forked from KolibriOS/kolibrios
247 lines
6.9 KiB
C++
247 lines
6.9 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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#include <limits.h>
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#include "main/compiler.h"
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#include "glsl_types.h"
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#include "loop_analysis.h"
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#include "ir_hierarchical_visitor.h"
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/**
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* Find an initializer of a variable outside a loop
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*
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* Works backwards from the loop to find the pre-loop value of the variable.
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* This is used, for example, to find the initial value of loop induction
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* variables.
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*
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* \param loop Loop where \c var is an induction variable
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* \param var Variable whose initializer is to be found
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*
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* \return
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* The \c ir_rvalue assigned to the variable outside the loop. May return
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* \c NULL if no initializer can be found.
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*/
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ir_rvalue *
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find_initial_value(ir_loop *loop, ir_variable *var)
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{
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for (exec_node *node = loop->prev;
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!node->is_head_sentinel();
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node = node->prev) {
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ir_instruction *ir = (ir_instruction *) node;
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switch (ir->ir_type) {
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case ir_type_call:
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case ir_type_loop:
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case ir_type_loop_jump:
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case ir_type_return:
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case ir_type_if:
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return NULL;
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case ir_type_function:
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case ir_type_function_signature:
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assert(!"Should not get here.");
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return NULL;
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case ir_type_assignment: {
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ir_assignment *assign = ir->as_assignment();
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ir_variable *assignee = assign->lhs->whole_variable_referenced();
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if (assignee == var)
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return (assign->condition != NULL) ? NULL : assign->rhs;
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break;
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}
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default:
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break;
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}
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}
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return NULL;
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}
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int
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calculate_iterations(ir_rvalue *from, ir_rvalue *to, ir_rvalue *increment,
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enum ir_expression_operation op)
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{
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if (from == NULL || to == NULL || increment == NULL)
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return -1;
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void *mem_ctx = ralloc_context(NULL);
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ir_expression *const sub =
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new(mem_ctx) ir_expression(ir_binop_sub, from->type, to, from);
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ir_expression *const div =
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new(mem_ctx) ir_expression(ir_binop_div, sub->type, sub, increment);
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ir_constant *iter = div->constant_expression_value();
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if (iter == NULL)
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return -1;
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if (!iter->type->is_integer()) {
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const ir_expression_operation op = iter->type->is_double()
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? ir_unop_d2i : ir_unop_f2i;
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ir_rvalue *cast =
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new(mem_ctx) ir_expression(op, glsl_type::int_type, iter, NULL);
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iter = cast->constant_expression_value();
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}
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int iter_value = iter->get_int_component(0);
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/* Make sure that the calculated number of iterations satisfies the exit
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* condition. This is needed to catch off-by-one errors and some types of
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* ill-formed loops. For example, we need to detect that the following
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* loop does not have a maximum iteration count.
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*
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* for (float x = 0.0; x != 0.9; x += 0.2)
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* ;
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*/
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const int bias[] = { -1, 0, 1 };
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bool valid_loop = false;
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for (unsigned i = 0; i < ARRAY_SIZE(bias); i++) {
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/* Increment may be of type int, uint or float. */
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switch (increment->type->base_type) {
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case GLSL_TYPE_INT:
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iter = new(mem_ctx) ir_constant(iter_value + bias[i]);
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break;
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case GLSL_TYPE_UINT:
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iter = new(mem_ctx) ir_constant(unsigned(iter_value + bias[i]));
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break;
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case GLSL_TYPE_FLOAT:
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iter = new(mem_ctx) ir_constant(float(iter_value + bias[i]));
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break;
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case GLSL_TYPE_DOUBLE:
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iter = new(mem_ctx) ir_constant(double(iter_value + bias[i]));
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break;
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default:
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unreachable("Unsupported type for loop iterator.");
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}
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ir_expression *const mul =
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new(mem_ctx) ir_expression(ir_binop_mul, increment->type, iter,
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increment);
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ir_expression *const add =
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new(mem_ctx) ir_expression(ir_binop_add, mul->type, mul, from);
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ir_expression *const cmp =
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new(mem_ctx) ir_expression(op, glsl_type::bool_type, add, to);
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ir_constant *const cmp_result = cmp->constant_expression_value();
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assert(cmp_result != NULL);
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if (cmp_result->get_bool_component(0)) {
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iter_value += bias[i];
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valid_loop = true;
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break;
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}
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}
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ralloc_free(mem_ctx);
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return (valid_loop) ? iter_value : -1;
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}
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namespace {
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class loop_control_visitor : public ir_hierarchical_visitor {
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public:
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loop_control_visitor(loop_state *state)
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{
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this->state = state;
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this->progress = false;
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}
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virtual ir_visitor_status visit_leave(ir_loop *ir);
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loop_state *state;
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bool progress;
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};
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} /* anonymous namespace */
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ir_visitor_status
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loop_control_visitor::visit_leave(ir_loop *ir)
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{
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loop_variable_state *const ls = this->state->get(ir);
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/* If we've entered a loop that hasn't been analyzed, something really,
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* really bad has happened.
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*/
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if (ls == NULL) {
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assert(ls != NULL);
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return visit_continue;
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}
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if (ls->limiting_terminator != NULL) {
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/* If the limiting terminator has an iteration count of zero, then we've
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* proven that the loop cannot run, so delete it.
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*/
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int iterations = ls->limiting_terminator->iterations;
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if (iterations == 0) {
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ir->remove();
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this->progress = true;
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return visit_continue;
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}
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}
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/* Remove the conditional break statements associated with all terminators
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* that are associated with a fixed iteration count, except for the one
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* associated with the limiting terminator--that one needs to stay, since
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* it terminates the loop. Exception: if the loop still has a normative
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* bound, then that terminates the loop, so we don't even need the limiting
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* terminator.
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*/
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foreach_in_list(loop_terminator, t, &ls->terminators) {
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if (t->iterations < 0)
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continue;
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if (t != ls->limiting_terminator) {
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t->ir->remove();
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assert(ls->num_loop_jumps > 0);
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ls->num_loop_jumps--;
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this->progress = true;
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}
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}
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return visit_continue;
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}
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bool
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set_loop_controls(exec_list *instructions, loop_state *ls)
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{
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loop_control_visitor v(ls);
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v.run(instructions);
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return v.progress;
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}
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