score: Add _CPU_Context_switch_no_return()

The __builtin_unreachable() cannot be used with current GCC versions to
tell the compiler that a function does not return to the caller, see:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99151

Add a no return variant of _CPU_Context_switch() to avoid generation of
dead code in _Thread_Start_multitasking() if RTEMS was built with SMP
support enabled.

1 files changed, 28 insertions, 4 deletions

diff --git a/cpukit/score/cpu/no_cpu/include/rtems/score/cpu.h b/cpukit/score/cpu/no_cpu/include/rtems/score/cpu.h
index c067501502..09f34b4acd 100644
--- a/cpukit/score/cpu/no_cpu/include/rtems/score/cpu.h
+++ b/cpukit/score/cpu/no_cpu/include/rtems/score/cpu.h
@@ -1054,23 +1054,47 @@ void _CPU_ISR_install_vector(
 void *_CPU_Thread_Idle_body( uintptr_t ignored );
 
 /**
+ * @brief Performs a context switch from the executing thread to the heir
+ *   thread.
+ *
  * @addtogroup RTEMSScoreCPUExampleContext
  * 
- * This routine switches from the run context to the heir context.
+ * This routine switches from the executing context to the heir context.
+ *
+ * @param[out] executing points to the context of the currently executing task.
  *
- * @param[in] run points to the context of the currently executing task
- * @param[in] heir points to the context of the heir task
+ * @param[in, out] heir points to the context of the heir task.
  *
  * Port Specific Information:
  *
  * XXX document implementation including references if appropriate
  */
 void _CPU_Context_switch(
-  Context_Control  *run,
+  Context_Control  *executing,
   Context_Control  *heir
 );
 
 /**
+ * @brief Performs a context switch from the executing thread to the heir
+ *   thread and does not return.
+ *
+ * @addtogroup RTEMSScoreCPUExampleContext
+ *
+ * This routine shall be a strong alias to _CPU_Context_switch().  It shall be
+ * provided for all target architectures which support an SMP build
+ * configuration (RTEMS_SMP).  The purpose is help to compiler to avoid
+ * generation of dead code in _Thread_Start_multitasking().
+ *
+ * @param[out] executing points to the context of the currently executing task.
+ *
+ * @param[in, out] heir points to the context of the heir task.
+ */
+RTEMS_NO_RETURN void _CPU_Context_switch_no_return(
+  Context_Control *executing,
+  Context_Control *heir
+);
+
+/**
  * @addtogroup RTEMSScoreCPUExampleContext
  * 
  * This routine is generally used only to restart self in an