diff options
Diffstat (limited to 'ir_dead_code_local.cpp')
| -rw-r--r-- | ir_dead_code_local.cpp | 222 |
1 files changed, 222 insertions, 0 deletions
diff --git a/ir_dead_code_local.cpp b/ir_dead_code_local.cpp new file mode 100644 index 00000000000..de6a4f5e5d9 --- /dev/null +++ b/ir_dead_code_local.cpp @@ -0,0 +1,222 @@ +/* + * 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 ir_dead_code_local.cpp + * + * Eliminates local dead assignments from the code. + * + * This operates on basic blocks, tracking assignments and finding if + * they're used before the variable is completely reassigned. + * + * Compare this to ir_dead_code.cpp, which operates globally looking + * for assignments to variables that are never read. + */ + +#include <stdio.h> +#include "ir.h" +#include "ir_visitor.h" +#include "ir_print_visitor.h" +#include "ir_basic_block.h" +#include "ir_visit_tree.h" +#include "ir_optimization.h" +#include "glsl_types.h" + +static bool debug = false; + +class assignment_entry : public exec_node +{ +public: + assignment_entry(ir_variable *lhs, ir_instruction *ir) + { + assert(lhs); + assert(ir); + this->lhs = lhs; + this->ir = ir; + } + + ir_variable *lhs; + ir_instruction *ir; +}; + +static void +ir_kill_for_derefs_callback(ir_instruction *ir, void *data) +{ + exec_list *assignments = (exec_list *)data; + ir_variable *var = ir->as_variable(); + + if (!var) + return; + + foreach_iter(exec_list_iterator, iter, *assignments) { + assignment_entry *entry = (assignment_entry *)iter.get(); + + if (entry->lhs == var) { + if (debug) + printf("kill %s\n", entry->lhs->name); + entry->remove(); + } + } +} + +static void +kill_for_derefs(ir_instruction *ir, exec_list *assignments) +{ + ir_visit_tree(ir, ir_kill_for_derefs_callback, assignments); +} + +/** + * Adds an entry to the available copy list if it's a plain assignment + * of a variable to a variable. + */ +static bool +process_assignment(ir_assignment *ir, exec_list *assignments) +{ + ir_variable *var = NULL; + bool progress = false; + ir_instruction *current; + + /* Kill assignment entries for things used to produce this assignment. */ + kill_for_derefs(ir->rhs, assignments); + if (ir->condition) { + kill_for_derefs(ir->condition, assignments); + } + + /* Walk down the dereference chain to find the variable at the end + * of it that we're actually modifying. Kill assignment enties used as + * array indices, too. + */ + for (current = ir->lhs; current != NULL;) { + ir_swizzle *swiz; + ir_dereference *deref; + + if ((swiz = current->as_swizzle())) { + current = swiz->val; + } else if ((deref = current->as_dereference())) { + if (deref->mode == ir_dereference::ir_reference_array) + kill_for_derefs(deref->selector.array_index, assignments); + current = deref->var; + } else { + var = current->as_variable(); + + current = NULL; + break; + } + } + + assert(var); + + bool always_assign = true; + if (ir->condition) { + ir_constant *condition = ir->condition->as_constant(); + if (!condition || !condition->value.b[0]) + always_assign = false; + } + + /* Now, check if we did a whole-variable assignment. */ + ir_dereference *lhs_deref = ir->lhs->as_dereference(); + if (always_assign && + lhs_deref && + lhs_deref->mode == ir_dereference::ir_reference_variable) { + /* We did a whole-variable assignment. So, any instruction in + * the assignment list with the same LHS is dead. + */ + if (debug) + printf("looking for %s to remove\n", var->name); + foreach_iter(exec_list_iterator, iter, *assignments) { + assignment_entry *entry = (assignment_entry *)iter.get(); + + if (entry->lhs == var) { + if (debug) + printf("removing %s\n", var->name); + entry->ir->remove(); + entry->remove(); + progress = true; + } + } + } + + /* Add this instruction to the assignment list. */ + assignment_entry *entry = new assignment_entry(var, ir); + assignments->push_tail(entry); + + if (debug) { + printf("add %s\n", var->name); + + printf("current entries\n"); + foreach_iter(exec_list_iterator, iter, *assignments) { + assignment_entry *entry = (assignment_entry *)iter.get(); + + printf(" %s\n", entry->lhs->name); + } + } + + return progress; +} + +static void +dead_code_local_basic_block(ir_instruction *first, + ir_instruction *last, + void *data) +{ + ir_instruction *ir, *ir_next; + /* List of avaialble_copy */ + exec_list assignments; + bool *out_progress = (bool *)data; + bool progress = false; + + /* Safe looping, since process_assignment */ + for (ir = first, ir_next = (ir_instruction *)first->next;; + ir = ir_next, ir_next = (ir_instruction *)ir->next) { + ir_assignment *ir_assign = ir->as_assignment(); + + if (debug) { + ir_print_visitor v; + ir->accept(&v); + printf("\n"); + } + + if (ir_assign) { + progress = process_assignment(ir_assign, &assignments) || progress; + } else { + kill_for_derefs(ir, &assignments); + } + + if (ir == last) + break; + } + *out_progress = progress; +} + +/** + * Does a copy propagation pass on the code present in the instruction stream. + */ +bool +do_dead_code_local(exec_list *instructions) +{ + bool progress = false; + + call_for_basic_blocks(instructions, dead_code_local_basic_block, &progress); + + return progress; +} |