ORCA-C/DAG.pas

{$optimize 7}
{---------------------------------------------------------------}
{                                                               }
{  DAG Creation							}
{                                                               }
{  Places intermediate codes into DAGs and trees.		}
{                                                               }
{---------------------------------------------------------------}

unit DAG;

interface

{$segment 'cg'}

{$LibPrefix '0/obj/'}

uses CCommon, CGI, CGC, Gen;

{---------------------------------------------------------------}

procedure DAG (code: icptr);

{ place an op code in a DAG or tree				}
{                                                               }
{ parameters:                                                   }
{       code - opcode						}

{---------------------------------------------------------------}

implementation

var
   c_ind: iclist;			{vars that can be changed by indirect stores}
   maxLoc: integer;			{max local label number used by compiler}
   memberOp: icptr;			{operation found by Member}
   optimizations: array[pcodes] of integer; {starting indexes into peeptable}
   peepTablesInitialized: boolean;	{have the peephole tables been initialized?}
   rescan: boolean;			{redo the optimization pass?}

{-- External unsigned math routines; imported from Expression.pas --}

function udiv (x,y: longint): longint; extern;

function umod (x,y: longint): longint; extern;

function umul (x,y: longint): longint; extern;

{---------------------------------------------------------------}

function CodesMatch (op1, op2: icptr; exact: boolean): boolean;

{ Check to see if the trees op1 and op2 are equivalent		}
{								}
{ parameters:							}
{    op1, op2 - trees to check					}
{    exact - is an exact match of operands required?		}
{								}
{ Returns: True if trees are equivalent, else false.		}


   function LongStrCmp (s1, s2: longStringPtr): boolean;

   { Are the strings s1 amd s2 equal?				}
   {								}
   { parameters:						}
   {    s1, s2 - strings to compare				}
   {								}
   { Returns: True if the strings are equal, else false		}

   label 1;

   var
      i: integer;			{loop/index variable}

   begin {LongStrCmp}
   LongStrCmp := false;
   if s1^.length = s2^.length then begin
      for i := 1 to s1^.length do
         if s1^.str[i] <> s2^.str[i] then
            goto 1;
      LongStrCmp := true;
      end; {if}
1:
   end; {LongStrCmp}


   function OpsEqual (op1, op2: icptr): boolean;

   { See if the operands are equal				}
   {								}
   { parameters:						}
   {    op1, op2 - operations to check				}
   {								}
   { Returns: True if the operands are equivalent, else		}
   {    false.							}

   var
      result: boolean;			{temp result}

   begin {OpsEqual}
   result := false;
   case op1^.opcode of
      pc_cup, pc_cui, pc_tl1, pc_bno:
         {this rule prevents optimizations from removing sensitive operations}
         ;

      pc_adi, pc_adl, pc_adr, pc_and, pc_lnd, pc_bnd, pc_bal, pc_bor,
      pc_blr, pc_bxr, pc_blx, pc_equ, pc_neq, pc_ior, pc_lor, pc_mpi,
      pc_umi, pc_mpl, pc_uml, pc_mpr: begin
         if op1^.left = op2^.left then
            if op1^.right = op2^.right then
               result := true;
         if not result then
            if op1^.left = op2^.right then
               if op1^.right = op2^.left then
                  result := true;
         if not result then
            if not exact then
               if CodesMatch(op1^.left, op2^.left, false) then
                  if CodesMatch(op1^.right, op2^.right, false) then
                     result := true;
         if not result then
            if not exact then
               if CodesMatch(op1^.left, op2^.right, false) then
                  if CodesMatch(op1^.right, op2^.left, false) then
                     result := true;
         end;

      otherwise: begin
         if op1^.left = op2^.left then
            if op1^.right = op2^.right then
               result := true;
         if not result then
            if not exact then
               i