cdep.c 5.79 KB
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/*
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 * Copyright (C) 1995-2007 University of Karlsruhe.  All right reserved.
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 *
 * This file is part of libFirm.
 *
 * This file may be distributed and/or modified under the terms of the
 * GNU General Public License version 2 as published by the Free Software
 * Foundation and appearing in the file LICENSE.GPL included in the
 * packaging of this file.
 *
 * Licensees holding valid libFirm Professional Edition licenses may use
 * this file in accordance with the libFirm Commercial License.
 * Agreement provided with the Software.
 *
 * This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
 * WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE.
 */

/**
 * @file
 * @brief   Implementation of cdep
 * @version $Id$
 */
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#include <assert.h>
#include <stdlib.h>
#include "irdom.h"
#include "irgraph.h"
#include "irgwalk.h"
#include "irnode.h"
#include "pmap.h"
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#include "obst.h"
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#include "xmalloc.h"
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#include "cdep.h"
#include "irprintf.h"
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#include "irdump.h"

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typedef struct cdep_info {
	pmap   *cdep_map;     /**< A map to find the list of all control dependence nodes for a block. */
	struct obstack obst;  /**< An obstack where all cdep data lives on. */
} cdep_info;
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static cdep_info *cdep_data;
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/* Return a list of all control dependences of a block. */
ir_cdep *find_cdep(const ir_node *block) {
	return pmap_get(cdep_data->cdep_map, (void *)block);
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}

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/* Replace the control dependence info of old by the info of nw. */
void exchange_cdep(ir_node *old, const ir_node *nw) {
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	ir_cdep *cdep = find_cdep(nw);
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	pmap_insert(cdep_data->cdep_map, old, cdep);
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}

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/**
 * Adds a control dependence from node to dep_on.
 */
static void add_cdep(ir_node *node, ir_node *dep_on) {
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	ir_cdep *dep = find_cdep(node);
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#if 0
	ir_fprintf(stderr, "Adding cdep of %+F on %+F\n", node, dep_on);
#endif

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	if (dep == NULL) {
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		ir_cdep *newdep = obstack_alloc(&cdep_data->obst, sizeof(*newdep));
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		newdep->node = dep_on;
		newdep->next = NULL;
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		pmap_insert(cdep_data->cdep_map, node, newdep);
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	} else {
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		ir_cdep *newdep;
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		for (;;) {
			if (dep->node == dep_on) return;
			if (dep->next == NULL) break;
			dep = dep->next;
		}
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		newdep = obstack_alloc(&cdep_data->obst, sizeof(*newdep));
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		newdep->node = dep_on;
		newdep->next = NULL;
		dep->next = newdep;
	}
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}

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typedef struct cdep_env {
	ir_node *start_block;
	ir_node *end_block;
} cdep_env;
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/**
 * Pre-block-walker: calculate the control dependence
 */
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static void cdep_pre(ir_node *node, void *ctx) {
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	cdep_env *env = ctx;
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	unsigned int n;
	unsigned int i;
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	/* special case:
	 * start and end block have no control dependency
	 */
	if (node == env->start_block) return;
	if (node == env->end_block) return;

	n = get_Block_n_cfgpreds(node);
	for (i = 0; i < n; i++) {
		ir_node *pred = get_Block_cfgpred_block(node, i);
		ir_node *pdom;
		ir_node *dependee;

		if (is_Bad(pred)) continue;

		pdom = get_Block_ipostdom(pred);
		for (dependee = node; dependee != pdom; dependee = get_Block_ipostdom(dependee)) {
			assert(!is_Bad(pdom));
			add_cdep(dependee, pred);
		}
	}
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}


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/**
 * A block edge hook: add all cdep edges of block.
 */
static int cdep_edge_hook(FILE *F, ir_node *block)
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{
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	ir_cdep *cd;
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#if 0
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	ir_node *pdom = get_Block_ipostdom(block);
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	if (pdom != NULL) {
		fprintf(
			F,
			"edge:{sourcename:\"n%ld\" targetname:\"n%ld\" color:gold}\n",
			get_irn_node_nr(pdom), get_irn_node_nr(block)
		);
	}
#endif

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	for (cd = find_cdep(block); cd != NULL; cd = cd->next) {
		fprintf(
			F,
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			"edge:{sourcename:\"n%ld\" targetname:\"n%ld\" "
			"linestyle:dashed color:gold}\n",
			get_irn_node_nr(block), get_irn_node_nr(cd->node)
		);
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	}
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	return 0;
}

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/* Compute the control dependence graph for a graph. */
void compute_cdep(ir_graph *irg) {
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	ir_node *start_block, *rem;
	cdep_env env;

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	free_cdep(irg);
	cdep_data = xmalloc(sizeof(*cdep_data));
	obstack_init(&cdep_data->obst);

	cdep_data->cdep_map = pmap_create();
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	assure_postdoms(irg);
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	/* we must temporary change the post dominator relation:
	   the ipdom of the startblock is the end block.
	   Firm does NOT add the phantom edge from Start to End.
	 */
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	start_block = get_irg_start_block(irg);
	rem = get_Block_ipostdom(start_block);
	set_Block_ipostdom(start_block, get_irg_end_block(irg));
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	env.start_block = get_irg_start_block(irg);
	env.end_block   = get_irg_end_block(irg);
	irg_block_walk_graph(irg, cdep_pre, NULL, &env);

#if 0
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	set_dump_block_edge_hook(cdep_edge_hook);
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	dump_ir_block_graph(irg, "_cdep");
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	set_dump_block_edge_hook(NULL);
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#else
	(void) cdep_edge_hook;
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#endif

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	/* restore the post dominator relation */
	set_Block_ipostdom(start_block, rem);
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}

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/* Free the control dependence info. */
void free_cdep(ir_graph *irg) {
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	(void) irg;
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	if (cdep_data != NULL) {
		pmap_destroy(cdep_data->cdep_map);
		obstack_free(&cdep_data->obst, NULL);
		xfree(cdep_data);
		cdep_data = NULL;
	}
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}

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/* Check whether dependee is (directly) control dependent on candidate. */
int is_cdep_on(const ir_node *dependee, const ir_node *candidate) {
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	const ir_cdep *dep;
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	for (dep = find_cdep(dependee); dep != NULL; dep = dep->next) {
		if (dep->node == candidate) return 1;
	}
	return 0;
}

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/* Check whether dependee is (possible iterated) control dependent on candidate. */
int is_iterated_cdep_on(ir_node *dependee, ir_node *candidate) {
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	const ir_cdep *dep;
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	while ((dep = find_cdep(dependee)) != NULL) {
		if (dep->next != NULL) return 0;
		if (dep->node == candidate) return 1;
		dependee = dep->node;
	}
	return 0;
}

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/* If block is control dependent on exactly one node, return this node, else NULL. */
ir_node *get_unique_cdep(const ir_node *block) {
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	ir_cdep *cdep = find_cdep(block);
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	return cdep != NULL && cdep->next == NULL ? cdep->node : NULL;
}

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/* Check if the given block is control dependent of more than one node. */
int has_multiple_cdep(const ir_node *block) {
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	ir_cdep *cdep = find_cdep(block);
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	return cdep != NULL && cdep->next != NULL;
}