[Mesa-dev] [PATCH v2] i965/fs: in MAD optimizations, switch last argument to be immediate

[Kenneth Graunke]

On Monday, March 16, 2015 10:08:08 AM Tapani Pälli wrote:
> Commit bb33a31 introduced optimizations that transform cases of MAD
> in to simpler forms but it did not take in to account that src[0]
> can not be immediate and did not report progress. Patch switches
> src[0] and src[1] if src[0] is immediate and adds progress
> reporting. If both sources are immediates, this is taken care of by
> the same opt_algebraic pass on later run.
> 
> v2: Fix for all cases, use temporary fs_reg (Matt, Kenneth)
> 
> Signed-off-by: Tapani Pälli <tapani.palli at intel.com>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89569
> Reviewed-by: Francisco Jerez <currojerez at riseup.net> (v1)
> ---
>  src/mesa/drivers/dri/i965/brw_fs.cpp | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
> index 8702ea8..53ceb29 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
> @@ -2491,6 +2491,7 @@ fs_visitor::opt_algebraic()
>              inst->opcode = BRW_OPCODE_MUL;
>              inst->src[0] = inst->src[2];
>              inst->src[2] = reg_undef;
> +            progress = true;

Ouch, good catch :(

>           } else if (inst->src[1].is_one()) {
>              inst->opcode = BRW_OPCODE_ADD;
>              inst->src[1] = inst->src[2];
> @@ -2521,8 +2522,16 @@ fs_visitor::opt_algebraic()
>        default:
>  	 break;
>        }
> -   }
>  
> +      /* Swap if src[0] is immediate. */
> +      if (progress && inst->is_commutative()) {
> +         if (inst->src[0].file == IMM) {
> +            fs_reg tmp = inst->src[1];
> +            inst->src[1] = inst->src[0];
> +            inst->src[0] = tmp;
> +         }
> +      }
> +   }
>     return progress;
>  }
>  
> 

Looks good to me!  Thanks!

Cc: "10.5" <mesa-stable at lists.freedesktop.org>
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
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