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
  12 int
  13 mono_is_power_of_two (guint32 val)
  14 {
  15         int i, j, k;
  16
  17         for (i = 0, j = 1, k = 0xfffffffe; i < 32; ++i, j = j << 1, k = k << 1) {
  18                 if (val & j)
  19                         break;
  20         }
  21         if (i == 32 || val & k)
  22                 return -1;
  23         return i;
  24 }
  25
  26 #define FOLD_BINOP(name,op)     \
  27         case name:      \
  28                 if (inst->inst_i0->opcode != OP_ICONST) \
  29                         return; \
  30                 if (inst->inst_i1->opcode == OP_ICONST) {       \
  31                         inst->opcode = OP_ICONST;       \
  32                         inst->inst_c0 = inst->inst_i0->inst_c0 op inst->inst_i1->inst_c0;       \
  33                 } \
  34                 return;
  35
  36 /*
  37  * We try to put constants on the left side of a commutative operation
  38  * because it reduces register pressure and it matches the usual cpu
  39  * instructions with immediates.
  40  */
  41 #define FOLD_BINOPCOMM(name,op) \
  42         case name:      \
  43                 if (inst->inst_i0->opcode == OP_ICONST) {\
  44                         if (inst->inst_i1->opcode == OP_ICONST) {       \
  45                                 inst->opcode = OP_ICONST;       \
  46                                 inst->inst_c0 = inst->inst_i0->inst_c0 op inst->inst_i1->inst_c0;       \
  47                                 return; \
  48                         } else { \
  49                                 MonoInst *tmp = inst->inst_i0;  \
  50                                 inst->inst_i0 = inst->inst_i1;  \
  51                                 inst->inst_i1 = tmp;    \
  52                        } \
  53                 } \
  54                 if (inst->inst_i1->opcode == OP_ICONST && inst->opcode == CEE_MUL) {    \
  55                         int power2;     \
  56                         if (inst->inst_i1->inst_c0 == 1) {      \
  57                                 *inst = *(inst->inst_i0);       \
  58                                 return; \
  59                         } else if (inst->inst_i1->inst_c0 == -1) {      \
  60                                 inst->opcode = CEE_NEG; \
  61                                 return; \
  62                         }       \
  63                         power2 = mono_is_power_of_two (inst->inst_i1->inst_c0); \
  64                         if (power2 < 0) return; \
  65                         inst->opcode = CEE_SHL; \
  66                         inst->inst_i1->inst_c0 = power2;        \
  67                 } \
  68                 return;
  69
  70 #ifndef G_MININT32
  71 #define MYGINT32_MAX 2147483647
  72 #define G_MININT32 (-MYGINT32_MAX -1)
  73 #endif
  74
  75 /*
  76  * We can't let this cause a division by zero exception since the division
  77  * might not be executed during runtime.
  78  */
  79 #define FOLD_BINOPZ(name,op,cast)       \
  80         case name:      \
  81                 if (inst->inst_i1->opcode == OP_ICONST && inst->opcode == CEE_REM_UN && inst->inst_i1->inst_c0 == 2) {  \
  82                         inst->opcode = CEE_AND; \
  83                         inst->inst_i1->inst_c0 = 1;     \
  84                         return; \
  85                 }       \
  86                 if (inst->inst_i1->opcode == OP_ICONST) {       \
  87                         if (!inst->inst_i1->inst_c0) return;    \
  88                         if (inst->inst_i0->opcode == OP_ICONST) {       \
  89                 if ((inst->inst_i0->inst_c0 == G_MININT32) && (inst->inst_i1->inst_c0 == -1)) \
  90                     return; \
  91                                 inst->inst_c0 = (cast)inst->inst_i0->inst_c0 op (cast)inst->inst_i1->inst_c0;   \
  92                                 inst->opcode = OP_ICONST;       \
  93                         } else {        \
  94                                 int power2 = mono_is_power_of_two (inst->inst_i1->inst_c0);     \
  95                                 if (power2 < 0) return; \
  96                                 if (inst->opcode == CEE_REM_UN) {       \
  97                                         inst->opcode = CEE_AND; \
  98                                         inst->inst_i1->inst_c0 = (1 << power2) - 1;     \
  99                                 } else if (inst->opcode == CEE_DIV_UN) {        \
 100                                         inst->opcode = CEE_SHR_UN;      \
 101                                         inst->inst_i1->inst_c0 = power2;        \
 102                                 }       \
 103                         }       \
 104                 } \
 105                 return;
 106
 107 #define FOLD_BINOPA(name,op,cast)       \
 108         case name:      \
 109                 if (inst->inst_i0->opcode != OP_ICONST) \
 110                         return; \
 111                 if (inst->inst_i1->opcode == OP_ICONST) {       \
 112                         inst->opcode = OP_ICONST;       \
 113                         inst->inst_c0 = (cast)inst->inst_i0->inst_c0 op (cast)inst->inst_i1->inst_c0;   \
 114                 } \
 115                 return;
 116
 117 #define FOLD_CXX(name,op,cast)  \
 118         case name:      \
 119                 if (inst->inst_i0->opcode != OP_COMPARE)        \
 120                         return; \
 121                 if (inst->inst_i0->inst_i0->opcode != OP_ICONST)        \
 122                         return; \
 123                 if (inst->inst_i0->inst_i1->opcode == OP_ICONST) {      \
 124                         inst->opcode = OP_ICONST;       \
 125                         inst->inst_c0 = (cast)inst->inst_i0->inst_i0->inst_c0 op (cast)inst->inst_i0->inst_i1->inst_c0; \
 126                 } \
 127                 return;
 128
 129 #define FOLD_UNOP(name,op)      \
 130         case name:      \
 131                 if (inst->inst_i0->opcode == OP_ICONST) {       \
 132                         inst->opcode = OP_ICONST;       \
 133                         inst->inst_c0 = op inst->inst_i0->inst_c0; \
 134                 } else if (inst->inst_i0->opcode == OP_I8CONST) { \
 135                         inst->opcode = OP_I8CONST;      \
 136                         inst->inst_l = op inst->inst_i0->inst_l; \
 137                 } return;
 138
 139 #define FOLD_BRBINOP(name,op,cast)      \
 140         case name:      \
 141                 if (inst->inst_i0->opcode != OP_COMPARE)        \
 142                         return; \
 143                 if (inst->inst_i0->inst_i0->opcode != OP_ICONST)        \
 144                         return; \
 145                 if (inst->inst_i0->inst_i1->opcode == OP_ICONST) {      \
 146                         if ((cast)inst->inst_i0->inst_i0->inst_c0 op (cast)inst->inst_i0->inst_i1->inst_c0)     \
 147                                 inst->opcode = CEE_BR;  \
 148                         else    \
 149                                 inst->opcode = CEE_NOP; \
 150                 } \
 151                 return;
 152
 153 /*
 154  * Helper function to do constant expression evaluation.
 155  * We do constant folding of integers only, FP stuff is much more tricky,
 156  * int64 probably not worth it.
 157  */
 158 void
 159 mono_constant_fold_inst (MonoInst *inst, gpointer data)
 160 {
 161         switch (inst->opcode) {
 162
 163         /* FIXME: the CEE_B* don't contain operands, need to use the OP_COMPARE instruction */
 164         /*FOLD_BRBINOP (CEE_BEQ,==,gint32)
 165         FOLD_BRBINOP (CEE_BGE,>=,gint32)
 166         FOLD_BRBINOP (CEE_BGT,>,gint32)
 167         FOLD_BRBINOP (CEE_BLE,<=,gint32)
 168         FOLD_BRBINOP (CEE_BLT,<,gint32)
 169         FOLD_BRBINOP (CEE_BNE_UN,!=,guint32)
 170         FOLD_BRBINOP (CEE_BGE_UN,>=,guint32)
 171         FOLD_BRBINOP (CEE_BGT_UN,>,guint32)
 172         FOLD_BRBINOP (CEE_BLE_UN,<=,guint32)
 173         FOLD_BRBINOP (CEE_BLT_UN,<,guint32)*/
 174
 175         FOLD_BINOPCOMM (CEE_MUL,*)
 176
 177         FOLD_BINOPCOMM (CEE_ADD,+)
 178         FOLD_BINOP (CEE_SUB,-)
 179         FOLD_BINOPZ (CEE_DIV,/,gint32)
 180         FOLD_BINOPZ (CEE_DIV_UN,/,guint32)
 181         FOLD_BINOPZ (CEE_REM,%,gint32)
 182         FOLD_BINOPZ (CEE_REM_UN,%,guint32)
 183         FOLD_BINOPCOMM (CEE_AND,&)
 184         FOLD_BINOPCOMM (CEE_OR,|)
 185         FOLD_BINOPCOMM (CEE_XOR,^)
 186         FOLD_BINOP (CEE_SHL,<<)
 187         FOLD_BINOP (CEE_SHR,>>)
 188         case CEE_SHR_UN:
 189                 if (inst->inst_i0->opcode != OP_ICONST)
 190                         return;
 191                 if (inst->inst_i1->opcode == OP_ICONST) {
 192                         inst->opcode = OP_ICONST;
 193                         inst->inst_c0 = (guint32)inst->inst_i0->inst_c0 >> (guint32)inst->inst_i1->inst_c0;
 194                 }
 195                 return;
 196         FOLD_UNOP (CEE_NEG,-)
 197         FOLD_UNOP (CEE_NOT,~)
 198         FOLD_CXX (OP_CEQ,==,gint32)
 199         FOLD_CXX (OP_CGT,>,gint32)
 200         FOLD_CXX (OP_CGT_UN,>,guint32)
 201         FOLD_CXX (OP_CLT,<,gint32)
 202         FOLD_CXX (OP_CLT_UN,<,guint32)
 203         case CEE_CONV_I8:
 204                 if (inst->inst_i0->opcode == OP_ICONST) {
 205                         inst->opcode = OP_I8CONST;
 206                         inst->inst_l = inst->inst_i0->inst_c0;
 207                 }
 208                 return;
 209         case CEE_CONV_I:
 210         case CEE_CONV_U:
 211                 if (inst->inst_i0->opcode == OP_ICONST) {
 212                         inst->opcode = OP_ICONST;
 213                         inst->inst_c0 = inst->inst_i0->inst_c0;
 214                 } else if (inst->inst_i0->opcode == CEE_LDIND_I) {
 215                         *inst = *inst->inst_i0;
 216                 }
 217                 return;
 218         /* we should be able to handle isinst and castclass as well */
 219         case CEE_ISINST:
 220         case CEE_CASTCLASS:
 221         /*
 222          * TODO:
 223          *      conv.* opcodes.
 224          *      *ovf* opcodes? I'ts slow and hard to do in C.
 225          *      switch can be replaced by a simple jump
 226          */
 227 #if SIZEOF_VOID_P == 4
 228         case CEE_CONV_I4:
 229                 if ((inst->inst_left->type == STACK_I4) || (inst->inst_left->type == STACK_PTR)) {
 230                         *inst = *inst->inst_left;
 231                 }
 232                 break;
 233 #endif
 234         default:
 235                 return;
 236         }
 237 }
 238
 239 void
 240 mono_constant_fold (MonoCompile *cfg)
 241 {
 242         MonoBasicBlock *bb;
 243
 244         for (bb = cfg->bb_entry; bb; bb = bb->next_bb) {
 245                 MonoInst *ins;
 246                 for (ins = bb->code; ins; ins = ins->next)
 247                         mono_inst_foreach (ins, mono_constant_fold_inst, NULL);
 248         }
 249 }
 250