[Mesa-dev] [PATCH 7/7] radeonsi: disable SPI color outputs the shader doesn't write

[Marek Olšák]

From: Marek Olšák <marek.olsak at amd.com>

---
 src/gallium/drivers/radeonsi/si_shader.h        |  4 ++++
 src/gallium/drivers/radeonsi/si_state_shaders.c | 12 ++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/src/gallium/drivers/radeonsi/si_shader.h b/src/gallium/drivers/radeonsi/si_shader.h
index f49290a..50375e2 100644
--- a/src/gallium/drivers/radeonsi/si_shader.h
+++ b/src/gallium/drivers/radeonsi/si_shader.h
@@ -213,6 +213,10 @@ struct si_shader_selector {
 
 	/* PS parameters. */
 	unsigned	db_shader_control;
+	/* Set 0xf or 0x0 (4 bits) per each written output.
+	 * ANDed with spi_shader_col_format.
+	 */
+	unsigned	colors_written_4bit;
 
 	/* masks of "get_unique_index" bits */
 	uint64_t	outputs_written;
diff --git a/src/gallium/drivers/radeonsi/si_state_shaders.c b/src/gallium/drivers/radeonsi/si_state_shaders.c
index 80126f2..9daa924 100644
--- a/src/gallium/drivers/radeonsi/si_state_shaders.c
+++ b/src/gallium/drivers/radeonsi/si_state_shaders.c
@@ -646,6 +646,12 @@ static inline void si_shader_selector_key(struct pipe_context *ctx,
 		if (sctx->b.chip_class <= CIK && sctx->b.family != CHIP_HAWAII)
 			key->ps.color_is_int8 = sctx->framebuffer.color_is_int8;
 
+		/* Disable unwritten outputs (if WRITE_ALL_CBUFS isn't enabled). */
+		if (!key->ps.last_cbuf) {
+			key->ps.spi_shader_col_format &= sel->colors_written_4bit;
+			key->ps.color_is_int8 &= sel->info.colors_written;
+		}
+
 		if (rs) {
 			bool is_poly = (sctx->current_rast_prim >= PIPE_PRIM_TRIANGLES &&
 					sctx->current_rast_prim <= PIPE_PRIM_POLYGON) ||
@@ -830,6 +836,12 @@ static void *si_create_shader_selector(struct pipe_context *ctx,
 		}
 		sel->esgs_itemsize = util_last_bit64(sel->outputs_written) * 16;
 		break;
+
+	case PIPE_SHADER_FRAGMENT:
+		for (i = 0; i < 8; i++)
+			if (sel->info.colors_written & (1 << i))
+				sel->colors_written_4bit |= 0xf << (4 * i);
+		break;
 	}
 
 	/* DB_SHADER_CONTROL */
-- 
2.1.4