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Diffstat (limited to 'src/compiler/glsl/opt_dead_code.cpp')
| -rw-r--r-- | src/compiler/glsl/opt_dead_code.cpp | 197 |
1 files changed, 197 insertions, 0 deletions
diff --git a/src/compiler/glsl/opt_dead_code.cpp b/src/compiler/glsl/opt_dead_code.cpp new file mode 100644 index 00000000000..dbdb7de8bb8 --- /dev/null +++ b/src/compiler/glsl/opt_dead_code.cpp @@ -0,0 +1,197 @@ +/* + * 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()->interface_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; +} |