From f76a724e06842119cbcac83e9c3c938ba9022b02 Mon Sep 17 00:00:00 2001 From: Kenneth Graunke Date: Tue, 27 Aug 2019 11:22:33 -0700 Subject: [PATCH] intel/compiler: Set "Null Render Target" ex_desc bit on Gen11 When there are no color regions (i.e. a depth only pass), we can set the "Null Render Target" bit in the Gen11 RT write extended message descriptor to indicate that it should behave as if it's writing to a null render target, without the need for a binding table entry. This lets drivers avoid setting up that null RT binding table entry, but more importantly means the HW doesn't actually have to bother looking up the surface state. Together with the next patch, this improves performance in Car Chase on an Icelake 8x8 (locked to 700Mhz) by 0.0445526% +/- 0.0132736% (n=832). Reviewed-by: Caio Marcelo de Oliveira Filho --- src/intel/compiler/brw_fs.cpp | 3 +++ 1 file changed, 3 insertions(+) diff --git a/src/intel/compiler/brw_fs.cpp b/src/intel/compiler/brw_fs.cpp index 086844ae433..a677c8fd968 100644 --- a/src/intel/compiler/brw_fs.cpp +++ b/src/intel/compiler/brw_fs.cpp @@ -4494,6 +4494,9 @@ lower_fb_write_logical_send(const fs_builder &bld, fs_inst *inst, * in the extended message descriptor, in lieu of using a header. */ ex_desc = inst->target << 12 | src0_alpha_present << 15; + + if (key->nr_color_regions == 0) + ex_desc |= 1 << 20; /* Null Render Target */ } inst->opcode = SHADER_OPCODE_SEND; -- 2.30.2