ARC: Exception Entry tweaks - SP saved from one location in code

Save k/u mode SP on kernel stack from single place.
This paves way for further simplifications.

There's an overhead of 1 insn for the non-common case of interrupt taken
from kernel mode.

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

diff --git a/arch/arc/include/asm/entry.h b/arch/arc/include/asm/entry.h
index 5191945f3d39bbe54e70cb36c7c191b45befed76..2cf6aa08cfca5b9eec1207bd70f346d10835c8e5 100644 (file)
--- a/arch/arc/include/asm/entry.h
+++ b/arch/arc/include/asm/entry.h
@@ -290,9 +290,8 @@
         * safe-keeping not really needed, but it keeps the epilogue code
         * (SP restore) simpler/uniform.
         */
-       b.d     77f
-
-       st.a    sp, [sp, -12]   ; Make room for orig_r0 and orig_r8
+       b.d     66f
+       mov     r9, sp
 
 88: /*------Intr/Ecxp happened in user mode, "switch" stack ------ */
 
@@ -311,6 +310,7 @@
        /* With current tsk in r9, get it's kernel mode stack base */
        GET_TSK_STACK_BASE  r9, r9
 
+66:
        /* Save Pre Intr/Exception User SP on kernel stack */
        st.a    sp, [r9, -12]   ; Make room for orig_r0 and orig_r8
 
@@ -323,7 +323,7 @@
        /* set SP to point to kernel mode stack */
        mov sp, r9
 
-77: /* ----- Stack Switched to kernel Mode, Now save REG FILE ----- */
+       /* ----- Stack Switched to kernel Mode, Now save REG FILE ----- */
 
 .endm