3 * File name: ir/opt/tailrec.c
4 * Purpose: tail-recursion optimization
9 * Copyright: (c) 2002-2004 Universität Karlsruhe
10 * Licence: This file protected by GPL - GNU GENERAL PUBLIC LICENSE.
24 #include "irgraph_t.h"
30 * the environment for colelcting data
32 typedef struct _collect_t {
33 ir_node *proj_X; /**< initial exec proj */
34 ir_node *block; /**< old first block */
35 int blk_idx; /**< cfgpred index of the initial exec in block */
36 ir_node *proj_m; /**< linked list of memory from start proj's */
37 ir_node *proj_data; /**< linked list of all parameter access proj's */
41 * walker for collecting data
43 static void collect_data(ir_node *node, void *env)
45 collect_t *data = env;
49 switch (get_irn_opcode(node)) {
51 pred = get_Proj_pred(node);
53 op = get_irn_op(pred);
55 ir_node *start = get_Proj_pred(pred);
57 if (get_irn_op(start) == op_Start) {
58 if (get_Proj_proj(pred) == pn_Start_T_args) {
59 /* found Proj(ProjT(Start)) */
60 set_irn_link(node, data->proj_data);
61 data->proj_data = node;
65 else if (op == op_Start) {
66 switch (get_Proj_proj(node)) {
68 /* found ProjM(Start) */
69 set_irn_link(node, data->proj_m);
72 case pn_Start_X_initial_exec:
73 /* found ProjX(Start) */
82 int i, n_pred = get_Block_n_cfgpreds(node);
85 * the first block has the initial exec as cfg predecessor
87 if (node != current_ir_graph->start_block) {
88 for (i = 0; i < n_pred; ++i) {
89 if (get_Block_cfgpred(node, i) == data->proj_X) {
104 * do the graph reconstruction for tail-recursion elimination
106 * @param irg the graph that will reconstructed
107 * @param rets linked list of all rets
108 * @param n_tail_calls number of tail-recursion calls
110 static void do_opt_tail_rec(ir_graph *irg, ir_node *rets, int n_tail_calls)
112 ir_graph *rem_irg = current_ir_graph;
113 ir_node *end_block = irg->end_block;
114 ir_node *block, *jmp, *call, *calls;
117 ir_node ***call_params;
121 int rem = get_optimize();
123 assert(n_tail_calls);
125 /* we add nwe nodes, so the outs are inconsistant */
126 set_irg_outs_inconsistent(irg);
128 /* we add new blocks and change the control flow */
129 set_irg_dom_inconsistent(irg);
131 /* we add a new loop */
132 set_irg_loopinfo_inconsistent(irg);
136 /* collect needed data */
141 data.proj_data = NULL;
142 irg_walk_graph(irg, NULL, collect_data, &data);
144 /* check number of arguments */
145 call = get_irn_link(end_block);
146 n_params = get_Call_n_params(call);
148 assert(data.proj_X && "Could not find initial exec from Start");
149 assert(data.block && "Could not find first block");
150 assert(data.proj_m && "Could not find ProjM(Start)");
151 assert((data.proj_data || n_params == 0) && "Could not find Proj(ProjT(Start)) of non-void function");
153 current_ir_graph = irg;
155 /* allocate in's for phi and block construction */
156 NEW_ARR_A(ir_node *, in, n_tail_calls + 1);
160 /* turn Return's into Jmp's */
161 for (i = 1, p = rets; p; p = get_irn_link(p)) {
164 set_cur_block(get_nodes_block(p));
167 exchange(p, new_Bad());
170 add_End_keepalive(get_irg_end(irg), jmp);
173 /* create a new block at start */
174 block = new_Block(n_tail_calls + 1, in);
177 /* the old first block is now the second one */
178 set_Block_cfgpred(data.block, data.blk_idx, jmp);
180 /* allocate phi's, position 0 contains the memory phi */
181 NEW_ARR_A(ir_node *, phis, n_params + 1);
183 /* build the memory phi */
185 in[i] = new_rd_Proj(NULL, irg, irg->start_block, irg->start, mode_M, pn_Start_M);
188 for (calls = call; calls; calls = get_irn_link(calls)) {
189 in[i] = get_Call_mem(calls);
192 assert(i == n_tail_calls + 1);
194 phis[0] = new_rd_Phi(NULL, irg, block, n_tail_calls + 1, in, mode_M);
196 /* build the data phi's */
200 NEW_ARR_A(ir_node **, call_params, n_params);
202 /* collect all parameters */
203 for (i = 0, calls = call; calls; calls = get_irn_link(calls)) {
204 call_params[i] = get_Call_param_arr(calls);
208 /* build new projs and Phi's */
209 for (i = 0; i < n_params; ++i) {
210 ir_mode *mode = get_irn_mode(call_params[0][i]);
212 in[0] = new_rd_Proj(NULL, irg, block, irg->args, mode, i);
213 for (j = 0; j < n_tail_calls; ++j)
214 in[j + 1] = call_params[j][i];
216 phis[i + 1] = new_rd_Phi(NULL, irg, block, n_tail_calls + 1, in, mode);
221 * ok, we are here, so we have build and collected all needed Phi's
222 * now exchange all Projs into links to Phi
224 for (p = data.proj_m; p; p = get_irn_link(p)) {
225 exchange(p, phis[0]);
227 for (p = data.proj_data; p; p = get_irn_link(p)) {
228 long proj = get_Proj_proj(p);
230 assert(0 <= proj && proj < n_params);
231 exchange(p, phis[proj + 1]);
234 current_ir_graph = rem_irg;
239 * convert simple tail-calls into loops
241 void opt_tail_rec_irg(ir_graph *irg)
243 ir_node *end_block = irg->end_block;
245 int i, n_tail_calls = 0;
246 ir_node *rets = NULL;
248 if (! get_opt_tail_recursion() || ! get_opt_optimize())
251 set_irn_link(end_block, NULL);
253 n_preds = get_Block_n_cfgpreds(end_block);
254 for (i = 0; i < n_preds; ++i) {
255 ir_node *ret = get_Block_cfgpred(end_block, i);
256 ir_node *proj_m, *call, *call_ptr;
261 /* search all returns of a block */
262 if (get_irn_op(ret) != op_Return)
265 /* check, if it's a Return self() */
266 proj_m = get_Return_mem(ret);
268 if (get_irn_op(proj_m) != op_Proj)
271 call = get_Proj_pred(proj_m);
272 if (get_irn_op(call) != op_Call)
275 /* check if it's a recursive call */
276 call_ptr = get_Call_ptr(call);
278 if (get_irn_op(call_ptr) != op_SymConst)
281 if (get_SymConst_kind(call_ptr) != symconst_addr_ent)
284 ent = get_SymConst_entity(call_ptr);
285 if (!ent || get_entity_irg(ent) != irg)
288 /* ok, mem is routed to a recursive call, check return args */
289 n_ress = get_Return_n_ress(ret);
290 ress = get_Return_res_arr(ret);
292 for (j = 0; j < n_ress; ++j) {
293 ir_node *proj = ress[j];
297 if (get_irn_op(proj) != op_Proj) {
298 /* not routed to a call */
302 proj_proj = get_Proj_pred(proj);
304 if (get_irn_op(proj) != op_Proj) {
305 /* not routed to a call */
309 irn = get_Proj_pred(proj_proj);
312 /* not routed to a call */
319 /* here, we have found a call */
320 set_irn_link(call, get_irn_link(end_block));
321 set_irn_link(end_block, call);
324 /* link all returns, we will need this */
325 set_irn_link(ret, rets);
329 /* now, end_block->link contains the list of all tail calls */
333 do_opt_tail_rec(irg, rets, n_tail_calls);
337 * optimize tail recursion away
339 void opt_tail_recursion(void)
343 if (! get_opt_tail_recursion() || ! get_opt_optimize())
346 for (i = 0; i < get_irp_n_irgs(); i++) {
347 current_ir_graph = get_irp_irg(i);
349 opt_tail_rec_irg(current_ir_graph);