/*
* 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 opt_dead_code.cpp
*
* Eliminates dead assignments and variable declarations from the code.
*/
#include "ir.h"
#include "ir_visitor.h"
#include "ir_variable_refcount.h"
#include "glsl_types.h"
#include "main/hash_table.h"
static bool debug = false;
/**
* Do a dead code pass over instructions and everything that instructions
* references.
*
* Note that this will remove assignments to globals, so it is not suitable
* for usage on an unlinked instruction stream.
*/
bool
do_dead_code(exec_list *instructions, bool uniform_locations_assigned)
{
ir_variable_refcount_visitor v;
bool progress = false;
v.run(instructions);
struct hash_entry *e;
hash_table_foreach(v.ht, e) {
ir_variable_refcount_entry *entry = (ir_variable_refcount_entry *)e->data;
/* Since each assignment is a reference, the refereneced count must be
* greater than or equal to the assignment count. If they are equal,
* then all of the references are assignments, and the variable is
* dead.
*
* Note that if the variable is neither assigned nor referenced, both
* counts will be zero and will be caught by the equality test.
*/
assert(entry->referenced_count >= entry->assigned_count);
if (debug) {
printf("%s@%p: %d refs, %d assigns, %sdeclared in our scope\n",
entry->var->name, (void *) entry->var,
entry->referenced_count, entry->assigned_count,
entry->declaration ? "" : "not ");
}
if ((entry->referenced_count > entry->assigned_count)
|| !entry->declaration)
continue;
if (entry->assign) {
/* Remove a single dead assignment to the variable we found.
* Don't do so if it's a shader or function output, though.
*/
if (entry->var->mode != ir_var_function_out &&
entry->var->mode != ir_var_function_inout &&
entry->var->mode != ir_var_shader_out) {
entry->assign->remove();
progress = true;
if (debug) {
printf("Removed assignment to %s@%p\n",
entry->var->name, (void *) entry->var);
}
}
} else {
/* If there are no assignments or references to the variable left,
* then we can remove its declaration.
*/
/* uniform initializers are precious, and could get used by another
* stage. Also, once uniform locations have been assigned, the
* declaration cannot be deleted.
*/
if (entry->var->mode == ir_var_uniform &&
(uniform_locations_assigned ||
entry->var->constant_value))
continue;
entry->var->remove();
progress = true;
if (debug) {
printf("Removed declaration of %s@%p\n",
entry->var->name, (void *) entry->var);
}
}
}
return progress;
}
/**
* Does a dead code pass on the functions present in the instruction stream.
*
* This is suitable for use while the program is not linked, as it will
* ignore variable declarations (and the assignments to them) for variables
* with global scope.
*/
bool
do_dead_code_unlinked(exec_list *instructions)
{
bool progress = false;
foreach_iter(exec_list_iterator, iter, *instructions) {
ir_instruction *ir = (ir_instruction *)iter.get();
ir_function *f = ir->as_function();
if (f) {
foreach_iter(exec_list_iterator, sigiter, *f) {
ir_function_signature *sig =
(ir_function_signature *) sigiter.get();
/* The setting of the uniform_locations_assigned flag here is
* irrelevent. If there is a uniform declaration encountered
* inside the body of the function, something has already gone
* terribly, terribly wrong.
*/
if (do_dead_code(&sig->body, false))
progress = true;
}
}
}
return progress;
}