mem.c

   1 #include "all.h"
   2
   3 static int
   4 loadsz(Ins *l)
   5 {
   6         switch (l->op) {
   7         case Oloadsb: case Oloadub: return 1;
   8         case Oloadsh: case Oloaduh: return 2;
   9         case Oloadsw: case Oloaduw: return 4;
  10         case Oload: return KWIDE(l->cls) ? 8 : 4;
  11         }
  12         die("unreachable");
  13 }
  14
  15 static int
  16 storesz(Ins *s)
  17 {
  18         switch (s->op) {
  19         case Ostoreb: return 1;
  20         case Ostoreh: return 2;
  21         case Ostorew: case Ostores: return 4;
  22         case Ostorel: case Ostored: return 8;
  23         }
  24         die("unreachable");
  25 }
  26
  27
  28 /* require use, maintains use counts */
  29 void
  30 memopt(Fn *fn)
  31 {
  32         Blk *b;
  33         Ins *i, *l;
  34         Tmp *t;
  35         Use *u, *ue;
  36         int s, k;
  37
  38         /* promote uniform stack slots to temporaries */
  39         b = fn->start;
  40         for (i=b->ins; i-b->ins < b->nins; i++) {
  41                 if (Oalloc > i->op || i->op > Oalloc1)
  42                         continue;
  43                 /* specific to NAlign == 3 */
  44                 assert(rtype(i->to) == RTmp);
  45                 t = &fn->tmp[i->to.val];
  46                 if (t->ndef != 1)
  47                         goto Skip;
  48                 k = -1;
  49                 s = -1;
  50                 for (u=t->use; u != &t->use[t->nuse]; u++) {
  51                         if (u->type != UIns)
  52                                 goto Skip;
  53                         l = u->u.ins;
  54                         if (isload(l->op))
  55                         if (s == -1 || s == loadsz(l)) {
  56                                 s = loadsz(l);
  57                                 continue;
  58                         }
  59                         if (isstore(l->op))
  60                         if (req(i->to, l->arg[1]) && !req(i->to, l->arg[0]))
  61                         if (s == -1 || s == storesz(l))
  62                         if (k == -1 || k == opdesc[l->op].argcls[0][0]) {
  63                                 s = storesz(l);
  64                                 k = opdesc[l->op].argcls[0][0];
  65                                 continue;
  66                         }
  67                         goto Skip;
  68                 }
  69                 /* get rid of the alloc and replace uses */
  70                 *i = (Ins){.op = Onop};
  71                 t->ndef--;
  72                 ue = &t->use[t->nuse];
  73                 for (u=t->use; u!=ue; u++) {
  74                         l = u->u.ins;
  75                         if (isstore(l->op)) {
  76                                 l->cls = k;
  77                                 l->op = Ocopy;
  78                                 l->to = l->arg[1];
  79                                 l->arg[1] = R;
  80                                 t->nuse--;
  81                                 t->ndef++;
  82                         } else {
  83                                 if (k == -1)
  84                                         err("slot %%%s is read but never stored to",
  85                                                 fn->tmp[l->arg[0].val].name);
  86                                 /* try to turn loads into copies so we
  87                                  * can eliminate them later */
  88                                 switch(l->op) {
  89                                 case Oload:
  90                                 case Oloadsw:
  91                                 case Oloaduw:
  92                                         if (KBASE(k) != KBASE(l->cls))
  93                                                 l->op = Ocast;
  94                                         else
  95                                                 l->op = Ocopy;
  96                                         break;
  97                                 default:
  98                                         l->op = Oextsb + (l->op - Oloadsb);
  99                                         break;
 100                                 }
 101                         }
 102                 }
 103         Skip:;
 104         }
 105         if (debug['M']) {
 106                 fprintf(stderr, "\n> After memory optimization:\n");
 107                 printfn(fn, stderr);
 108         }
 109 }