ARCv2: spinlock/rwlock/atomics: reduce 1 instruction in exponential backoff
The increment of delay counter was 2 instructions:
Arithmatic Shfit Left (ASL) + set to 1 on overflow
This can be done in 1 using ROtate Left (ROL)
Suggested-by: Nigel Topham <ntopham@synopsys.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
diff --git a/arch/arc/include/asm/atomic.h b/arch/arc/include/asm/atomic.h
index 629dfd0..87d18ae 100644
--- a/arch/arc/include/asm/atomic.h
+++ b/arch/arc/include/asm/atomic.h
@@ -34,8 +34,7 @@
" mov %[tmp], %[delay] \n" /* tmp = delay */ \
"2: brne.d %[tmp], 0, 2b \n" /* while (tmp != 0) */ \
" sub %[tmp], %[tmp], 1 \n" /* tmp-- */ \
- " asl.f %[delay], %[delay], 1 \n" /* delay *= 2 */ \
- " mov.z %[delay], 1 \n" /* handle overflow */ \
+ " rol %[delay], %[delay] \n" /* delay *= 2 */ \
" b 1b \n" /* start over */ \
"4: ; --- success --- \n" \