Re: [PATCH 2/2] drm/i915: Silence smatch for cmdparser

Jani Nikula
2017-01-25T11:16:19Z

On Fri, 20 Jan 2017, Chris Wilson <chris@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@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@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