ARC: entry.S: micro-optimize Trap handler

Elide the need to re-read ECR in Trap handler by ensuring that
EXCEPTION_PROLOGUE does that at the very end just before returning
to Trap handler

ARCv2 EXCEPTION_PROLOGUE already did that, so same for ARcompact and the
common trap handler adjusted to use cached ECR

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

diff --git a/arch/arc/include/asm/entry-compact.h b/arch/arc/include/asm/entry-compact.h
index 6c0a81b..8b65eb3 100644 (file)
--- a/arch/arc/include/asm/entry-compact.h
+++ b/arch/arc/include/asm/entry-compact.h
@@ -181,8 +181,6 @@
        /* ARC700 doesn't provide auto-stack switching */
        SWITCH_TO_KERNEL_STK
 
-       lr      r9, [ecr]
-       st      r9, [sp, 8]    /* ECR */
        st      r0, [sp, 4]    /* orig_r0, needed only for sys calls */
 
        /* Restore r9 used to code the early prologue */
@@ -198,6 +196,9 @@
        PUSHAX  lp_end
        PUSHAX  lp_start
        PUSHAX  erbta
+
+       lr      r9, [ecr]
+       st      r9, [sp, PT_event]    /* EV_Trap expects r9 to have ECR */
 .endm
 
 /*--------------------------------------------------------------

diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S
index 603266e..f7a82fd 100644 (file)
--- a/arch/arc/kernel/entry.S
+++ b/arch/arc/kernel/entry.S
@@ -258,8 +258,8 @@ ENTRY(EV_Trap)
        EXCEPTION_PROLOGUE
 
        ;============ TRAP 1   :breakpoints
-       lr     r10, [ecr]
-       bmsk.f 0, r10, 7
+       ; Check ECR for trap with arg (PROLOGUE ensures r9 has ECR)
+       bmsk.f 0, r9, 7
        bnz    trap_with_param
 
        ;============ TRAP  (no param): syscall top level