freepascal.compiler/compiler/xtensa/aoptcpu.pas

{
    Copyright (c) 1998-2002 by Jonas Maebe, member of the Free Pascal
    Development Team

    This unit implements the ARM64 optimizer object

    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 aoptcpu;

{$i fpcdefs.inc}

{ $define DEBUG_AOPTCPU}

Interface

    uses
      globtype, globals,
      cutils,
      cgbase, cpubase, aasmtai, aasmcpu, aopt, aoptcpub;

    Type
      TCpuAsmOptimizer = class(TAsmOptimizer)
        { uses the same constructor as TAopObj }
        function RegLoadedWithNewValue(reg: tregister; hp: tai): boolean;override;
        function InstructionLoadsFromReg(const reg: TRegister; const hp: tai): boolean;override;
        function GetNextInstructionUsingReg(Current : tai; out Next : tai; reg : TRegister) : Boolean;
        procedure DebugMsg(const s : string; p : tai);
      private
        function RemoveSuperfluousMove(const p: tai; movp: tai; const optimizer: string): boolean;
      End;

Implementation

  uses
    aasmbase,
    aoptutils,
    cgutils,
    verbose;

{$ifdef DEBUG_AOPTCPU}
  procedure TCpuAsmOptimizer.DebugMsg(const s: string;p : tai);
    begin
      asml.insertbefore(tai_comment.Create(strpnew(s)), p);
    end;
{$else DEBUG_AOPTCPU}
  procedure TCpuAsmOptimizer.DebugMsg(const s: string;p : tai);inline;
    begin
    end;
{$endif DEBUG_AOPTCPU}

  function CanBeCond(p : tai) : boolean;
    begin
      result:=(p.typ=ait_instruction) and (taicpu(p).condition=C_None);
    end;


  function RefsEqual(const r1, r2: treference): boolean;
    begin
      refsequal :=
        (r1.offset = r2.offset) and
        (r1.base = r2.base) and
        (r1.index = r2.index) and (r1.scalefactor = r2.scalefactor) and
        (r1.symbol=r2.symbol) and (r1.refaddr = r2.refaddr) and
        (r1.relsymbol = r2.relsymbol) and
        (r1.volatility=[]) and
        (r2.volatility=[]);
    end;


  function MatchInstruction(const instr: tai; const op: TAsmOp): boolean;
    begin
      result :=
        (instr.typ = ait_instruction) and
        (taicpu(instr).opcode = op);
    end;


  function MatchOperand(const oper: TOper; const reg: TRegister): boolean; inline;
    begin
      result := (oper.typ = top_reg) and (oper.reg = reg);
    end;


  function MatchOperand(const oper1: TOper; const oper2: TOper): boolean; inline;
    begin
      result := oper1.typ = oper2.typ;

      if result then
        case oper1.typ of
          top_const:
            Result:=oper1.val = oper2.val;
          top_reg:
            Result:=oper1.reg = oper2.reg;
          top_ref:
            Result:=RefsEqual(oper1.ref^, oper2.ref^);
          else Result:=false;
        end
    end;


  function TCpuAsmOptimizer.GetNextInstructionUsingReg(Current: tai;
    Out Next: tai; reg: TRegister): Boolean;
    begin
      Next:=Current;
      repeat
        Result:=GetNextInstruction(Next,Next);
      until not (Result) or
            not(cs_opt_level3 in current_settings.optimizerswitches) or
            (Next.typ<>ait_instruction) or
            RegInInstruction(reg,Next) or
            is_calljmp(taicpu(Next).opcode);
    end;


  function TCpuAsmOptimizer.RegLoadedWithNewValue(reg: tregister; hp: tai): boolean;
    var
      p: taicpu;
    begin
      p := taicpu(hp);
      Result := false;
      if not ((assigned(hp)) and (hp.typ = ait_instruction)) then
        exit;
    end;


  function TCpuAsmOptimizer.InstructionLoadsFromReg(const reg: TRegister; const hp: tai): boolean;
    var
      p: taicpu;
      i: longint;
    begin
      instructionLoadsFromReg := false;
      if not (assigned(hp) and (hp.typ = ait_instruction)) then
        exit;
      p:=taicpu(hp);

      i:=1;

      { Start on oper[0]? }
      if taicpu(hp).spilling_get_operation_type(0) in [operand_read, operand_readwrite] then
        i:=0;

      while(i<p.ops) do
        begin
          case p.oper[I]^.typ of
            top_reg:
              Result := (p.oper[I]^.reg = reg);
            top_ref:
              Result :=
                (p.oper[I]^.ref^.base = reg) or
                (p.oper[I]^.ref^.index = reg);
            else
              ;
          end;
          { Bailout if we found something }
          if Result then
            exit;
          Inc(I);
        end;
    end;


  function TCpuAsmOptimizer.RemoveSuperfluousMove(const p: tai; movp: tai; const optimizer: string):boolean;
    var
      alloc,
      dealloc : tai_regalloc;
      hp1 : tai;
    begin
      Result:=false;
      if MatchInstruction(movp, A_MOV) and
        (taicpu(p).ops>=3) and
        { We can't optimize if there is a shiftop }
        (taicpu(movp).ops=2) and
        MatchOperand(taicpu(movp).oper[1]^, taicpu(p).oper[0]^.reg) and
       { the destination register of the mov might not be used beween p and movp }
        not(RegUsedBetween(taicpu(movp).oper[0]^.reg,p,movp)) and
        { Take care to only do this for instructions which REALLY load to the first register.
          Otherwise
            str reg0, [reg1]
            mov reg2, reg0
          will be optimized to
            str reg2, [reg1]
        }
        RegLoadedWithNewValue(taicpu(p).oper[0]^.reg, p) then
        begin
          dealloc:=FindRegDeAlloc(taicpu(p).oper[0]^.reg,tai(movp.Next));
          if assigned(dealloc) then
            begin
              DebugMsg('Peephole '+optimizer+' removed superfluous mov', movp);
              result:=true;

              { taicpu(p).oper[0]^.reg is not used anymore, try to find its allocation
                and remove it if possible }
              asml.Remove(dealloc);
              alloc:=FindRegAllocBackward(taicpu(p).oper[0]^.reg,tai(p.previous));
              if assigned(alloc) then
                begin
                  asml.Remove(alloc);
                  alloc.free;
                  dealloc.free;
                end
              else
                asml.InsertAfter(dealloc,p);

              { try to move the allocation of the target register }
              GetLastInstruction(movp,hp1);
              alloc:=FindRegAlloc(taicpu(movp).oper[0]^.reg,tai(hp1.Next));
              if assigned(alloc) then
                begin
                  asml.Remove(alloc);
                  asml.InsertBefore(alloc,p);
                  { adjust used regs }
                  IncludeRegInUsedRegs(taicpu(movp).oper[0]^.reg,UsedRegs);
                end;

              { finally get rid of the mov }
              taicpu(p).loadreg(0,taicpu(movp).oper[0]^.reg);
              { Remove preindexing and postindexing for LDR in some cases.
                For example:
                  ldr	reg2,[reg1, xxx]!
                  mov reg1,reg2
                must be translated to:
                  ldr	reg1,[reg1, xxx]

                Preindexing must be removed there, since the same register is used as the base and as the target.
                Such case is not allowed for ARM CPU and produces crash. }
              //if (taicpu(p).opcode = A_LDR) and (taicpu(p).oper[1]^.typ = top_ref)
              //  and (taicpu(movp).oper[0]^.reg = taicpu(p).oper[1]^.ref^.base)
              //then
              //  taicpu(p).oper[1]^.ref^.addressmode:=AM_OFFSET;
              asml.remove(movp);
              movp.free;
            end;
        end;
    end;

begin
  casmoptimizer:=TCpuAsmOptimizer;
End.