6 * File name: ir/opt/strength_red.c
7 * Purpose: Make strength reduction .
8 * Author: Beyhan Veliev
12 * Copyright: (c) 2003 Universität Karlsruhe
13 * Licence: This file protected by GPL - GNU GENERAL PUBLIC LICENSE.
17 # include "strength_red.h"
20 # include "irnode_t.h"
22 # include "irloop_t.h"
28 /* The information needed for an induction variable */
29 struct induct_var_info {
30 ir_op *operation_code;
31 ir_node *increment, *init, *op;
36 static struct induct_var_info ivi;
38 /** Counter for verbose information about optimization. */
39 static int n_reduced_expressions;
41 /** Detect basic iteration variables.
43 * The variable ir represented by a subgraph as this:
53 * Where op is a Add or Sub, and init is loop invariant.
54 * @@@ So far we only accept Phi nodes with two predecessors.
55 * We could expand this to Phi nodes where all preds are either
56 * op or loop invariant.
58 * @param n A phi node.
60 static struct induct_var_info *is_induction_variable (ir_node *n) {
62 ir_node *phi_pred_0, *phi_pred_1, *add_r, *add_l, *sub_r, *sub_l ;
63 ir_op *phi_pred_0_op, *phi_pred_1_op;
64 struct induct_var_info *info;
67 info->operation_code = NULL;
68 info->increment = NULL;
72 info->init_pred_pos = -1;
73 info->op_pred_pos = -1;
75 assert(get_irn_op(n) == op_Phi);
77 /* The necessary conditions for the phi node. */
78 if (get_irn_arity(n) != 2 ||
79 !has_backedges(get_nodes_block(n)) )
82 /* The predecessors of the phi node. */
83 phi_pred_0 = get_Phi_pred(n, 0);
84 phi_pred_1 = get_Phi_pred(n, 1);
86 /*The operation of the predecessors. */
87 phi_pred_0_op = get_irn_op(get_Phi_pred(n, 0));
88 phi_pred_1_op = get_irn_op(get_Phi_pred(n, 1));
90 /*Compute if the induction variable is added or substracted wiht a constant . */
91 if (phi_pred_0_op == op_Add){
92 info->operation_code = op_Add;
93 add_l = get_Add_left(phi_pred_0);
94 add_r = get_Add_right(phi_pred_0);
95 info->op_pred_pos = 0;
97 info->increment = add_r;
98 } else if (add_r == n){
99 info->increment = add_l;
101 } else if (phi_pred_1_op == op_Add){
102 info->operation_code = op_Add ;
103 add_l = get_Add_left(phi_pred_1);
104 add_r = get_Add_right(phi_pred_1);
105 info->op_pred_pos = 1;
107 info->increment = add_r;
108 } else if (add_r == n){
109 info->increment = add_l;
111 } else if (phi_pred_0_op == op_Sub){
112 info->operation_code = op_Sub;
113 sub_r = get_Sub_right(phi_pred_0);
114 sub_l = get_Sub_left(phi_pred_0);
115 info->op_pred_pos = 0;
117 info->increment = sub_r;
118 } else if (sub_r == n){
119 info->increment = sub_l;
121 } else if (phi_pred_1_op == op_Sub){
122 info->operation_code = op_Sub;
123 sub_r = get_Sub_right(phi_pred_1);
124 sub_l = get_Sub_left(phi_pred_1);
125 info->op_pred_pos = 1;
127 info->increment = sub_r;
132 /*Compute the position of the backedge. */
133 if (is_backedge(get_nodes_block(n), 0)){
135 info->init_pred_pos = 1;
136 info->op = get_Phi_pred(n, 0);
137 info->init = get_Phi_pred(n, 1);
138 } else if (is_backedge(get_nodes_block(n), 1)){
140 info->init_pred_pos = 0;
141 info->op = get_Phi_pred(n, 1);
142 info->init = get_Phi_pred(n, 0);
145 if (info->be_pos == 0) {
146 if (get_Block_dom_depth(get_nodes_block(phi_pred_1)) >=
147 get_Block_dom_depth(get_nodes_block(n))) {
150 } else if (get_Block_dom_depth(get_nodes_block(phi_pred_0)) >=
151 get_Block_dom_depth(get_nodes_block(n))) return NULL;
153 if (get_Block_dom_depth(get_nodes_block(info->increment)) >=
154 get_Block_dom_depth(get_nodes_block(n))) return NULL;
160 const char *get_irg_dump_name(ir_graph *irg);
165 * @param *srong The node to be reduce.
166 * @param *env Free environment pointer.
168 * The node for reduce mus be in a loop whit *phi and *add.The *phi node muss
169 * have 2 predecessors a Const and a Add node. The predecessors of Add node muss
170 * be *phi and a Const node. The nodes a, b, c muss be Const with dom_depth <
174 void reduce_itervar(ir_node *itervar_phi, void *env) {
175 ir_node *strong = NULL, *cmp = NULL, *c, *cmp_const;
176 int phi_pred, strong_in_Phi = 0, cmp_in_phi = 0, out_loop_res = 1;
178 // This "if" finds the node to reduce.
180 // This "if" finds the Phi predecessors for the node that must be reduced.
181 if ((get_irn_op(itervar_phi) == op_Phi) &&
182 is_induction_variable(itervar_phi) != NULL ) {
183 phi_pred = get_irn_n_outs(itervar_phi);
184 ir_loop *l_itervar_phi = get_irn_loop(get_nodes_block(itervar_phi));
186 for (int i = 0; i < phi_pred; i++) {
187 ir_node *out = get_irn_out(itervar_phi, i);
188 ir_op *out_op = get_irn_op(out);
189 if (get_irn_loop(get_nodes_block(out)) != l_itervar_phi)
191 if (out_op == op_Mul){
194 }else if (out_op == op_Cmp){
199 if (strong == NULL || (strong_in_Phi > 1)) return;
201 if(get_irn_op(get_Mul_right(strong)) == op_Phi)
202 c = get_Mul_left(strong);
204 c = get_Mul_right(strong);
207 if (get_Block_dom_depth(get_nodes_block(c)) >=
208 get_Block_dom_depth(get_nodes_block(itervar_phi))) return;
210 if (get_opt_strength_red_verbose() && get_firm_verbosity() > 1) {
211 printf("The constant of Reducing node is: "); DDMN(c);
212 printf("The Phi node is"); DDMN(itervar_phi);
213 printf("Reducing node: "); DDMN(strong);
214 printf(" iter var is "); DDMN(ivi.op);
215 printf(" in graph "); DDMG(current_ir_graph);
218 ir_node *inc , *init , *new_phi, *in[2], *new_op = NULL, *block_init, *block_inc;
220 ir_node *init_block = get_nodes_block(ivi.init);
221 ir_node *increment_block = get_nodes_block(ivi.increment);
222 ir_node *c_block = get_nodes_block(c) ;
224 if (get_Block_dom_depth(increment_block) >= get_Block_dom_depth(c_block))
225 block_inc = increment_block;
229 if (get_Block_dom_depth(init_block) >= get_Block_dom_depth(c_block))
230 block_init = init_block;
232 block_init = c_block;
234 /* Compute new loop invariant increment and initialization values. */
235 inc = new_r_Mul (current_ir_graph, block_inc, ivi.increment, c, get_irn_mode(c));
236 init = new_r_Mul (current_ir_graph, block_init, ivi.init, c, get_irn_mode(ivi.init));
238 /* Generate a new basic induction variable. Break the data flow loop
239 initially by using an Unknown node. */
240 in[ivi.op_pred_pos] = new_Unknown(get_irn_mode(init));
241 in[ivi.init_pred_pos] = init;
242 new_phi = new_r_Phi(current_ir_graph, get_nodes_block(itervar_phi), 2, in, get_irn_mode(init));
243 mark_irn_visited(new_phi);
245 if (ivi.operation_code == op_Add)
246 new_op = new_r_Add(current_ir_graph, get_nodes_block(ivi.op), inc, new_phi,
248 else if (ivi.operation_code == op_Sub)
249 new_op = new_r_Sub(current_ir_graph, get_nodes_block(ivi.op), new_phi, inc,
251 set_Phi_pred(new_phi, ivi.op_pred_pos, new_op);
253 /* Replace the use of the strength reduced value. */
254 exchange(strong, new_phi);
256 if (cmp == NULL || cmp_in_phi > 1 || out_loop_res == 0) return;
258 if (get_irn_op(get_Cmp_left(cmp)) == op_Const)
259 cmp_const = get_Cmp_left(cmp);
261 cmp_const = get_Cmp_right(cmp);
263 if (get_irn_loop(get_nodes_block(cmp)) != l_itervar_phi) return;
265 if (get_opt_strength_red_verbose() && get_firm_verbosity() > 1) {
266 printf("It is possibale to exchange the Cmp with a new Cmp \n");
267 printf("The constant of Cmp node is: "); DDMN(cmp_const);
268 printf("The Phi node is"); DDMN(itervar_phi);
269 printf("Cmp node: "); DDMN(cmp);
270 printf(" in graph "); DDMG(current_ir_graph);
273 ir_node *new_cmp_const, *new_cmp, *cmp_const_block = get_nodes_block(cmp_const);
275 if (get_Block_dom_depth(init_block) >= get_Block_dom_depth(cmp_const_block))
276 block_init = init_block;
278 block_init = cmp_const_block;
280 new_cmp_const = new_r_Mul (current_ir_graph, block_init, cmp_const,
281 c, get_irn_mode(ivi.init));
282 new_cmp = new_r_Cmp (current_ir_graph, get_nodes_block(cmp),
283 new_phi, new_cmp_const);
284 exchange(cmp, new_cmp);
289 /* Performs strength reduction for the passed graph. */
290 void reduce_strength(ir_graph *irg) {
291 ir_graph *rem = current_ir_graph;
292 current_ir_graph = irg;
294 if (!get_optimize() || !get_opt_strength_red()) return;
296 n_reduced_expressions = 0;
298 /* -- Precompute some information -- */
299 /* Call algorithm that computes the backedges */
300 construct_cf_backedges(irg);
301 /* Call algorithm that computes the dominator trees. */
303 /* Call algorithm that computes the out edges */
305 /* -- Search expressions that can be optimized -- */
306 irg_walk_graph(irg, NULL, reduce_itervar, NULL);
308 if (get_opt_strength_red_verbose())
309 printf("Reduced %d iteration variables in graph %s.%s\n.", n_reduced_expressions,
310 get_type_name(get_entity_owner(get_irg_entity(irg))),
311 get_entity_name(get_irg_entity(irg)));
313 current_ir_graph = rem;