[Intel-gfx] [PATCH 2/2] drm/i915: Silence smatch for cmdparser

[Jani Nikula]

On Fri, 20 Jan 2017, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> drivers/gpu/drm/i915/i915_cmd_parser.c:808:23: error: not an lvalue
> drivers/gpu/drm/i915/i915_cmd_parser.c:811:23: error: not an lvalue
> drivers/gpu/drm/i915/i915_cmd_parser.c:814:23: error: not an lvalue
> drivers/gpu/drm/i915/i915_cmd_parser.c:808:23: error: not an lvalue
> drivers/gpu/drm/i915/i915_cmd_parser.c:811:23: error: not an lvalue
> drivers/gpu/drm/i915/i915_cmd_parser.c:814:23: error: not an lvalue
> drivers/gpu/drm/i915/i915_cmd_parser.c:808:23: error: not an lvalue
> drivers/gpu/drm/i915/i915_cmd_parser.c:811:23: error: not an lvalue
> drivers/gpu/drm/i915/i915_cmd_parser.c:814:23: error: not an lvalue
> drivers/gpu/drm/i915/i915_cmd_parser.c:808:23: error: not an lvalue
> drivers/gpu/drm/i915/i915_cmd_parser.c:811:23: error: not an lvalue
> drivers/gpu/drm/i915/i915_cmd_parser.c:814:23: error: not an lvalue

I don't understand the error, but the change is sane

Reviewed-by: Jani Nikula <jani.nikula at intel.com>


>
> If we move the shift into each case not only do we kill the warning from
> smatch, but we shrink the code slightly:
>
>    text	   data	    bss	    dec	    hex	filename
> 1267906	  20587	   3168	1291661	 13b58d	before
> 1267890	  20587	   3168	1291645	 13b57d	after
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_cmd_parser.c | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_cmd_parser.c b/drivers/gpu/drm/i915/i915_cmd_parser.c
> index 420bbc220f35..650ee34f5786 100644
> --- a/drivers/gpu/drm/i915/i915_cmd_parser.c
> +++ b/drivers/gpu/drm/i915/i915_cmd_parser.c
> @@ -800,22 +800,15 @@ struct cmd_node {
>   */
>  static inline u32 cmd_header_key(u32 x)
>  {
> -	u32 shift;
> -
>  	switch (x >> INSTR_CLIENT_SHIFT) {
>  	default:
>  	case INSTR_MI_CLIENT:
> -		shift = STD_MI_OPCODE_SHIFT;
> -		break;
> +		return x >> STD_MI_OPCODE_SHIFT;
>  	case INSTR_RC_CLIENT:
> -		shift = STD_3D_OPCODE_SHIFT;
> -		break;
> +		return x >> STD_3D_OPCODE_SHIFT;
>  	case INSTR_BC_CLIENT:
> -		shift = STD_2D_OPCODE_SHIFT;
> -		break;
> +		return x >> STD_2D_OPCODE_SHIFT;
>  	}
> -
> -	return x >> shift;
>  }
>  
>  static int init_hash_table(struct intel_engine_cs *engine,

-- 
Jani Nikula, Intel Open Source Technology Center