On 12/07/2017 1:04 AM, Greg Kroah-Hartman wrote:
On Mon, Jul 10, 2017 at 04:57:31PM +0800, Rui Teng wrote:
This patch sets memory to zero directly to avoid unnecessary shift and
bitwise operations on bool type, which can fix a sparse warning and also
improve performance.
It does? How did you measure the performance impact? What was now
faster?
It can avoid 3 times right shift and 3 times bitwise operations.
And once memory set should also faster than 4 times copy operations.
And add number 4 once should also faster than 4 times plus plus.
thanks,
greg k-h
Signed-off-by: Rui Teng <rui.teng@xxxxxxxxxxxxxxxxxx>
---
drivers/staging/wilc1000/host_interface.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/drivers/staging/wilc1000/host_interface.c b/drivers/staging/wilc1000/host_interface.c
index 2568dfc15181..036c5c19a016 100644
--- a/drivers/staging/wilc1000/host_interface.c
+++ b/drivers/staging/wilc1000/host_interface.c
@@ -2416,10 +2416,9 @@ static void Handle_SetMulticastFilter(struct wilc_vif *vif,
goto ERRORHANDLER;
pu8CurrByte = wid.val;
- *pu8CurrByte++ = (strHostIfSetMulti->enabled & 0xFF);
- *pu8CurrByte++ = ((strHostIfSetMulti->enabled >> 8) & 0xFF);
- *pu8CurrByte++ = ((strHostIfSetMulti->enabled >> 16) & 0xFF);
- *pu8CurrByte++ = ((strHostIfSetMulti->enabled >> 24) & 0xFF);
+ memset(pu8CurrByte, 0, 4);
+ *pu8CurrByte = (strHostIfSetMulti->enabled & 0xFF);
+ pu8CurrByte += 4;
Are you sure enabled isn't larger than 8 bits?
The size of bool may larger than 8 bits. But when we assign any value
to bool type, the value of bool type will only be 1 or 0.
For example, the following output will be 1 other than 0x100.
bool b = 0x100;
printf("b: %d\n", b);
Or I think it should change 'enabled' type from bool to u32, to make
sure that the right shift operation can take effect.
thanks,
greg k-h
