iris: Skip allocating a null surface when there are 0 color regions.

The compiler now sets the "Null Render Target" bit in the RT write
extended message descriptor, causing it to write to an implicit null
surface without us needing to set one up in the binding table.

Together with the last 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 <caio.oliveira@intel.com>
This commit is contained in:
Kenneth Graunke 2019-08-27 11:32:24 -07:00
parent f76a724e06
commit f8c44e4ed7
2 changed files with 9 additions and 2 deletions

View file

@ -1522,8 +1522,15 @@ iris_compile_fs(struct iris_context *ice,
*/ */
brw_nir_lower_fs_outputs(nir); brw_nir_lower_fs_outputs(nir);
/* On Gen11+, shader RT write messages have a "Null Render Target" bit
* and do not need a binding table entry with a null surface. Earlier
* generations need an entry for a null surface.
*/
int null_rts = devinfo->gen < 11 ? 1 : 0;
struct iris_binding_table bt; struct iris_binding_table bt;
iris_setup_binding_table(devinfo, nir, &bt, MAX2(key->nr_color_regions, 1), iris_setup_binding_table(devinfo, nir, &bt,
MAX2(key->nr_color_regions, null_rts),
num_system_values, num_cbufs); num_system_values, num_cbufs);
brw_nir_analyze_ubo_ranges(compiler, nir, NULL, prog_data->ubo_ranges); brw_nir_analyze_ubo_ranges(compiler, nir, NULL, prog_data->ubo_ranges);

View file

@ -4337,7 +4337,7 @@ iris_populate_binding_table(struct iris_context *ice,
} }
push_bt_entry(addr); push_bt_entry(addr);
} }
} else { } else if (GEN_GEN < 11) {
uint32_t addr = use_null_fb_surface(batch, ice); uint32_t addr = use_null_fb_surface(batch, ice);
push_bt_entry(addr); push_bt_entry(addr);
} }