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fpc/compiler/csopt386.pas

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{
$Id$
Copyright (c) 1997-98 by Jonas Maebe
This unit contains the common subexpression elimination procedure.
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 CSOpt386;
Interface
Uses aasm;
{Procedure CSOpt386(First, Last: Pai);}
Procedure CSE(AsmL: PAasmOutput; First, Last: Pai);
Implementation
Uses CObjects, verbose
{$ifdef i386}
,i386, DAOpt386
{$endif i386}
;
Function CheckSequence(p: Pai; Reg: TRegister; Var Found: Longint): Boolean;
{checks whether the current instruction sequence (starting with p) and the
one between StartMod and EndMod of Reg are the same. If so, the number of
instructions that match is stored in Found and true is returned, otherwise
Found holds the number of instructions between StartMod and EndMod and false
is returned}
Var hp2, hp3, EndMod: Pai;
Counter: Byte;
Begin {CheckSequence}
Reg := Reg32(Reg);
Found := 0;
hp3 := p;
While GetLastInstruction(hp3, hp3) And
PPAiProp(hp3^.fileinfo.line)^.CanBeRemoved Do;
hp2 := PPaiProp(hp3^.fileinfo.line)^.Regs[Reg].StartMod;
EndMod := hp2;
If (PPaiProp(hp3^.fileinfo.line)^.Regs[Reg].NrOfMods = 1)
Then Counter := 1
Else
For Counter := 2 to PPaiProp(hp3^.fileinfo.line)^.Regs[Reg].NrOfMods Do
GetNextInstruction(EndMod, EndMod);
hp3 := p;
While (Found <> Counter) And
InstructionsEqual(hp2, hp3) Do
Begin
GetNextInstruction(hp2, hp2);
GetNextInstruction(hp3, hp3);
Inc(Found)
End;
If (Found <> Counter)
Then
Begin
If ((Found+1) = Counter) And
Assigned(hp2) And
(Pai(hp2)^.typ = ait_instruction) And
(Pai386(hp2)^._operator In [A_MOV, A_MOVZX]) And
(Pai386(hp2)^.op1t = top_ref) And
(Pai386(hp2)^.op2t = top_reg) And
Assigned(hp3) And
(Pai(hp3)^.typ = ait_instruction) And
(Pai386(hp3)^._operator In [A_MOV, A_MOVZX]) And
(Pai386(hp3)^.op1t = top_ref) And
(Pai386(hp3)^.op2t = top_reg) And
(Pai386(hp2)^._operator <> Pai386(hp3)^._operator) And
RefsEqual(TReference(Pai386(hp2)^.op1^),TReference(Pai386(hp3)^.op1^))
Then
{hack to be able to optimize
mov (mem), reg
mov (reg), reg
mov (reg), reg [*]
test reg, reg and the oposite (where the marked instructions are
jne l1 switched)
mov (mem), reg
mov (reg), reg
movzx (reg), reg [*]}
If (Pai386(hp2)^._operator = A_MOV)
Then
Begin
If (Pai386(hp2)^.Size = S_B) And
(Reg8toReg32(TRegister(Pai386(hp2)^.op2)) =
TRegister(Pai386(hp3)^.op2))
Then
Begin
Pai386(hp2)^._operator := A_MOVZX;
Pai386(hp2)^.op2 := Pai386(hp3)^.op2;
Pai386(hp2)^.Size := S_BL;
Inc(Found);
CheckSequence := True;
End
Else
Begin
CheckSequence := False;
If (Found > 0) Then
Found := PPaiProp(Pai(p)^.fileinfo.line)^.Regs[Reg].NrOfMods
End
End
Else
Begin
If (Pai386(hp3)^.Size = S_B) And
(Reg8toReg32(TRegister(Pai386(hp3)^.op2)) =
TRegister(Pai386(hp2)^.op2))
Then
Begin
CheckSequence := True;
Inc(Found)
End
Else
Begin
CheckSequence := False;
If (Found > 0) Then
Found := PPaiProp(Pai(p)^.fileinfo.line)^.Regs[Reg].NrOfMods
End
End
Else
Begin
CheckSequence := False;
If (found > 0) then
{this is correct because we only need to turn off the CanBeRemoved flag
when an instruction has already been processed by CheckSequence
(otherwise CanBeRemoved can't be true and thus can't have to be turned off).
If it has already been processed by CheckSequence and flagged to be
removed, it means that it has been checked against a previous sequence
and that it was equal (otherwise CheckSequence would have returned false
and the instruction wouldn't have been removed). If this "If found > 0"
check is left out, incorrect optimizations are performed.}
Found := PPaiProp(Pai(p)^.fileinfo.line)^.Regs[Reg].NrOfMods
End
End
Else CheckSequence := True;
End; {CheckSequence}
Procedure DoCSE(First, Last: Pai);
{marks the instructions that can be removed by RemoveInstructs. They're not
removed immediately because sometimes an instruction needs to be checked in
two different sequences}
Var Cnt, Cnt2: Longint;
p, hp1, hp2: Pai;
Begin
p := First;
If (p^.typ in SkipInstr) Then
GetNextInstruction(p, p);
First := p;
While Assigned(p) Do
Begin
Case p^.typ Of
ait_label, ait_labeled_instruction:;
ait_instruction:
Begin
Case Pai386(p)^._operator Of
A_CLD: If GetLastInstruction(p, hp1) And
(PPaiProp(hp1^.fileinfo.line)^.DirFlag = F_NotSet) Then
PPaiProp(Pai(p)^.fileinfo.line)^.CanBeRemoved := True;
A_MOV, A_MOVZX, A_MOVSX:
Begin
Case Pai386(p)^.op1t Of
{ Top_Reg:
Case Pai386(p)^.op2t Of
Top_Reg:;
Top_Ref:;
End;}
Top_Ref:
Begin {destination is always a register in this case}
With PPaiProp(p^.fileinfo.line)^.Regs[Reg32(Tregister(Pai386(p)^.op2))] Do
Begin
If GetLastInstruction(p, hp1) And
(PPaiProp(hp1^.fileinfo.line)^.
Regs[Reg32(TRegister(Pai386(p)^.op2))].typ = con_ref) Then
{so we don't try to check a sequence when the register only contains a constant}
If CheckSequence(p, TRegister(Pai386(p)^.op2), Cnt) And
(Cnt > 0)
Then
Begin
hp1 := nil;
{although it's perfectly ok to remove an instruction which doesn't contain
the register that we've just checked (CheckSequence takes care of that),
the sequence containing this other register should also be completely
checked and removed, otherwise we may get situations like this:
movl 12(%ebp), %edx movl 12(%ebp), %edx
movl 16(%ebp), %eax movl 16(%ebp), %eax
movl 8(%edx), %edx movl 8(%edx), %edx
movl (%eax), eax movl (%eax), eax
cmpl %eax, %edx cmpl %eax, %edx
jnz l123 getting converted to jnz l123
movl 12(%ebp), %edx movl 4(%eax), eax
movl 16(%ebp), %eax
movl 8(%edx), %edx
movl 4(%eax), eax}
hp2 := p;
Cnt2 := 1;
While Cnt2 <= Cnt Do
Begin
If (hp1 = nil) And
Not(RegInInstruction(Tregister(Pai386(hp2)^.op2), p))
Then hp1 := p;
PPaiProp(p^.fileinfo.line)^.CanBeRemoved := True;
Inc(Cnt2);
GetNextInstruction(p, p);
End;
If hp1 <> nil Then p := hp1;
Continue;
End
Else
If (Cnt > 0) And
(PPaiProp(p^.fileinfo.line)^.CanBeRemoved) Then
Begin
hp2 := p;
Cnt2 := 1;
While Cnt2 <= Cnt Do
Begin
If RegInInstruction(Tregister(Pai386(hp2)^.op2), p)
Then PPaiProp(p^.fileinfo.line)^.CanBeRemoved := False;
Inc(Cnt2);
GetNextInstruction(p, p);
End;
Continue;
End;
End;
End;
Top_Const:
Begin
Case Pai386(p)^.op2t Of
Top_Reg:
Begin
If GetLastInstruction(p, hp1) Then
With PPaiProp(hp1^.fileinfo.line)^.Regs[Reg32(TRegister(Pai386(p)^.op2))] Do
If (Typ = Con_Const) And
(StartMod = Pai386(p)^.op1) Then
PPaiProp(p^.fileinfo.line)^.CanBeRemoved := True;
End;
{ Top_Ref:;}
End;
End;
End;
End;
A_STD: If GetLastInstruction(p, hp1) And
(PPaiProp(hp1^.fileinfo.line)^.DirFlag = F_Set) Then
PPaiProp(Pai(p)^.fileinfo.line)^.CanBeRemoved := True;
A_XOR:
Begin
If (Pai386(p)^.op1t = top_reg) And
(Pai386(p)^.op2t = top_reg) And
(Pai386(p)^.op1 = Pai386(p)^.op2) And
GetLastInstruction(p, hp1) And
(PPaiProp(hp1^.fileinfo.line)^.Regs[Reg32(Tregister(Pai386(p)^.op1))].typ = con_const) And
(PPaiProp(hp1^.fileinfo.line)^.Regs[Reg32(Tregister(Pai386(p)^.op1))].StartMod = Pointer(0))
Then PPaiProp(p^.fileinfo.line)^.CanBeRemoved := True
End
End
End;
End;
GetNextInstruction(p, p);
End;
End;
Procedure RemoveInstructs(AsmL: PAasmOutput; First, Last: Pai);
{Removes the marked instructions and disposes the PPaiProps of the other
instructions, restoring theirline number}
Var p, hp1: Pai;
TmpLine, InstrCnt: Longint;
Begin
p := First;
If (p^.typ in SkipInstr) Then
GetNextInstruction(p, p);
InstrCnt := 1;
While Assigned(p) Do
If PPaiProp(p^.fileinfo.line)^.CanBeRemoved
Then
Begin
{$IfDef TP}
Dispose(PPaiProp(p^.fileinfo.line));
{$EndIf}
GetNextInstruction(p, hp1);
AsmL^.Remove(p);
Dispose(p, Done);
p := hp1;
Inc(InstrCnt)
End
Else
Begin
{$IfDef TP}
TmpLine := PPaiProp(p^.fileinfo.line)^.linesave;
Dispose(PPaiProp(p^.fileinfo.line));
p^.fileinfo.line := TmpLine;
{$Else TP}
p^.fileinfo.line := PPaiProp(p^.fileinfo.line)^.linesave;
{$EndIf TP}
GetNextInstruction(p, p);
Inc(InstrCnt)
End;
{$IfNDef TP}
FreeMem(PaiPropBlock, NrOfPaiObjs*(((SizeOf(TPaiProp)+3)div 4)*4))
{$EndIf TP}
End;
Procedure CSE(AsmL: PAasmOutput; First, Last: Pai);
Begin
DoCSE(First, Last);
RemoveInstructs(AsmL, First, Last);
End;
End.
{
$Log$
Revision 1.7 1998-09-20 17:12:35 jonas
* small fix for uncertain optimizations & more cleaning up
Revision 1.5 1998/09/16 17:59:59 jonas
* optimizer now completely dependant on GetNext/GetLast instruction, works again with -dRegAlloc
Revision 1.4 1998/08/06 19:40:27 jonas
* removed $ before and after Log in comment
Revision 1.3 1998/08/05 16:00:12 florian
* some fixes for ansi strings
* log to Log changed
}
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