fpc/compiler/optcse.pas

unit optcse;

  interface

    procedure docse(rootnode : tnode);

  implementation

    procedure docse(rootnode : tnode);
      begin
        { create a linear list of nodes }

        { create hash values }

        { sort by hash values, taking care of nf_csebarrier and keeping the
          original order of the nodes }

        { compare nodes with equal hash values }

        { search barrier }
        for i:=0 to nodelist.length-1 do
          begin
            { and then search backward so we get always the largest equal trees }
            j:=i+1;
            { collect equal nodes }
            while (j<=nodelist.length-1) and
              nodelist[i].docompare(nodelist[j]) do
              inc(j);
            dec(j);
            if j>i then
              begin
                { cse found }

                { create temp. location }

                { replace first node by
                  - temp. creation
                  - expression calculation
                  - assignment of expression to temp. }
                tempnode:=ctempcreatenode.create(nodelist[i].resulttype,nodelist[i].resulttype.def.size,tt_persistent,
                  nodelist[i].resulttype.def.is_intregable or nodelist[i].resulttype.def.is_fpuregable);
                addstatement(createstatement,tempnode);
                addstatement(createstatement,cassignmentnode.create(ctemprefnode.create(tempnode),
                      caddrnode.create_internal(para.left)));
                    para.left := ctypeconvnode.create_internal(cderefnode.create(ctemprefnode.create(tempnode)),para.left.resulttype);
                    addstatement(deletestatement,ctempdeletenode.create(tempnode));

                { replace next nodes by loading the temp. reference }

                { replace last node by loading the temp. reference and
                  delete the temp. }
              end;
          end;
      end;

end.