passes/pmgen/peepopt_dffmux.pmg

   1 pattern dffmux
   2
   3 state <IdString> cemuxAB
   4
   5 match dff
   6         select dff->type == $dff
   7         select GetSize(port(dff, \D)) > 1
   8 endmatch
   9
  10 match cemux
  11         select cemux->type == $mux
  12         select GetSize(port(cemux, \Y)) > 1
  13         index <SigSpec> port(cemux, \Y) === port(dff, \D)
  14         choice <IdString> AB {\A, \B}
  15         index <SigSpec> port(cemux, AB) === port(dff, \Q)
  16         set cemuxAB AB
  17 endmatch
  18
  19 code
  20         SigSpec &D = cemux->connections_.at(cemuxAB == \A ? \B : \A);
  21         SigSpec &Q = dff->connections_.at(\Q);
  22         int width = GetSize(D);
  23
  24         if (D[width-1] == D[width-2]) {
  25                 did_something = true;
  26
  27                 SigBit sign = D[width-1];
  28                 bool is_signed = sign.wire;
  29                 int i;
  30                 for (i = width-1; i >= 2; i--) {
  31                         if (!is_signed) {
  32                                 module->connect(Q[i], sign);
  33                                 if (D[i-1] != sign)
  34                                         break;
  35                         }
  36                         else {
  37                                 module->connect(Q[i], Q[i-1]);
  38                                 if (D[i-2] != sign)
  39                                         break;
  40                         }
  41                 }
  42
  43                 cemux->connections_.at(\A).remove(i, width-i);
  44                 cemux->connections_.at(\B).remove(i, width-i);
  45                 cemux->connections_.at(\Y).remove(i, width-i);
  46                 cemux->fixup_parameters();
  47                 dff->connections_.at(\D).remove(i, width-i);
  48                 dff->connections_.at(\Q).remove(i, width-i);
  49                 dff->fixup_parameters();
  50
  51                 log("dffcemux pattern in %s: dff=%s, cemux=%s; removed top %d bits.\n", log_id(module), log_id(dff), log_id(cemux), width-i);
  52                 accept;
  53         }
  54         else {
  55                 int count = 0;
  56                 for (int i = width-1; i >= 0; i--) {
  57                         if (D[i].wire)
  58                                 continue;
  59                         Wire *w = Q[i].wire;
  60                         auto it = w->attributes.find(\init);
  61                         State init;
  62                         if (it != w->attributes.end())
  63                                 init = it->second[Q[i].offset];
  64                         else
  65                                 init = State::Sx;
  66
  67                         if (init == State::Sx || init == D[i].data) {
  68                                 count++;
  69                                 module->connect(Q[i], D[i]);
  70                                 cemux->connections_.at(\A).remove(i);
  71                                 cemux->connections_.at(\B).remove(i);
  72                                 cemux->connections_.at(\Y).remove(i);
  73                                 dff->connections_.at(\D).remove(i);
  74                                 dff->connections_.at(\Q).remove(i);
  75                         }
  76                 }
  77                 if (count > 0) {
  78                         did_something = true;
  79                         cemux->fixup_parameters();
  80                         dff->fixup_parameters();
  81                         log("dffcemux pattern in %s: dff=%s, cemux=%s; removed %d constant bits.\n", log_id(module), log_id(dff), log_id(cemux), count);
  82                 }
  83
  84                 accept;
  85         }
  86 endcode