radv: implement RB+ depth-only rendering for better perf

For RB+ depth-only, the following registers must be configured like:

 - CB_COLOR_CONTROL.MODE = CB_DISABLE
 - CB_COLOR0_INFO.FORMAT = COLOR_32
 - CB_COLOR0_INFO.NUMBER_TYPE = NUMBER_FLOAT
 - SPI_SHADER_COL_FORMAT.COL0_EXPORT_FORMAT = SPI_SHADER_32_R
 - SX_PS_DOWNCONVERT.MRT0 = SX_RT_EXPORT_32_R

This might increase performance for depth-only rendering passes on
GFX9+.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28590>
This commit is contained in:
Samuel Pitoiset 2025-07-02 11:26:07 +02:00 committed by Marge Bot
parent 26d98d283b
commit 4580293ab2

View file

@ -1967,6 +1967,12 @@ radv_emit_rbplus_state(struct radv_cmd_buffer *cmd_buffer)
}
}
/* If there are no color outputs, the first color export is always enabled as 32_R, so also set
* this to enable RB+.
*/
if (!sx_ps_downconvert)
sx_ps_downconvert = V_028754_SX_RT_EXPORT_32_R;
/* Do not set the DISABLE bits for the unused attachments, as that
* breaks dual source blending in SkQP and does not seem to improve
* performance. */
@ -4637,6 +4643,23 @@ radv_emit_framebuffer_state(struct radv_cmd_buffer *cmd_buffer)
radv_load_color_clear_metadata(cmd_buffer, iview, i);
}
/* When there are no color outputs, always set the first color output as 32_R for RB+ depth-only. */
if (pdev->info.rbplus_allowed && render->color_att_count == 0) {
radeon_begin(cmd_buffer->cs);
if (pdev->info.gfx_level >= GFX12) {
radeon_set_context_reg(R_028EC0_CB_COLOR0_INFO + i * 4,
S_028EC0_FORMAT(V_028EC0_COLOR_32) | S_028EC0_NUMBER_TYPE(V_028C70_NUMBER_FLOAT));
} else {
const uint32_t cb_color0_info = (pdev->info.gfx_level >= GFX11 ? S_028C70_FORMAT_GFX11(V_028C70_COLOR_32)
: S_028C70_FORMAT_GFX6(V_028C70_COLOR_32)) |
S_028C70_NUMBER_TYPE(V_028C70_NUMBER_FLOAT);
radeon_set_context_reg(R_028C70_CB_COLOR0_INFO + i * 0x3C, cb_color0_info);
}
radeon_end();
++i;
}
for (; i < cmd_buffer->state.last_subpass_color_count; i++) {
radeon_begin(cs);
if (pdev->info.gfx_level >= GFX12) {
@ -7574,6 +7597,37 @@ radv_bind_shader(struct radv_cmd_buffer *cmd_buffer, struct radv_shader *shader,
radv_cs_add_buffer(device->ws, cs->b, shader->bo);
}
static bool
radv_can_enable_rbplus_depth_only(const struct radv_cmd_buffer *cmd_buffer, const struct radv_shader *ps,
uint32_t col_format, uint32_t custom_blend_mode)
{
const struct radv_device *device = radv_cmd_buffer_device(cmd_buffer);
const struct radv_physical_device *pdev = radv_device_physical(device);
if (!pdev->info.rbplus_allowed)
return false;
/* Enable RB+ for depth-only rendering. Registers must be programmed as follows:
* CB_COLOR_CONTROL.MODE = CB_DISABLE
* CB_COLOR0_INFO.FORMAT = COLOR_32
* CB_COLOR0_INFO.NUMBER_TYPE = NUMBER_FLOAT
* SPI_SHADER_COL_FORMAT.COL0_EXPORT_FORMAT = SPI_SHADER_32_R
* SX_PS_DOWNCONVERT.MRT0 = SX_RT_EXPORT_32_R
*
* col_format == 0 implies no color outputs written and no alpha to coverage.
*/
/* Do not enable for secondaries because it depends on states that we might not know. */
if (cmd_buffer->vk.level == VK_COMMAND_BUFFER_LEVEL_SECONDARY)
return false;
/* Do not enable for internal operations which program CB_MODE differently. */
if (custom_blend_mode)
return false;
return !col_format && (!ps || !ps->info.ps.writes_memory);
}
static void
radv_bind_fragment_output_state(struct radv_cmd_buffer *cmd_buffer, const struct radv_shader *ps,
const struct radv_shader_part *ps_epilog, uint32_t custom_blend_mode)
@ -7596,7 +7650,10 @@ radv_bind_fragment_output_state(struct radv_cmd_buffer *cmd_buffer, const struct
cb_shader_mask = 0xf;
}
if (radv_needs_null_export_workaround(device, ps, custom_blend_mode) && !col_format)
const bool rbplus_depth_only_enabled =
radv_can_enable_rbplus_depth_only(cmd_buffer, ps, col_format, custom_blend_mode);
if ((radv_needs_null_export_workaround(device, ps, custom_blend_mode) && !col_format) || rbplus_depth_only_enabled)
col_format = V_028714_SPI_SHADER_32_R;
if (cmd_buffer->state.spi_shader_col_format != col_format) {