On Fri, Feb 26, 2021 at 09:22:18AM +0800, Huacai Chen wrote:

Hi, Yury,

On Thu, Feb 25, 2021 at 9:59 PM Yury Norov [off-list ref] wrote:

quoted

From: Alexander Lobakin <redacted>

MIPS doesn't have architecture-optimized bitsearching functions,
like find_{first,next}_bit() etc.

Emm, I think MIPS can use clo/clz to optimize bitsearching functions.

find_{first,next}_bit() is about manipulating the bitmaps bigger that
a single word, and some arches (arm) implement their own find_bit()
functions. find_bit() is not a replacement of __ffs() and ffz().

Huacai

quoted

It's absolutely harmless to enable GENERIC_FIND_FIRST_BIT as this
functionality is not new at all and well-tested. It provides more
optimized code and saves some .text memory (32 R2):

add/remove: 4/1 grow/shrink: 1/53 up/down: 216/-372 (-156)

Users of for_each_set_bit() like hotpath gic_handle_shared_int()
will also benefit from this.

Suggested-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Alexander Lobakin <redacted>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
---
 arch/mips/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index d89efba3d8a4..164bdd715d4b 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig

@@ -26,6 +26,7 @@ config MIPS
        select GENERIC_ATOMIC64 if !64BIT
        select GENERIC_CMOS_UPDATE
        select GENERIC_CPU_AUTOPROBE
+       select GENERIC_FIND_FIRST_BIT
        select GENERIC_GETTIMEOFDAY
        select GENERIC_IOMAP
        select GENERIC_IRQ_PROBE
--

2.25.1