simpl.c

   1 #include "all.h"
   2
   3 static void
   4 blit(Ref sd[2], int sz, Fn *fn)
   5 {
   6         struct { int st, ld, cls, size; } *p, tbl[] = {
   7                 { Ostorel, Oload,   Kl, 8 },
   8                 { Ostorew, Oload,   Kw, 4 },
   9                 { Ostoreh, Oloaduh, Kw, 2 },
  10                 { Ostoreb, Oloadub, Kw, 1 }
  11         };
  12         Ref r, r1, ro;
  13         int off, fwd, n;
  14
  15         fwd = sz >= 0;
  16         sz = abs(sz);
  17         off = fwd ? sz : 0;
  18         for (p=tbl; sz; p++)
  19                 for (n=p->size; sz>=n; sz-=n) {
  20                         off -= fwd ? n : 0;
  21                         r = newtmp("blt", Kl, fn);
  22                         r1 = newtmp("blt", Kl, fn);
  23                         ro = getcon(off, fn);
  24                         emit(p->st, 0, R, r, r1);
  25                         emit(Oadd, Kl, r1, sd[1], ro);
  26                         r1 = newtmp("blt", Kl, fn);
  27                         emit(p->ld, p->cls, r, r1, R);
  28                         emit(Oadd, Kl, r1, sd[0], ro);
  29                         off += fwd ? 0 : n;
  30                 }
  31 }
  32
  33 static void
  34 ins(Ins **pi, int *new, Blk *b, Fn *fn)
  35 {
  36         ulong ni;
  37         Ins *i;
  38
  39         i = *pi;
  40         /* simplify more instructions here;
  41          * copy 0 into xor, mul 2^n into shift,
  42          * bit rotations, ... */
  43         switch (i->op) {
  44         case Oblit1:
  45                 assert(i > b->ins);
  46                 assert((i-1)->op == Oblit0);
  47                 if (!*new) {
  48                         curi = &insb[NIns];
  49                         ni = &b->ins[b->nins] - (i+1);
  50                         curi -= ni;
  51                         icpy(curi, i+1, ni);
  52                         *new = 1;
  53                 }
  54                 blit((i-1)->arg, rsval(i->arg[0]), fn);
  55                 *pi = i-1;
  56                 break;
  57         default:
  58                 if (*new)
  59                         emiti(*i);
  60                 break;
  61         }
  62 }
  63
  64 void
  65 simpl(Fn *fn)
  66 {
  67         Blk *b;
  68         Ins *i;
  69         int new;
  70
  71         for (b=fn->start; b; b=b->link) {
  72                 new = 0;
  73                 for (i=&b->ins[b->nins]; i!=b->ins;) {
  74                         --i;
  75                         ins(&i, &new, b, fn);
  76                 }
  77                 if (new) {
  78                         b->nins = &insb[NIns] - curi;
  79                         idup(&b->ins, curi, b->nins);
  80                 }
  81         }
  82 }