irextbb2.c 5.2 KB
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/*
 * Project:     libFIRM
 * File name:   ir/ana/irextbb2.c
 * Purpose:     Alternate extended basic block computation
 * Author:      Matthias Braun
 * Created:     5.2005
 * CVS-ID:      $Id$
 * Copyright:   (c) 2002-2005 Universitt Karlsruhe
 * Licence:     This file protected by GPL -  GNU GENERAL PUBLIC LICENSE.
 */

/**
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 * @file irextbb2.c
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 *
 *  Alternative algorithm for computing extended basic blocks (using out edges
 *  and execution frequencies)
 *
 *  @author Matthias Braun
 */
#include "irextbb_t.h"
#include "irgwalk.h"
#include "irnode_t.h"
#include "irgraph_t.h"
#include "iredges_t.h"
#include "irouts.h"
#include "xmalloc.h"
#include "irprintf.h"
#include "execfreq.h"

typedef struct _env {
  	struct obstack *obst;   /**< the obstack where allocations took place */
	ir_extblk *head;        /**< head of the list of all extended blocks */
	exec_freq_t *execfreqs;
} env_t;

/**
 * allocate a new extended block header.
 */
static ir_extblk *allocate_extblk(ir_node *block, env_t *env)
{
	ir_extblk *extblk = obstack_alloc(env->obst, sizeof(*extblk));

	extblk->kind    = k_ir_extblk;
	extblk->visited = 1;
	extblk->blks    = (ir_node **)env->head;
	extblk->link    = block;
	env->head       = extblk;

	set_Block_extbb(block, extblk);
	set_irn_link(block, NULL);

	return extblk;
}

/**
 * add a block to an extended block
 */
static void addto_extblk(ir_extblk *extblk, ir_node *block)
{
	/* link all blocks belonging to this extended block */
	set_irn_link(block, extblk->link);

	extblk->link = block;
	extblk->visited++;

	set_Block_extbb(block, extblk);
}

/**
 * Returns the number of block successors.
 * we are interested only in 1, 2 and >2.
 */
static int get_block_n_succs(ir_node *block) {
	if (edges_activated(current_ir_graph)) {
		const ir_edge_t *edge;

		edge = get_block_succ_first(block);
		if (! edge)
			return 0;
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		edge = get_block_succ_next(block, edge);
		if (! edge)
			return 1;
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		edge = get_block_succ_next(block, edge);
		return edge ? 3 : 2;
	}

	return get_Block_n_cfg_outs(block);
}

static void pick_successor(ir_node *block, ir_extblk *extblk, env_t *env);

static void create_extblk(ir_node *block, env_t *env)
{
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	ir_extblk *extblk;

	if (irn_visited(block))
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		return;

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	extblk = allocate_extblk(block, env);
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	mark_irn_visited(block);

	pick_successor(block, extblk, env);
}

static void pick_successor(ir_node *block, ir_extblk *extblk, env_t *env)
{
	const ir_edge_t *edge;
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	ir_node         *best_succ    = NULL;
	double          best_execfreq = -1;

 	/*
		More than two successors means we have a jump table.
		we cannot include a jump target into the current extended
		basic block, so create a new one here.
	*/
	if (get_block_n_succs(block) > 2) {
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		const ir_edge_t *edge;

		foreach_block_succ(block, edge) {
			ir_node *succ = get_edge_src_irn(edge);
			create_extblk(succ, env);
		}

		return;
	}

	foreach_block_succ(block, edge) {
		ir_node *succ = get_edge_src_irn(edge);
		double execfreq;

		if(get_Block_n_cfgpreds(succ) > 1) {
			create_extblk(succ, env);
			continue;
		}

		execfreq = get_block_execfreq(env->execfreqs, succ);

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		/*
			Remember best successor and make non best successor with only 1
			pred block to new extbb leaders.
		*/
		if (execfreq > best_execfreq) {
			if (best_succ != NULL) {
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				create_extblk(best_succ, env);
			}

			best_execfreq = execfreq;
			best_succ = succ;
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		}
		else {
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			create_extblk(succ, env);
		}
	}

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	/* add best successor and recursively try to pick more */
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	if(best_succ != NULL) {
		addto_extblk(extblk, best_succ);
		mark_irn_visited(best_succ);
		pick_successor(best_succ, extblk, env);
	}
}

/*
 * Compute the extended basic blocks for a graph
 */
void compute_extbb_execfreqs(ir_graph *irg, exec_freq_t *execfreqs) {
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  	env_t     env;
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	ir_extblk *extbb, *next;
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	ir_node   *endblock;
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	if (irg->extbb_obst) {
		obstack_free(irg->extbb_obst, NULL);
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	}
	else {
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		irg->extbb_obst = xmalloc(sizeof(*irg->extbb_obst));
	}
	obstack_init(irg->extbb_obst);

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	env.obst      = irg->extbb_obst;
	env.head      = NULL;
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	env.execfreqs = execfreqs;

	assure_irg_outs(irg);

	/* we must mark nodes, so increase the visited flag */
	inc_irg_visited(irg);
	create_extblk(get_irg_start_block(irg), &env);

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	/* the end block needs a extbb assigned (even for endless loops) */
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	endblock = get_irg_end_block(irg);
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	if (! irn_visited(endblock)) {
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		create_extblk(endblock, &env);
	}

	/*
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		Ok, we have now the list of all extended blocks starting with env.head
		every extended block "knowns" the number of blocks in visited and
		the blocks are linked in link.
		Now we can create arrays that hold the blocks, some kind of "out" edges
		for the extended block
	*/
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	for (extbb = env.head; extbb; extbb = next) {
		int i, len = (int)extbb->visited;
		ir_node *block;

		next = (ir_extblk *)extbb->blks;

		extbb->blks = NEW_ARR_D(ir_node *, env.obst, len);

		for (block = extbb->link, i = 0; i < len; ++i) {
			ir_node *nblock = get_irn_link(block);

			/* ensure that the leader is the first one */
			extbb->blks[len - 1 - i] = block;
			set_irn_link(block, NULL);
			block = nblock;
		}

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#if 0
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		for(i = 0; i < len; ++i) {
			if(i > 0)
				printf(", ");
			ir_printf("%+F", extbb->blks[i]);
		}
		printf("\n");
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#endif
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		extbb->link    = NULL;
		extbb->visited = 0;
	}

	irg->extblk_state = extblk_valid;
}