linux-kernel - Re: [PATCH] drm/amd/amdgpu: get rid of else branch

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Date:   Thu, 4 May 2017 15:14:36 +0200
From:   Christian König <christian.koenig@....com>
To:     Nikola Pajkovsky <npajkovsky@...e.cz>,
        <linux-kernel@...r.kernel.org>
CC:     Alex Deucher <alexander.deucher@....com>,
        David Airlie <airlied@...ux.ie>,
        <amd-gfx@...ts.freedesktop.org>, <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] drm/amd/amdgpu: get rid of else branch

Am 04.05.2017 um 14:52 schrieb Nikola Pajkovsky:
> else branch is pointless if it's right at the end of function and use
> unlikely() on err path.
>
> Signed-off-by: Nikola Pajkovsky <npajkovsky@...e.cz>

Reviewed-by: Christian König <christian.koenig@....com>

> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu.h | 45 +++++++++++++++++++------------------
>   1 file changed, 23 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index c1b913541739..8ab250d4761a 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -1594,30 +1594,31 @@ static inline void amdgpu_ring_write_multiple(struct amdgpu_ring *ring, void *sr
>   	unsigned occupied, chunk1, chunk2;
>   	void *dst;
>   
> -	if (ring->count_dw < count_dw) {
> +	if (unlikely(ring->count_dw < count_dw)) {
>   		DRM_ERROR("amdgpu: writing more dwords to the ring than expected!\n");
> -	} else {
> -		occupied = ring->wptr & ring->ptr_mask;
> -		dst = (void *)&ring->ring[occupied];
> -		chunk1 = ring->ptr_mask + 1 - occupied;
> -		chunk1 = (chunk1 >= count_dw) ? count_dw: chunk1;
> -		chunk2 = count_dw - chunk1;
> -		chunk1 <<= 2;
> -		chunk2 <<= 2;
> -
> -		if (chunk1)
> -			memcpy(dst, src, chunk1);
> -
> -		if (chunk2) {
> -			src += chunk1;
> -			dst = (void *)ring->ring;
> -			memcpy(dst, src, chunk2);
> -		}
> -
> -		ring->wptr += count_dw;
> -		ring->wptr &= ring->ptr_mask;
> -		ring->count_dw -= count_dw;
> +		return;
>   	}
> +
> +	occupied = ring->wptr & ring->ptr_mask;
> +	dst = (void *)&ring->ring[occupied];
> +	chunk1 = ring->ptr_mask + 1 - occupied;
> +	chunk1 = (chunk1 >= count_dw) ? count_dw: chunk1;
> +	chunk2 = count_dw - chunk1;
> +	chunk1 <<= 2;
> +	chunk2 <<= 2;
> +
> +	if (chunk1)
> +		memcpy(dst, src, chunk1);
> +
> +	if (chunk2) {
> +		src += chunk1;
> +		dst = (void *)ring->ring;
> +		memcpy(dst, src, chunk2);
> +	}
> +
> +	ring->wptr += count_dw;
> +	ring->wptr &= ring->ptr_mask;
> +	ring->count_dw -= count_dw;
>   }
>   
>   static inline struct amdgpu_sdma_instance *