[Intel-gfx] [PATCH 2/2] drm/i915: Consolidate gen8_emit_pipe_control

[Tvrtko Ursulin]

On 15/02/2017 16:33, Chris Wilson wrote:
> On Wed, Feb 15, 2017 at 04:06:34PM +0000, Tvrtko Ursulin wrote:
>> +static inline u32 *gen8_emit_pipe_control(u32 *batch, u32 flags, u32 offset)
>> +{
>> +	static const u32 pc6[6] = { GFX_OP_PIPE_CONTROL(6), 0, 0, 0, 0, 0 };
>> +
>> +	memcpy(batch, pc6, sizeof(pc6));
>> +
>> +	batch[1] = flags;
>> +	batch[2] = offset;
>> +
>> +	return batch + 6;
>
> godbolt would seem to say it is best to use
> static inline u32 *gen8_emit_pipe_control(u32 *batch, u32 flags, u32 offset)
> {
> 	batch[0] = GFX_OP_PIPE_CONTROL(6);
> 	batch[1] = flags;
> 	batch[2] = offset;
> 	batch[3] = 0;
> 	batch[4] = 0;
> 	batch[5] = 0;
>
> 	return batch + 6;
> }

Yeah agreed, it was a bit silly. I falsely remember it had quite good 
effects on the optimisation gcc was able to do but couldn't repro that.

How about though replacing the last three assignments with 
memset(&batch[3], 0, 3 * sizeof(u32))? That is indeed helpful on 64-bit.

Regards,

Tvrtko