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/*
* 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 lower_discard.cpp
*
* This pass moves discards out of if-statements.
*
* Case 1: The "then" branch contains a conditional discard:
* ---------------------------------------------------------
*
* if (cond1) {
* s1;
* discard cond2;
* s2;
* } else {
* s3;
* }
*
* becomes:
*
* temp = false;
* if (cond1) {
* s1;
* temp = cond2;
* s2;
* } else {
* s3;
* }
* discard temp;
*
* Case 2: The "else" branch contains a conditional discard:
* ---------------------------------------------------------
*
* if (cond1) {
* s1;
* } else {
* s2;
* discard cond2;
* s3;
* }
*
* becomes:
*
* temp = false;
* if (cond1) {
* s1;
* } else {
* s2;
* temp = cond2;
* s3;
* }
* discard temp;
*
* Case 3: Both branches contain a conditional discard:
* ----------------------------------------------------
*
* if (cond1) {
* s1;
* discard cond2;
* s2;
* } else {
* s3;
* discard cond3;
* s4;
* }
*
* becomes:
*
* temp = false;
* if (cond1) {
* s1;
* temp = cond2;
* s2;
* } else {
* s3;
* temp = cond3;
* s4;
* }
* discard temp;
*
* If there are multiple conditional discards, we need only deal with one of
* them. Repeatedly applying this pass will take care of the others.
*
* Unconditional discards are treated as having a condition of "true".
*/
#include "compiler/glsl_types.h"
#include "ir.h"
namespace {
class lower_discard_visitor : public ir_hierarchical_visitor {
public:
lower_discard_visitor()
{
this->progress = false;
}
ir_visitor_status visit_leave(ir_if *);
bool progress;
};
} /* anonymous namespace */
bool
lower_discard(exec_list *instructions)
{
lower_discard_visitor v;
visit_list_elements(&v, instructions);
return v.progress;
}
static ir_discard *
find_discard(exec_list &instructions)
{
foreach_in_list(ir_instruction, node, &instructions) {
ir_discard *ir = node->as_discard();
if (ir != NULL)
return ir;
}
return NULL;
}
static void
replace_discard(void *mem_ctx, ir_variable *var, ir_discard *ir)
{
ir_rvalue *condition = ir->condition;
/* For unconditional discards, use "true" as the condition. */
if (condition == NULL)
condition = new(mem_ctx) ir_constant(true);
ir_assignment *assignment =
new(mem_ctx) ir_assignment(new(mem_ctx) ir_dereference_variable(var),
condition);
ir->replace_with(assignment);
}
ir_visitor_status
lower_discard_visitor::visit_leave(ir_if *ir)
{
ir_discard *then_discard = find_discard(ir->then_instructions);
ir_discard *else_discard = find_discard(ir->else_instructions);
if (then_discard == NULL && else_discard == NULL)
return visit_continue;
void *mem_ctx = ralloc_parent(ir);
ir_variable *temp = new(mem_ctx) ir_variable(glsl_type::bool_type,
"discard_cond_temp",
ir_var_temporary);
ir_assignment *temp_initializer =
new(mem_ctx) ir_assignment(new(mem_ctx) ir_dereference_variable(temp),
new(mem_ctx) ir_constant(false));
ir->insert_before(temp);
ir->insert_before(temp_initializer);
if (then_discard != NULL)
replace_discard(mem_ctx, temp, then_discard);
if (else_discard != NULL)
replace_discard(mem_ctx, temp, else_discard);
ir_discard *discard = then_discard != NULL ? then_discard : else_discard;
discard->condition = new(mem_ctx) ir_dereference_variable(temp);
ir->insert_after(discard);
this->progress = true;
return visit_continue;
}