mirror of https://gitlab.freedesktop.org/mesa/mesa
226 lines
5.9 KiB
C++
226 lines
5.9 KiB
C++
/*
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* Copyright © 2010 Intel Corporation
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*/
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/**
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* \file ir_dead_code_local.cpp
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*
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* Eliminates local dead assignments from the code.
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*
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* This operates on basic blocks, tracking assignments and finding if
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* they're used before the variable is completely reassigned.
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*
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* Compare this to ir_dead_code.cpp, which operates globally looking
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* for assignments to variables that are never read.
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*/
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#include <stdio.h>
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#include "ir.h"
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#include "ir_print_visitor.h"
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#include "ir_basic_block.h"
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#include "ir_optimization.h"
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#include "glsl_types.h"
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static bool debug = false;
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class assignment_entry : public exec_node
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{
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public:
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assignment_entry(ir_variable *lhs, ir_instruction *ir)
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{
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assert(lhs);
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assert(ir);
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this->lhs = lhs;
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this->ir = ir;
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}
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ir_variable *lhs;
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ir_instruction *ir;
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};
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class kill_for_derefs_visitor : public ir_hierarchical_visitor {
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public:
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kill_for_derefs_visitor(exec_list *assignments)
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{
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this->assignments = assignments;
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}
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virtual ir_visitor_status visit(ir_dereference_variable *ir)
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{
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ir_variable *const var = ir->variable_referenced();
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foreach_iter(exec_list_iterator, iter, *this->assignments) {
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assignment_entry *entry = (assignment_entry *)iter.get();
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if (entry->lhs == var) {
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if (debug)
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printf("kill %s\n", entry->lhs->name);
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entry->remove();
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}
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}
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return visit_continue;
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}
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private:
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exec_list *assignments;
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};
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class array_index_visit : public ir_hierarchical_visitor {
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public:
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array_index_visit(ir_hierarchical_visitor *v)
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{
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this->visitor = v;
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}
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virtual ir_visitor_status visit_enter(class ir_dereference_array *ir)
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{
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ir->array_index->accept(visitor);
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return visit_continue;
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}
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static void run(ir_instruction *ir, ir_hierarchical_visitor *v)
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{
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array_index_visit top_visit(v);
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ir->accept(& top_visit);
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}
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ir_hierarchical_visitor *visitor;
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};
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/**
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* Adds an entry to the available copy list if it's a plain assignment
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* of a variable to a variable.
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*/
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static bool
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process_assignment(ir_assignment *ir, exec_list *assignments)
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{
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ir_variable *var = NULL;
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bool progress = false;
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kill_for_derefs_visitor v(assignments);
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/* Kill assignment entries for things used to produce this assignment. */
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ir->rhs->accept(&v);
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if (ir->condition) {
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ir->condition->accept(&v);
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}
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/* Kill assignment enties used as array indices.
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*/
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array_index_visit::run(ir->lhs, &v);
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var = ir->lhs->variable_referenced();
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assert(var);
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bool always_assign = true;
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if (ir->condition) {
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ir_constant *condition = ir->condition->as_constant();
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if (!condition || !condition->value.b[0])
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always_assign = false;
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}
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/* Now, check if we did a whole-variable assignment. */
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if (always_assign && (ir->lhs->whole_variable_referenced() != NULL)) {
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/* We did a whole-variable assignment. So, any instruction in
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* the assignment list with the same LHS is dead.
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*/
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if (debug)
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printf("looking for %s to remove\n", var->name);
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foreach_iter(exec_list_iterator, iter, *assignments) {
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assignment_entry *entry = (assignment_entry *)iter.get();
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if (entry->lhs == var) {
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if (debug)
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printf("removing %s\n", var->name);
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entry->ir->remove();
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entry->remove();
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progress = true;
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}
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}
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}
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/* Add this instruction to the assignment list. */
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assignment_entry *entry = new assignment_entry(var, ir);
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assignments->push_tail(entry);
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if (debug) {
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printf("add %s\n", var->name);
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printf("current entries\n");
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foreach_iter(exec_list_iterator, iter, *assignments) {
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assignment_entry *entry = (assignment_entry *)iter.get();
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printf(" %s\n", entry->lhs->name);
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}
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}
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return progress;
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}
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static void
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dead_code_local_basic_block(ir_instruction *first,
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ir_instruction *last,
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void *data)
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{
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ir_instruction *ir, *ir_next;
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/* List of avaialble_copy */
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exec_list assignments;
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bool *out_progress = (bool *)data;
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bool progress = false;
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/* Safe looping, since process_assignment */
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for (ir = first, ir_next = (ir_instruction *)first->next;;
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ir = ir_next, ir_next = (ir_instruction *)ir->next) {
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ir_assignment *ir_assign = ir->as_assignment();
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if (debug) {
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ir_print_visitor v;
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ir->accept(&v);
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printf("\n");
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}
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if (ir_assign) {
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progress = process_assignment(ir_assign, &assignments) || progress;
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} else {
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kill_for_derefs_visitor kill(&assignments);
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ir->accept(&kill);
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}
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if (ir == last)
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break;
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}
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*out_progress = progress;
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}
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/**
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* Does a copy propagation pass on the code present in the instruction stream.
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*/
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bool
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do_dead_code_local(exec_list *instructions)
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{
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bool progress = false;
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call_for_basic_blocks(instructions, dead_code_local_basic_block, &progress);
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return progress;
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}
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