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.
21 # include "strength_red.h"
24 # include "irnode_t.h"
26 # include "irloop_t.h"
34 /* The information needed for a induction variable*/
35 struct induct_var_info {
36 ir_op *operation_code;
37 ir_node *increment, *init, *op;
42 static struct induct_var_info ivi;
44 /** Counter for verbose information about optimization. */
45 static int n_reduced_expressions;
47 /** Detect basic iteration variables.
49 * The variable ir represented by a subgraph as this:
59 * Where op is a Add or Sub, and init is loop invariant.
60 * @@@ So far we only accept Phi nodes with two predecessors.
61 * We could expand this to Phi nodes where all preds are either
62 * op or loop invariant.
64 * @param n A phi node.
66 static struct induct_var_info *is_induction_variable (ir_node *n) {
68 ir_node *phi_pred_0, *phi_pred_1, *add_r, *add_l, *sub_r, *sub_l ;
69 ir_op *phi_pred_0_op, *phi_pred_1_op;
70 struct induct_var_info *info;
73 info->operation_code = NULL;
74 info->increment = NULL;
78 info->init_pred_pos = -1;
79 info->op_pred_pos = -1;
81 assert(get_irn_op(n) == op_Phi);
83 /* The necessary conditions for the phi node. */
84 if (get_irn_arity(n) != 2 ||
85 !has_backedges(get_nodes_block(n)) )
88 /* The predecessors of the phi node. */
89 phi_pred_0 = get_Phi_pred(n, 0);
90 phi_pred_1 = get_Phi_pred(n, 1);
92 /*The operation of the predecessors. */
93 phi_pred_0_op = get_irn_op(get_Phi_pred(n, 0));
94 phi_pred_1_op = get_irn_op(get_Phi_pred(n, 1));
96 /*Compute if the induction variable is added or substracted wiht a constant . */
97 if (phi_pred_0_op == op_Add){
98 info->operation_code = op_Add;
99 add_l = get_Add_left(phi_pred_0);
100 add_r = get_Add_right(phi_pred_0);
101 info->op_pred_pos = 0;
103 info->increment = add_r;
104 } else if (add_r == n){
105 info->increment = add_l;
107 } else if (phi_pred_1_op == op_Add){
108 info->operation_code = op_Add ;
109 add_l = get_Add_left(phi_pred_1);
110 add_r = get_Add_right(phi_pred_1);
111 info->op_pred_pos = 1;
113 info->increment = add_r;
114 } else if (add_r == n){
115 info->increment = add_l;
117 } else if (phi_pred_0_op == op_Sub){
118 info->operation_code = op_Sub;
119 sub_r = get_Sub_right(phi_pred_0);
120 sub_l = get_Sub_left(phi_pred_0);
121 info->op_pred_pos = 0;
123 info->increment = sub_r;
124 } else if (sub_r == n){
125 info->increment = sub_l;
127 } else if (phi_pred_1_op == op_Sub){
128 info->operation_code = op_Sub;
129 sub_r = get_Sub_right(phi_pred_1);
130 sub_l = get_Sub_left(phi_pred_1);
131 info->op_pred_pos = 1;
133 info->increment = sub_r;
138 /*Compute the position of the backedge. */
139 if (is_backedge(get_nodes_block(n), 0)){
141 info->init_pred_pos = 1;
142 info->op = get_Phi_pred(n, 0);
143 info->init = get_Phi_pred(n, 1);
144 } else if (is_backedge(get_nodes_block(n), 1)){
146 info->init_pred_pos = 0;
147 info->op = get_Phi_pred(n, 1);
148 info->init = get_Phi_pred(n, 0);
151 if (info->be_pos == 0) {
152 if (get_Block_dom_depth(get_nodes_block(phi_pred_1)) >=
153 get_Block_dom_depth(get_nodes_block(n))) {
156 } else if (get_Block_dom_depth(get_nodes_block(phi_pred_0)) >=
157 get_Block_dom_depth(get_nodes_block(n))) return NULL;
159 if (get_Block_dom_depth(get_nodes_block(info->increment)) >=
160 get_Block_dom_depth(get_nodes_block(n))) return NULL;
166 const char *get_irg_dump_name(ir_graph *irg);
171 * @param *srong The node to be reduce.
172 * @param *env Free environment pointer.
174 * The node for reduce mus be in a loop whit *phi and *add.The *phi node muss
175 * have 2 predecessors a Const and a Add node. The predecessors of Add node muss
176 * be *phi and a Const node. The nodes a, b, c muss be Const with dom_depth <
180 void reduce_itervar(ir_node *itervar_phi, void *env) {
181 ir_node *strong = NULL, *cmp = NULL, *c, *cmp_const;
182 int phi_pred, strong_in_Phi = 0, cmp_in_phi = 0, out_loop_res = 1;
184 // This "if" finds the node for reduce.
187 // This "if" finds the Phi predecessors for the node that must be reduced.
188 if ((get_irn_op(itervar_phi) == op_Phi) &&
189 is_induction_variable(itervar_phi) != NULL ) {
190 phi_pred = get_irn_n_outs(itervar_phi);
191 ir_loop *l_itervar_phi = get_irn_loop(get_nodes_block(itervar_phi));
193 for (int i = 0; i < phi_pred; i++) {
194 ir_node *out = get_irn_out(itervar_phi, i);
195 ir_op *out_op = get_irn_op(out);
196 if (get_irn_loop(get_nodes_block(out)) != l_itervar_phi)
198 if (out_op == op_Mul){
201 }else if (out_op == op_Cmp){
206 if (strong == NULL || (strong_in_Phi > 1)) return;
208 if(get_irn_op(get_Mul_right(strong)) == op_Phi)
209 c = get_Mul_left(strong);
211 c = get_Mul_right(strong);
215 if (get_Block_dom_depth(get_nodes_block(c)) >=
216 get_Block_dom_depth(get_nodes_block(itervar_phi))) return;
218 // if (get_opt_strength_red_verbosity() == 2) {
220 printf("The constant of Reducing node is: "); DDMN(c);
221 printf("The Phi node is"); DDMN(itervar_phi);
222 printf("Reducing node: "); DDMN(strong);
223 printf(" iter var is "); DDMN(ivi.op);
224 printf(" in graph "); DDMG(current_ir_graph);
227 ir_node *inc , *init , *new_phi, *in[2], *new_op = NULL, *block_init, *block_inc;
229 ir_node *init_block = get_nodes_block(ivi.init);
230 ir_node *increment_block = get_nodes_block(ivi.increment);
231 ir_node *c_block = get_nodes_block(c) ;
233 if (get_Block_dom_depth(increment_block) >= get_Block_dom_depth(c_block))
234 block_inc = increment_block;
238 if (get_Block_dom_depth(init_block) >= get_Block_dom_depth(c_block))
239 block_init = init_block;
241 block_init = c_block;
243 /* Compute new loop invariant increment and initialization values. */
244 inc = new_r_Mul (current_ir_graph, block_inc, ivi.increment, c, get_irn_mode(c));
245 init = new_r_Mul (current_ir_graph, block_init, ivi.init, c, get_irn_mode(ivi.init));
247 /* Generate a new basic induction variable. Break the data flow loop
248 initially by using an Unknown node. */
249 in[ivi.op_pred_pos] = new_Unknown(get_irn_mode(init));
250 in[ivi.init_pred_pos] = init;
251 new_phi = new_r_Phi(current_ir_graph, get_nodes_block(itervar_phi), 2, in, get_irn_mode(init));
252 mark_irn_visited(new_phi);
254 if (ivi.operation_code == op_Add)
255 new_op = new_r_Add(current_ir_graph, get_nodes_block(ivi.op), inc, new_phi,
257 else if (ivi.operation_code == op_Sub)
258 new_op = new_r_Sub(current_ir_graph, get_nodes_block(ivi.op), new_phi, inc,
260 set_Phi_pred(new_phi, ivi.op_pred_pos, new_op);
262 /* Replace the use of the strength reduced value. */
263 exchange(strong, new_phi);
265 if (cmp == NULL || cmp_in_phi > 1 || out_loop_res == 0) return;
267 if (get_irn_op(get_Cmp_left(cmp)) == op_Const)
268 cmp_const = get_Cmp_left(cmp);
270 cmp_const = get_Cmp_right(cmp);
272 if (get_irn_loop(get_nodes_block(cmp)) != l_itervar_phi) return;
275 printf("It is possibale to exchange the Cmp with a new Cmp \n");
276 printf("The constant of Cmp node is: "); DDMN(cmp_const);
277 printf("The Phi node is"); DDMN(itervar_phi);
278 printf("Cmp node: "); DDMN(cmp);
279 printf(" in graph "); DDMG(current_ir_graph);
282 ir_node *new_cmp_const, *new_cmp, *cmp_const_block = get_nodes_block(cmp_const);
284 if (get_Block_dom_depth(init_block) >= get_Block_dom_depth(cmp_const_block))
285 block_init = init_block;
287 block_init = cmp_const_block;
289 new_cmp_const = new_r_Mul (current_ir_graph, block_init, cmp_const,
290 c, get_irn_mode(ivi.init));
291 new_cmp = new_r_Cmp (current_ir_graph, get_nodes_block(cmp),
292 new_phi, new_cmp_const);
293 exchange(cmp, new_cmp);
298 /* Performs strength reduction for the passed graph. */
299 void reduce_strength(ir_graph *irg) {
300 ir_graph *rem = current_ir_graph;
301 current_ir_graph = irg;
303 if (!get_optimize() || !get_opt_strength_red()) return;
305 /* -- Precompute some information -- */
306 /* Call algorithm that computes the backedges */
307 construct_cf_backedges(irg);
308 /* Call algorithm that computes the dominator trees. */
310 /* Call algorithm that computes the out edges */
312 /* -- Search expressions that can be optimized -- */
313 irg_walk_graph(irg, NULL, reduce_itervar, NULL);
315 current_ir_graph = rem;