/* * Copyright © 2010 Intel Corporation * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice (including the next * paragraph) shall be included in all copies or substantial portions of the * Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER * DEALINGS IN THE SOFTWARE. */ /** * \file opt_dead_code.cpp * * Eliminates dead assignments and variable declarations from the code. */ #include "ir.h" #include "ir_visitor.h" #include "ir_variable_refcount.h" #include "compiler/glsl_types.h" #include "util/hash_table.h" static bool debug = false; /** * Do a dead code pass over instructions and everything that instructions * references. * * Note that this will remove assignments to globals, so it is not suitable * for usage on an unlinked instruction stream. */ bool do_dead_code(exec_list *instructions, bool uniform_locations_assigned) { ir_variable_refcount_visitor v; bool progress = false; v.run(instructions); struct hash_entry *e; hash_table_foreach(v.ht, e) { ir_variable_refcount_entry *entry = (ir_variable_refcount_entry *)e->data; /* Since each assignment is a reference, the refereneced count must be * greater than or equal to the assignment count. If they are equal, * then all of the references are assignments, and the variable is * dead. * * Note that if the variable is neither assigned nor referenced, both * counts will be zero and will be caught by the equality test. */ assert(entry->referenced_count >= entry->assigned_count); if (debug) { printf("%s@%p: %d refs, %d assigns, %sdeclared in our scope\n", entry->var->name, (void *) entry->var, entry->referenced_count, entry->assigned_count, entry->declaration ? "" : "not "); } if ((entry->referenced_count > entry->assigned_count) || !entry->declaration) continue; /* Section 7.4.1 (Shader Interface Matching) of the OpenGL 4.5 * (Core Profile) spec says: * * "With separable program objects, interfaces between shader * stages may involve the outputs from one program object and the * inputs from a second program object. For such interfaces, it is * not possible to detect mismatches at link time, because the * programs are linked separately. When each such program is * linked, all inputs or outputs interfacing with another program * stage are treated as active." */ if (entry->var->data.always_active_io) continue; if (!entry->assign_list.is_empty()) { /* Remove all the dead assignments to the variable we found. * Don't do so if it's a shader or function output, though. */ if (entry->var->data.mode != ir_var_function_out && entry->var->data.mode != ir_var_function_inout && entry->var->data.mode != ir_var_shader_out && entry->var->data.mode != ir_var_shader_storage) { while (!entry->assign_list.is_empty()) { struct assignment_entry *assignment_entry = exec_node_data(struct assignment_entry, entry->assign_list.head, link); assignment_entry->assign->remove(); if (debug) { printf("Removed assignment to %s@%p\n", entry->var->name, (void *) entry->var); } assignment_entry->link.remove(); free(assignment_entry); } progress = true; } } if (entry->assign_list.is_empty()) { /* If there are no assignments or references to the variable left, * then we can remove its declaration. */ /* uniform initializers are precious, and could get used by another * stage. Also, once uniform locations have been assigned, the * declaration cannot be deleted. */ if (entry->var->data.mode == ir_var_uniform || entry->var->data.mode == ir_var_shader_storage) { if (uniform_locations_assigned || entry->var->constant_initializer) continue; /* Section 2.11.6 (Uniform Variables) of the OpenGL ES 3.0.3 spec * says: * * "All members of a named uniform block declared with a * shared or std140 layout qualifier are considered active, * even if they are not referenced in any shader in the * program. The uniform block itself is also considered * active, even if no member of the block is referenced." * * If the variable is in a uniform block with one of those * layouts, do not eliminate it. */ if (entry->var->is_in_buffer_block()) { if (entry->var->get_interface_type_packing() != GLSL_INTERFACE_PACKING_PACKED) continue; } if (entry->var->type->is_subroutine()) continue; } entry->var->remove(); progress = true; if (debug) { printf("Removed declaration of %s@%p\n", entry->var->name, (void *) entry->var); } } } return progress; } /** * Does a dead code pass on the functions present in the instruction stream. * * This is suitable for use while the program is not linked, as it will * ignore variable declarations (and the assignments to them) for variables * with global scope. */ bool do_dead_code_unlinked(exec_list *instructions) { bool progress = false; foreach_in_list(ir_instruction, ir, instructions) { ir_function *f = ir->as_function(); if (f) { foreach_in_list(ir_function_signature, sig, &f->signatures) { /* The setting of the uniform_locations_assigned flag here is * irrelevent. If there is a uniform declaration encountered * inside the body of the function, something has already gone * terribly, terribly wrong. */ if (do_dead_code(&sig->body, false)) progress = true; } } } return progress; }