[Mesa-dev] [PATCH 01/11] radeonsi/gfx9: insert the barrier between merged shaders inside the if block

[Marek Olšák]

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

---
 src/gallium/drivers/radeonsi/si_shader.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/src/gallium/drivers/radeonsi/si_shader.c b/src/gallium/drivers/radeonsi/si_shader.c
index d2b9b73e039..a0a00d722cb 100644
--- a/src/gallium/drivers/radeonsi/si_shader.c
+++ b/src/gallium/drivers/radeonsi/si_shader.c
@@ -6147,30 +6147,38 @@ static bool si_compile_tgsi_main(struct si_shader_context *ctx,
 		    (ctx->type == PIPE_SHADER_TESS_EVAL ||
 		     (ctx->type == PIPE_SHADER_VERTEX &&
 		      !si_vs_needs_prolog(sel, &shader->key.part.vs.prolog)))) {
 			si_init_exec_from_input(ctx,
 						ctx->param_merged_wave_info, 0);
 		} else if (ctx->type == PIPE_SHADER_TESS_CTRL ||
 			   ctx->type == PIPE_SHADER_GEOMETRY) {
 			if (!is_monolithic)
 				ac_init_exec_full_mask(&ctx->ac);
 
-			/* The barrier must execute for all shaders in a
-			 * threadgroup.
-			 */
-			si_llvm_emit_barrier(NULL, bld_base, NULL);
-
 			LLVMValueRef num_threads = si_unpack_param(ctx, ctx->param_merged_wave_info, 8, 8);
 			LLVMValueRef ena =
 				LLVMBuildICmp(ctx->ac.builder, LLVMIntULT,
 					    ac_get_thread_id(&ctx->ac), num_threads, "");
 			lp_build_if(&ctx->merged_wrap_if_state, &ctx->gallivm, ena);
+
+			/* The barrier must execute for all shaders in a
+			 * threadgroup.
+			 *
+			 * Execute the barrier inside the conditional block,
+			 * so that empty waves can jump directly to s_endpgm,
+			 * which will also signal the barrier.
+			 *
+			 * If the shader is TCS and the TCS epilog is present
+			 * and contains a barrier, it will wait there and then
+			 * reach s_endpgm.
+			 */
+			si_llvm_emit_barrier(NULL, bld_base, NULL);
 		}
 	}
 
 	if (ctx->type == PIPE_SHADER_TESS_CTRL &&
 	    sel->tcs_info.tessfactors_are_def_in_all_invocs) {
 		for (unsigned i = 0; i < 6; i++) {
 			ctx->invoc0_tess_factors[i] =
 				lp_build_alloca_undef(&ctx->gallivm, ctx->i32, "");
 		}
 	}
-- 
2.17.1