Fix AMD live debugging regression for shadow thread

Author: Jeffrey Tan

lldb/source/Plugins/Process/Utility/RegisterContextAmdGpuImpl.cpp

@@ -28,8 +28,8 @@ std::unordered_map<uint64_t,
 static std::unordered_map<uint64_t, std::once_flag> s_register_info_init_flags;
 
 RegisterContextAmdGpuImpl::RegisterContextAmdGpuImpl(
-    amd_dbgapi_architecture_id_t architecture_id)
-    : m_architecture_id(architecture_id) {
+    amd_dbgapi_architecture_id_t architecture_id, bool is_shadow_thread)
+    : m_architecture_id(architecture_id), m_is_shadow_thread(is_shadow_thread) {
   InitializeRegisterInfo();
   InitializeRegisterData();
 }
@@ -365,8 +365,8 @@ Status RegisterContextAmdGpuImpl::ReadRegister(
 
   auto amd_reg_id = arch_info.lldb_num_to_amd_reg_id.at(lldb_reg_num);
 
-  if (!wave_id) {
-    // No wave ID, return without error (dummy values)
+  if (!wave_id || m_is_shadow_thread) {
+    // No wave ID or shawdown thread, return without error (dummy values)
     return error;
   }
 

lldb/source/Plugins/Process/Utility/RegisterContextAmdGpuImpl.h

@@ -28,7 +28,8 @@ class RegisterValue;
 /// register information and reading/writing register values.
 class RegisterContextAmdGpuImpl {
 public:
-  RegisterContextAmdGpuImpl(amd_dbgapi_architecture_id_t architecture_id);
+  RegisterContextAmdGpuImpl(amd_dbgapi_architecture_id_t architecture_id,
+                            bool is_shadow_thread);
   ~RegisterContextAmdGpuImpl() = default;
 
   /// Invalidate all register values.
@@ -94,6 +95,7 @@ class RegisterContextAmdGpuImpl {
   // AMD dbgapi architecture ID
   amd_dbgapi_architecture_id_t m_architecture_id;
 
+  bool m_is_shadow_thread;
   // Register data and validity tracking (per-instance)
   std::vector<uint8_t> m_register_data;
   std::vector<bool> m_register_valid;

lldb/source/Plugins/Process/amdgpu-core/RegisterContextAmdGpu.cpp

@@ -21,7 +21,8 @@ RegisterContextAmdGpu::RegisterContextAmdGpu(Thread &thread)
   amd_dbgapi_architecture_id_t architecture_id =
       amdgpu_thread->GetArchitectureId();
 
-  m_impl = std::make_unique<RegisterContextAmdGpuImpl>(architecture_id);
+  m_impl = std::make_unique<RegisterContextAmdGpuImpl>(
+      architecture_id, /*is_shawdow_thread=*/false);
 }
 
 void RegisterContextAmdGpu::InvalidateAllRegisters() {

lldb/tools/lldb-server/Plugins/AMDGPU/RegisterContextAmdGpu.cpp

@@ -25,7 +25,8 @@ RegisterContextAmdGpu::RegisterContextAmdGpu(
   amd_dbgapi_architecture_id_t architecture_id =
       thread->GetProcess().m_debugger->m_architecture_id;
 
-  m_impl = std::make_unique<RegisterContextAmdGpuImpl>(architecture_id);
+  m_impl = std::make_unique<RegisterContextAmdGpuImpl>(
+      architecture_id, /*is_shawdow_thread=*/thread->IsShadowThread());
 }
 
 void RegisterContextAmdGpu::InvalidateAllRegisters() {