/*
* Copyright © 2012 Vincent Lejeune
* Copyright © 2012 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.
*/
#include "ir.h"
#include "program/hash_table.h"
/**
* \file lower_output_reads.cpp
*
* In GLSL, shader output variables (such as varyings) can be both read and
* written. However, on some hardware, reading an output register causes
* trouble.
*
* This pass creates temporary shadow copies of every (used) shader output,
* and replaces all accesses to use those instead. It also adds code to the
* main() function to copy the final values to the actual shader outputs.
*/
class output_read_remover : public ir_hierarchical_visitor {
protected:
/**
* A hash table mapping from the original ir_variable shader outputs
* (ir_var_shader_out mode) to the new temporaries to be used instead.
*/
hash_table *replacements;
void *mem_ctx;
public:
output_read_remover();
~output_read_remover();
virtual ir_visitor_status visit(class ir_dereference_variable *);
virtual ir_visitor_status visit_leave(class ir_return *);
virtual ir_visitor_status visit_leave(class ir_function_signature *);
};
/**
* Hash function for the output variables - computes the hash of the name.
* NOTE: We're using the name string to ensure that the hash doesn't depend
* on any random factors, otherwise the output_read_remover could produce
* the random order of the assignments.
*
* NOTE: If you want to reuse this function please take into account that
* generally the names of the variables are non-unique.
*/
static unsigned
hash_table_var_hash(const void *key)
{
const ir_variable * var = static_cast<const ir_variable *>(key);
return hash_table_string_hash(var->name);
}
output_read_remover::output_read_remover()
{
mem_ctx = ralloc_context(NULL);
replacements =
hash_table_ctor(0, hash_table_var_hash, hash_table_pointer_compare);
}
output_read_remover::~output_read_remover()
{
hash_table_dtor(replacements);
ralloc_free(mem_ctx);
}
ir_visitor_status
output_read_remover::visit(ir_dereference_variable *ir)
{
if (ir->var->mode != ir_var_shader_out)
return visit_continue;
ir_variable *temp = (ir_variable *) hash_table_find(replacements, ir->var);
/* If we don't have an existing temporary, create one. */
if (temp == NULL) {
void *var_ctx = ralloc_parent(ir->var);
temp = new(var_ctx) ir_variable(ir->var->type, ir->var->name,
ir_var_temporary);
hash_table_insert(replacements, temp, ir->var);
ir->var->insert_after(temp);
}
/* Update the dereference to use the temporary */
ir->var = temp;
return visit_continue;
}
/**
* Create an assignment to copy a temporary value back to the actual output.
*/
static ir_assignment *
copy(void *ctx, ir_variable *output, ir_variable *temp)
{
ir_dereference_variable *lhs = new(ctx) ir_dereference_variable(output);
ir_dereference_variable *rhs = new(ctx) ir_dereference_variable(temp);
return new(ctx) ir_assignment(lhs, rhs);
}
/** Insert a copy-back assignment before a "return" statement */
static void
emit_return_copy(const void *key, void *data, void *closure)
{
ir_return *ir = (ir_return *) closure;
ir->insert_before(copy(ir, (ir_variable *) key, (ir_variable *) data));
}
/** Insert a copy-back assignment at the end of the main() function */
static void
emit_main_copy(const void *key, void *data, void *closure)
{
ir_function_signature *sig = (ir_function_signature *) closure;
sig->body.push_tail(copy(sig, (ir_variable *) key, (ir_variable *) data));
}
ir_visitor_status
output_read_remover::visit_leave(ir_return *ir)
{
hash_table_call_foreach(replacements, emit_return_copy, ir);
return visit_continue;
}
ir_visitor_status
output_read_remover::visit_leave(ir_function_signature *sig)
{
if (strcmp(sig->function_name(), "main") != 0)
return visit_continue;
hash_table_call_foreach(replacements, emit_main_copy, sig);
return visit_continue;
}
void
lower_output_reads(exec_list *instructions)
{
output_read_remover v;
visit_list_elements(&v, instructions);
}