commit 9fabcc636bf57dcb9c6fc5b1f34861c548944fd4
author Vineet Gupta <vgupta@synopsys.com> Thu Oct 08 17:52:27 2015 +0530
committer Vineet Gupta <vgupta@synopsys.com> Sat Oct 17 17:48:23 2015 +0530
tree a3924e140769864304736e3f8354e62761bf693c
parent 5f888087455c5199195c2ba17b91ac7285a33921

ARC: [arcompact] entry.S: Elide extra check/branch in exception ret path

This is done by improving the laddering logic !

Before:

   if Exception
      goto excep_or_pure_k_ret

   if !Interrupt(L2)
      goto l1_chk
   else
      INTERRUPT_EPILOGUE 2

 l1_chk:
   if !Interrupt(L1)  (i.e. pure kernel mode)
      goto excep_or_pure_k_ret
   else
      INTERRUPT_EPILOGUE 1

 excep_or_pure_k_ret:
   EXCEPTION_EPILOGUE

Now:

   if !Interrupt(L1 or L2) (i.e. exception or pure kernel mode)
      goto excep_or_pure_k_ret

  ; guaranteed to be an interrupt
   if !Interrupt(L2)
      goto l1_ret
   else
      INTERRUPT_EPILOGUE 2

 ; by virtue of above, no need to chk for L1 active
 l1_ret:
    INTERRUPT_EPILOGUE 1

 excep_or_pure_k_ret:
    EXCEPTION_EPILOGUE

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>