mono/mini/cprop.c

   1 /*
   2  * cprop.c: Constant propagation.
   3  *
   4  * Author:
   5  *   Paolo Molaro (lupus@ximian.com)
   6  *
   7  * (C) 2003 Ximian, Inc.
   8  */
   9
  10 /* dumb list-based implementation for now */
  11
  12 typedef struct _MiniACP MiniACP;
  13
  14 struct _MiniACP {
  15         MiniACP *next;
  16         short dreg;
  17         short sreg;
  18         int type;
  19 };
  20
  21 static int
  22 copy_value (MiniACP *acp, int reg, int type)
  23 {
  24         MiniACP *tmp = acp;
  25
  26         //g_print ("search reg %d '%c'\n", reg, type);
  27         while (tmp) {
  28         //      g_print ("considering dreg %d, sreg %d '%c'\n", tmp->dreg, tmp->sreg, tmp->type);
  29                 if (tmp->type == type && tmp->dreg == reg) {
  30         //              g_print ("copy prop from %d to %d\n", tmp->sreg, tmp->dreg);
  31                         return tmp->sreg;
  32                 }
  33                 tmp = tmp->next;
  34         }
  35         return reg;
  36 }
  37
  38 static MiniACP*
  39 remove_acp (MiniACP *acp, int reg, int type)
  40 {
  41         MiniACP *tmp = acp;
  42         MiniACP *prev = NULL;
  43
  44         while (tmp) {
  45                 if (tmp->type == type && (tmp->dreg == reg || tmp->sreg == reg)) {
  46                         if (prev)
  47                                 prev->next = tmp->next;
  48                         else
  49                                 acp = tmp->next;
  50                 } else {
  51                         prev = tmp;
  52                 }
  53                 tmp = tmp->next;
  54         }
  55         return acp;
  56 }
  57
  58 static MiniACP*
  59 add_acp (MonoCompile *cfg, MiniACP *acp, int sreg, int dreg, int type)
  60 {
  61         MiniACP *newacp = mono_mempool_alloc (cfg->mempool, sizeof (MiniACP));;
  62         newacp->type = type;
  63         newacp->sreg = sreg;
  64         newacp->dreg = dreg;
  65
  66         newacp->next = acp;
  67         return newacp;
  68 }
  69
  70 static void
  71 local_copy_prop (MonoCompile *cfg, MonoInst *code)
  72 {
  73         MiniACP *acp = NULL;
  74         const char *spec;
  75         MonoInst *ins = code;
  76
  77         //g_print ("starting BB\n");
  78
  79         while (ins) {
  80                 spec = ins_get_spec (ins->opcode);
  81                 //print_ins (0, ins);
  82
  83                 if (spec [MONO_INST_CLOB] != 's' && spec [MONO_INST_CLOB] != '1' && spec [MONO_INST_CLOB] != 'd' && spec [MONO_INST_CLOB] != 'a' && spec [MONO_INST_CLOB] != 'c') {
  84                         if (spec [MONO_INST_SRC1] == 'f') {
  85                                 ins->sreg1 = copy_value (acp, ins->sreg1, 'f');
  86                         } else if (spec [MONO_INST_SRC1]) {
  87                                 ins->sreg1 = copy_value (acp, ins->sreg1, 'i');
  88                         }
  89                 }
  90
  91                 if (spec [MONO_INST_CLOB] != 's') {
  92                         if (spec [MONO_INST_SRC2] == 'f') {
  93                                 ins->sreg2 = copy_value (acp, ins->sreg2, 'f');
  94                         } else if (spec [MONO_INST_SRC2]) {
  95                                 ins->sreg2 = copy_value (acp, ins->sreg2, 'i');
  96                         }
  97                 }
  98
  99                 /* invalidate pairs */
 100                 if (spec [MONO_INST_DEST] == 'f') {
 101                         acp = remove_acp (acp, ins->dreg, 'f');
 102                 } else if (spec [MONO_INST_DEST]) {
 103                         acp = remove_acp (acp, ins->dreg, 'i');
 104                 }
 105
 106                 /* insert pairs */
 107                 /*
 108                  * Later copy-propagate also immediate values and memory stores.
 109                  */
 110                 if (ins->opcode == OP_MOVE && ins->sreg1 != ins->dreg) {
 111         //              g_print ("added acp of %d <- %d '%c'\n", ins->dreg, ins->sreg1, spec [MONO_INST_SRC1]);
 112                         acp = add_acp (cfg, acp, ins->sreg1, ins->dreg, spec [MONO_INST_SRC1]);
 113                 }
 114
 115                 if (spec [MONO_INST_CLOB] == 'c') {
 116                         /* this is a call, invalidate all the pairs */
 117                         acp = NULL;
 118                 } else if ((ins->opcode) == OP_BR || (ins->opcode >= CEE_BEQ && ins->opcode <= CEE_BLT) ||
 119                                 (ins->opcode >= CEE_BNE_UN && ins->opcode <= CEE_BLT_UN)) {
 120                         acp = NULL; /* invalidate all pairs */
 121                         /* it's not enough to invalidate the pairs, because we don't always
 122                          * generate extended basic blocks (the BRANCH_LABEL stuff in the burg rules)
 123                          * This issue is going to reduce a lot the possibilities for optimization!
 124                          */
 125                         return;
 126                 }
 127                 ins = ins->next;
 128         }
 129 }
 130