[SR-15703] Fix missing hop in error path of foreign async throws call

resolves rdar://89479707

Author: kavon

lib/SILGen/ExecutorBreadcrumb.h

@@ -37,6 +37,11 @@ class ExecutorBreadcrumb {
   // Emits the hop back sequence, if any, necessary to get back to
   // the executor represented by this breadcrumb.
   void emit(SILGenFunction &SGF, SILLocation loc);
+
+#ifndef NDEBUG
+  // FOR ASSERTS ONLY: returns true if calling `emit` will emit a hop-back.
+  bool needsEmit() const { return mustReturnToExecutor; }
+#endif
 };
 
 } // namespace Lowering

lib/SILGen/SILGenApply.cpp

@@ -4414,6 +4414,27 @@ class FixLifetimeDestroyCleanup : public Cleanup {
 #endif
   }
 };
+
+class EmitBreadcrumbCleanup : public Cleanup {
+  ExecutorBreadcrumb breadcrumb;
+
+public:
+  EmitBreadcrumbCleanup(ExecutorBreadcrumb &&breadcrumb)
+    : breadcrumb(std::move(breadcrumb)) {}
+
+  void emit(SILGenFunction &SGF, CleanupLocation l,
+            ForUnwind_t forUnwind) override {
+    breadcrumb.emit(SGF, l);
+  }
+
+  void dump(SILGenFunction &SGF) const override {
+#ifndef NDEBUG
+    llvm::errs() << "EmitBreadcrumbCleanup "
+                 << "State:" << getState()
+                 << "NeedsEmit:" << breadcrumb.needsEmit();
+#endif
+  }
+};
 } // end anonymous namespace
 
 //===----------------------------------------------------------------------===//
@@ -4660,12 +4681,14 @@ RValue SILGenFunction::emitApply(
                               *foreignError, calleeTypeInfo.foreign.async);
   }
 
-  // For objc async calls, push cleanup to be used on
+  // For objc async calls, push cleanups to be used on
   // both result and throw paths prior to finishing the result plan.
   if (calleeTypeInfo.foreign.async) {
     for (auto unmanagedCopy : unmanagedCopies) {
       Cleanups.pushCleanup<FixLifetimeDestroyCleanup>(unmanagedCopy);
     }
+    // save breadcrumb as a clean-up so it is emitted in result / throw cases.
+    Cleanups.pushCleanup<EmitBreadcrumbCleanup>(std::move(breadcrumb));
   } else {
     assert(unmanagedCopies.empty());
   }
@@ -4675,10 +4698,6 @@ RValue SILGenFunction::emitApply(
                                      directResultsArray, bridgedForeignError);
   assert(directResultsArray.empty() && "didn't claim all direct results");
 
-  if (calleeTypeInfo.foreign.async) {
-    breadcrumb.emit(*this, loc);
-  }
-
   return result;
 }
 

test/SILGen/objc_async.swift

@@ -201,3 +201,43 @@ func testSlowServerFromMain(slowServer: SlowServer) async throws {
   // CHECK: dealloc_stack [[RESUME_BUF]]
   let _: Int = await slowServer.doSomethingSlow("mail")
 }
+
+// CHECK-LABEL: sil {{.*}}@${{.*}}26testThrowingMethodFromMain
+@MainActor
+func testThrowingMethodFromMain(slowServer: SlowServer) async -> String {
+// CHECK:  [[RESULT_BUF:%.*]] = alloc_stack $String
+// CHECK:  [[STRING_ARG:%.*]] = apply {{%.*}}({{%.*}}) : $@convention(method) (@guaranteed String) -> @owned NSString
+// CHECK:  [[METH:%.*]] = objc_method {{%.*}} : $SlowServer, #SlowServer.doSomethingDangerous!foreign
+// CHECK:  [[RAW_CONT:%.*]] = get_async_continuation_addr [throws] String, [[RESULT_BUF]] : $*String
+// CHECK:  [[CONT:%.*]] = struct $UnsafeContinuation<String, Error> ([[RAW_CONT]] : $Builtin.RawUnsafeContinuation)
+// CHECK:  [[STORE_ALLOC:%.*]] = alloc_stack $@block_storage UnsafeContinuation<String, Error>
+// CHECK:  [[PROJECTED:%.*]] = project_block_storage [[STORE_ALLOC]] : $*@block_storage
+// CHECK:  store [[CONT]] to [trivial] [[PROJECTED]] : $*UnsafeContinuation<String, Error>
+// CHECK:  [[INVOKER:%.*]] = function_ref @$sSo8NSStringCSgSo7NSErrorCSgIeyByy_SSTz_
+// CHECK:  [[BLOCK:%.*]] = init_block_storage_header [[STORE_ALLOC]] {{.*}}, invoke [[INVOKER]]
+// CHECK:  [[OPTIONAL_BLK:%.*]] = enum {{.*}}, #Optional.some!enumelt, [[BLOCK]]
+// CHECK:  %28 = apply [[METH]]([[STRING_ARG]], [[OPTIONAL_BLK]], {{%.*}}) : $@convention(objc_method) (NSString, Optional<@convention(block) (Optional<NSString>, Optional<NSError>) -> ()>, SlowServer) -> ()
+// CHECK:  [[STRING_ARG_COPY:%.*]] = copy_value [[STRING_ARG]] : $NSString
+// CHECK:  dealloc_stack [[STORE_ALLOC]] : $*@block_storage UnsafeContinuation<String, Error>
+// CHECK:  destroy_value [[STRING_ARG]] : $NSString
+// CHECK:  await_async_continuation [[RAW_CONT]] : $Builtin.RawUnsafeContinuation, resume [[RESUME:bb[0-9]+]], error [[ERROR:bb[0-9]+]]
+
+// CHECK: [[RESUME]]
+// CHECK:   {{.*}} = load [take] [[RESULT_BUF]] : $*String
+// CHECK:   hop_to_executor {{%.*}} : $MainActor
+// CHECK:   fix_lifetime [[STRING_ARG_COPY]] : $NSString
+// CHECK:   destroy_value [[STRING_ARG_COPY]] : $NSString
+// CHECK:   dealloc_stack [[RESULT_BUF]] : $*String
+
+// CHECK: [[ERROR]]
+// CHECK:   hop_to_executor {{%.*}} : $MainActor
+// CHECK:   fix_lifetime [[STRING_ARG_COPY]] : $NSString
+// CHECK:   destroy_value [[STRING_ARG_COPY]] : $NSString
+// CHECK:   dealloc_stack [[RESULT_BUF]] : $*String
+
+  do {
+    return try await slowServer.doSomethingDangerous("run-with-scissors")
+  } catch {
+    return "none"
+  }
+}

test/SILGen/objc_async_from_swift.swift

@@ -25,19 +25,28 @@ func testSlowServing(p: SlowServing) async throws {
     // CHECK: hop_to_executor [[GENERIC_EXECUTOR]] :
     let _: String = await p.requestString()
 
-    // CHECK: objc_method {{.*}} $@convention(objc_method) <τ_0_0 where τ_0_0 : SlowServing> (@convention(block) (Optional<NSString>, Optional<NSError>) -> (), τ_0_0) -> ()
-    // CHECK: hop_to_executor [[GENERIC_EXECUTOR]] :
-    let _: String = try await p.tryRequestString()
-
     // CHECK: objc_method {{.*}} $@convention(objc_method) <τ_0_0 where τ_0_0 : SlowServing> (@convention(block) (Int, NSString) -> (), τ_0_0) -> ()
     // CHECK: hop_to_executor [[GENERIC_EXECUTOR]] :
     let _: (Int, String) = await p.requestIntAndString()
 
     // CHECK: objc_method {{.*}} $@convention(objc_method) <τ_0_0 where τ_0_0 : SlowServing> (@convention(block) (Int, Optional<NSString>, Optional<NSError>) -> (), τ_0_0) -> ()
     // CHECK: hop_to_executor [[GENERIC_EXECUTOR]] :
+    // CHECK:      builtin "willThrow"
+    // CHECK-NEXT: hop_to_executor [[GENERIC_EXECUTOR]] :
     let _: (Int, String) = try await p.tryRequestIntAndString()
 }
 
+// CHECK-LABEL: sil {{.*}}@{{.*}}20testSlowServingAgain
+func testSlowServingAgain(p: SlowServing) async throws {
+  // CHECK: [[GENERIC_EXECUTOR:%.*]] = enum $Optional<Builtin.Executor>, #Optional.none
+  // CHECK: hop_to_executor [[GENERIC_EXECUTOR]] :
+  // CHECK: objc_method {{.*}} $@convention(objc_method) <τ_0_0 where τ_0_0 : SlowServing> (@convention(block) (Optional<NSString>, Optional<NSError>) -> (), τ_0_0) -> ()
+  // CHECK: hop_to_executor [[GENERIC_EXECUTOR]] :
+  // CHECK:      builtin "willThrow"
+  // CHECK-NEXT: hop_to_executor [[GENERIC_EXECUTOR]] :
+  let _: String = try await p.tryRequestString()
+}
+
 class SlowSwiftServer: NSObject, SlowServing {
     // CHECK-LABEL: sil {{.*}} @$s21objc_async_from_swift15SlowSwiftServerC10requestIntSiyYaF
     // CHECK:         [[GENERIC_EXECUTOR:%.*]] = enum $Optional<Builtin.Executor>, #Optional.none