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"
31 * the environment for colelcting data
33 typedef struct _collect_t {
34 ir_node *proj_X; /**< initial exec proj */
35 ir_node *block; /**< old first block */
36 int blk_idx; /**< cfgpred index of the initial exec in block */
37 ir_node *proj_m; /**< linked list of memory from start proj's */
38 ir_node *proj_data; /**< linked list of all parameter access proj's */
42 * walker for collecting data
44 static void collect_data(ir_node *node, void *env)
46 collect_t *data = env;
50 switch (intern_get_irn_opcode(node)) {
52 pred = get_Proj_pred(node);
54 op = intern_get_irn_op(pred);
56 ir_node *start = get_Proj_pred(pred);
58 if (intern_get_irn_op(start) == op_Start) {
59 if (get_Proj_proj(pred) == pn_Start_T_args) {
60 /* found Proj(ProjT(Start)) */
61 set_irn_link(node, data->proj_data);
62 data->proj_data = node;
66 else if (op == op_Start) {
67 switch (get_Proj_proj(node)) {
69 /* found ProjM(Start) */
70 set_irn_link(node, data->proj_m);
73 case pn_Start_X_initial_exec:
74 /* found ProjX(Start) */
83 int i, n_pred = get_Block_n_cfgpreds(node);
86 * the first block has the initial exec as cfg predecessor
88 if (node != current_ir_graph->start_block) {
89 for (i = 0; i < n_pred; ++i) {
90 if (get_Block_cfgpred(node, i) == data->proj_X) {
105 * do the graph reconstruction for tail-recursion elimination
107 * @param irg the graph that will reconstructed
108 * @param rets linked list of all rets
109 * @param n_tail_calls number of tail-recursion calls
111 static void do_opt_tail_rec(ir_graph *irg, ir_node *rets, int n_tail_calls)
113 ir_graph *rem_irg = current_ir_graph;
114 ir_node *end_block = irg->end_block;
115 ir_node *block, *jmp, *call, *calls;
118 ir_node ***call_params;
122 int rem = get_optimize();
124 assert(n_tail_calls);
126 /* we add nwe nodes, so the outs are inconsistant */
127 set_irg_outs_inconsistent(irg);
129 /* we add new blocks and change the control flow */
130 set_irg_dom_inconsistent(irg);
132 /* we add a new loop */
133 set_irg_loopinfo_inconsistent(irg);
137 /* collect needed data */
142 data.proj_data = NULL;
143 irg_walk_graph(irg, NULL, collect_data, &data);
145 /* check number of arguments */
146 call = get_irn_link(end_block);
147 n_params = get_Call_n_params(call);
149 assert(data.proj_X && "Could not find initial exec from Start");
150 assert(data.block && "Could not find first block");
151 assert(data.proj_m && "Could not find ProjM(Start)");
152 assert((data.proj_data || n_params == 0) && "Could not find Proj(ProjT(Start)) of non-void function");
154 current_ir_graph = irg;
156 /* allocate in's for phi and block construction */
157 NEW_ARR_A(ir_node *, in, n_tail_calls + 1);
161 /* turn Return's into Jmp's */
162 for (i = 1, p = rets; p; p = get_irn_link(p)) {
165 switch_block(get_nodes_Block(p));
168 exchange(p, new_Bad());
171 add_End_keepalive(get_irg_end(irg), jmp);
174 /* create a new block at start */
175 block = new_Block(n_tail_calls + 1, in);
178 /* the old first block is now the second one */
179 set_Block_cfgpred(data.block, data.blk_idx, jmp);
181 /* allocate phi's, position 0 contains the memory phi */
182 NEW_ARR_A(ir_node *, phis, n_params + 1);
184 /* build the memory phi */
186 in[i] = new_rd_Proj(NULL, irg, irg->start_block, irg->start, mode_M, pn_Start_M);
189 for (calls = call; calls; calls = get_irn_link(calls)) {
190 in[i] = get_Call_mem(calls);
193 phis[0] = new_rd_Phi(NULL, irg, block, n_tail_calls + 1, in, mode_M);
195 /* build the data phi's */
199 NEW_ARR_A(ir_node **, call_params, n_params);
201 /* collect all parameters */
202 for (i = 0, calls = call; calls; calls = get_irn_link(calls)) {
203 call_params[i] = get_Call_param_arr(calls);
207 /* build new projs and Phi's */
208 for (i = 0; i < n_params; ++i) {
209 ir_mode *mode = get_irn_mode(call_params[0][i]);
211 in[0] = new_rd_Proj(NULL, irg, block, irg->args, mode, i);
212 for (j = 0; j < n_tail_calls; ++j)
213 in[j + 1] = call_params[j][i];
215 phis[i + 1] = new_rd_Phi(NULL, irg, block, n_tail_calls + 1, in, mode);
220 * ok, we are here, so we have build and collected all needed Phi's
221 * now exchange all Projs into links to Phi
223 for (p = data.proj_m; p; p = get_irn_link(p)) {
224 exchange(p, phis[0]);
226 for (p = data.proj_data; p; p = get_irn_link(p)) {
227 long proj = get_Proj_proj(p);
229 assert(0 <= proj && proj < n_params);
230 exchange(p, phis[proj + 1]);
233 current_ir_graph = rem_irg;
238 * convert simple tail-calls into loops
240 void opt_tail_rec_irg(ir_graph *irg)
242 ir_node *end_block = irg->end_block;
244 int i, n_tail_calls = 0;
245 ir_node *rets = NULL;
247 if (! get_opt_tail_recursion() || ! get_opt_optimize())
250 set_irn_link(end_block, NULL);
252 n_preds = get_Block_n_cfgpreds(end_block);
253 for (i = 0; i < n_preds; ++i) {
254 ir_node *ret = get_Block_cfgpred(end_block, i);
255 ir_node *proj_m, *call, *call_ptr;
261 /* search all returns of a block */
262 if (intern_get_irn_op(ret) != op_Return)
265 /* check, if it's a Return self() */
266 proj_m = get_Return_mem(ret);
268 if (intern_get_irn_op(proj_m) != op_Proj)
271 call = get_Proj_pred(proj_m);
272 if (intern_get_irn_op(call) != op_Call)
275 /* check if it's a recursive call */
276 call_ptr = get_Call_ptr(call);
278 if (intern_get_irn_op(call_ptr) != op_Const)
281 tv = get_Const_tarval(call_ptr);
282 if (! tarval_is_entity(tv))
285 ent = tarval_to_entity(tv);
286 if (!ent || get_entity_irg(ent) != irg)
289 /* ok, mem is routed to a recursive call, check return args */
290 n_ress = get_Return_n_ress(ret);
291 ress = get_Return_res_arr(ret);
293 for (j = 0; j < n_ress; ++j) {
294 ir_node *proj = ress[j];
298 if (intern_get_irn_op(proj) != op_Proj) {
299 /* not routed to a call */
303 proj_proj = get_Proj_pred(proj);
305 if (intern_get_irn_op(proj) != op_Proj) {
306 /* not routed to a call */
310 irn = get_Proj_pred(proj_proj);
313 /* not routed to a call */
320 /* here, we have found a call */
321 set_irn_link(call, get_irn_link(end_block));
322 set_irn_link(end_block, call);
325 /* link all returns, we will need this */
326 set_irn_link(ret, rets);
330 /* now, end_block->link contains the list of all tail calls */
334 do_opt_tail_rec(irg, rets, n_tail_calls);
338 * optimize tail recursion away
340 void opt_tail_recursion(void)
344 if (! get_opt_tail_recursion() || ! get_opt_optimize())
347 for (i = 0; i < get_irp_n_irgs(); i++) {
348 current_ir_graph = get_irp_irg(i);
350 opt_tail_rec_irg(current_ir_graph);