[ARM] 3115/1: small optimizations to exception vector entry code

Patch from Nicolas Pitre

Since we know the value of cpsr on entry, we can replace the bic+orr with
a single eor.  Also remove a possible result delay (at least on XScale).
Signed-off-by: NNicolas Pitre <nico@cam.org>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/entry-armv.S

@@ -785,7 +785,7 @@ __kuser_helper_end:
  * SP points to a minimal amount of processor-private memory, the address
  * of which is copied into r0 for the mode specific abort handler.
  */
-	.macro	vector_stub, name, correction=0
+	.macro	vector_stub, name, mode, correction=0
 	.align	5
 
 vector_\name:
@@ -805,15 +805,14 @@ vector_\name:
 	@ Prepare for SVC32 mode.  IRQs remain disabled.
 	@
 	mrs	r0, cpsr
-	bic	r0, r0, #MODE_MASK
-	orr	r0, r0, #SVC_MODE
+	eor	r0, r0, #(\mode ^ SVC_MODE)
 	msr	spsr_cxsf, r0
 
 	@
 	@ the branch table must immediately follow this code
 	@
-	mov	r0, sp
 	and	lr, lr, #0x0f
+	mov	r0, sp
 	ldr	lr, [pc, lr, lsl #2]
 	movs	pc, lr			@ branch to handler in SVC mode
 	.endm
@@ -823,7 +822,7 @@ __stubs_start:
 /*
  * Interrupt dispatcher
  */
-	vector_stub	irq, 4
+	vector_stub	irq, IRQ_MODE, 4
 
 	.long	__irq_usr			@  0  (USR_26 / USR_32)
 	.long	__irq_invalid			@  1  (FIQ_26 / FIQ_32)
@@ -846,7 +845,7 @@ __stubs_start:
  * Data abort dispatcher
  * Enter in ABT mode, spsr = USR CPSR, lr = USR PC
  */
-	vector_stub	dabt, 8
+	vector_stub	dabt, ABT_MODE, 8
 
 	.long	__dabt_usr			@  0  (USR_26 / USR_32)
 	.long	__dabt_invalid			@  1  (FIQ_26 / FIQ_32)
@@ -869,7 +868,7 @@ __stubs_start:
  * Prefetch abort dispatcher
  * Enter in ABT mode, spsr = USR CPSR, lr = USR PC
  */
-	vector_stub	pabt, 4
+	vector_stub	pabt, ABT_MODE, 4
 
 	.long	__pabt_usr			@  0 (USR_26 / USR_32)
 	.long	__pabt_invalid			@  1 (FIQ_26 / FIQ_32)
@@ -892,7 +891,7 @@ __stubs_start:
  * Undef instr entry dispatcher
  * Enter in UND mode, spsr = SVC/USR CPSR, lr = SVC/USR PC
  */
-	vector_stub	und
+	vector_stub	und, UND_MODE
 
 	.long	__und_usr			@  0 (USR_26 / USR_32)
 	.long	__und_invalid			@  1 (FIQ_26 / FIQ_32)