuffer._rawValue
+        resultBuffer: resultBuffer._rawValue,
+        substitutions: UnsafeRawPointer(substitutionsBuffer)
       )
 
       func onReturn<R>(_ resultTy: R.Type) async throws {
@@ -327,7 +328,8 @@ func _executeDistributedTarget(
   _ targetName: UnsafePointer<UInt8>, _ targetNameLength: UInt,
   argumentBuffer: Builtin.RawPointer, // HeterogeneousBuffer of arguments
   argumentTypes: Builtin.RawPointer,
-  resultBuffer: Builtin.RawPointer
+  resultBuffer: Builtin.RawPointer,
+  substitutions: UnsafeRawPointer?
 ) async throws
 
 // ==== ----------------------------------------------------------------------------------------------------------------