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.
23 #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 ir_node *proj_m; /**< linked list of memory from start proj's */
36 ir_node *proj_data; /**< linked list of all parameter access proj's */
40 * walker for collecting data
42 static void collect_data(ir_node *node, void *env)
44 collect_t *data = env;
48 switch (intern_get_irn_opcode(node)) {
50 pred = get_Proj_pred(node);
52 op = intern_get_irn_op(pred);
54 ir_node *start = get_Proj_pred(pred);
56 if (intern_get_irn_op(start) == op_Start) {
57 if (get_Proj_proj(pred) == pn_Start_T_args) {
58 /* found Proj(ProjT(Start)) */
59 set_irn_link(node, data->proj_data);
60 data->proj_data = node;
64 else if (op == op_Start) {
65 switch (get_Proj_proj(node)) {
67 /* found ProjM(Start) */
68 set_irn_link(node, data->proj_m);
71 case pn_Start_X_initial_exec:
72 /* found ProjX(Start) */
81 int i, n_pred = get_Block_n_cfgpreds(node);
84 * the first block has the initial exec as cfg predecessor
86 if (node != current_ir_graph->start_block) {
87 for (i = 0; i < n_pred; ++i) {
88 if (get_Block_cfgpred(node, i) == data->proj_X) {
102 * do the graph reconstruction for tail-recursion elimination
104 * @param irg the graph that will reconstructed
105 * @param rets linked list of all rets
106 * @param n_tail_calls number of tail-recursion calls
108 static void do_opt_tail_rec(ir_graph *irg, ir_node *rets, int n_tail_calls)
110 ir_graph *rem_irg = current_ir_graph;
111 ir_node *end_block = irg->end_block;
112 ir_node *block, *jmp, *call, *calls;
115 ir_node ***call_params;
119 int rem = get_optimize();
121 assert(n_tail_calls);
125 /* collect needed data */
129 data.proj_data = NULL;
130 irg_walk_graph(irg, NULL, collect_data, &data);
132 /* check number of arguments */
133 call = get_irn_link(end_block);
134 n_params = get_Call_n_params(call);
136 assert(data.proj_X && "Could not find initial exec from Start");
137 assert(data.block && "Could not find first block");
138 assert(data.proj_m && "Could not find ProjM(Start)");
139 assert((data.proj_data || n_params == 0) && "Could not find Proj(ProjT(Start)) of non-void function");
141 current_ir_graph = irg;
143 /* allocate in's for phi and block construction */
144 NEW_ARR_A(ir_node *, in, n_tail_calls + 1);
148 /* turn Return's into Jmp's */
149 for (i = 1, p = rets; p; p = get_irn_link(p)) {
152 switch_block(get_nodes_Block(p));
155 exchange(p, new_Bad());
158 add_End_keepalive(get_irg_end(irg), jmp);
161 /* create a new block at start */
162 block = new_Block(n_tail_calls + 1, in);
165 /* the old first block is now the second one */
166 for (i = 0; i < get_Block_n_cfgpreds(data.block); ++i) {
167 if (get_Block_cfgpred(data.block, i) == data.proj_X) {
168 set_Block_cfgpred(data.block, i, jmp);
173 /* allocate phi's, position 0 contains the memory phi */
174 NEW_ARR_A(ir_node *, phis, n_params + 1);
176 /* build the memory phi */
178 in[i] = new_rd_Proj(NULL, irg, irg->start_block, irg->start, mode_M, pn_Start_M);
181 for (calls = call; calls; calls = get_irn_link(calls)) {
182 in[i] = get_Call_mem(calls);
185 phis[0] = new_rd_Phi(NULL, irg, block, n_tail_calls + 1, in, mode_M);
187 /* build the data phi's */
191 NEW_ARR_A(ir_node **, call_params, n_params);
193 /* collect all parameters */
194 for (i = 0, calls = call; calls; calls = get_irn_link(calls)) {
195 call_params[i] = get_Call_param_arr(calls);
199 /* build new projs and Phi's */
200 for (i = 0; i < n_params; ++i) {
201 ir_mode *mode = get_irn_mode(call_params[0][i]);
203 in[0] = new_rd_Proj(NULL, irg, block, irg->args, mode, i);
204 for (j = 0; j < n_tail_calls; ++j)
205 in[j + 1] = call_params[j][i];
207 phis[i + 1] = new_rd_Phi(NULL, irg, block, n_tail_calls + 1, in, mode);
212 * ok, we are here, so we have build and collected all needed Phi's
213 * now exchange all Projs into links to Phi
215 for (p = data.proj_m; p; p = get_irn_link(p)) {
216 exchange(p, phis[0]);
218 for (p = data.proj_data; p; p = get_irn_link(p)) {
219 long proj = get_Proj_proj(p);
221 assert(0 <= proj && proj < n_params);
222 exchange(p, phis[proj + 1]);
225 current_ir_graph = rem_irg;
230 * convert simple tail-calls into loops
232 void optimize_tail_rec_irg(ir_graph *irg)
234 ir_node *end_block = irg->end_block;
236 int i, n_tail_calls = 0;
237 ir_node *rets = NULL;
239 if (! get_opt_tail_recursion() || ! get_opt_optimize())
242 set_irn_link(end_block, NULL);
244 n_preds = get_Block_n_cfgpreds(end_block);
245 for (i = 0; i < n_preds; ++i) {
246 ir_node *ret = get_Block_cfgpred(end_block, i);
247 ir_node *proj_m, *call, *call_ptr;
253 /* search all returns of a block */
254 if (intern_get_irn_op(ret) != op_Return)
257 /* check, if it's a Return self() */
258 proj_m = get_Return_mem(ret);
260 if (intern_get_irn_op(proj_m) != op_Proj)
263 call = get_Proj_pred(proj_m);
264 if (intern_get_irn_op(call) != op_Call)
267 /* check if it's a recursive call */
268 call_ptr = get_Call_ptr(call);
270 if (intern_get_irn_op(call_ptr) != op_Const)
273 tv = get_Const_tarval(call_ptr);
274 if (! tarval_is_entity(tv))
277 ent = tarval_to_entity(tv);
278 if (!ent || get_entity_irg(ent) != irg)
281 /* ok, mem is routed to a recursive call, check return args */
282 n_ress = get_Return_n_ress(ret);
283 ress = get_Return_res_arr(ret);
285 for (j = 0; j < n_ress; ++j) {
286 ir_node *proj = ress[j];
290 if (intern_get_irn_op(proj) != op_Proj) {
291 /* not routed to a call */
295 proj_proj = get_Proj_pred(proj);
297 if (intern_get_irn_op(proj) != op_Proj) {
298 /* not routed to a call */
302 irn = get_Proj_pred(proj_proj);
305 /* not routed to a call */
312 /* here, we have found a call */
313 set_irn_link(call, get_irn_link(end_block));
314 set_irn_link(end_block, call);
317 /* link all returns, we will need this */
318 set_irn_link(ret, rets);
322 /* now, end_block->link contains the list of all tail calls */
326 do_opt_tail_rec(irg, rets, n_tail_calls);
330 * optimize tail recursion away
332 void optimize_tail_recursion(void)
334 if (! get_opt_tail_recursion() || ! get_opt_optimize())
337 for (i = 0; i < get_irp_n_irgs(); i++) {
338 current_ir_graph = get_irp_irg(i);
340 optimize_tail_rec_irg(current_ir_graph);