/**
* mds — A micro-display server
* Copyright © 2014 Mattias Andrée (maandree@member.fsf.org)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "eliminate-dead-code.h"
#include "include-stack.h"
#include <stdlib.h>
#include <errno.h>
/**
* Tree type constant shortener
*/
#define C(TYPE) MDS_KBDC_TREE_TYPE_##TYPE
/**
* Add an error with “included from here”-notes to the error list
*
* @param NODE:const mds_kbdc_tree_t* The node the triggered the error
* @param PTR:size_t The number of “included from here”-notes
* @param SEVERITY:identifier * in `MDS_KBDC_PARSE_ERROR_*` to indicate severity
* @param ...:const char*, ... Error description format string and arguments
* @scope error:mds_kbdc_parse_error_t* Variable where the new error will be stored
*/
#define NEW_ERROR(NODE, PTR, SEVERITY, ...) \
NEW_ERROR_WITH_INCLUDES(NODE, PTR, SEVERITY, __VA_ARGS__)
/**
* Variable whether the latest created error is stored
*/
static mds_kbdc_parse_error_t* error;
/**
* The parameter of `eliminate_dead_code`
*/
static mds_kbdc_parsed_t* restrict result;
/**
* 2: Eliminating because of a return-statement
* 1: Eliminating because of a break- or continue-statement
* 0: Not eliminating
*/
static int elimination_level = 0;
/**
* Eliminate dead code in a subtree
*
* @param tree The tree to reduce
* @return Zero on success, -1 on error
*/
static int eliminate_subtree(mds_kbdc_tree_t* restrict tree);
/**
* Eliminate dead code in an include-statement
*
* @param tree The tree to reduce
* @return Zero on success, -1 on error
*/
static int eliminate_include(mds_kbdc_tree_include_t* restrict tree)
{
void* data;
int r;
if (mds_kbdc_include_stack_push(tree, &data))
return -1;
r = eliminate_subtree(tree->inner);
mds_kbdc_include_stack_pop(data);
return r;
}
/**
* Eliminate dead code in an if-statement
*
* @param tree The tree to reduce
* @return Zero on success, -1 on error
*/
static int eliminate_if(mds_kbdc_tree_if_t* restrict tree)
{
int elimination;
fail_if (eliminate_subtree(tree->inner));
elimination = elimination_level, elimination_level = 0;
fail_if (eliminate_subtree(tree->otherwise));
if (elimination > elimination_level)
elimination = elimination_level;
return 0;
pfail:
return -1;
}
/**
* Eliminate dead code in a subtree
*
* @param tree The tree to reduce
* @return Zero on success, -1 on error
*/
static int eliminate_subtree(mds_kbdc_tree_t* restrict tree)
{
#define e(type) if ((r = eliminate_##type(&(tree->type)))) return r
#define E(type) if ((r = eliminate_##type(&(tree->type##_)))) return r
int r;
again:
if (tree == NULL)
return 0;
switch (tree->type)
{
case C(INCLUDE): e(include); break;
case C(IF): E(if); break;
case C(INFORMATION):
case C(FUNCTION):
case C(MACRO):
case C(ASSUMPTION):
case C(FOR):
if ((r = eliminate_subtree(tree->information.inner)))
return r;
if ((tree->type == C(FUNCTION)) || (tree->type == C(MACRO))) elimination_level = 0;
else if ((tree->type == C(FOR)) && (elimination_level == 1)) elimination_level = 0;
break;
case C(RETURN):
case C(BREAK):
case C(CONTINUE):
elimination_level = tree->type == C(RETURN) ? 2 : 1;
break;
default:
break;
}
if (tree->next && elimination_level)
{
NEW_ERROR(tree->next, includes_ptr, WARNING, "statement is unreachable");
mds_kbdc_tree_free(tree->next), tree->next = NULL;
}
tree = tree->next;
goto again;
pfail:
return -1;
#undef E
#undef e
}
/**
* Eliminate and warn about dead code
*
* @param result_ `result` from `validate_tree`, will be updated
* @return -1 if an error occursed that cannot be stored in `result`, zero otherwise
*/
int eliminate_dead_code(mds_kbdc_parsed_t* restrict result_)
{
int r;
mds_kbdc_include_stack_begin(result = result_);
r = eliminate_subtree(result_->tree);
return mds_kbdc_include_stack_end(), r;
}
#undef NEW_ERROR
#undef C
