From 960d722bf7db636863a05ddf9258236fccb58ecd Mon Sep 17 00:00:00 2001 From: Ian Romanick Date: Fri, 21 Oct 2011 11:21:02 -0700 Subject: [PATCH] linker: Eliminate more dead code after demoting shader inputs and outputs MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Consider the following vertex shader and fragment shader: // vertex shader varying vec4 v; uniform vec4 u; void main() { gl_Position = vec4(0.0); v = u; } // fragment shader void main() { gl_FragColor = vec4(0.0); } Since the fragment shader does not use 'v', it is demoted from a varying to a simple global variable. Once that happens, the assignment to 'v' is useless, and it should be removed. In addition, 'u' is no longer active, and it should also be removed. Performing extra dead code elimination after demoting shader inputs and outputs takes care of this. This elimination must occur before assigning uniform locations, or the declaration of 'u' cannot be removed. This change *breaks* the piglit test getuniform-01, but that test is already incorrect. The test uses a vertex shader that assigns to a user-defined varying, but it has no fragment shader. Since Mesa does not support ARB_separate_shader_objects (we only support the EXT version), the linker correctly eliminates the user-defined varying. The cascading effect is that the uniform queried by the C code of the test is also (correctly) eliminated. Signed-off-by: Ian Romanick Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=41980 Tested-by: Brian Paul Cc: Bryan Cain Cc: Vinson Lee Cc: José Fonseca Reviewed-by: Kenneth Graunke Reviewed-by: Yuanhan Liu --- src/glsl/linker.cpp | 26 ++++++++++++++++++++++---- 1 file changed, 22 insertions(+), 4 deletions(-) diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp index d4d2496..beadec6 100644 --- a/src/glsl/linker.cpp +++ b/src/glsl/linker.cpp @@ -1746,10 +1746,6 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog) ; } - update_array_sizes(prog); - - assign_uniform_locations(prog); - /* FINISHME: The value of the max_attribute_index parameter is * FINISHME: implementation dependent based on the value of * FINISHME: GL_MAX_VERTEX_ATTRIBS. GL_MAX_VERTEX_ATTRIBS must be @@ -1785,6 +1781,12 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog) if (prog->_LinkedShaders[MESA_SHADER_VERTEX] != NULL) { demote_shader_inputs_and_outputs(prog->_LinkedShaders[MESA_SHADER_VERTEX], ir_var_out); + + /* Eliminate code that is now dead due to unused vertex outputs being + * demoted. + */ + while (do_dead_code(prog->_LinkedShaders[MESA_SHADER_VERTEX]->ir, false)) + ; } if (prog->_LinkedShaders[MESA_SHADER_GEOMETRY] != NULL) { @@ -1793,14 +1795,30 @@ link_shaders(struct gl_context *ctx, struct gl_shader_program *prog) demote_shader_inputs_and_outputs(sh, ir_var_in); demote_shader_inputs_and_outputs(sh, ir_var_inout); demote_shader_inputs_and_outputs(sh, ir_var_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)) + ; } if (prog->_LinkedShaders[MESA_SHADER_FRAGMENT] != NULL) { gl_shader *const sh = prog->_LinkedShaders[MESA_SHADER_FRAGMENT]; demote_shader_inputs_and_outputs(sh, ir_var_in); + + /* 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. + */ + while (do_dead_code(prog->_LinkedShaders[MESA_SHADER_FRAGMENT]->ir, false)) + ; } + update_array_sizes(prog); + assign_uniform_locations(prog); + /* OpenGL ES requires that a vertex shader and a fragment shader both be * present in a linked program. By checking for use of shading language * version 1.00, we also catch the GL_ARB_ES2_compatibility case. -- 2.7.4