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/*
* Copyright © 2016 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 propagate_invariance.cpp
* Propagate the "invariant" and "precise" qualifiers to variables used to
* compute invariant or precise values.
*
* The GLSL spec (depending on what version you read) says, among the
* conditions for getting bit-for-bit the same values on an invariant output:
*
* "All operations in the consuming expressions and any intermediate
* expressions must be the same, with the same order of operands and same
* associativity, to give the same order of evaluation."
*
* This effectively means that if a variable is used to compute an invariant
* value then that variable becomes invariant. The same should apply to the
* "precise" qualifier.
*/
#include "ir.h"
#include "ir_visitor.h"
#include "ir_rvalue_visitor.h"
#include "ir_optimization.h"
#include "compiler/glsl_types.h"
namespace {
class ir_invariance_propagation_visitor : public ir_hierarchical_visitor {
public:
ir_invariance_propagation_visitor()
{
this->progress = false;
this->dst_var = NULL;
}
virtual ~ir_invariance_propagation_visitor()
{
/* empty */
}
virtual ir_visitor_status visit_enter(ir_assignment *ir);
virtual ir_visitor_status visit_leave(ir_assignment *ir);
virtual ir_visitor_status visit(ir_dereference_variable *ir);
ir_variable *dst_var;
bool progress;
};
} /* unnamed namespace */
ir_visitor_status
ir_invariance_propagation_visitor::visit_enter(ir_assignment *ir)
{
assert(this->dst_var == NULL);
ir_variable *var = ir->lhs->variable_referenced();
if (var->data.invariant || var->data.precise) {
this->dst_var = var;
return visit_continue;
} else {
return visit_continue_with_parent;
}
}
ir_visitor_status
ir_invariance_propagation_visitor::visit_leave(ir_assignment *ir)
{
this->dst_var = NULL;
return visit_continue;
}
ir_visitor_status
ir_invariance_propagation_visitor::visit(ir_dereference_variable *ir)
{
if (this->dst_var == NULL)
return visit_continue;
if (this->dst_var->data.invariant) {
if (!ir->var->data.invariant)
this->progress = true;
ir->var->data.invariant = true;
}
if (this->dst_var->data.precise) {
if (!ir->var->data.precise)
this->progress = true;
ir->var->data.precise = true;
}
return visit_continue;
}
void
propagate_invariance(exec_list *instructions)
{
ir_invariance_propagation_visitor visitor;
do {
visitor.progress = false;
visit_list_elements(&visitor, instructions);
} while (visitor.progress);
}
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