freedreno/ir3: support load_base_instance

Not supported by hardware, uses same mechanism as base vertex.

Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3162>

src/freedreno/ir3/ir3_compiler_nir.c

@@ -1671,6 +1671,12 @@ emit_intrinsic(struct ir3_context *ctx, nir_intrinsic_instr *intr)
 		}
 		dst[0] = ctx->basevertex;
 		break;
+	case nir_intrinsic_load_base_instance:
+		if (!ctx->base_instance) {
+			ctx->base_instance = create_driver_param(ctx, IR3_DP_INSTID_BASE);
+		}
+		dst[0] = ctx->base_instance;
+		break;
 	case nir_intrinsic_load_vertex_id_zero_base:
 	case nir_intrinsic_load_vertex_id:
 		if (!ctx->vertex_id) {

src/freedreno/ir3/ir3_context.h

@@ -83,7 +83,7 @@ struct ir3_context {
 	struct ir3_instruction *frag_face, *frag_coord;
 
 	/* For vertex shaders, keep track of the system values sources */
-	struct ir3_instruction *vertex_id, *basevertex, *instance_id;
+	struct ir3_instruction *vertex_id, *basevertex, *instance_id, *base_instance;
 
 	/* For fragment shaders: */
 	struct ir3_instruction *samp_id, *samp_mask_in;

src/freedreno/ir3/ir3_nir.c

@@ -415,6 +415,10 @@ ir3_nir_scan_driver_consts(nir_shader *shader,
 					layout->num_driver_params =
 						MAX2(layout->num_driver_params, IR3_DP_VTXID_BASE + 1);
 					break;
+				case nir_intrinsic_load_base_instance:
+					layout->num_driver_params =
+						MAX2(layout->num_driver_params, IR3_DP_INSTID_BASE + 1);
+					break;
 				case nir_intrinsic_load_user_clip_plane:
 					layout->num_driver_params =
 						MAX2(layout->num_driver_params, IR3_DP_UCP7_W + 1);

src/freedreno/ir3/ir3_shader.h

@@ -57,6 +57,7 @@ enum ir3_driver_param {
 	/* vertex shader driver params: */
 	IR3_DP_VTXID_BASE = 0,
 	IR3_DP_VTXCNT_MAX = 1,
+	IR3_DP_INSTID_BASE = 2,
 	/* user-clip-plane components, up to 8x vec4's: */
 	IR3_DP_UCP0_X     = 4,
 	/* .... */