[Mesa-dev] [PATCH 2/2] i965: Don't add base_binding_table_index if it's zero

[Ben Widawsky]

On Fri, May 29, 2015 at 02:53:35PM +0100, Neil Roberts wrote:
> When calculating the binding table index for non-constant sampler
> array indexing it needs to add the base binding table index which is a
> constant within the generated code. Often this base is zero so we can
> avoid a redundant instruction in that case.
> 
> It looks like nothing in shader-db is doing non-constant sampler array
> indexing so this patch doesn't make any difference but it might be
> worth having anyway.
> ---
>  src/mesa/drivers/dri/i965/brw_fs_generator.cpp   | 3 ++-
>  src/mesa/drivers/dri/i965/brw_vec4_generator.cpp | 3 ++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
> index ea46b1a..40a3db3 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
> @@ -789,7 +789,8 @@ fs_generator::generate_tex(fs_inst *inst, struct brw_reg dst, struct brw_reg src
>  
>        /* addr = ((sampler * 0x101) + base_binding_table_index) & 0xfff */
>        brw_MUL(p, addr, sampler_reg, brw_imm_ud(0x101));
> -      brw_ADD(p, addr, addr, brw_imm_ud(base_binding_table_index));
> +      if (base_binding_table_index)
> +         brw_ADD(p, addr, addr, brw_imm_ud(base_binding_table_index));
>        brw_AND(p, addr, addr, brw_imm_ud(0xfff));
>  
>        brw_pop_insn_state(p);
> diff --git a/src/mesa/drivers/dri/i965/brw_vec4_generator.cpp b/src/mesa/drivers/dri/i965/brw_vec4_generator.cpp
> index 1d3f5ed..cf1aa83 100644
> --- a/src/mesa/drivers/dri/i965/brw_vec4_generator.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_vec4_generator.cpp
> @@ -409,7 +409,8 @@ vec4_generator::generate_tex(vec4_instruction *inst,
>  
>        /* addr = ((sampler * 0x101) + base_binding_table_index) & 0xfff */
>        brw_MUL(p, addr, sampler_reg, brw_imm_ud(0x101));
> -      brw_ADD(p, addr, addr, brw_imm_ud(base_binding_table_index));
> +      if (base_binding_table_index)
> +         brw_ADD(p, addr, addr, brw_imm_ud(base_binding_table_index));
>        brw_AND(p, addr, addr, brw_imm_ud(0xfff));
>  
>        brw_pop_insn_state(p);

Both are:
Acked-by: Ben Widawsky <ben at bwidawsk.net>

(More knowledgeable people have left their review already, I just want it merged
ASAP).

-- 
Ben Widawsky, Intel Open Source Technology Center