Implemented simple switch lowering

[r20872]

include/libfirm/lowering.h

@@ -149,6 +149,15 @@ void lower_calls_with_compounds(const lower_params_t *params);
  */
 void lower_CopyB(ir_graph *irg, unsigned max_size, unsigned native_mode_bytes);
 
+/**
+ * Lowers all Switches (Cond nodes with non-boolean mode) depending on spare_size.
+ * They will either remain the same or be converted into if-cascades.
+ *
+ * @param irg        The ir graph to be lowered.
+ * @param spare_size Allowed spare size for table switches in machine words.
+ *                   (Default in edgfe: 128)
+ */
+void lower_Switch(ir_graph *irg, unsigned spare_size);
 
 /**
  * A callback type for creating an intrinsic entity for a given opcode.

ir/Makefile.am

@@ -198,6 +198,7 @@ libfirm_la_SOURCES = \
 	lower/lower_hl.c \
 	lower/lower_intrinsics.c \
 	lower/lower_mode_b.c \
+	lower/lower_switch.c \
 	net/firmnet.c \
 	obstack/obstack.c \
 	obstack/obstack_printf.c \

ir/lower/lower_switch.c

+/*
+ * Copyright (C) 1995-2008 University of Karlsruhe.  All right reserved.
+ *
+ * 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   Lowering of Switches if necessary or advantageous.
+ * @author  Moritz Kroll
+ * @version $Id$
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "ircons.h"
+#include "irgwalk.h"
+#include "irnode_t.h"
+#include "irouts.h"
+
+#define foreach_out_irn(irn, i, outirn) for(i = get_irn_n_outs(irn) - 1;\
+	i >= 0 && (outirn = get_irn_out(irn, i)); --i)
+
+typedef struct walk_env {
+	unsigned         spare_size;		/**< the allowed spare size for table switches */
+	struct obstack   obst;              /**< the obstack where data is allocated on */
+	int              changed;           /**< indicates whether a change was performed */
+} walk_env_t;
+
+typedef struct case_data {
+	long     value;
+	ir_node *target;
+} case_data_t;
+
+/**
+ * Add the new predecessor x to node node, which is either a Block or a Phi
+ */
+static void add_pred(ir_node* node, ir_node* x)
+{
+	ir_node** ins;
+	int n;
+	int i;
+
+	assert(is_Block(node) || is_Phi(node));
+
+	n = get_irn_arity(node);
+	NEW_ARR_A(ir_node*, ins, n + 1);
+	for (i = 0; i < n; i++)
+		ins[i] = get_irn_n(node, i);
+	ins[n] = x;
+	set_irn_in(node, n + 1, ins);
+}
+
+/**
+ * Remove the predecessor x from node node one time, which is either a Block or a Phi
+ */
+static void remove_pred(ir_node* node, ir_node* x)
+{
+	ir_node** ins;
+	int n;
+	int i, j;
+
+	assert(is_Block(node) || is_Phi(node));
+
+	n = get_irn_arity(node);
+	NEW_ARR_A(ir_node*, ins, n - 1);
+	for (i = 0, j = -1; i < n - 1; i++)
+	{
+		ins[++j] = get_irn_n(node, i);
+		if(ins[i] == x) j--;
+	}
+	assert(i == j + 1 && "x is not a pred of node");
+	set_irn_in(node, n - 1, ins);
+}
+
+/**
+ * Evaluate a switch and decide whether we should build a table switch.
+ *
+ * @param cond       The Cond node representing the switch.
+ * @param spare_size Allowed spare size for table switches in machine words.
+ *                   (Default in edgfe: 128)
+ */
+static int should_do_table_switch(ir_node *cond, unsigned spare_size)
+{
+	long     default_pn;
+	int      i;
+	ir_node *proj;
+	long switch_min = LONG_MAX, switch_max = LONG_MIN;
+	unsigned long spare, num_cases = 0;
+
+	/* TODO: Minimum size for jump table? */
+	if(get_irn_n_outs(cond) <= 4)
+		return;
+
+	default_pn = get_Cond_defaultProj(cond);
+
+	foreach_out_irn(cond, i, proj) {
+		long pn = get_Proj_proj(proj);
+		if(pn == default_pn)
+			continue;
+
+		if(pn < switch_min)
+			switch_min = pn;
+		if(pn > switch_max)
+			switch_max = pn;
+		num_cases++;
+	}
+
+	/*
+	 * Here we have: num_cases and [switch_min, switch_max] interval.
+	 * We do an if-cascade if there are too many spare numbers.
+	 */
+	spare = (unsigned long) switch_max - (unsigned long) switch_min - num_cases + 1;
+	return spare < spare_size;
+}
+
+static int casecmp(const void *a, const void *b)
+{
+	return ((case_data_t *) a)->value - ((case_data_t *) b)->value;
+}
+
+/**
+ * Creates an if cascade realizing binary search.
+ */
+static void create_if_cascade(ir_node *sel, ir_node *curblock, ir_node *defblock,
+							  case_data_t *curcases, int numcases)
+{
+	set_cur_block(curblock);
+
+	if(numcases == 1)
+	{
+		/* only one case: "if(sel == val) goto target else goto default;" */
+		ir_node *val  = new_Const_long(get_irn_mode(sel), curcases[0].value);
+		ir_node *cmp  = new_Cmp(sel, val);
+		ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
+		ir_node *cond = new_Cond(proj);
+		add_pred(curcases[0].target, new_Proj(cond, mode_X, pn_Cond_true));
+		add_pred(defblock,           new_Proj(cond, mode_X, pn_Cond_false));
+		return;
+	} else if(numcases == 2) {
+		/* only two cases: "if(sel == val[0]) goto target[0];" */
+		ir_node *val  = new_Const_long(get_irn_mode(sel), curcases[0].value);
+		ir_node *cmp  = new_Cmp(sel, val);
+		ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
+		ir_node *cond = new_Cond(proj);
+		ir_node *in[1];
+		ir_node *neblock;
+
+		add_pred(curcases[0].target, new_Proj(cond, mode_X, pn_Cond_true));
+		in[0] = new_Proj(cond, mode_X, pn_Cond_false);
+		neblock = new_Block(1, in);
+
+		/* second part: "else if(sel == val[1]) goto target[1] else goto default;" */
+		val  = new_Const_long(get_irn_mode(sel), curcases[1].value);
+		cmp  = new_Cmp(sel, val);
+		proj = new_Proj(cmp, mode_b, pn_Cmp_Eq);
+		cond = new_Cond(proj);
+		add_pred(curcases[1].target, new_Proj(cond, mode_X, pn_Cond_true));
+		add_pred(defblock,           new_Proj(cond, mode_X, pn_Cond_false));
+		return;
+	} else {
+		/* recursive case: split cases in the middle */
+		int midcase = numcases / 2;
+		ir_node *val  = new_Const_long(get_irn_mode(sel), curcases[midcase].value);
+		ir_node *cmp  = new_Cmp(sel, val);
+		ir_node *proj = new_Proj(cmp, mode_b, pn_Cmp_Lt);
+		ir_node *cond = new_Cond(proj);
+		ir_node *in[1];
+		ir_node *ltblock;
+		ir_node *geblock;
+
+		in[0] = new_Proj(cond, mode_X, pn_Cond_true);
+		ltblock = new_Block(1, in);
+
+		set_cur_block(curblock);
+		in[0] = new_Proj(cond, mode_X, pn_Cond_false);
+		geblock = new_Block(1, in);
+
+		create_if_cascade(sel, ltblock, defblock, curcases, midcase);
+		create_if_cascade(sel, geblock, defblock, curcases + midcase, numcases - midcase);
+	}
+}
+
+/**
+ * Block-Walker: searches for Cond nodes with a non-boolean mode
+ */
+static void find_cond_nodes(ir_node *block, void *ctx)
+{
+	walk_env_t  *env = ctx;
+	ir_node     *projx;
+	ir_node     *cond;
+	ir_node     *sel;
+	ir_mode     *sel_mode;
+	long         default_pn;
+	int          i, j = 0, numcases;
+	ir_node     *proj;
+	case_data_t *cases;
+	ir_node     *condblock;
+	ir_node     *defblock = NULL;
+
+	if(get_Block_n_cfgpreds(block) != 1)
+		return;
+
+	projx = get_Block_cfgpred(block, 0);
+	if(!is_Proj(projx))
+		return;
+	assert(get_irn_mode(projx) == mode_X);
+
+	cond = get_Proj_pred(projx);
+	if(!is_Cond(cond))
+		return;
+
+	sel      = get_Cond_selector(cond);
+	sel_mode = get_irn_mode(sel);
+
+	if(sel_mode == mode_b)    /* not a switch? */
+		return;
+
+	if(should_do_table_switch(cond, env->spare_size))
+		return;
+
+	/*
+	 * Switch should be transformed into an if cascade.
+	 * So first order the cases, so we can do a binary search on them.
+	 */
+
+	numcases = get_irn_n_outs(cond) - 1;      // does not contain default case
+	cases    = obstack_alloc(&env->obst, numcases * sizeof(*cases));
+
+	default_pn = get_Cond_defaultProj(cond);
+
+	foreach_out_irn(cond, i, proj) {
+		long pn = get_Proj_proj(proj);
+		if(pn == default_pn)
+		{
+			defblock = get_irn_out(proj, 0);
+			remove_pred(defblock, proj);
+			continue;
+		}
+
+		cases[j].value  = pn;
+		cases[j].target = get_irn_out(proj, 0);
+		remove_pred(cases[j].target, proj);
+		j++;
+	}
+	assert(defblock != NULL && "Switch without default proj");
+	qsort(cases, numcases, sizeof(*cases), casecmp);
+
+	/* Now create the if cascade */
+	condblock = get_nodes_block(cond);
+	create_if_cascade(sel, condblock, defblock, cases, numcases);
+
+	obstack_free(&env->obst, cases);
+}
+
+/**
+ * Lowers all Switches (Cond nodes with non-boolean mode) depending on spare_size.
+ * They will either remain the same or be converted into if-cascades.
+ *
+ * @param irg        The ir graph to be lowered.
+ * @param spare_size Allowed spare size for table switches in machine words.
+ *                   (Default in edgfe: 128)
+ */
+void lower_Switch(ir_graph *irg, unsigned spare_size)
+{
+	walk_env_t env;
+	ir_graph *rem = current_ir_graph;
+
+	current_ir_graph = irg;
+
+	obstack_init(&env.obst);
+	env.spare_size = spare_size;
+
+	assure_irg_outs(irg);
+
+	irg_block_walk_graph(irg, find_cond_nodes, NULL, &env);
+
+	if(env.changed) {
+		/* control flow changed */
+		set_irg_outs_inconsistent(irg);
+		set_irg_doms_inconsistent(irg);
+		set_irg_extblk_inconsistent(irg);
+		set_irg_loopinfo_inconsistent(irg);
+	}
+
+	obstack_free(&env.obst, NULL);
+	current_ir_graph = rem;
+}

vc2005/libfirm.vcproj

@@ -6458,6 +6458,10 @@
 					RelativePath="..\ir\lower\lower_mode_b.c"
 					>
 				</File>
+				<File
+					RelativePath="..\ir\lower\lower_switch.c"
+					>
+				</File>
 			</Filter>
 			<Filter
 				Name="net"