decoder.c

   1
   2 #include <string.h>
   3
   4 #include "code.h"
   5 #include "utils.h"
   6
   7 int decode_instructions (struct code *c)
   8 {
   9   struct location *base;
  10   uint32 i, numopc, size, address;
  11   const uint8 *code;
  12   int slot = FALSE;
  13
  14   address = c->file->programs->vaddr;
  15   size = c->file->modinfo->expvaddr - 4;
  16   code = c->file->programs->data;
  17
  18   numopc = size >> 2;
  19
  20   if ((size & 0x03) || (address & 0x03)) {
  21     error (__FILE__ ": size/address is not multiple of 4");
  22     return 0;
  23   }
  24
  25   base = (struct location *) xmalloc ((numopc) * sizeof (struct location));
  26   memset (base, 0, (numopc) * sizeof (struct location));
  27
  28   c->base = base;
  29   c->end = &base[numopc - 1];
  30   c->baddr = address;
  31   c->numopc = numopc;
  32
  33   for (i = 0; i < numopc; i++) {
  34     struct location *loc = &base[i];
  35     uint32 tgt;
  36
  37
  38     loc->opc = code[i << 2];
  39     loc->opc |= code[(i << 2) + 1] << 8;
  40     loc->opc |= code[(i << 2) + 2] << 16;
  41     loc->opc |= code[(i << 2) + 3] << 24;
  42     loc->insn = allegrex_decode (loc->opc, FALSE);
  43     loc->address = address + (i << 2);
  44
  45     if (loc->insn == NULL) {
  46       loc->error = ERROR_INVALID_OPCODE;
  47       slot = FALSE;
  48       continue;
  49     }
  50
  51     /*
  52     if (INSN_TYPE (loc->insn->flags) != INSN_ALLEGREX) {
  53       slot = FALSE;
  54       continue;
  55     }
  56     */
  57
  58     if (loc->insn->flags & (INSN_BRANCH | INSN_JUMP)) {
  59       if (slot) c->base[i - 1].error = ERROR_DELAY_SLOT;
  60       slot = TRUE;
  61     } else {
  62       slot = FALSE;
  63     }
  64
  65     if (loc->insn->flags & INSN_BRANCH) {
  66       tgt = loc->opc & 0xFFFF;
  67       if (tgt & 0x8000) { tgt |= ~0xFFFF;  }
  68       tgt += i + 1;
  69       if (tgt < numopc) {
  70         loc->target = &base[tgt];
  71       } else {
  72         loc->error = ERROR_TARGET_OUTSIDE_FILE;
  73       }
  74
  75       if (location_gpr_used (loc) == 0 ||
  76           ((loc->insn->flags & INSN_READ_GPR_T) && RS (loc->opc) == RT (loc->opc))) {
  77         switch (loc->insn->insn) {
  78         case I_BEQ:
  79         case I_BEQL:
  80         case I_BGEZ:
  81         case I_BGEZAL:
  82         case I_BGEZL:
  83         case I_BLEZ:
  84         case I_BLEZL:
  85           loc->branchalways = TRUE;
  86           break;
  87         case I_BGTZ:
  88         case I_BGTZL:
  89         case I_BLTZ:
  90         case I_BLTZAL:
  91         case I_BLTZALL:
  92         case I_BLTZL:
  93         case I_BNE:
  94         case I_BNEL:
  95           loc->error = ERROR_ILLEGAL_BRANCH;
  96           break;
  97         default:
  98           loc->branchalways = FALSE;
  99         }
 100       }
 101
 102     } else if (loc->insn->insn == I_J || loc->insn->insn == I_JAL) {
 103       uint32 target_addr = (loc->opc & 0x3FFFFFF) << 2;;
 104       target_addr |= ((loc->address) & 0xF0000000);
 105       tgt = (target_addr - address) >> 2;
 106       if (tgt < numopc) {
 107         loc->target = &base[tgt];
 108       } else {
 109         loc->error = ERROR_TARGET_OUTSIDE_FILE;
 110       }
 111     }
 112   }
 113
 114   if (slot) {
 115     c->base[i - 1].error = ERROR_TARGET_OUTSIDE_FILE;
 116   }
 117
 118   return 1;
 119 }
 120
 121 uint32 location_gpr_used (struct location *loc)
 122 {
 123   uint32 result = 0;
 124
 125   if (loc->insn->flags & INSN_READ_GPR_S) {
 126     if (RS (loc->opc) != 0)
 127       result |= 1 << (RS (loc->opc));
 128   }
 129
 130   if (loc->insn->flags & INSN_READ_GPR_T) {
 131     if (RT (loc->opc) != 0)
 132       result |= 1 << (RT (loc->opc));
 133   }
 134
 135   if (loc->insn->flags & INSN_READ_GPR_D) {
 136     if (RD (loc->opc) != 0)
 137       result |= 1 << (RD (loc->opc));
 138   }
 139
 140   return result;
 141 }
 142
 143 uint32 location_gpr_defined (struct location *loc)
 144 {
 145   uint32 result = 0;
 146
 147   if (loc->insn->flags & INSN_LINK) {
 148     result |= 1 << 31;
 149   }
 150
 151   if (loc->insn->flags & INSN_WRITE_GPR_D) {
 152     if (RD (loc->opc) != 0)
 153       result |= 1 << (RD (loc->opc));
 154   }
 155
 156   if (loc->insn->flags & INSN_WRITE_GPR_T) {
 157     if (RT (loc->opc) != 0)
 158       result |= 1 << (RT (loc->opc));
 159   }
 160   return result;
 161 }
 162
 163 int location_branch_may_swap (struct location *branch)
 164 {
 165   int gpr_used, gpr_defined;
 166
 167   gpr_used = location_gpr_used (branch);
 168   gpr_defined = location_gpr_defined (&branch[1]);
 169   return  (!(gpr_used & gpr_defined));
 170 }