[Mesa-dev] [PATCH 4/6] i965/fs: Implement SIMD16 integer multiplies on Gen 7.

[Ian Romanick]

On 09/28/2014 01:26 PM, Matt Turner wrote:
> ---
>  src/mesa/drivers/dri/i965/brw_fs_visitor.cpp | 22 ++++++++++++++++------
>  1 file changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> index e1f5735..e6c34fa 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
> @@ -634,14 +634,24 @@ fs_visitor::visit(ir_expression *ir)
>              else
>                 emit(MUL(this->result, op[0], op[1]));
>           } else {
> -            if (brw->gen >= 7)
> -               no16("SIMD16 explicit accumulator operands unsupported\n");
> -
>              struct brw_reg acc = retype(brw_acc_reg(), this->result.type);
>  
> -            emit(MUL(acc, op[0], op[1]));
> -            emit(MACH(reg_null_d, op[0], op[1]));
> -            emit(MOV(this->result, fs_reg(acc)));
> +            fs_inst *mul = emit(MUL(acc, op[0], op[1]));
> +            fs_inst *mach = emit(MACH(reg_null_d, op[0], op[1]));
> +            fs_inst *mov = emit(MOV(this->result, fs_reg(acc)));
> +
> +            if (brw->gen == 7 && dispatch_width == 16) {
> +               mul->force_uncompressed = true;
> +               mach->force_uncompressed = true;
> +               mov->force_uncompressed = true;
> +
> +               mul = emit(MUL(acc, half(op[0], 1), half(op[1], 1)));
> +               mul->force_sechalf = true;
> +               mach = emit(MACH(reg_null_d, half(op[0], 1), half(op[1], 1)));
> +               mach->force_sechalf = true;
> +               mov = emit(MOV(half(this->result, 1), fs_reg(acc)));
> +               mov->force_sechalf = true;
> +            }

Are there a bunch of cases where we double emit things for SIMD16?
Would it make more sense to have a generic function that took a list of
instructions, duplicated them, and did the force_uncompressed /
force_sechalf modification?

>           }
>        } else {
>  	 emit(MUL(this->result, op[0], op[1]));
>