src/vm/jit/optimizing/ssa_phi.c

   1 /* src/vm/jit/optimizing/ssa.c - static single-assignment form
   2
   3    Copyright (C) 2005-2007, 2008
   4    CACAOVM - Verein zur Foerderung der freien virtuellen Maschine CACAO
   5
   6    This file is part of CACAO.
   7
   8    This program is free software; you can redistribute it and/or
   9    modify it under the terms of the GNU General Public License as
  10    published by the Free Software Foundation; either version 2, or (at
  11    your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful, but
  14    WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16    General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program; if not, write to the Free Software
  20    Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  21    02111-1307, USA.
  22
  23 */
  24
  25
  26 #include "config.h"
  27
  28 #include <stdio.h>
  29 #include <stdlib.h>
  30
  31 #include "mm/memory.h"
  32
  33 #include "toolbox/bitvector.h"
  34 #include "toolbox/worklist.h"
  35
  36 #include "vm/jit/builtin.hpp"
  37
  38 #include "vm/jit/jit.hpp" /* icmd_table */
  39
  40 #include "vm/jit/optimizing/dominators.hpp"
  41 #include "vm/jit/optimizing/graph.h"
  42 #include "vm/jit/optimizing/lifetimes.h"
  43 #include "vm/jit/optimizing/lsra.h"
  44 #include "vm/jit/optimizing/ssa.h"
  45 #include "vm/jit/optimizing/ssa_phi.h"
  46
  47 #if defined(SSA_DEBUG_VERBOSE)
  48 #include "vm/options.h"   /* compileverbose */
  49 #endif
  50
  51 /* ssa_place_phi_functions *****************************************************
  52
  53 Algorithm is based on "modern compiler implementation in C" from andrew
  54 w. appel, edition 2004
  55
  56 Corrections:
  57 page 441 Algorithm 19.6. Inserting phi-functions:
  58
  59 ...
  60     for each Y in DF[n]
  61 -       if Y not element of A phi [n]
  62 +       if a not element of A phi [n]
  63             insert the statment a <- ...
  64 ...
  65 ...
  66 -       A phi [n] <- A phi [n] join {Y}
  67 +       A phi [n] <- A phi [n] join {a}
  68 -      if Y not element of A orig [n]
  69 +      if a not element of A orig [Y]
  70            W <- W join {Y}
  71
  72
  73 ls->phi[n][a][p] is created and populated.
  74
  75 n in [0..ls->basicblockcount[
  76 a in [0..ls->ssavarcount[
  77 p in [1..Count of Predecessors of Basicblock n]
  78
  79 For each basicblock Y in the dominance frontier of a basicblock n (0 <= n <
  80 ls->basicblockcount) in which a variable (0 <= a < ls->ssavarcount) is defined
  81 an entry in ls->phi[Y][a] is created.
  82 This entry is an array with the number of predecessors of Y elements + 1
  83 elements.
  84 This elements are all set to the variable a and represent the phi function which
  85 will get ai = phi(ai1, ai2, ..., aip) after ssa_rename.
  86
  87
  88 ls->phi[n][a] == NULL, if no phi function for Variable a for Basicblock n exists
  89
  90 or
  91
  92 ls->phi[n][a][0] == a, representing the result of the phi function and
  93 ls->phi[n][a][p] == a, representing the arguments of the phi function.
  94
  95 *******************************************************************************/
  96
  97
  98 void ssa_place_phi_functions(jitdata *jd, graphdata *gd, dominatordata *dd)
  99 {
 100         int a,i,j,n,Y;
 101         bitvector *def_sites;
 102         bitvector *A_phi;    /* [0..ls->basicblockcount[ of */
 103                              /* ls->ssavarcount Bit         */
 104         worklist *W;
 105         int num_pred;
 106
 107         lsradata *ls;
 108
 109         ls = jd->ls;
 110
 111         W = wl_new(ls->basicblockcount);
 112
 113         def_sites = DMNEW(bitvector, ls->ssavarcount);
 114         for(a = 0; a < ls->ssavarcount; a++)
 115                 def_sites[a] = bv_new(ls->basicblockcount);
 116
 117         ls->phi = DMNEW(int **, ls->basicblockcount);
 118         A_phi = DMNEW(bitvector, ls->basicblockcount);
 119         for(i = 0; i < ls->basicblockcount; i++) {
 120                 ls->phi[i] = DMNEW(int *, ls->ssavarcount);
 121                 for(j = 0; j < ls->ssavarcount; j++)
 122                         ls->phi[i][j] = NULL;
 123                 A_phi[i] = bv_new(ls->ssavarcount);
 124         }
 125
 126         /* copy var_def to def_sites */
 127         /* var_def is valid for 0.. jd->basicblockcount (bb 0 for param init) */
 128
 129         for(n = 0; n <= jd->basicblockcount; n++)
 130                 for(a = 0; a < ls->ssavarcount; a++)
 131                         if (bv_get_bit(ls->var_def[n], a))
 132                                 bv_set_bit(def_sites[a], n);
 133 #ifdef SSA_DEBUG_VERBOSE
 134         if (compileverbose) {
 135                 printf("var Definitions:\n");
 136                 for(i = 0; i < ls->ssavarcount; i++) {
 137                         printf("def_sites[%3i]=%p:",i,(void *)def_sites[i]);
 138                         for(j = 0; j < ls->basicblockcount; j++) {
 139                                 if ((j % 5) == 0) printf(" ");
 140                                 if (bv_get_bit(def_sites[i], j))
 141                                         printf("1");
 142                                 else
 143                                         printf("0");
 144                         }
 145                         printf(" (");
 146
 147                         printf("\n");
 148                 }
 149         }
 150 #endif
 151
 152         for(a = 0; a < ls->ssavarcount; a++) {
 153
 154                 /* W<-def_sites(a) */
 155
 156                 for(n = 0; n < ls->basicblockcount; n++)
 157                         if (bv_get_bit(def_sites[a],n)) {
 158                                 wl_add(W, n);
 159                         }
 160
 161                 while (!wl_is_empty(W)) { /* W not empty */
 162                         n = wl_get(W);
 163
 164                         for(i = 0; i < dd->num_DF[n]; i++) {
 165                                 Y = dd->DF[n][i];
 166
 167                                 /* Node Y is in Dominance Frontier of n -> */
 168                                 /* insert phi function for a at top of Y*/
 169
 170                                 _SSA_CHECK_BOUNDS(Y, 0, ls->basicblockcount);
 171                                 if (bv_get_bit( A_phi[Y], a) == 0) {
 172
 173                                         /* a is not a Element of A_phi[Y] */
 174                                         /* a <- phi(a,a...,a) to be inserted at top of Block Y */
 175                                         /* phi has as many arguments, as Y has predecessors    */
 176
 177                                         num_pred =  graph_get_num_predecessor(gd, Y);
 178                                         ls->phi[Y][a] = DMNEW(int, num_pred + 1);
 179                                         for (j = 0; j < num_pred + 1; j++)
 180                                                 ls->phi[Y][a][j] = a;
 181
 182                                         /* increment the number of definitions of a by one */
 183                                         /* for this phi function */
 184
 185                                         ls->num_defs[a]++;
 186
 187                                         bv_set_bit(A_phi[Y], a);
 188                                         if (bv_get_bit(ls->var_def[Y],a)==0) {
 189
 190                                                 /* Iterated Dominance Frontier Criterion:  */
 191                                                 /* if Y had no definition for a, insert it */
 192                                                 /* into the Worklist, since now it         */
 193                                                 /* defines a through the phi function      */
 194
 195                                                 wl_add(W, Y);
 196                                         }
 197                                 }
 198                         }
 199                 }
 200         }
 201 }
 202
 203 void ssa_generate_phi_moves(jitdata *jd, graphdata *gd) {
 204         int a, i, j, pred;
 205         graphiterator iter;
 206         lsradata *ls;
 207
 208         ls = jd->ls;
 209
 210         /* count moves to be inserted at the end of each block in moves[] */
 211
 212         ls->num_phi_moves = DMNEW(int, ls->basicblockcount);
 213         for(i = 0; i < ls->basicblockcount; i++)
 214                 ls->num_phi_moves[i] = 0;
 215         for(i = 0; i < ls->basicblockcount; i++)
 216                 for(a = 0; a < ls->ssavarcount; a++)
 217                         if (ls->phi[i][a] != NULL) {
 218 #if 0
 219                                 if (ls->lifetime[ls->phi[i][a][0]].use == NULL) {
 220                                         /* Var defined (only <- SSA Form!) in this phi function */
 221                                         /* and not used anywhere -> delete phi function and set */
 222                                         /* var to unused */
 223
 224                                         /* TODO: first delete use sites of arguments of phi */
 225                                         /* function */
 226                                         VAR(ls->lifetime[ls->phi[i][a][0]].v_index)->type = UNUSED;
 227                                         ls->lifetime[ls->phi[i][a][0]].def = NULL;
 228                                         ls->phi[i][a] = NULL;
 229                                 }
 230                                 else
 231 #endif
 232                                         {
 233                                         pred = graph_get_first_predecessor(gd, i, &iter);
 234                                         for(; pred != -1; pred = graph_get_next(&iter)) {
 235                                                 ls->num_phi_moves[pred]++;
 236                                         }
 237                                 }
 238                         }
 239
 240         /* allocate ls->phi_moves */
 241
 242         ls->phi_moves = DMNEW( int **, ls->basicblockcount);
 243         for(i = 0; i < ls->basicblockcount; i++) {
 244                 ls->phi_moves[i] = DMNEW( int *, ls->num_phi_moves[i]);
 245                 for(j = 0; j <ls->num_phi_moves[i]; j++)
 246                         ls->phi_moves[i][j] = DMNEW(int, 2);
 247 #ifdef SSA_DEBUG_VERBOSE
 248                 if (compileverbose)
 249                         printf("ssa_generate_phi_moves: ls_num_phi_moves[%3i] = %3i\n",
 250                                    i, ls->num_phi_moves[i]);
 251 #endif
 252         }
 253
 254         /* populate ls->phi_moves */
 255
 256         for(i = 0; i < ls->basicblockcount; i++)
 257                 ls->num_phi_moves[i] = 0;
 258         for(i = 0; i < ls->basicblockcount; i++)
 259                 for(a = 0; a < ls->ssavarcount; a++)
 260                         if (ls->phi[i][a] != NULL) {
 261                                 pred = graph_get_first_predecessor(gd, i, &iter);
 262                                 for(j = 0; pred != -1; j++, pred = graph_get_next(&iter)) {
 263                                         /* target is phi[i][a][0] */
 264                                         /* source is phi[i][a][j+1] */
 265                                         if (ls->phi[i][a][j+1] != ls->varcount_with_indices) {
 266                                                 /* valid move */
 267                                                 if (ls->phi[i][a][0] != ls->phi[i][a][j+1]) {
 268                                                         ls->phi_moves[pred][ls->num_phi_moves[pred]][0] =
 269                                                                 ls->phi[i][a][0];
 270                                                         ls->phi_moves[pred][(ls->num_phi_moves[pred])++][1]=
 271                                                                 ls->phi[i][a][j+1];
 272                                                 }
 273                                         }
 274                                 }
 275                         }
 276 }
 277
 278 #ifdef SSA_DEBUG_VERBOSE
 279 void ssa_print_phi(lsradata *ls, graphdata *gd) {
 280         int i,j,k;
 281
 282         printf("phi Functions (varcount_with_indices: %3i):\n",
 283                    ls->varcount_with_indices);
 284         for(i = 0; i < ls->basicblockcount; i++) {
 285                 for(j = 0; j < ls->ssavarcount; j++) {
 286                         if (ls->phi[i][j] != NULL) {
 287                                 printf("BB %3i %3i = phi(", i, ls->phi[i][j][0]);
 288                                 for(k = 1; k <= graph_get_num_predecessor(gd, i); k++)
 289                                         printf("%3i ",ls->phi[i][j][k]);
 290                                 printf(")\n");
 291                         }
 292                 }
 293         }
 294
 295 }
 296 #endif
 297
 298 /*
 299  * These are local overrides for various environment variables in Emacs.
 300  * Please do not remove this and leave it at the end of the file, where
 301  * Emacs will automagically detect them.
 302  * ---------------------------------------------------------------------
 303  * Local variables:
 304  * mode: c
 305  * indent-tabs-mode: t
 306  * c-basic-offset: 4
 307  * tab-width: 4
 308  * End:
 309  */