[Mesa-dev] Bug in 48157b904a9 found by Coverity

[Damien Lespiau]

On Wed, Nov 19, 2014 at 12:13:41PM -0500, Ilia Mirkin wrote:
> Hey guys,
> 
> Just got around to looking at the Coverity email about newly
> introduced bugs, and this seems like a legit issue. Based on the
> context of the code, I'm guessing you meant to do (input_index - 16)
> << 1.

Oh my. The proposed fix looks good, mind crafting a patch?

-- 
Damien

> 
> Cheers,
> 
>   -ilia
> 
> ** CID 1251308:  Bad bit shift operation  (BAD_SHIFT)
> /src/mesa/drivers/dri/i965/gen8_sf_state.c: 99 in upload_sbe()
> 
> ________________________________________________________________________________________________________
> *** CID 1251308:  Bad bit shift operation  (BAD_SHIFT)
> /src/mesa/drivers/dri/i965/gen8_sf_state.c: 99 in upload_sbe()
> 93              if (!(brw->fragment_program->Base.InputsRead &
> BITFIELD64_BIT(attr)))
> 94                 continue;
> 95
> 96              if (input_index < 16)
> 97                 dw4 |= (GEN9_SBE_ACTIVE_COMPONENT_XYZW <<
> (input_index << 1));
> 98              else
> >>>     CID 1251308:  Bad bit shift operation  (BAD_SHIFT)
> >>>     In expression "3 << (input_index << 1)", left shifting by more than 31 bits has undefined behavior.  The shift amount, "input_index << 1", is 32.
> 99                 dw5 |= (GEN9_SBE_ACTIVE_COMPONENT_XYZW <<
> (input_index << 1));
> 100
> 101              ++input_index;
> 102           }
> 103        }
> 104        BEGIN_BATCH(sbe_cmd_length);