| /* |
| * 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_print_visitor.h" |
| #include "ir_basic_block.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; |
| }; |
| |
| class kill_for_derefs_visitor : public ir_hierarchical_visitor { |
| public: |
| kill_for_derefs_visitor(exec_list *assignments) |
| { |
| this->assignments = assignments; |
| } |
| |
| virtual ir_visitor_status visit(ir_dereference_variable *ir) |
| { |
| ir_variable *const var = ir->variable_referenced(); |
| |
| foreach_iter(exec_list_iterator, iter, *this->assignments) { |
| assignment_entry *entry = (assignment_entry *)iter.get(); |
| |
| if (entry->lhs == var) { |
| if (debug) |
| printf("kill %s\n", entry->lhs->name); |
| entry->remove(); |
| } |
| } |
| |
| return visit_continue; |
| } |
| |
| private: |
| exec_list *assignments; |
| }; |
| |
| class array_index_visit : public ir_hierarchical_visitor { |
| public: |
| array_index_visit(ir_hierarchical_visitor *v) |
| { |
| this->visitor = v; |
| } |
| |
| virtual ir_visitor_status visit_enter(class ir_dereference_array *ir) |
| { |
| ir->array_index->accept(visitor); |
| return visit_continue; |
| } |
| |
| static void run(ir_instruction *ir, ir_hierarchical_visitor *v) |
| { |
| array_index_visit top_visit(v); |
| ir->accept(& top_visit); |
| } |
| |
| ir_hierarchical_visitor *visitor; |
| }; |
| |
| |
| /** |
| * 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; |
| kill_for_derefs_visitor v(assignments); |
| |
| /* Kill assignment entries for things used to produce this assignment. */ |
| ir->rhs->accept(&v); |
| if (ir->condition) { |
| ir->condition->accept(&v); |
| } |
| |
| /* Kill assignment enties used as array indices. |
| */ |
| array_index_visit::run(ir->lhs, &v); |
| var = ir->lhs->variable_referenced(); |
| 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. */ |
| if (always_assign && (ir->lhs->whole_variable_referenced() != NULL)) { |
| /* 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_visitor kill(&assignments); |
| ir->accept(&kill); |
| } |
| |
| 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; |
| } |