radeonsi: add support for gl_PrimitiveID in the fragment shader

It must be obtained from the VS.

The GS scenario A must be enabled for PrimID to be generated for the VS.

+ 4 piglits

Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>

src/gallium/drivers/radeonsi/si_shader.c

@@ -73,6 +73,7 @@ struct si_shader_context
 	int param_streamout_offset[4];
 	int param_vertex_id;
 	int param_rel_auto_id;
+	int param_vs_prim_id;
 	int param_instance_id;
 	int param_tes_u;
 	int param_tes_v;
@@ -486,6 +487,9 @@ static LLVMValueRef get_primitive_id(struct lp_build_tgsi_context *bld_base,
 		return bld_base->uint_bld.zero;
 
 	switch (si_shader_ctx->type) {
+	case TGSI_PROCESSOR_VERTEX:
+		return LLVMGetParam(si_shader_ctx->radeon_bld.main_fn,
+				    si_shader_ctx->param_vs_prim_id);
 	case TGSI_PROCESSOR_TESS_CTRL:
 		return LLVMGetParam(si_shader_ctx->radeon_bld.main_fn,
 				    SI_PARAM_PATCH_ID);
@@ -2027,7 +2031,7 @@ static void si_llvm_emit_vs_epilogue(struct lp_build_tgsi_context * bld_base)
 	struct si_shader_output_values *outputs = NULL;
 	int i,j;
 
-	outputs = MALLOC(info->num_outputs * sizeof(outputs[0]));
+	outputs = MALLOC((info->num_outputs + 1) * sizeof(outputs[0]));
 
 	for (i = 0; i < info->num_outputs; i++) {
 		outputs[i].name = info->output_semantic_name[i];
@@ -2040,7 +2044,19 @@ static void si_llvm_emit_vs_epilogue(struct lp_build_tgsi_context * bld_base)
 					      "");
 	}
 
-	si_llvm_export_vs(bld_base, outputs, info->num_outputs);
+	/* Export PrimitiveID when PS needs it. */
+	if (si_vs_exports_prim_id(si_shader_ctx->shader)) {
+		outputs[i].name = TGSI_SEMANTIC_PRIMID;
+		outputs[i].sid = 0;
+		outputs[i].values[0] = bitcast(bld_base, TGSI_TYPE_FLOAT,
+					       get_primitive_id(bld_base, 0));
+		outputs[i].values[1] = bld_base->base.undef;
+		outputs[i].values[2] = bld_base->base.undef;
+		outputs[i].values[3] = bld_base->base.undef;
+		i++;
+	}
+
+	si_llvm_export_vs(bld_base, outputs, i);
 	FREE(outputs);
 }
 
@@ -3415,7 +3431,7 @@ static void create_function(struct si_shader_context *si_shader_ctx)
 		/* VGPRs */
 		params[si_shader_ctx->param_vertex_id = num_params++] = i32;
 		params[si_shader_ctx->param_rel_auto_id = num_params++] = i32;
-		params[num_params++] = i32; /* unused */
+		params[si_shader_ctx->param_vs_prim_id = num_params++] = i32;
 		params[si_shader_ctx->param_instance_id = num_params++] = i32;
 		break;
 

src/gallium/drivers/radeonsi/si_shader.h

@@ -221,6 +221,7 @@ union si_shader_key {
 		uint64_t	es_enabled_outputs;
 		unsigned	as_es:1; /* export shader */
 		unsigned	as_ls:1; /* local shader */
+		unsigned	export_prim_id; /* when PS needs it and GS is disabled */
 	} vs;
 	struct {
 		unsigned	prim_mode:3;
@@ -231,6 +232,7 @@ union si_shader_key {
 		 * This describes how outputs are laid out in memory. */
 		uint64_t	es_enabled_outputs;
 		unsigned	as_es:1; /* export shader */
+		unsigned	export_prim_id; /* when PS needs it and GS is disabled */
 	} tes; /* tessellation evaluation shader */
 };
 
@@ -289,6 +291,16 @@ static inline struct si_shader* si_get_vs_state(struct si_context *sctx)
 		return sctx->vs_shader->current;
 }
 
+static inline bool si_vs_exports_prim_id(struct si_shader *shader)
+{
+	if (shader->selector->type == PIPE_SHADER_VERTEX)
+		return shader->key.vs.export_prim_id;
+	else if (shader->selector->type == PIPE_SHADER_TESS_EVAL)
+		return shader->key.tes.export_prim_id;
+	else
+		return false;
+}
+
 /* radeonsi_shader.c */
 int si_shader_create(struct si_screen *sscreen, LLVMTargetMachineRef tm,
 		     struct si_shader *shader);

src/gallium/drivers/radeonsi/si_state.c

@@ -3136,7 +3136,6 @@ static void si_init_config(struct si_context *sctx)
 	si_pm4_set_reg(pm4, R_028A58_VGT_ES_PER_GS, 0x40);
 	si_pm4_set_reg(pm4, R_028A5C_VGT_GS_PER_VS, 0x2);
 
-	si_pm4_set_reg(pm4, R_028A84_VGT_PRIMITIVEID_EN, 0x0);
 	si_pm4_set_reg(pm4, R_028A8C_VGT_PRIMITIVEID_RESET, 0x0);
 	si_pm4_set_reg(pm4, R_028AB8_VGT_VTX_CNT_EN, 0);
 	si_pm4_set_reg(pm4, R_028B28_VGT_STRMOUT_DRAW_OPAQUE_OFFSET, 0);

src/gallium/drivers/radeonsi/si_state_shaders.c

@@ -308,6 +308,7 @@ static void si_shader_vs(struct si_shader *shader)
 	uint64_t va;
 	unsigned window_space =
 	   shader->selector->info.properties[TGSI_PROPERTY_VS_WINDOW_SPACE_POSITION];
+	bool enable_prim_id = si_vs_exports_prim_id(shader);
 
 	pm4 = shader->pm4 = CALLOC_STRUCT(si_pm4_state);
 
@@ -317,8 +318,12 @@ static void si_shader_vs(struct si_shader *shader)
 	/* If this is the GS copy shader, the GS state writes this register.
 	 * Otherwise, the VS state writes it.
 	 */
-	if (!shader->is_gs_copy_shader)
+	if (!shader->is_gs_copy_shader) {
-		si_pm4_set_reg(pm4, R_028A40_VGT_GS_MODE, 0);
+		si_pm4_set_reg(pm4, R_028A40_VGT_GS_MODE,
+			       S_028A40_MODE(enable_prim_id ? V_028A40_GS_SCENARIO_A : 0));
+		si_pm4_set_reg(pm4, R_028A84_VGT_PRIMITIVEID_EN, enable_prim_id);
+	} else
+		si_pm4_set_reg(pm4, R_028A84_VGT_PRIMITIVEID_EN, 0);
 
 	va = shader->bo->gpu_address;
 	si_pm4_add_bo(pm4, shader->bo, RADEON_USAGE_READ, RADEON_PRIO_SHADER_DATA);
@@ -327,7 +332,7 @@ static void si_shader_vs(struct si_shader *shader)
 		vgpr_comp_cnt = 0; /* only VertexID is needed for GS-COPY. */
 		num_user_sgprs = SI_GSCOPY_NUM_USER_SGPR;
 	} else if (shader->selector->type == PIPE_SHADER_VERTEX) {
-		vgpr_comp_cnt = shader->uses_instanceid ? 3 : 0;
+		vgpr_comp_cnt = shader->uses_instanceid ? 3 : (enable_prim_id ? 2 : 0);
 		num_user_sgprs = SI_VS_NUM_USER_SGPR;
 	} else if (shader->selector->type == PIPE_SHADER_TESS_EVAL) {
 		vgpr_comp_cnt = 3; /* all components are needed for TES */
@@ -534,6 +539,10 @@ static inline void si_shader_selector_key(struct pipe_context *ctx,
 			key->vs.as_es = 1;
 			key->vs.es_enabled_outputs = sctx->gs_shader->inputs_read;
 		}
+
+		if (!sctx->gs_shader && sctx->ps_shader &&
+		    sctx->ps_shader->info.uses_primid)
+			key->vs.export_prim_id = 1;
 		break;
 	case PIPE_SHADER_TESS_CTRL:
 		key->tcs.prim_mode =
@@ -543,7 +552,8 @@ static inline void si_shader_selector_key(struct pipe_context *ctx,
 		if (sctx->gs_shader) {
 			key->tes.as_es = 1;
 			key->tes.es_enabled_outputs = sctx->gs_shader->inputs_read;
-		}
+		} else if (sctx->ps_shader && sctx->ps_shader->info.uses_primid)
+			key->tes.export_prim_id = 1;
 		break;
 	case PIPE_SHADER_GEOMETRY:
 		break;
@@ -977,7 +987,10 @@ bcolor:
 			}
 		}
 
-		if (j == vsinfo->num_outputs && !G_028644_PT_SPRITE_TEX(tmp)) {
+		if (name == TGSI_SEMANTIC_PRIMID)
+			/* PrimID is written after the last output. */
+			tmp |= S_028644_OFFSET(vs->vs_output_param_offset[vsinfo->num_outputs]);
+		else if (j == vsinfo->num_outputs && !G_028644_PT_SPRITE_TEX(tmp)) {
 			/* No corresponding output found, load defaults into input.
 			 * Don't set any other bits.
 			 * (FLAT_SHADE=1 completely changes behavior) */