[lldb][swift][NFC] Move code task_switch to helper function

This will enable us to share code and handle more functions similar to
swift_task_switch in a subsequent commit.

(cherry picked from commit 92b6c3c)

Author: felipepiovezan

lldb/source/Plugins/LanguageRuntime/Swift/SwiftLanguageRuntimeNames.cpp

@@ -361,23 +361,13 @@ class ThreadPlanRunToAddressOnAsyncCtx : public ThreadPlan {
 
 /// Given a thread that is stopped at the start of swift_task_switch, create a
 /// thread plan that runs to the address of the resume function.
-static ThreadPlanSP CreateRunThroughTaskSwitchThreadPlan(Thread &thread) {
-  // The signature for `swift_task_switch` is as follows:
-  //   SWIFT_CC(swiftasync)
-  //   void swift_task_switch(
-  //     SWIFT_ASYNC_CONTEXT AsyncContext *resumeContext,
-  //     TaskContinuationFunction *resumeFunction,
-  //     ExecutorRef newExecutor);
-  //
-  // The async context given as the first argument is not passed using the
-  // calling convention's first register, it's passed in the platform's async
-  // context register. This means the `resumeFunction` parameter uses the
-  // first ABI register (ex: x86-64: rdi, arm64: x0).
+static ThreadPlanSP
+CreateRunThroughTaskSwitchThreadPlan(Thread &thread,
+                                     unsigned resume_fn_generic_regnum) {
   RegisterContextSP reg_ctx =
       thread.GetStackFrameAtIndex(0)->GetRegisterContext();
-  constexpr unsigned resume_fn_regnum = LLDB_REGNUM_GENERIC_ARG1;
   unsigned resume_fn_reg = reg_ctx->ConvertRegisterKindToRegisterNumber(
-      RegisterKind::eRegisterKindGeneric, resume_fn_regnum);
+      RegisterKind::eRegisterKindGeneric, resume_fn_generic_regnum);
   uint64_t resume_fn_ptr = reg_ctx->ReadRegisterAsUnsigned(resume_fn_reg, 0);
   if (!resume_fn_ptr)
     return {};
@@ -397,6 +387,29 @@ static ThreadPlanSP CreateRunThroughTaskSwitchThreadPlan(Thread &thread) {
       thread, resume_fn_ptr, async_ctx);
 }
 
+/// Creates a thread plan to step over swift runtime functions that can trigger
+/// a task switch, like `async_task_switch` or `swift_asyncLet_get`.
+static ThreadPlanSP
+CreateRunThroughTaskSwitchingTrampolines(Thread &thread,
+                                         StringRef trampoline_name) {
+  // The signature for `swift_task_switch` is as follows:
+  //   SWIFT_CC(swiftasync)
+  //   void swift_task_switch(
+  //     SWIFT_ASYNC_CONTEXT AsyncContext *resumeContext,
+  //     TaskContinuationFunction *resumeFunction,
+  //     ExecutorRef newExecutor);
+  //
+  // The async context given as the first argument is not passed using the
+  // calling convention's first register, it's passed in the platform's async
+  // context register. This means the `resumeFunction` parameter uses the
+  // first ABI register (ex: x86-64: rdi, arm64: x0).
+  if (trampoline_name == "swift_task_switch")
+    return CreateRunThroughTaskSwitchThreadPlan(thread,
+                                                LLDB_REGNUM_GENERIC_ARG1);
+
+  return nullptr;
+}
+
 static lldb::ThreadPlanSP GetStepThroughTrampolinePlan(Thread &thread,
                                                        bool stop_others) {
   // Here are the trampolines we have at present.
@@ -429,8 +442,9 @@ static lldb::ThreadPlanSP GetStepThroughTrampolinePlan(Thread &thread,
   Mangled &mangled_symbol_name = symbol->GetMangled();
   const char *symbol_name = mangled_symbol_name.GetMangledName().AsCString();
 
-  if (mangled_symbol_name.GetDemangledName() == "swift_task_switch")
-    return CreateRunThroughTaskSwitchThreadPlan(thread);
+  if (ThreadPlanSP thread_plan = CreateRunThroughTaskSwitchingTrampolines(
+          thread, mangled_symbol_name.GetDemangledName()))
+    return thread_plan;
 
   ThunkKind thunk_kind = GetThunkKind(symbol);
   ThunkAction thunk_action = GetThunkAction(thunk_kind);