mono/mini/cfold.c

   1 /*
   2  * cfold.c: Constant folding support
   3  *
   4  * Author:
   5  *   Paolo Molaro (lupus@ximian.com)
   6  *   Dietmar Maurer (dietmar@ximian.com)
   7  *
   8  * (C) 2003 Ximian, Inc.  http://www.ximian.com
   9  */
  10 #include "mini.h"
  11 #include "ir-emit.h"
  12
  13 int
  14 mono_is_power_of_two (guint32 val)
  15 {
  16         int i, j, k;
  17
  18         for (i = 0, j = 1, k = 0xfffffffe; i < 32; ++i, j = j << 1, k = k << 1) {
  19                 if (val & j)
  20                         break;
  21         }
  22         if (i == 32 || val & k)
  23                 return -1;
  24         return i;
  25 }
  26
  27 #ifndef G_MININT32
  28 #define MYGINT32_MAX 2147483647
  29 #define G_MININT32 (-MYGINT32_MAX -1)
  30 #endif
  31
  32 #define FOLD_UNOP(name,op)      \
  33         case name:      \
  34             dest->inst_c0 = op arg1->inst_c0; \
  35         break;
  36
  37 #define FOLD_BINOP(name, op) \
  38         case name:      \
  39             dest->inst_c0 = arg1->inst_c0 op arg2->inst_c0;     \
  40         break;
  41
  42 #define FOLD_BINOPC(name,op,cast)       \
  43         case name:      \
  44             dest->inst_c0 = (cast)arg1->inst_c0 op (cast)arg2->inst_c0; \
  45         break;
  46
  47 #define FOLD_BINOP2_IMM(name, op) \
  48         case name:      \
  49             dest->inst_c0 = arg1->inst_c0 op ins->inst_imm;     \
  50         break;
  51
  52 #define FOLD_BINOPC2_IMM(name, op, cast) \
  53         case name:      \
  54             dest->inst_c0 = (cast)arg1->inst_c0 op (cast)ins->inst_imm; \
  55         break;
  56
  57 #define FOLD_BINOPCXX(name,op,cast)     \
  58         case name:      \
  59             res = (cast)arg1->inst_c0 op (cast)arg2->inst_c0;   \
  60         break; \
  61
  62 #define ALLOC_DEST(cfg, dest, ins) do { \
  63     if (!(dest)) { \
  64         MONO_INST_NEW ((cfg), (dest), -1); \
  65         (dest)->dreg = (ins)->dreg; \
  66     } \
  67 } while (0)
  68
  69 /**
  70  * mono_constant_fold_ins:
  71  *
  72  * Perform constant folding on INS, using ARG1 and ARG2 as the arguments. If OVERWRITE is
  73  * true, then store the result back into INS and return INS. Otherwise allocate a new ins,
  74  * store the result into it and return it. If constant folding cannot be performed, return
  75  * NULL.
  76  */
  77 MonoInst*
  78 mono_constant_fold_ins (MonoCompile *cfg, MonoInst *ins, MonoInst *arg1, MonoInst *arg2, gboolean overwrite)
  79 {
  80         MonoInst *dest = NULL;
  81
  82         if (overwrite)
  83                 dest = ins;
  84
  85         switch (ins->opcode) {
  86         case OP_IMUL:
  87         case OP_IADD:
  88         case OP_IAND:
  89         case OP_IOR:
  90         case OP_IXOR:
  91                 if (arg2->opcode == OP_ICONST) {
  92                         if (arg1->opcode == OP_ICONST) {
  93                                 ALLOC_DEST (cfg, dest, ins);
  94                                 switch (ins->opcode) {
  95                                         FOLD_BINOP (OP_IMUL, *);
  96                                         FOLD_BINOP (OP_IADD, +);
  97                                         FOLD_BINOP (OP_IAND, &);
  98                                         FOLD_BINOP (OP_IOR, |);
  99                                         FOLD_BINOP (OP_IXOR, ^);
 100                                 }
 101                                 dest->opcode = OP_ICONST;
 102                                 MONO_INST_NULLIFY_SREGS (dest);
 103                         }
 104                 } else if (arg1->opcode == OP_ICONST) {
 105                         /*
 106                          * This is commutative so swap the arguments, allowing the _imm variant
 107                          * to be used later.
 108                          */
 109                         if (mono_op_to_op_imm (ins->opcode) != -1) {
 110                                 ALLOC_DEST (cfg, dest, ins);
 111                                 dest->opcode = mono_op_to_op_imm (ins->opcode);
 112                                 dest->sreg1 = ins->sreg2;
 113                                 dest->sreg2 = -1;
 114                                 dest->inst_imm = arg1->inst_c0;
 115                         }
 116                 }
 117                 break;
 118         case OP_IMUL_IMM:
 119         case OP_IADD_IMM:
 120         case OP_IAND_IMM:
 121         case OP_IOR_IMM:
 122         case OP_IXOR_IMM:
 123         case OP_ISUB_IMM:
 124         case OP_ISHL_IMM:
 125         case OP_ISHR_IMM:
 126         case OP_ISHR_UN_IMM:
 127         case OP_SHL_IMM:
 128                 if (arg1->opcode == OP_ICONST) {
 129                         ALLOC_DEST (cfg, dest, ins);
 130                         switch (ins->opcode) {
 131                                 FOLD_BINOP2_IMM (OP_IMUL_IMM, *);
 132                                 FOLD_BINOP2_IMM (OP_IADD_IMM, +);
 133                                 FOLD_BINOP2_IMM (OP_IAND_IMM, &);
 134                                 FOLD_BINOP2_IMM (OP_IOR_IMM, |);
 135                                 FOLD_BINOP2_IMM (OP_IXOR_IMM, ^);
 136                                 FOLD_BINOP2_IMM (OP_ISUB_IMM, -);
 137                                 FOLD_BINOPC2_IMM (OP_ISHL_IMM, <<, gint32);
 138                                 FOLD_BINOPC2_IMM (OP_ISHR_IMM, >>, gint32);
 139                                 FOLD_BINOPC2_IMM (OP_ISHR_UN_IMM, >>, guint32);
 140                                 FOLD_BINOP2_IMM (OP_SHL_IMM, <<);
 141                         }
 142                         dest->opcode = OP_ICONST;
 143                         MONO_INST_NULLIFY_SREGS (dest);
 144                 }
 145                 break;
 146         case OP_ISUB:
 147         case OP_ISHL:
 148         case OP_ISHR:
 149         case OP_ISHR_UN:
 150                 if ((arg1->opcode == OP_ICONST) && (arg2->opcode == OP_ICONST)) {
 151                         ALLOC_DEST (cfg, dest, ins);
 152                         switch (ins->opcode) {
 153                                 FOLD_BINOP (OP_ISUB, -);
 154                                 FOLD_BINOP (OP_ISHL, <<);
 155                                 FOLD_BINOP (OP_ISHR, >>);
 156                                 FOLD_BINOPC (OP_ISHR_UN, >>, guint32);
 157                         }
 158                         dest->opcode = OP_ICONST;
 159                         MONO_INST_NULLIFY_SREGS (dest);
 160                 }
 161                 break;
 162         case OP_IDIV:
 163         case OP_IDIV_UN:
 164         case OP_IREM:
 165         case OP_IREM_UN:
 166                 if ((arg1->opcode == OP_ICONST) && (arg2->opcode == OP_ICONST)) {
 167                         if ((arg2->inst_c0 == 0) || ((arg1->inst_c0 == G_MININT32) && (arg2->inst_c0 == -1)))
 168                                 return NULL;
 169                         ALLOC_DEST (cfg, dest, ins);
 170                         switch (ins->opcode) {
 171                                 FOLD_BINOPC (OP_IDIV, /, gint32);
 172                                 FOLD_BINOPC (OP_IDIV_UN, /, guint32);
 173                                 FOLD_BINOPC (OP_IREM, %, gint32);
 174                                 FOLD_BINOPC (OP_IREM_UN, %, guint32);
 175                         }
 176                         dest->opcode = OP_ICONST;
 177                         MONO_INST_NULLIFY_SREGS (dest);
 178                 }
 179                 break;
 180         case OP_IDIV_IMM:
 181         case OP_IDIV_UN_IMM:
 182         case OP_IREM_IMM:
 183         case OP_IREM_UN_IMM:
 184                 if (arg1->opcode == OP_ICONST) {
 185                         if ((ins->inst_imm == 0) || ((arg1->inst_c0 == G_MININT32) && (ins->inst_imm == -1)))
 186                                 return NULL;
 187                         ALLOC_DEST (cfg, dest, ins);
 188                         switch (ins->opcode) {
 189                                 FOLD_BINOPC2_IMM (OP_IDIV_IMM, /, gint32);
 190                                 FOLD_BINOPC2_IMM (OP_IDIV_UN_IMM, /, guint32);
 191                                 FOLD_BINOPC2_IMM (OP_IREM_IMM, %, gint32);
 192                                 FOLD_BINOPC2_IMM (OP_IREM_UN_IMM, %, guint32);
 193                         default:
 194                                 g_assert_not_reached ();
 195                         }
 196                         dest->opcode = OP_ICONST;
 197                         MONO_INST_NULLIFY_SREGS (dest);
 198                 }
 199                 break;
 200                 /* case OP_INEG: */
 201         case OP_INOT:
 202         case OP_INEG:
 203                 if (arg1->opcode == OP_ICONST) {
 204                         /* INEG sets cflags on x86, and the LNEG decomposition depends on that */
 205                         if ((ins->opcode == OP_INEG) && ins->next && (ins->next->opcode == OP_ADC_IMM))
 206                                 return NULL;
 207                         ALLOC_DEST (cfg, dest, ins);
 208                         switch (ins->opcode) {
 209                                 FOLD_UNOP (OP_INEG,-);
 210                                 FOLD_UNOP (OP_INOT,~);
 211                         }
 212                         dest->opcode = OP_ICONST;
 213                         MONO_INST_NULLIFY_SREGS (dest);
 214                 }
 215                 break;
 216         case OP_MOVE:
 217 #if SIZEOF_REGISTER == 8
 218                 if ((arg1->opcode == OP_ICONST) || (arg1->opcode == OP_I8CONST)) {
 219 #else
 220                 if (arg1->opcode == OP_ICONST) {
 221 #endif
 222                         ALLOC_DEST (cfg, dest, ins);
 223                         dest->opcode = arg1->opcode;
 224                         MONO_INST_NULLIFY_SREGS (dest);
 225                         dest->inst_c0 = arg1->inst_c0;
 226                 }
 227                 break;
 228         case OP_VMOVE:
 229                 if (arg1->opcode == OP_VZERO) {
 230                         ALLOC_DEST (cfg, dest, ins);
 231                         dest->opcode = OP_VZERO;
 232                         dest->sreg1 = -1;
 233                 }
 234                 break;
 235         case OP_XMOVE:
 236                 if (arg1->opcode == OP_XZERO) {
 237                         ALLOC_DEST (cfg, dest, ins);
 238                         dest->opcode = OP_XZERO;
 239                         dest->sreg1 = -1;
 240                 }
 241                 break;
 242         case OP_COMPARE:
 243         case OP_ICOMPARE:
 244         case OP_COMPARE_IMM:
 245         case OP_ICOMPARE_IMM: {
 246                 MonoInst dummy_arg2;
 247                 if (ins->sreg2 == -1) {
 248                         arg2 = &dummy_arg2;
 249                         arg2->opcode = OP_ICONST;
 250                         arg2->inst_c0 = ins->inst_imm;
 251                 }
 252
 253                 if ((arg1->opcode == OP_ICONST) && (arg2->opcode == OP_ICONST) && ins->next) {
 254                         MonoInst *next = ins->next;
 255                         gboolean res = FALSE;
 256
 257                         switch (next->opcode) {
 258                         case OP_CEQ:
 259                         case OP_ICEQ:
 260                         case OP_CGT:
 261                         case OP_ICGT:
 262                         case OP_CGT_UN:
 263                         case OP_ICGT_UN:
 264                         case OP_CLT:
 265                         case OP_ICLT:
 266                         case OP_CLT_UN:
 267                         case OP_ICLT_UN:
 268                                 switch (next->opcode) {
 269                                         FOLD_BINOPCXX (OP_CEQ,==,gint32);
 270                                         FOLD_BINOPCXX (OP_ICEQ,==,gint32);
 271                                         FOLD_BINOPCXX (OP_CGT,>,gint32);
 272                                         FOLD_BINOPCXX (OP_ICGT,>,gint32);
 273                                         FOLD_BINOPCXX (OP_CGT_UN,>,guint32);
 274                                         FOLD_BINOPCXX (OP_ICGT_UN,>,guint32);
 275                                         FOLD_BINOPCXX (OP_CLT,<,gint32);
 276                                         FOLD_BINOPCXX (OP_ICLT,<,gint32);
 277                                         FOLD_BINOPCXX (OP_CLT_UN,<,guint32);
 278                                         FOLD_BINOPCXX (OP_ICLT_UN,<,guint32);
 279                                 }
 280
 281                                 if (overwrite) {
 282                                         NULLIFY_INS (ins);
 283                                         next->opcode = OP_ICONST;
 284                                         next->inst_c0 = res;
 285                                         MONO_INST_NULLIFY_SREGS (next);
 286                                 } else {
 287                                         ALLOC_DEST (cfg, dest, ins);
 288                                         dest->opcode = OP_ICONST;
 289                                         dest->inst_c0 = res;
 290                                 }
 291                                 break;
 292                         case OP_IBEQ:
 293                         case OP_IBNE_UN:
 294                         case OP_IBGT:
 295                         case OP_IBGT_UN:
 296                         case OP_IBGE:
 297                         case OP_IBGE_UN:
 298                         case OP_IBLT:
 299                         case OP_IBLT_UN:
 300                         case OP_IBLE:
 301                         case OP_IBLE_UN:
 302                                 switch (next->opcode) {
 303                                         FOLD_BINOPCXX (OP_IBEQ,==,gint32);
 304                                         FOLD_BINOPCXX (OP_IBNE_UN,!=,guint32);
 305                                         FOLD_BINOPCXX (OP_IBGT,>,gint32);
 306                                         FOLD_BINOPCXX (OP_IBGT_UN,>,guint32);
 307                                         FOLD_BINOPCXX (OP_IBGE,>=,gint32);
 308                                         FOLD_BINOPCXX (OP_IBGE_UN,>=,guint32);
 309                                         FOLD_BINOPCXX (OP_IBLT,<,gint32);
 310                                         FOLD_BINOPCXX (OP_IBLT_UN,<,guint32);
 311                                         FOLD_BINOPCXX (OP_IBLE,<=,gint32);
 312                                         FOLD_BINOPCXX (OP_IBLE_UN,<=,guint32);
 313                                 }
 314
 315                                 if (overwrite) {
 316                                         /*
 317                                          * Can't nullify OP_COMPARE here since the decompose long branch
 318                                          * opcodes depend on it being executed. Also, the branch might not
 319                                          * be eliminated after all if loop opts is disabled, for example.
 320                                          */
 321                                         if (res)
 322                                                 next->flags |= MONO_INST_CFOLD_TAKEN;
 323                                         else
 324                                                 next->flags |= MONO_INST_CFOLD_NOT_TAKEN;
 325                                 } else {
 326                                         ALLOC_DEST (cfg, dest, ins);
 327                                         dest->opcode = OP_ICONST;
 328                                         dest->inst_c0 = res;
 329                                 }
 330                                 break;
 331                         case OP_NOP:
 332                         case OP_BR:
 333                                 /* This happens when a conditional branch is eliminated */
 334                                 if (next->next == NULL) {
 335                                         /* Last ins */
 336                                         if (overwrite)
 337                                                 NULLIFY_INS (ins);
 338                                 }
 339                                 break;
 340                         default:
 341                                 return NULL;
 342                         }
 343                 }
 344                 break;
 345         }
 346         case OP_FMOVE:
 347                 if (arg1->opcode == OP_R8CONST) {
 348                         ALLOC_DEST (cfg, dest, ins);
 349                         dest->opcode = OP_R8CONST;
 350                         dest->sreg1 = -1;
 351                         dest->inst_p0 = arg1->inst_p0;
 352                 }
 353                 break;
 354
 355                 /*
 356                  * TODO:
 357                  *      conv.* opcodes.
 358                  *      *ovf* opcodes? It's slow and hard to do in C.
 359                  *      switch can be replaced by a simple jump
 360                  */
 361         default:
 362                 return NULL;
 363         }
 364
 365     return dest;
 366 }