--- /dev/null
+/*
+ * 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;
+}
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