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Diffstat (limited to 'src/glsl/opt_dead_code.cpp')
| -rw-r--r-- | src/glsl/opt_dead_code.cpp | 142 |
1 files changed, 142 insertions, 0 deletions
diff --git a/src/glsl/opt_dead_code.cpp b/src/glsl/opt_dead_code.cpp new file mode 100644 index 00000000000..cb500d2d105 --- /dev/null +++ b/src/glsl/opt_dead_code.cpp @@ -0,0 +1,142 @@ +/* + * 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 "glsl_types.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) +{ + ir_variable_refcount_visitor v; + bool progress = false; + + v.run(instructions); + + foreach_iter(exec_list_iterator, iter, v.variable_list) { + variable_entry *entry = (variable_entry *)iter.get(); + + /* 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; + + if (entry->assign) { + /* Remove a single dead assignment to the variable we found. + * Don't do so if it's a shader output, though. + */ + if (entry->var->mode != ir_var_out && + entry->var->mode != ir_var_inout && + !ir_has_call(entry->assign)) { + entry->assign->remove(); + progress = true; + + if (debug) { + printf("Removed assignment to %s@%p\n", + entry->var->name, (void *) entry->var); + } + } + } else { + /* 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. + */ + if (entry->var->mode == ir_var_uniform && + entry->var->constant_value) + 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_iter(exec_list_iterator, iter, *instructions) { + ir_instruction *ir = (ir_instruction *)iter.get(); + ir_function *f = ir->as_function(); + if (f) { + foreach_iter(exec_list_iterator, sigiter, *f) { + ir_function_signature *sig = + (ir_function_signature *) sigiter.get(); + if (do_dead_code(&sig->body)) + progress = true; + } + } + } + + return progress; +} |