--- /dev/null
+/*
+ * Project: libFIRM
+ * File name: ir/opt/return.c
+ * Purpose: normalize returns
+ * Author:
+ * Created:
+ * CVS-ID: $Id$
+ * Copyright: (c) 1998-2005 Universität Karlsruhe
+ * Licence: This file protected by GPL - GNU GENERAL PUBLIC LICENSE.
+ */
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#ifdef HAVE_ALLOCA_H
+# include <alloca.h>
+#endif
+#ifdef HAVE_MALLOC_H
+# include <malloc.h>
+#endif
+
+#include "irgraph_t.h"
+#include "ircons_t.h"
+#include "irnode_t.h"
+#include "irgmod.h"
+
+#define set_bit(n) (returns[(n) >> 3] |= 1 << ((n) & 7))
+#define get_bit(n) (returns[(n) >> 3] & (1 << ((n) & 7)))
+
+#undef IMAX
+#define IMAX(a, b) ((a) > (b) ? (a) : (b))
+
+/*
+ * Normalize the Returns of a graph by creating a new End block
+ * with One Return(Phi).
+ * This is the prefered input for the if-conversion.
+ *
+ * In pseudocode, it means:
+ *
+ * if (a)
+ * return b;
+ * else
+ * return c;
+ *
+ * is transformed into
+ *
+ * if (a)
+ * res = b;
+ * else
+ * res = c;
+ * return res;
+ */
+void normalize_one_return(ir_graph *irg)
+{
+ ir_node *endbl = get_irg_end_block(irg);
+ int i, j, k, n, last_idx, n_rets, n_ret_vals = -1;
+ unsigned char *returns;
+ ir_node **in, **retvals;
+
+ ir_node *block, *new_ret;
+
+ /* look, if we have more than one return */
+ n = get_Block_n_cfgpreds(endbl);
+ returns = alloca((n + 7) >> 3);
+ memset(returns, 0, (n + 7) >> 3);
+
+ for (n_rets = i = 0; i < n; ++i) {
+ ir_node *node = get_Block_cfgpred(endbl, i);
+
+ if (get_irn_op(node) == op_Return) {
+ ++n_rets;
+
+ set_bit(i);
+
+ if (n_ret_vals < 0)
+ n_ret_vals = get_irn_arity(node);
+ }
+ }
+
+ /* there should be at least one Return node in Firm */
+ if (n_rets <= 1)
+ return;
+
+ in = alloca(sizeof(*in) * IMAX(n_rets, n_ret_vals));
+ retvals = alloca(sizeof(*in) * n_rets * n_ret_vals);
+
+ for (j = i = 0; i < n; ++i) {
+ if (get_bit(i)) {
+ ir_node *ret = get_Block_cfgpred(endbl, i);
+ ir_node *block = get_nodes_block(ret);
+
+ /* create a new Jmp for every Ret and place the in in */
+ in[j] = new_r_Jmp(irg, block);
+
+ /* save the return values and shuffle them */
+ for (k = 0; k < n_ret_vals; ++k)
+ retvals[j + k*n_ret_vals] = get_irn_n(ret, k);
+
+ ++j;
+
+ set_Block_cfgpred(endbl, i, new_r_Bad(irg));
+ last_idx = i;
+ }
+ }
+
+ /* ok, create a new block with all created in's */
+ block = new_r_Block(irg, n_rets, in);
+
+ /* now create the Phi nodes */
+ for (j = i = 0; i < n_ret_vals; ++i, j += n_rets) {
+ /* the return values are already shuffled */
+ in[i] = new_r_Phi(irg, block, n_rets, &retvals[j], get_irn_mode(retvals[j]));
+ }
+
+ new_ret = new_r_Return(irg, block, in[0], n_ret_vals-1, &in[1]);
+
+ set_Block_cfgpred(endbl, last_idx, new_ret);
+
+ /* invalidate analysis information:
+ * a new Block was added, so dominator, outs and loop are inconsistent,
+ * trouts and callee-state should be still valid
+ */
+ set_irg_dom_inconsistent(irg);
+ set_irg_outs_inconsistent(irg);
+ set_irg_loopinfo_state(current_ir_graph, loopinfo_cf_inconsistent);
+}
+
+/**
+ * check, whether a Ret can be moved on block upwards.
+ *
+ * In a block with a Return, all live nodes must be linked
+ * with the Return, otherwise they are dead (because the Return leaves
+ * the graph, so no more users of the other nodes can exists.
+ *
+ * We can move a Return, if it's predecessors are Phi nodes or
+ * comes from another block. In the later case, it is always possible
+ * to move the Return one block up, because the predecessor block must
+ * dominate the Return block (SSA) and then it dominates the predecessor
+ * block of the Return block as well.
+ *
+ * All predecessors of the Return block must be Jmp's of course, or we
+ * cannot move it up, so we check this either.
+ */
+static int can_move_ret(ir_node *ret)
+{
+ ir_node *retbl = get_nodes_block(ret);
+ int i, n = get_irn_arity(ret);
+
+ for (i = 0; i < n; ++i) {
+ ir_node *pred = get_irn_n(ret, i);
+
+ if (! is_Phi(pred) && retbl == get_nodes_block(pred)) {
+ /* first condition failed, found a non-Phi predecessor
+ * then is in the Return block */
+ return 0;
+ }
+ }
+
+ /* check, that predecessors are Jmps */
+ n = get_Block_n_cfgpreds(retbl);
+ for (i = 0; i < n; ++i)
+ if (get_irn_op(get_Block_cfgpred(retbl, i)) != op_Jmp)
+ return 0;
+
+ /* if we have 0 control flow predecessors, we cannot move :-) */
+ return n > 0;
+}
+
+/*
+ * Normalize the Returns of a graph by moving
+ * the Returns upwards as much as possible.
+ * This might be prefered for code generation.
+ *
+ * In pseudocode, it means:
+ *
+ * if (a)
+ * res = b;
+ * else
+ * res = c;
+ * return res;
+ *
+ * is transformed into
+ *
+ * if (a)
+ * return b;
+ * else
+ * return c;
+ */
+void normalize_n_returns(ir_graph *irg)
+{
+ int i, j, n, n_rets, n_finals, n_ret_vals;
+ ir_node *list = NULL;
+ ir_node *final = NULL;
+ ir_node **in;
+ ir_node *endbl = get_irg_end_block(irg);
+
+ /* first, link all returns */
+ n = get_Block_n_cfgpreds(endbl);
+ for (n_finals = n_rets = i = 0; i < n; ++i) {
+ ir_node *ret = get_Block_cfgpred(endbl, i);
+
+ if (get_irn_op(ret) == op_Return && can_move_ret(ret)) {
+ /*
+ * Ok, all conditions met, we can move this Return, put it
+ * on our work list.
+ */
+ set_irn_link(ret, list);
+ list = ret;
+ ++n_rets;
+ }
+ else {
+ /* Put all nodes that are not changed on the final list. */
+ set_irn_link(ret, final);
+ final = ret;
+ ++n_finals;
+ }
+ }
+
+ if (n_rets <= 0)
+ return;
+
+ /*
+ * Now move the Returns upwards. We move always one block up (and create n
+ * new Returns), than we check if a newly created Return can be moved even further.
+ * If yes, we simply add it to our work list, else to the final list.
+ */
+ n_ret_vals = get_irn_arity(list);
+ in = alloca(sizeof(*in) * n_ret_vals);
+ while (list) {
+ ir_node *ret = list;
+ ir_node *block = get_nodes_block(ret);
+
+ list = get_irn_link(ret);
+ --n_rets;
+
+ n = get_Block_n_cfgpreds(block);
+ for (i = 0; i < n; ++i) {
+ ir_node *jmp = get_Block_cfgpred(block, i);
+ ir_node *new_bl = get_nodes_block(jmp);
+ ir_node *new_ret;
+
+ /* create the in-array for the new Ret */
+ for (j = 0; j < n_ret_vals; ++j) {
+ ir_node *pred = get_irn_n(ret, j);
+
+ in[j] = is_Phi(pred) ? get_Phi_pred(pred, i) : pred;
+ }
+
+ new_ret = new_r_Return(irg, new_bl, in[0], n_ret_vals - 1, &in[1]);
+
+ if (can_move_ret(new_ret)) {
+ set_irn_link(new_ret, list);
+ list = new_ret;
+ ++n_rets;
+ }
+ else {
+ set_irn_link(new_ret, final);
+ final = new_ret;
+ ++n_finals;
+ }
+ }
+ }
+
+ /*
+ * Last step: Create a new endblock, with all nodes on the final
+ * list as predecessors.
+ */
+ in = alloca(sizeof(*in) * n_finals);
+
+ for (i = 0; final; ++i, final = get_irn_link(final))
+ in[i] = final;
+
+ exchange(endbl, new_r_Block(irg, n_finals, in));
+
+ /* the end block is not automatically skiped, so do it here */
+ set_irg_end_block(irg, skip_Id(get_irg_end_block(irg)));
+
+ /* Invalidate analysis information:
+ * Blocks become dead and new Eeturns were deleted, so dominator, outs and loop are inconsistent,
+ * trouts and callee-state should be still valid
+ */
+ set_irg_dom_inconsistent(irg);
+ set_irg_outs_inconsistent(irg);
+ set_irg_loopinfo_state(current_ir_graph, loopinfo_cf_inconsistent);
+}
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