From fe15d04505e9c505dbc3a9c7a1f17f41eb2ca26e Mon Sep 17 00:00:00 2001
From: Arnold Schwaighofer <aschwaighofer@apple.com>
Date: Tue, 10 Sep 2024 13:29:16 -0700
Subject: [PATCH 1/2] IRGen: Async throwing functions with empty error types
 pass the error indirectly

rdar://135304464
---
 lib/IRGen/GenCall.cpp       |  5 ++++-
 test/IRGen/typed_throws.sil | 31 +++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/lib/IRGen/GenCall.cpp b/lib/IRGen/GenCall.cpp
index c8a7bdc8d637f..d6e8596faf07d 100644
--- a/lib/IRGen/GenCall.cpp
+++ b/lib/IRGen/GenCall.cpp
@@ -3030,7 +3030,10 @@ class AsyncCallEmission final : public CallEmission {
             IGF.IGM.getTypeInfo(silErrorTy).nativeReturnValueSchema(IGF.IGM);
 
         if (nativeSchema.requiresIndirect() ||
-            errorSchema.shouldReturnTypedErrorIndirectly()) {
+            errorSchema.shouldReturnTypedErrorIndirectly() ||
+            errorSchema.empty()) { // direct empty typed errors are passed
+                                   // indirectly for compatibility with generic
+                                   // functions.
           // Return the error indirectly.
           auto buf = IGF.getCalleeTypedErrorResultSlot(silErrorTy);
           Args[--LastArgWritten] = buf.getAddress();
diff --git a/test/IRGen/typed_throws.sil b/test/IRGen/typed_throws.sil
index 3e5ca9cdc7c09..b1f7d32735ba5 100644
--- a/test/IRGen/typed_throws.sil
+++ b/test/IRGen/typed_throws.sil
@@ -458,3 +458,34 @@ bb6:
   %t = tuple()
   return %t : $()
 }
+
+sil @callee : $@convention(thin) @async (Int64) -> (@out (), @error Never) {
+bb0(%0 : $*(), %1: $Int64):
+  %17 = tuple ()
+  return %17 : $()
+}
+
+// CHECK: define{{.*}} swifttailcc void @callee(ptr {{.*}} %0, ptr swiftasync %1, i64 %2, ptr %3)
+
+// CHECK: define{{.*}} swifttailcc void @caller(ptr swiftasync %0) {{.*}} {
+// CHECK-NOT: define
+// CHECK: [[CTXT:%.*]] = call swiftcc ptr @swift_task_alloc
+// CHECK-NOT: define
+// CHECK: call {{.*}} @llvm.coro.suspend.async.sl_p0p0s(i32 256, ptr {{.*}}, ptr @__swift_async_resume_project_context, ptr @caller.0, ptr @callee, ptr undef, ptr [[CTXT]], i64 66, ptr %swifterror)
+
+sil @caller : $@convention(thin) @async () -> () {
+bb0:
+  %5 = integer_literal $Builtin.Int64, 66
+  %6 = struct $Int64 (%5 : $Builtin.Int64)
+  %9 = alloc_stack $()
+  %10 = function_ref @callee : $@convention(thin) @async (Int64) -> (@out (), @error Never)
+  try_apply %10(%9, %6) : $@convention(thin) @async (Int64) -> (@out (), @error Never), normal bb1, error bb2
+
+bb1(%12 : $()):
+  dealloc_stack %9 : $*()
+  %17 = tuple ()
+  return %17 : $()
+
+bb2(%19 : $Never):
+  unreachable
+}

From ede9f33c52889e41089ed86509940d617e58a349 Mon Sep 17 00:00:00 2001
From: Arnold Schwaighofer <aschwaighofer@apple.com>
Date: Wed, 11 Sep 2024 08:20:48 -0700
Subject: [PATCH 2/2] Fix the fix

---
 lib/IRGen/GenCall.cpp       |  2 +-
 test/IRGen/typed_throws.sil | 27 +++++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/lib/IRGen/GenCall.cpp b/lib/IRGen/GenCall.cpp
index d6e8596faf07d..a201435ce7135 100644
--- a/lib/IRGen/GenCall.cpp
+++ b/lib/IRGen/GenCall.cpp
@@ -3031,7 +3031,7 @@ class AsyncCallEmission final : public CallEmission {
 
         if (nativeSchema.requiresIndirect() ||
             errorSchema.shouldReturnTypedErrorIndirectly() ||
-            errorSchema.empty()) { // direct empty typed errors are passed
+            (errorSchema.empty() && fnConv.hasIndirectSILResults())) { // direct empty typed errors are passed
                                    // indirectly for compatibility with generic
                                    // functions.
           // Return the error indirectly.
diff --git a/test/IRGen/typed_throws.sil b/test/IRGen/typed_throws.sil
index b1f7d32735ba5..8d5caa462ee53 100644
--- a/test/IRGen/typed_throws.sil
+++ b/test/IRGen/typed_throws.sil
@@ -489,3 +489,30 @@ bb1(%12 : $()):
 bb2(%19 : $Never):
   unreachable
 }
+
+sil @callee2 : $@convention(thin) @async (Int) -> (Int, @error Never) {
+bb0(%0 :  $Int):
+  %5 = integer_literal $Builtin.Int64, 66
+  %6 = struct $Int (%5 : $Builtin.Int64)
+  return %6 : $Int
+}
+
+// CHECK: define{{.*}} swifttailcc void @callee2(ptr swiftasync %0, i64 %1)
+
+// CHECK: define{{.*}} swifttailcc void @caller2(ptr swiftasync %0)
+// CHECK: [[CTXT:%.*]] = call swiftcc ptr @swift_task_alloc
+// CHECK: @llvm.coro.suspend.async.sl_p0i64p0s({{.*}} ptr @callee2, ptr [[CTXT]], i64 67)
+sil @caller2 : $@convention(thin) @async () -> () {
+bb0:
+  %5 = integer_literal $Builtin.Int64, 67
+  %6 = struct $Int (%5 : $Builtin.Int64)
+  %10 = function_ref @callee2 : $@convention(thin) @async (Int) -> (Int, @error Never)
+  try_apply %10(%6) : $@convention(thin) @async (Int) -> (Int, @error Never), normal bb1, error bb2
+
+bb1(%12 : $Int):
+  %17 = tuple ()
+  return %17 : $()
+
+bb2(%19 : $Never):
+  unreachable
+}