From 284d9549123d7a5417310d359c2c46a4317e47bb Mon Sep 17 00:00:00 2001 From: Marek Olšák Date: Wed, 12 Jun 2013 02:18:09 +0200 Subject: glsl/linker: link shaders in the opposite order (from fragment to vertex) This ensures that inter-shader outputs and inputs are properly eliminated across 3 or more shader stages. The behavior is unchanged with 2 or less shader stages. For example, elimination of unused FS inputs causes elimination of matching GS outputs, which causes elimination of the GS inputs that were needed for evaluation of the eliminated GS outputs, which causes elimination of matching VS outputs. An unused FS input is all that's needed to trigger this chain reaction. Reviewed-by: Ian Romanick --- src/glsl/linker.cpp | 108 ++++++++++++++++++++++++++++------------------------ 1 file changed, 58 insertions(+), 50 deletions(-) diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp index 61405ea71b8..3adcddd16b6 100644 --- a/src/glsl/linker.cpp +++ b/src/glsl/linker.cpp @@ -1836,9 +1836,9 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog) goto done; } - unsigned prev; - for (prev = 0; prev < MESA_SHADER_TYPES; prev++) { - if (prog->_LinkedShaders[prev] != NULL) + unsigned first; + for (first = 0; first < MESA_SHADER_TYPES; first++) { + if (prog->_LinkedShaders[first] != NULL) break; } @@ -1850,7 +1850,7 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog) * non-zero, but the program object has no vertex or geometry * shader; */ - if (prev >= MESA_SHADER_FRAGMENT) { + if (first >= MESA_SHADER_FRAGMENT) { linker_error(prog, "Transform feedback varyings specified, but " "no vertex or geometry shader is present."); goto done; @@ -1864,69 +1864,77 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog) goto done; } - for (unsigned i = prev + 1; i < MESA_SHADER_TYPES; i++) { - if (prog->_LinkedShaders[i] == NULL) - continue; - - if (!assign_varying_locations( - ctx, mem_ctx, prog, prog->_LinkedShaders[prev], prog->_LinkedShaders[i], - i == MESA_SHADER_FRAGMENT ? num_tfeedback_decls : 0, - tfeedback_decls)) - goto done; - - prev = i; + /* Linking the stages in the opposite order (from fragment to vertex) + * ensures that inter-shader outputs written to in an earlier stage are + * eliminated if they are (transitively) not used in a later stage. + */ + int last, next; + for (last = MESA_SHADER_TYPES-1; last >= 0; last--) { + if (prog->_LinkedShaders[last] != NULL) + break; } - if (prev != MESA_SHADER_FRAGMENT && num_tfeedback_decls != 0) { - /* There was no fragment shader, but we still have to assign varying - * locations for use by transform feedback. - */ - if (!assign_varying_locations( - ctx, mem_ctx, prog, prog->_LinkedShaders[prev], NULL, num_tfeedback_decls, - tfeedback_decls)) - goto done; - } + if (last >= 0 && last < MESA_SHADER_FRAGMENT) { + gl_shader *const sh = prog->_LinkedShaders[last]; - if (!store_tfeedback_info(ctx, prog, num_tfeedback_decls, tfeedback_decls)) - goto done; + if (num_tfeedback_decls != 0) { + /* There was no fragment shader, but we still have to assign varying + * locations for use by transform feedback. + */ + if (!assign_varying_locations(ctx, mem_ctx, prog, + sh, NULL, + num_tfeedback_decls, tfeedback_decls)) + goto done; + } - if (prog->_LinkedShaders[MESA_SHADER_VERTEX] != NULL) { - demote_shader_inputs_and_outputs(prog->_LinkedShaders[MESA_SHADER_VERTEX], - ir_var_shader_out); + demote_shader_inputs_and_outputs(sh, ir_var_shader_out); - /* Eliminate code that is now dead due to unused vertex outputs being - * demoted. + /* Eliminate code that is now dead due to unused outputs being demoted. */ - while (do_dead_code(prog->_LinkedShaders[MESA_SHADER_VERTEX]->ir, false)) - ; + while (do_dead_code(sh->ir, false)) + ; } - - if (prog->_LinkedShaders[MESA_SHADER_GEOMETRY] != NULL) { - gl_shader *const sh = prog->_LinkedShaders[MESA_SHADER_GEOMETRY]; + else if (first == MESA_SHADER_FRAGMENT) { + /* If the program only contains a fragment shader, just demote + * user-defined varyings. + */ + gl_shader *const sh = prog->_LinkedShaders[first]; demote_shader_inputs_and_outputs(sh, ir_var_shader_in); - demote_shader_inputs_and_outputs(sh, ir_var_shader_out); - /* Eliminate code that is now dead due to unused geometry outputs being - * demoted. - */ - while (do_dead_code(prog->_LinkedShaders[MESA_SHADER_GEOMETRY]->ir, false)) - ; + while (do_dead_code(sh->ir, false)) + ; } - if (prog->_LinkedShaders[MESA_SHADER_FRAGMENT] != NULL) { - gl_shader *const sh = prog->_LinkedShaders[MESA_SHADER_FRAGMENT]; + next = last; + for (int i = next - 1; i >= 0; i--) { + if (prog->_LinkedShaders[i] == NULL) + continue; - demote_shader_inputs_and_outputs(sh, ir_var_shader_in); + gl_shader *const sh_i = prog->_LinkedShaders[i]; + gl_shader *const sh_next = prog->_LinkedShaders[next]; - /* Eliminate code that is now dead due to unused fragment inputs being - * demoted. This shouldn't actually do anything other than remove - * declarations of the (now unused) global variables. + if (!assign_varying_locations(ctx, mem_ctx, prog, sh_i, sh_next, + next == MESA_SHADER_FRAGMENT ? num_tfeedback_decls : 0, + tfeedback_decls)) + goto done; + + demote_shader_inputs_and_outputs(sh_i, ir_var_shader_out); + demote_shader_inputs_and_outputs(sh_next, ir_var_shader_in); + + /* Eliminate code that is now dead due to unused outputs being demoted. */ - while (do_dead_code(prog->_LinkedShaders[MESA_SHADER_FRAGMENT]->ir, false)) - ; + while (do_dead_code(sh_i->ir, false)) + ; + while (do_dead_code(sh_next->ir, false)) + ; + + next = i; } + if (!store_tfeedback_info(ctx, prog, num_tfeedback_decls, tfeedback_decls)) + goto done; + update_array_sizes(prog); link_assign_uniform_locations(prog); store_fragdepth_layout(prog); -- cgit v1.2.3