freepascal.compiler/compiler/new/aopt.pas

{
    $Id$
    Copyright (c) 1999 by Jonas Maebe, member of the Free Pascal
    Development Team

    This unit contains the interface routines between the code generator
    and the optimizer.

    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.

 ****************************************************************************
}
Unit aopt;

Interface

Uses Aasm, cobjects, aoptobj, aoptda, aoptcs, aoptpeep, aoptcpu;

Type

  TAsmOptimizer = Object
    { the PAasmOutput list this optimizer instance works on }
    AsmL: PAasmOutput;

    { The labeltable contains the addresses of the Pai objects that are }
    { labels                                                            }
    LabelInfo: PLabelInfo;

    { Start and end of the block that is currently being optimized, }
    { initialized by InitDFA                                        }
    BlockStart, BlockEnd: Pai;

    { _AsmL is the PAasmOutpout list that has to be optimized }
    Constructor Init(_AsmL: PAasmOutput);

    { call the necessary optimizer procedures }
    Procedure Optimize;
    Destructor Done;

    private

    Function FindLoHiLabels: Pai;

  End;

Implementation

Constructor TAsmOptimizer.Init(_AsmL: PAasmOutput);
Begin
  AsmL := _AsmL;
End;

Function TAsmOptimizer.FindLoHiLabels: Pai;
{ Walks through the paasmlist to find the lowest and highest label number.  }
{ Returns the last Pai object of the current block                          }
Var LabelFound: Boolean;
    P: Pai;
Begin
  LabelFound := False;
  P := BlockStart;
  While Assigned(P) And
        ((P^.typ <> Ait_Marker) Or
         (Pai_Marker(P)^.Kind <> AsmBlockStart)) Do
    Begin
      If (Pai(p)^.typ = ait_label) Then
        If (Pai_Label(p)^.l^.is_used)
          Then
            Begin
              LabelFound := True;
              If (Pai_Label(p)^.l^.labelnr < LowLabel) Then
                LowLabel := Pai_Label(p)^.l^.labelnr;
              If (Pai_Label(p)^.l^.labelnr > HighLabel) Then
                HighLabel := Pai_Label(p)^.l^.labelnr;
            End;
      GetNextInstruction(p, p);
    End;
  FindLoHiLabels := p;
  If LabelFound
    Then LabelDif := HighLabel-LowLabel+1
    Else LabelDif := 0;
End;

Procedure TAsmOptimizer.BuildLabelTableAndFixRegAlloc;
{ Builds a table with the locations of the labels in the paasmoutput.       }
{ Also fixes some RegDeallocs like "# %eax released; push (%eax)"           }
Var p, hp1, hp2: Pai;
    UsedRegs: TRegSet;
Begin
  UsedRegs := [];
  With LabelInfo Do
    If (LabelDif <> 0) Then
      Begin
        GetMem(LabelTable, LabelDif*SizeOf(TLabelTableItem));
        FillChar(LabelTable^, LabelDif*SizeOf(TLabelTableItem), 0);
        p := BlockStart;
        While (P <> BlockEnd) Do
          Begin
            Case p^.typ Of
              ait_Label:
                If Pai_Label(p)^.l^.is_used Then
                  LabelTable^[Pai_Label(p)^.l^.labelnr-LowLabel].PaiObj := p;
              ait_regAlloc:
                begin
                  if PairegAlloc(p)^.Allocation then
                    Begin
                      If Not(PaiRegAlloc(p)^.Reg in UsedRegs) Then
                        UsedRegs := UsedRegs + [PaiRegAlloc(p)^.Reg]
                      Else
                        Begin
                          hp1 := p;
                          hp2 := nil;
                          While GetLastInstruction(hp1, hp1) And
                                Not(RegInInstruction(PaiRegAlloc(p)^.Reg, hp1)) Do
                            hp2 := hp1;
                          If hp2 <> nil Then
                            Begin
                              hp1 := New(PaiRegAlloc, DeAlloc(PaiRegAlloc(p)^.Reg));
                              InsertLLItem(AsmL, Pai(hp2^.previous), hp2, hp1);
                            End;
                        End;
                    End
                  else
                    Begin
                      UsedRegs := UsedRegs - [PaiRegAlloc(p)^.Reg];
                      hp1 := p;
                      hp2 := nil;
                      While Not(FindRegAlloc(PaiRegAlloc(p)^.Reg, Pai(hp1^.Next))) And
                            GetNextInstruction(hp1, hp1) And
                            RegInInstruction(PaiRegAlloc(p)^.Reg, hp1) Do
                        hp2 := hp1;
                      If hp2 <> nil Then
                        Begin
                          hp1 := Pai(p^.previous);
                          AsmL^.Remove(p);
                          InsertLLItem(AsmL, hp2, Pai(hp2^.Next), p);
                          p := hp1;
                        End;
                End;
            end;
          End;
        P := Pai(p^.Next);
        While Assigned(p) And
              (p^.typ in (SkipInstr - [ait_regalloc])) Do
          P := Pai(P^.Next);
      End;
End;



Procedure TAsmOptimizer.Optimize;
Var HP: Pai;
    AsmDFA: TAsmDFA;
Begin
{setup labeltable, always necessary}
  BlockStart := Pai(AsmL^.First);
{Blockend now either contains an ait_marker with Kind = AsmBlockStart, or nil}
  While Assigned(BlockStart) Do
    Begin
      { Initialize BlockEnd and the LabelInfo (low and high label) }
      BlockEnd := FindLoHiLabels;
      { initialize the LabelInfo (labeltable) and fix the regalloc info }
      BuilLabelTableAndFixRegAlloc;
      { peephole optimizations, twice because you can't do them all in one }
      { pass                                                               }
      PeepHoleOptPass1;
      PeepHoleOptPass1;
      If (cs_slowoptimize in aktglobalswitches) Then
        Begin
          { data flow analyzer }
          DFAPass2;
          { common subexpression elimination }
          CSE;
        End;
      { more peephole optimizations }
      PeepHoleOptPass2;
      {dispose labeltabel}
      If Assigned(LabelInfo.LabelTable) Then
        Begin
          Dispose(LabelInfo.LabelTable);
          LabelInfo := Nil
        End;
      { continue where we left off, BlockEnd is either the start of an }
      { assembler block or nil}
      BlockStart := BlockEnd;
      While Assigned(BlockStart) And
            (BlockStart^.typ = ait_Marker) And
            (Pai_Marker(BlockStart)^.Kind = AsmBlockStart) Do
        Begin
         { we stopped at an assembler block, so skip it }
          While GetNextInstruction(BlockStart, BlockStart) And
                ((BlockStart^.Typ <> Ait_Marker) Or
                 (Pai_Marker(Blockstart)^.Kind <> AsmBlockEnd)) Do;
         { blockstart now contains a pai_marker(asmblockend) }
          If Not(GetNextInstruction(BlockStart, HP) And
                 ((HP^.typ <> ait_Marker) Or
                  (Pai_Marker(HP)^.Kind <> AsmBlockStart)
                 )
                ) Then
           {skip the next assembler block }
           BlockStart := HP;
         { otherwise there is no assembler block anymore after the current }
         { one, so optimize the next block of "normal" instructions        }
        End
   End
End;

Destructor TAsmOptimizer.Done;
Begin
End;

{Virtual methods, most have to be overridden by processor dependent methods}

{
 $Log$
 Revision 1.2  1999-08-09 14:07:22  jonas
 commit.msg

 Revision 1.1  1999/08/08 13:24:50  jonas
   + added copyright header/GNU license info
   * made the assembler optimizer almost completely OOP
   * some code style clean up and extra comments
   * moved from the new/aopt to the /new and /new/i386 dirs

}