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Commit 9fabcc63 authored by Vineet Gupta's avatar Vineet Gupta
Browse files

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: default avatarVineet Gupta <vgupta@synopsys.com>
parent 5f888087

arch/arc/kernel/entry-compact.S

+6 −12
Original line number Diff line number Diff line
@@ -333,11 +333,10 @@ END(call_do_page_fault) 
	; Note that we use realtime STATUS32 (not pt_regs->status32) to

	; decide that.



	; if Returning from Exception

	btst   r10, STATUS_AE_BIT

	bnz    .Lexcep_ret

	and.f	0, r10, (STATUS_A1_MASK|STATUS_A2_MASK)

	bz	.Lexcep_or_pure_K_ret



	; Not Exception so maybe Interrupts (Level 1 or 2)

	; Returning from Interrupts (Level 1 or 2)



#ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS
@@ -378,8 +377,7 @@ END(call_do_page_fault) 
	st      r9, [r10, THREAD_INFO_PREEMPT_COUNT]



149:

	;return from level 2

	INTERRUPT_EPILOGUE 2

	INTERRUPT_EPILOGUE 2	; return from level 2 interrupt

debug_marker_l2:

	rtie
@@ -387,15 +385,11 @@ not_level2_interrupt: 


#endif



	bbit0  r10, STATUS_A1_BIT, .Lpure_k_mode_ret



	;return from level 1

	INTERRUPT_EPILOGUE 1

	INTERRUPT_EPILOGUE 1	; return from level 1 interrupt

debug_marker_l1:

	rtie



.Lexcep_ret:

.Lpure_k_mode_ret:

.Lexcep_or_pure_K_ret:



	;this case is for syscalls or Exceptions or pure kernel mode