alternative algo for computing extbbs

[r8173]

ir/ana/irextbb2.c

+/*
+ * Project:     libFIRM
+ * File name:   ir/ana/irextbb2.c
+ * Purpose:     Alternate extended basic block computation
+ * Author:      Matthias Braun
+ * Modified by:
+ * Created:     5.2005
+ * CVS-ID:      $Id$
+ * Copyright:   (c) 2002-2005 Universitt Karlsruhe
+ * Licence:     This file protected by GPL -  GNU GENERAL PUBLIC LICENSE.
+ */
+
+/**
+ * @file irextbb.c
+ *
+ *  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;
+		edge = get_block_succ_next(block, edge);
+		if (! edge)
+			return 1;
+		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)
+{
+	if(irn_visited(block))
+		return;
+
+	ir_extblk *extblk = allocate_extblk(block, env);
+	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;
+	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) {
+		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);
+
+		// remember best sucessor and make non best successor with only 1
+		// pred block to new extbb leaders
+		if(execfreq > best_execfreq) {
+			if(best_succ != NULL) {
+				create_extblk(best_succ, env);
+			}
+
+			best_execfreq = execfreq;
+			best_succ = succ;
+		} else {
+			create_extblk(succ, env);
+		}
+	}
+
+	// add best successor and recursively try to pick more
+	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) {
+  	env_t env;
+	ir_extblk *extbb, *next;
+	ir_node *endblock;
+
+	if (irg->extbb_obst) {
+		obstack_free(irg->extbb_obst, NULL);
+	} else {
+		irg->extbb_obst = xmalloc(sizeof(*irg->extbb_obst));
+	}
+	obstack_init(irg->extbb_obst);
+
+	env.obst = irg->extbb_obst;
+	env.head = NULL;
+	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);
+
+	// the end block needs a extbb assigned (even for endless loops)
+	endblock = get_irg_end_block(irg);
+	if(!irn_visited(endblock)) {
+		create_extblk(endblock, &env);
+	}
+
+	/*
+	 * 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
+	 */
+	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;
+		}
+
+		for(i = 0; i < len; ++i) {
+			if(i > 0)
+				printf(", ");
+			ir_printf("%+F", extbb->blks[i]);
+		}
+		printf("\n");
+
+		extbb->link    = NULL;
+		extbb->visited = 0;
+	}
+
+	irg->extblk_state = extblk_valid;
+}