[Mesa-dev] [PATCH 1/4] i965: Don't emit saturates for instructions without destinations.

[Ian Romanick]

On 02/10/2015 11:09 AM, Matt Turner wrote:
> We were special casing OPCODE_END but no other instructions that have no
> destination, like OPCODE_KIL, leading us to emitting MOVs with null
> destinations.

Should we (or do we somehow already) handle instructions with null
destinations?   So...

	ADD.sat.nz	null, g38, g22

Or is that just impossible?

> total instructions in shared programs: 5950886 -> 5947182 (-0.06%)
> instructions in affected programs:     139700 -> 135996 (-2.65%)
> helped:                                904
> ---
>  src/mesa/drivers/dri/i965/brw_fs_fp.cpp   | 2 +-
>  src/mesa/drivers/dri/i965/brw_vec4_vp.cpp | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_fp.cpp b/src/mesa/drivers/dri/i965/brw_fs_fp.cpp
> index 7f2874d..dd3d331 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_fp.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_fp.cpp
> @@ -517,7 +517,7 @@ fs_visitor::emit_fragment_program_code()
>        /* To handle saturates, we emit a MOV with a saturate bit, which
>         * optimization should fold into the preceding instructions when safe.
>         */
> -      if (fpi->Opcode != OPCODE_END) {
> +      if (_mesa_num_inst_dst_regs(fpi->Opcode) != 0) {
>           fs_reg real_dst = get_fp_dst_reg(&fpi->DstReg);
>  
>           for (int i = 0; i < 4; i++) {
> diff --git a/src/mesa/drivers/dri/i965/brw_vec4_vp.cpp b/src/mesa/drivers/dri/i965/brw_vec4_vp.cpp
> index 85f2de5..434f032 100644
> --- a/src/mesa/drivers/dri/i965/brw_vec4_vp.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_vec4_vp.cpp
> @@ -387,7 +387,7 @@ vec4_vs_visitor::emit_program_code()
>        }
>  
>        /* Copy the temporary back into the actual destination register. */
> -      if (vpi->Opcode != OPCODE_END) {
> +      if (_mesa_num_inst_dst_regs(vpi->Opcode) != 0) {
>           emit(MOV(get_vp_dst_reg(vpi->DstReg), src_reg(dst)));
>        }
>     }