From 9fabcc636bf57dcb9c6fc5b1f34861c548944fd4 Mon Sep 17 00:00:00 2001 From: Vineet Gupta Date: Thu, 8 Oct 2015 17:52:27 +0530 Subject: [PATCH] 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 --- arch/arc/kernel/entry-compact.S | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-) diff --git a/arch/arc/kernel/entry-compact.S b/arch/arc/kernel/entry-compact.S index d9087a1236eb..5221f194602b 100644 --- a/arch/arc/kernel/entry-compact.S +++ b/arch/arc/kernel/entry-compact.S @@ -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 -- 2.20.1