freepascal.compiler/compiler/optdfa.pas

{
    DFA

    Copyright (c) 2007 by Florian Klaempfl

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

 ****************************************************************************
}

{ $define DEBUG_DFA}
{ $define EXTDEBUG_DFA}

{ this unit implements routines to perform dfa }
unit optdfa;

{$i fpcdefs.inc}

  interface

    uses
      node,optutils;

    type
      TDFABuilder = class
      protected
        procedure CreateLifeInfo(node : tnode;map : TIndexedNodeSet);
      public
        resultnode : tnode;
        nodemap : TIndexedNodeSet;
        { reset all dfa info, this is required before creating dfa info
          if the tree has been changed without updating dfa }
        procedure resetdfainfo(node : tnode);

        procedure createdfainfo(node : tnode);
        destructor destroy;override;
      end;

  implementation

    uses
      globtype,globals,
      verbose,
      cpuinfo,
      symconst,symdef,
      defutil,
      procinfo,
      nutils,
      nbas,nflw,ncon,ninl,ncal,nset,
      optbase;


    (*
    function initnodes(var n:tnode; arg: pointer) : foreachnoderesult;
      begin
        { node worth to add? }
        if (node_complexity(n)>1) and (tstoreddef(n.resultdef).is_intregable or tstoreddef(n.resultdef).is_fpuregable) then
          begin
            plists(arg)^.nodelist.Add(n);
            plists(arg)^.locationlist.Add(@n);
            result:=fen_false;
          end
        else
          result:=fen_norecurse_false;
      end;
    *)

    {
      x:=f;         read: [f]

      while x do    read: []

        a:=b;       read: [a,b,d]  def: [a]       life:  read*def=[a]
          c:=d;     read: [a,d]    def: [a,c]     life:  read*def=[a]
            e:=a;   read: [a]      def: [a,c,e]   life:  read*def=[a]


      function f(b,d,x : type) : type;

        begin
          while x do        alive: b,d,x
            begin
              a:=b;         alive: b,d,x
              c:=d;         alive: a,d,x
              e:=a+c;       alive: a,c,x
              dec(x);       alive: c,e,x
            end;
          result:=c+e;      alive: c,e
        end;                alive: result

    }

    type
      tdfainfo = record
        use : PDFASet;
        def : PDFASet;
        map : TIndexedNodeSet
      end;
      pdfainfo = ^tdfainfo;

    function AddDefUse(var n: tnode; arg: pointer): foreachnoderesult;
      begin
        case n.nodetype of
          temprefn,
          loadn:
            begin
              pdfainfo(arg)^.map.Add(n);
              if nf_modify in n.flags then
                begin
                  DFASetInclude(pdfainfo(arg)^.use^,n.optinfo^.index);
                  DFASetInclude(pdfainfo(arg)^.def^,n.optinfo^.index)
                end
              else if nf_write in n.flags then
                DFASetInclude(pdfainfo(arg)^.def^,n.optinfo^.index)
              else
                DFASetInclude(pdfainfo(arg)^.use^,n.optinfo^.index);
              {
              write('Use Set: ');
              PrintDFASet(output,pdfainfo(arg)^.use^);
              write(' Def Set: ');
              PrintDFASet(output,pdfainfo(arg)^.def^);
              writeln;
              }
            end;
        end;
        result:=fen_false;
      end;


    function ResetProcessing(var n: tnode; arg: pointer): foreachnoderesult;
      begin
        exclude(n.flags,nf_processing);
        result:=fen_false;
      end;


    function ResetDFA(var n: tnode; arg: pointer): foreachnoderesult;
      begin
        if assigned(n.optinfo) then
          begin
            with n.optinfo^ do
              begin
                life:=nil;
                def:=nil;
                use:=nil;
                defsum:=nil;
              end;
          end;
        result:=fen_false;
      end;


    procedure TDFABuilder.CreateLifeInfo(node : tnode;map : TIndexedNodeSet);

      var
        changed : boolean;

      procedure CreateInfo(node : tnode);

        { update life entry of a node with l, set changed if this changes
          life info for the node
        }
        procedure updatelifeinfo(n : tnode;l : TDFASet);
          var
            b : boolean;
          begin
            b:=DFASetNotEqual(l,n.optinfo^.life);
            {
            if b then
              begin
                printnode(output,n);
                printdfaset(output,l);
                writeln;
                printdfaset(output,n.optinfo^.life);
                writeln;
              end;
            }
{$ifdef DEBUG_DFA}
            if not(changed) and b then
              begin
                writeln('Another DFA pass caused by: ',nodetype2str[n.nodetype],'(',n.fileinfo.line,',',n.fileinfo.column,')');
                write('  Life info set was:     ');PrintDFASet(Output,n.optinfo^.life);writeln;
                write('  Life info set will be: ');PrintDFASet(Output,l);writeln;
              end;
{$endif DEBUG_DFA}

            changed:=changed or b;
            n.optinfo^.life:=l;
          end;

        procedure calclife(n : tnode);
          var
            l : TDFASet;
          begin
            if assigned(n.successor) then
              begin
                { ensure we can access optinfo }
                DFASetDiff(l,n.successor.optinfo^.life,n.optinfo^.def);
                DFASetIncludeSet(l,n.optinfo^.use);
                DFASetIncludeSet(l,n.optinfo^.life);
              end
            else
              begin
                l:=n.optinfo^.use;
                DFASetIncludeSet(l,n.optinfo^.life);
              end;
            updatelifeinfo(n,l);
          end;

        var
          dfainfo : tdfainfo;
          l : TDFASet;
          save: TDFASet;
          i : longint;
          counteruse_after_loop : boolean;
        begin
          if node=nil then
            exit;

          { ensure we've already optinfo set }
          node.allocoptinfo;

          if nf_processing in node.flags then
            exit;
          include(node.flags,nf_processing);

          if not(assigned(node.successor)) and (node<>resultnode) and
            not((node.nodetype=calln) and (cnf_call_never_returns in tcallnode(node).callnodeflags)) and
            not(node.nodetype in [raisen,exitn]) then
            node.successor:=resultnode;

          if assigned(node.successor) then
            CreateInfo(node.successor);

{$ifdef EXTDEBUG_DFA}
          writeln('Handling: ',nodetype2str[node.nodetype],'(',node.fileinfo.line,',',node.fileinfo.column,')');
{$endif EXTDEBUG_DFA}
          { life:=succesorlive-definition+use }

          case node.nodetype of
            whilerepeatn:
              begin
                { analyze the loop condition }
                if not(assigned(node.optinfo^.def)) and
                   not(assigned(node.optinfo^.use)) then
                  begin
                    dfainfo.use:[email protected]^.use;
                    dfainfo.def:[email protected]^.def;
                    dfainfo.map:=map;
                    foreachnodestatic(pm_postprocess,twhilerepeatnode(node).left,@AddDefUse,@dfainfo);
                  end;

                { NB: this node should typically have empty def set }
                if assigned(node.successor) then
                  DFASetDiff(l,node.successor.optinfo^.life,node.optinfo^.def)
                else if assigned(resultnode) then
                  DFASetDiff(l,resultnode.optinfo^.life,node.optinfo^.def)
                else
                  l:=nil;

                { for repeat..until, node use set in included at the end of loop }
                if not (lnf_testatbegin in twhilerepeatnode(node).loopflags) then
                  DFASetIncludeSet(l,node.optinfo^.use);

                DFASetIncludeSet(l,node.optinfo^.life);

                save:=node.optinfo^.life;
                { to process body correctly, we need life info in place (because
                  whilerepeatnode is successor of its body). }
                node.optinfo^.life:=l;

                { now process the body }
                CreateInfo(twhilerepeatnode(node).right);

                { restore, to prevent infinite recursion via changed flag }
                node.optinfo^.life:=save;

                { for while loops, node use set is included at the beginning of loop }
                l:=twhilerepeatnode(node).right.optinfo^.life;
                if lnf_testatbegin in twhilerepeatnode(node).loopflags then
                  DFASetIncludeSet(l,node.optinfo^.use);

                UpdateLifeInfo(node,l);

                { ... and a second iteration for fast convergence }
                CreateInfo(twhilerepeatnode(node).right);
              end;

            forn:
              begin
                {
                  left: loopvar
                  right: from
                  t1: to
                  t2: body
                }
                node.allocoptinfo;
                tfornode(node).loopiteration.allocoptinfo;
                if not(assigned(node.optinfo^.def)) and
                   not(assigned(node.optinfo^.use)) then
                  begin
                    dfainfo.use:[email protected]^.use;
                    dfainfo.def:[email protected]^.def;
                    dfainfo.map:=map;
                    foreachnodestatic(pm_postprocess,tfornode(node).left,@AddDefUse,@dfainfo);
                    foreachnodestatic(pm_postprocess,tfornode(node).right,@AddDefUse,@dfainfo);
                    foreachnodestatic(pm_postprocess,tfornode(node).t1,@AddDefUse,@dfainfo);
                  end;

                { create life for the body }
                CreateInfo(tfornode(node).t2);

                { is the counter living after the loop?

                  if left is a record element, it might not be tracked by dfa, so
                  optinfo might not be assigned
                }
                counteruse_after_loop:=assigned(tfornode(node).left.optinfo) and
                  DFASetIn(node.successor.optinfo^.life,tfornode(node).left.optinfo^.index);

                { if yes, then we should warn }
                { !!!!!! }

                { first update the dummy node }

                { get the life of the loop block }
                l:=copy(tfornode(node).t2.optinfo^.life);

                { take care of the sucessor }
                DFASetIncludeSet(l,node.successor.optinfo^.life);

                { the counter variable is living as well inside the for loop

                  if left is a record element, it might not be tracked by dfa, so
                  optinfo might not be assigned
                }
                if assigned(tfornode(node).left.optinfo) then
                  DFASetInclude(l,tfornode(node).left.optinfo^.index);

                { force block node life info }
                UpdateLifeInfo(tfornode(node).loopiteration,l);

                { now update the for node itself }

                { get the life of the loop block }
                l:=copy(tfornode(node).t2.optinfo^.life);

                { take care of the sucessor as it's possible that we don't have one execution of the body }
                if not(tfornode(node).right.nodetype=ordconstn) or not(tfornode(node).t1.nodetype=ordconstn) then
                  DFASetIncludeSet(l,node.successor.optinfo^.life);

                {
                  the counter variable is not living at the entry of the for node

                  if left is a record element, it might not be tracked by dfa, so
                    optinfo might not be assigned
                }
                if assigned(tfornode(node).left.optinfo) then
                  DFASetExclude(l,tfornode(node).left.optinfo^.index);

                { ... but it could be that left/right use it, so do this after
                  removing the def of the counter variable }
                DFASetIncludeSet(l,node.optinfo^.use);

                UpdateLifeInfo(node,l);

                { ... and a second iteration for fast convergence }
                CreateInfo(tfornode(node).t2);
              end;

            temprefn,
            loadn,
            typeconvn,
            assignn:
              begin
                if not(assigned(node.optinfo^.def)) and
                  not(assigned(node.optinfo^.use)) then
                  begin
                    dfainfo.use:[email protected]^.use;
                    dfainfo.def:[email protected]^.def;
                    dfainfo.map:=map;
                    foreachnodestatic(pm_postprocess,node,@AddDefUse,@dfainfo);
                  end;
                calclife(node);
              end;

            statementn:
              begin
                { nested statement }
                CreateInfo(tstatementnode(node).statement);
                { inherit info }
                node.optinfo^.life:=tstatementnode(node).statement.optinfo^.life;
              end;

            blockn:
              begin
                CreateInfo(tblocknode(node).statements);
                { ensure that we don't remove life info }
                l:=node.optinfo^.life;
                if assigned(node.successor) then
                  DFASetIncludeSet(l,node.successor.optinfo^.life);
                UpdateLifeInfo(node,l);
              end;

            ifn:
              begin
                { get information from cond. expression }
                if not(assigned(node.optinfo^.def)) and
                   not(assigned(node.optinfo^.use)) then
                  begin
                    dfainfo.use:[email protected]^.use;
                    dfainfo.def:[email protected]^.def;
                    dfainfo.map:=map;
                    foreachnodestatic(pm_postprocess,tifnode(node).left,@AddDefUse,@dfainfo);
                  end;

                { create life info for then and else node }
                CreateInfo(tifnode(node).right);
                CreateInfo(tifnode(node).t1);

                { ensure that we don't remove life info }
                l:=node.optinfo^.life;

                { get life info from then branch }
                if assigned(tifnode(node).right) then
                  DFASetIncludeSet(l,tifnode(node).right.optinfo^.life);
                { get life info from else branch }
                if assigned(tifnode(node).t1) then
                  DFASetIncludeSet(l,tifnode(node).t1.optinfo^.life)
                else
                  if assigned(node.successor) then
                    DFASetIncludeSet(l,node.successor.optinfo^.life)
                  { last node and function? }
                else
                  if assigned(resultnode) then
                    DFASetIncludeSet(l,resultnode.optinfo^.life);

                { add use info from the cond. expression }
                DFASetIncludeSet(l,tifnode(node).optinfo^.use);
                { finally, update the life info of the node }
                UpdateLifeInfo(node,l);
              end;

            casen:
              begin
                { get information from "case" expression }
                if not(assigned(node.optinfo^.def)) and
                   not(assigned(node.optinfo^.use)) then
                  begin
                    dfainfo.use:[email protected]^.use;
                    dfainfo.def:[email protected]^.def;
                    dfainfo.map:=map;
                    foreachnodestatic(pm_postprocess,tcasenode(node).left,@AddDefUse,@dfainfo);
                  end;

                { create life info for block and else nodes }
                for i:=0 to tcasenode(node).blocks.count-1 do
                  CreateInfo(pcaseblock(tcasenode(node).blocks[i])^.statement);

                CreateInfo(tcasenode(node).elseblock);

                { ensure that we don't remove life info }
                l:=node.optinfo^.life;

                { get life info from case branches }
                for i:=0 to tcasenode(node).blocks.count-1 do
                  DFASetIncludeSet(l,pcaseblock(tcasenode(node).blocks[i])^.statement.optinfo^.life);

                { get life info from else branch or the succesor }
                if assigned(tcasenode(node).elseblock) then
                  DFASetIncludeSet(l,tcasenode(node).elseblock.optinfo^.life)
                else
                  if assigned(node.successor) then
                    DFASetIncludeSet(l,node.successor.optinfo^.life)
                  { last node and function? }
                else
                  if assigned(resultnode) then
                    DFASetIncludeSet(l,resultnode.optinfo^.life);

                { add use info from the "case" expression }
                DFASetIncludeSet(l,tcasenode(node).optinfo^.use);

                { finally, update the life info of the node }
                UpdateLifeInfo(node,l);
              end;

            exitn:
              begin
                if not(is_void(current_procinfo.procdef.returndef)) then
                  begin
                    if not(assigned(node.optinfo^.def)) and
                       not(assigned(node.optinfo^.use)) then
                      begin
                        if assigned(texitnode(node).left) then
                          begin
                            node.optinfo^.def:=resultnode.optinfo^.def;

                            dfainfo.use:[email protected]^.use;
                            dfainfo.def:[email protected]^.def;
                            dfainfo.map:=map;
                            foreachnodestatic(pm_postprocess,texitnode(node).left,@AddDefUse,@dfainfo);
                            calclife(node);
                          end
                        else
                          begin
                            { get info from faked resultnode }
                            node.optinfo^.use:=resultnode.optinfo^.use;
                            node.optinfo^.life:=node.optinfo^.use;
                            changed:=true;
                          end;
                      end;
                  end;
              end;

            inlinen,
            calln:
              begin
                if not(assigned(node.optinfo^.def)) and
                  not(assigned(node.optinfo^.use)) then
                  begin
                    dfainfo.use:[email protected]^.use;
                    dfainfo.def:[email protected]^.def;
                    dfainfo.map:=map;
                    foreachnodestatic(pm_postprocess,node,@AddDefUse,@dfainfo);
                  end;
                calclife(node);
              end;

            tempcreaten,
            tempdeleten,
            nothingn,
            continuen,
            goton,
            breakn,
            labeln:
              begin
                calclife(node);
              end;
            else
              if node<>resultnode then
                begin
                  writeln(nodetype2str[node.nodetype]);
                  internalerror(2007050502);
                end;
          end;

          // exclude(node.flags,nf_processing);
        end;

      var
        runs : integer;
        dfarec : tdfainfo;
      begin
        runs:=0;
        if not(is_void(current_procinfo.procdef.returndef)) then
          begin
            { create a fake node using the result }
            if current_procinfo.procdef.proctypeoption=potype_constructor then
              resultnode:=load_self_node
            else
              resultnode:=load_result_node;
            resultnode.allocoptinfo;
            dfarec.use:[email protected]^.use;
            dfarec.def:[email protected]^.def;
            dfarec.map:=map;
            AddDefUse(resultnode,@dfarec);
            resultnode.optinfo^.life:=resultnode.optinfo^.use;
          end
        else
          begin
            resultnode:=cnothingnode.create;
            resultnode.allocoptinfo;
          end;

        repeat
          inc(runs);
          changed:=false;
          CreateInfo(node);
          foreachnodestatic(pm_postprocess,node,@ResetProcessing,nil);
{$ifdef DEBUG_DFA}
          PrintIndexedNodeSet(output,map);
          PrintDFAInfo(output,node);
{$endif DEBUG_DFA}
        until not(changed);
{$ifdef DEBUG_DFA}
        writeln('DFA solver iterations: ',runs);
{$endif DEBUG_DFA}
      end;


    { reset all dfa info, this is required before creating dfa info
      if the tree has been changed without updating dfa }
    procedure TDFABuilder.resetdfainfo(node : tnode);
      begin
        foreachnodestatic(pm_postprocess,node,@ResetDFA,nil);
      end;


    procedure TDFABuilder.createdfainfo(node : tnode);
      begin
        if not(assigned(nodemap)) then
          nodemap:=TIndexedNodeSet.Create;
        { add controll flow information }
        SetNodeSucessors(node,resultnode);
        { now, collect life information }
        CreateLifeInfo(node,nodemap);
      end;


    destructor TDFABuilder.Destroy;
      begin
        Resultnode.free;
        nodemap.free;
        inherited destroy;
      end;

end.