Re: [PATCH] drm/amd/powerplay: use ARRAY_SIZE() for size of array

[Jani Nikula]

On Wed, 11 May 2016, Muhammad Falak R Wani <falakreyaz@xxxxxxxxx> wrote:
> Use ARRAY_SIZE() for the size calculation of the array. Also move the
> condition evaulation function out of the for loop.
> Although, any respectable c-compiler would optimize this and evaluate
> the function only once outside the loop, but the optimzation engine
> of gcc is bit brain-dead, and at times needs some hand holding.

This just caught my eye. ARRAY_SIZE is a macro that expands to a compile
time constant. Arguably adding the the local variable here gives GCC
more chances to go wrong than keeping the ARRAY_SIZE in the loop
condition.

BR,
Jani.

>
> Signed-off-by: Muhammad Falak R Wani <falakreyaz@xxxxxxxxx>
> ---
>  drivers/gpu/drm/amd/powerplay/smumgr/cz_smumgr.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/powerplay/smumgr/cz_smumgr.c b/drivers/gpu/drm/amd/powerplay/smumgr/cz_smumgr.c
> index da18f44..718a551 100644
> --- a/drivers/gpu/drm/amd/powerplay/smumgr/cz_smumgr.c
> +++ b/drivers/gpu/drm/amd/powerplay/smumgr/cz_smumgr.c
> @@ -636,10 +636,11 @@ static int cz_smu_populate_firmware_entries(struct pp_smumgr *smumgr)
>  	int ret;
>  	enum cgs_ucode_id ucode_id;
>  	struct cgs_firmware_info info = {0};
> +	int n = ARRAY_SIZE(firmware_list);
>  
>  	cz_smu->driver_buffer_length = 0;
>  
> -	for (i = 0; i < sizeof(firmware_list)/sizeof(*firmware_list); i++) {
> +	for (i = 0; i < n; i++) {
>  
>  		firmware_type = cz_translate_firmware_enum_to_arg(smumgr,
>  					firmware_list[i]);

-- 
Jani Nikula, Intel Open Source Technology Center