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fpc/compiler/aoptcs.pas
fpc 790a4fe2d3 * log and id tags removed 
git-svn-id: trunk@42 -
2005-05-21 09:42:41 +00:00

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{
Copyright (c) 1998-2002 by Jonas Maebe, member of the Free Pascal
Development Team
This unit contains the common subexpression elimination object of the
assembler 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 aoptcs;
interface
uses aasm, aoptcpu, aoptobj;
{ ************************************************************************* }
{ info about the equivalence of registers when comparing two code sequences }
{ ************************************************************************* }
TRegInfo = Object(TAoptBaseCpu)
{ registers encountered in the new and old sequence }
NewRegsEncountered, OldRegsEncountered,
{ registers which only have been loaded for use as base or index in a }
{ reference later on }
RegsLoadedForRef: TRegSet;
{ to which register in the old sequence corresponds every register in }
{ the new sequence }
New2OldReg: TRegArray;
Constructor init;
{ clear all information store in the object }
Procedure Clear;
{ the contents of OldReg in the old sequence are now being loaded into }
{ NewReg in the new sequence }
Procedure AddReg(OldReg, NewReg: TRegister); Virtual;
{ the contents of OldOp in the old sequence are now being loaded into }
{ NewOp in the new sequence. It is assumed that OldOp and NewOp are }
{ equivalent }
Procedure AddOp(const OldOp, NewOp:Toper);
{ check if a register in the old sequence (OldReg) can be equivalent to }
{ a register in the new sequence (NewReg) if the operation OpAct is }
{ performed on it. The RegInfo is updated (not necessary to call AddReg }
{ afterwards) }
Function RegsEquivalent(OldReg, NewReg: TRegister; OpAct: TopAction):
Boolean;
{ check if a reference in the old sequence (OldRef) can be equivalent }
{ to a reference in the new sequence (NewRef) if the operation OpAct is }
{ performed on it. The RegInfo is updated (not necessary to call AddOp }
{ afterwards) }
Function RefsEquivalent(Const OldRef, NewRef: TReference; OpAct:
TOpAction): Boolean;
{ check if an operand in the old sequence (OldOp) can be equivalent to }
{ an operand in the new sequence (NewOp) if the operation OpAct is }
{ performed on it. The RegInfo is updated (not necessary to call AddOp }
{ afterwards) }
Function OpsEquivalent(const OldOp, NewOp: toper; OpAct: TopAction):
Boolean;
{ check if an instruction in the old sequence (OldP) can be equivalent }
{ to an instruction in the new sequence (Newp). The RegInfo is updated }
Function InstructionsEquivalent(OldP, NewP: Pai): Boolean;
End;
{ ************************************************************************* }
{ *************** The common subexpression elimination object ************* }
{ ************************************************************************* }
Type TAoptCSE = Object(TAoptObj)
{ returns true if the instruction p1 modifies the register Reg }
Function RegModifiedByInstruction(Reg: TRegister; p1: Pai): Boolean;
End;
Implementation
{ ************************************************************************* }
{ ******************************* TReginfo ******************************** }
{ ************************************************************************* }
Constructor TRegInfo.Init;
Begin
Clear;
End;
Procedure TRegInfo.Clear;
Begin
RegsLoadedForRef := [];
NewRegsEncountered := [FRAME_POINTER_REG, STACK_POINTER_REG];
OldRegsEncountered := [FRAME_POINTER_REG, STACK_POINTER_REG];
New2OldReg[FRAME_POINTER_REG] := FRAME_POINTER_REG;
New2OldReg[STACK_POINTER_REG] := STACK_POINTER_REG;
End;
Procedure TRegInfo.AddReg(OldReg, NewReg: TRegister);
{ updates the ???RegsEncountered and ???2???Reg fields of RegInfo. Assumes }
{ that OldReg and NewReg have the same size (has to be chcked in advance }
{ with RegsSameSize) and that neither equals R_NO }
{ has to be overridden for architectures like the 80x86 when not all GP }
{ regs are of the same size }
Begin
NewRegsEncountered := NewRegsEncountered + [NewReg];
OldRegsEncountered := OldRegsEncountered + [OldReg];
New2OldReg[NewReg] := OldReg;
End;
Procedure TRegInfo.AddOp(const OldOp, NewOp:Toper);
Begin
Case OldOp.typ Of
Top_Reg:
If (OldOp.reg <> R_NO) Then
AddReg(OldOp.reg, NewOp.reg);
Top_Ref:
Begin
If OldOp.ref^.base <> R_NO Then
AddReg(OldOp.ref^.base, NewOp.ref^.base);
{$ifdef RefsHaveIndexReg}
If OldOp.ref^.index <> R_NO Then
AddReg(OldOp.ref^.index, NewOp.ref^.index);
{$endif RefsHaveIndexReg}
End;
End;
End;
Function TRegInfo.RegsEquivalent(OldReg, NewReg: TRegister;
OPAct: TOpAction): Boolean;
Begin
If Not((OldReg = R_NO) Or (NewReg = R_NO)) Then
If RegsSameSize(OldReg, NewReg) Then
{ here we always check for the 32 bit component, because it is possible }
{ that the 8 bit component has not been set, event though NewReg already }
{ has been processed. This happens if it has been compared with a register }
{ that doesn't have an 8 bit component (such as EDI). In that case the 8 }
{ bit component is still set to R_NO and the comparison in the Else-part }
{ will fail }
If (RegMaxSize(OldReg) in OldRegsEncountered) Then
If (RegMaxSize(NewReg) in NewRegsEncountered) Then
RegsEquivalent := (OldReg = New2OldReg[NewReg])
{ If we haven't encountered the new register yet, but we have encountered }
{ the old one already, the new one can only be correct if it's being }
{ written to (and consequently the old one is also being written to), }
{ otherwise }
{ }
{ movl -8(%ebp), %eax and movl -8(%ebp), %eax }
{ movl (%eax), %eax movl (%edx), %edx }
{ }
{ are considered equivalent }
Else
If (OpAct = OpAct_Write) Then
Begin
AddReg(OldReg, NewReg);
RegsEquivalent := True
End
Else Regsequivalent := False
Else
If Not(RegMaxSize(NewReg) in NewRegsEncountered) Then
Begin
AddReg(OldReg, NewReg);
RegsEquivalent := True
End
Else RegsEquivalent := False
Else RegsEquivalent := False
Else RegsEquivalent := OldReg = NewReg
End;
Function TRegInfo.RefsEquivalent(Const OldRef, NewRef: TReference;
OpAct: TOpAction): Boolean;
Begin
If OldRef.is_immediate Then
RefsEquivalent := NewRef.is_immediate and (OldRef.Offset = NewRef.Offset)
Else
RefsEquivalent := (OldRef.Offset+OldRef.OffsetFixup =
NewRef.Offset+NewRef.OffsetFixup) And
RegsEquivalent(OldRef.Base, NewRef.Base, OpAct)
{$ifdef RefsHaveindexReg}
And RegsEquivalent(OldRef.Index, NewRef.Index, OpAct)
{$endif RefsHaveIndexReg}
{$ifdef RefsHaveScale}
And (OldRef.ScaleFactor = NewRef.ScaleFactor)
{$endif RefsHaveScale}
And (OldRef.Symbol = NewRef.Symbol)
{$ifdef RefsHaveSegment}
And (OldRef.Segment = NewRef.Segment)
{$endif RefsHaveSegment}
;
End;
Function TRegInfo.OpsEquivalent(const OldOp, NewOp: toper; OpAct: TopAction):
Boolean;
Begin
OpsEquivalent := False;
if OldOp.typ=NewOp.typ then
Case OldOp.typ Of
Top_Const: OpsEquivalent := OldOp.val = NewOp.val;
Top_Reg: OpsEquivalent := RegsEquivalent(OldOp.reg,NewOp.reg, OpAct);
Top_Ref: OpsEquivalent := RefsEquivalent(OldOp.ref^, NewOp.ref^, OpAct);
Top_None: OpsEquivalent := True
End;
End;
Function TRegInfo.InstructionsEquivalent(OldP, NewP: Pai): Boolean;
Function OperandTypesEqual: Boolean;
Var Count: AWord;
Begin
OperandTypesEqual := False;
For Count := 0 to max_operands-1 Do
If (PInstr(OldP)^.oper[Count].typ <> PInstr(NewP)^.oper[Count].typ) Then
Exit;
OperandTypesEqual := True
End;
Var Count: AWord;
TmpResult: Boolean;
Begin
If Assigned(OldP) And Assigned(NewP) And
(Pai(OldP)^.typ = ait_instruction) And
(Pai(NewP)^.typ = ait_instruction) And
(PInstr(OldP)^.opcode = PInstr(NewP)^.opcode) And
OperandTypesEqual
Then
{ both instructions have the same structure: }
{ "<operator> <operand of type1>, <operand of type 2>, ..." }
If IsLoadMemReg(OldP) Then
{ then also NewP = loadmemreg because of the previous check }
If Not(RegInRef(PInstr(OldP)^.oper[LoadDst].reg,
PInstr(OldP)^.oper[LoadSrc].ref^)) Then
{ the "old" instruction is a load of a register with a new value, not with }
{ a value based on the contents of this register (so no "mov (reg), reg") }
If Not(RegInRef(PInstr(NewP)^.oper[LoadDst].reg,
PInstr(NewP)^.oper[LoadSrc].ref^)) And
RefsEqual(PInstr(OldP)^.oper[LoadSrc].ref^,
PInstr(NewP)^.oper[LoadSrc].ref^)
Then
{ the "new" instruction is also a load of a register with a new value, and }
{ this value is fetched from the same memory location }
Begin
With PInstr(NewP)^.oper[LoadSrc].ref^ Do
Begin
If Not(Base in [ProcInfo.FramePointer, R_NO, STACK_POINTER_REG])
{ it won't do any harm if the register is already in RegsLoadedForRef }
Then RegsLoadedForRef := RegsLoadedForRef + [Base];
{$ifdef RefsHaveIndexReg}
If Not(Index in [ProcInfo.FramePointer, R_NO, STACK_POINTER_REG])
Then RegsLoadedForRef := RegsLoadedForRef + [Index];
{$endif RefsHaveIndexReg}
End;
{ add the registers from the reference (.oper[Src]) to the RegInfo, all }
{ registers from the reference are the same in the old and in the new }
{ instruction sequence (refsequal returned true) }
AddOp(PInstr(OldP)^.oper[LoadSrc], PInstr(OldP)^.oper[LoadSrc]);
{ the registers from .oper[Dest] have to be equivalent, but not necessarily }
{ equal }
InstructionsEquivalent :=
RegsEquivalent(PInstr(OldP)^.oper[LoadDst].reg,
PInstr(NewP)^.oper[LoadDst].reg, OpAct_Write);
End
{ the registers are loaded with values from different memory locations. If }
{ this were allowed, the instructions "mov -4(%esi),%eax" and }
{ "mov -4(%ebp),%eax" would be considered equivalent }
Else InstructionsEquivalent := False
Else
{ load register with a value based on the current value of this register }
Begin
With PInstr(NewP)^.oper[0].ref^ Do
{ Assume the registers occurring in the reference have only been loaded with }
{ the value they contain now to calculate an address (so the value they have }
{ now, won't be stored to memory later on) }
Begin
If Not(Base in [ProcInfo.FramePointer,
RegMaxSize(PInstr(NewP)^.oper[LoadDst].reg),
R_NO,STACK_POINTER_REG])
{ It won't do any harm if the register is already in RegsLoadedForRef }
Then
Begin
RegsLoadedForRef := RegsLoadedForRef + [Base];
{$ifdef csdebug}
Writeln(std_reg2str[base], ' added');
{$endif csdebug}
end;
{$Ifdef RefsHaveIndexReg}
If Not(Index in [ProcInfo.FramePointer,
RegMaxSize(PInstr(NewP)^.oper[LoadDst].reg),
R_NO,StackPtr])
Then
Begin
RegsLoadedForRef := RegsLoadedForRef + [Index];
{$ifdef csdebug}
Writeln(std_reg2str[index], ' added');
{$endif csdebug}
end;
{$endif RefsHaveIndexReg}
End;
{ now, remove the destination register of the load from the }
{ RegsLoadedForReg, since if it's loaded with a new value, it certainly }
{ will still be used later on }
If Not(RegMaxSize(PInstr(NewP)^.oper[LoadDst].reg) In
[ProcInfo.FramePointer,R_NO,STACK_POINTER_REG])
Then
Begin
RegsLoadedForRef := RegsLoadedForRef -
[RegMaxSize(PInstr(NewP)^.oper[LoadDst].reg)];
{$ifdef csdebug}
Writeln(std_reg2str[RegMaxSize(PInstr(NewP)^.oper[1].reg)], ' removed');
{$endif csdebug}
end;
InstructionsEquivalent :=
OpsEquivalent(PInstr(OldP)^.oper[LoadSrc],
PInstr(NewP)^.oper[LoadSrc], OpAct_Read) And
OpsEquivalent(PInstr(OldP)^.oper[LoadDst],
PInstr(NewP)^.oper[LoadDst], OpAct_Write)
End
Else
{ OldP and NewP are not a load instruction, but have the same structure }
{ (opcode, operand types), so they're equivalent if all operands are }
{ equivalent }
Begin
Count := 0;
TmpResult := true;
Repeat
TmpResult :=
OpsEquivalent(PInstr(OldP)^.oper[Count], PInstr(NewP)^.oper[Count],
OpAct_Unknown);
Inc(Count)
Until (Count = MaxOps) or not(TmpResult);
InstructionsEquivalent := TmpResult
End
{ the instructions haven't even got the same structure, so they're certainly }
{ not equivalent }
Else InstructionsEquivalent := False;
End;
Function TRegInfo.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}
{ note: the NrOfMods field can hold two deifferent values depending on }
{ which instruction it belongs to: }
{ * if it is the first instruction of a sequence that describes the }
{ contents of a register, NrOfMods contains how many instructions are }
{ in the sequence }
{ * otherwise, NrOfMods contains how many instructions are in the }
{ describing the contents of the register after the current instruction }
{ has been executed }
Var oldp, newp: Pai;
PrevNonRemovablePai: Pai;
OrgRegInfo, HighRegInfo: PRegInfo;
HighFound, OrgRegFound: Byte;
RegCounter: TRegister;
OrgRegResult: Boolean;
TmpResult: Boolean;
OldNrOfMods: Byte;
Begin {CheckSequence}
Reg := RegMaxSize(Reg);
{ have we found a sequence of instructions equivalent to the new one? }
TmpResult := False;
{ HighRegInfo will contain the RegInfo for the longest sequence of matching }
{ instructions found }
New(HighRegInfo, Init);
{ how many instructions are in the sequence describing the content of Reg }
{ (the parameter) in the old sequence }
OrgRegFound := 0;
{ how many instructions are in the longest sequence of matching }
{ instructions found until now? }
HighFound := 0;
{ does the content of Reg in the old equence match the content of Reg in }
{ the new sequence }
OrgRegResult := False;
RegCounter := LoGPReg;
{ PrevNonRemovablePai's OptInfo contains the contents of the registers }
{ before the current instruction is executed. It will be used to compare }
{ the new contents with and to see whether the new instructions can be }
{ removed }
GetLastInstruction(p, PrevNonRemovablePai);
{ don't check registers that only contain a constant or something unknown }
While (RegCounter <= HiGPReg And
(PPaiProp(PrevNonRemovablePai^.OptInfo)^.Regs[RegCounter].Typ <> Con_Ref) Do
Inc(RegCounter);
While (RegCounter <= HiGPReg) Do
Begin
{ reinitialize the reginfo fields }
Init;
{ no matching instructions found yet }
Found := 0;
With PPaiProp(PrevNonRemovablePai^.OptInfo)^.Regs[RegCounter] Do
Begin
{ get the first instruction that describes the content of the }
{ the register we're going to check the way it was before the }
{ current instruction got executed }
oldp := StartMod;
{ how many instructions describe the content of the register }
{ before the current instructions got executed? }
OldNrOfMods := NrOfMods
End;
{ p is the first instruction that describes the content of Reg }
{ after p (= the current instruction) got executed }
newp := p;
{ it's possible that the old contents of the current register are }
{ described by a sequence of instructions that also contains the }
{ one in parameter p. In that case, we have to compare until we }
{ encounter p. Otherwise, compare as much instructions as there are }
{ in the old sequence or until there's a mismatch }
While (p <> oldp) And
(Found < OldNrOfMods) And
{ old new }
InstructionsEquivalent(oldp, newp, RegInfo) Do
Begin
GetNextInstruction(oldp, oldp);
GetNextInstruction(newp, newp);
Inc(Found)
End;
If (Found < OldNrOfMods) Then
Begin
{ the old sequence was longer than than the new one, so no match }
TmpResult := False;
{ If there is no match, we have to set the CanBeRemoved flag of }
{ all pai objects part of the new sequence to false, because it's }
{ possible that some of them have already been scheduled for }
{ removal after checking another sequence (an instruction can be }
{ of more than one sequence). If we return false, the number }
{ returned in found denotes how many instructions have to have }
{ their CanBeRemoved flag set to false }
{ We only have to set those flags to false if their was a partial }
{ match of instructions (found > 0), because otherwise they can't }
{ have been set to true in a previous comparison }
If (found > 0) Then
Found := PPaiProp(Pai(p)^.OptInfo)^.Regs[Reg].NrOfMods
End
Else TmpResult := True;
If (RegCounter = Reg) Then
Begin
OrgRegFound := Found;
OrgRegResult := TmpResult;
New(OrgRegInfo, InitWithValue(RegInfo));
End
Else
If TmpResult And
(Found > HighFound) Then
Begin
HighFound := Found;
HighRegInfo^.InitWithValue(RegInfo);
End;
RegInfo.Done;
Repeat
Inc(RegCounter);
Until (RegCounter > HiGPReg) or
(PPaiProp(PrevNonRemovablePai^.OptInfo)^.Regs[RegCounter].Typ =
Con_Ref);
End;
If (HighFound > 0) And
(Not(OrgRegResult) Or
(HighFound > OrgRegFound)) Then
Begin
CheckSequence := True;
Found := HighFound
InitWithValue(HighRegInfo);
End
Else
Begin
CheckSequence := OrgRegResult;
Found := OrgRegFound;
InitWithValue(OrgRegInfo);
End;
Dispose(HighRegInfo, Done);
Dispose(OrgRegInfo, Done)
End; {CheckSequence}
{ ************************************************************************* }
{ ******************************* TAOptCSE ******************************** }
{ ************************************************************************* }
Function TAOptCSE.RegModifiedByInstruction(Reg: TRegister; p1: Pai): Boolean;
Var hp: Pai;
Begin
If GetLastInstruction(p1, hp)
Then
RegModifiedByInstruction :=
PPAiProp(p1^.OptInfo)^.GetWState <>
PPAiProp(hp^.OptInfo)^.GetWState
Else RegModifiedByInstruction := True;
End;
Procedure TAoptCSE.RestoreContents(Current: Pai; Reg: TRegister);
Var Prev, hp3, hp5: Pai;
TmpState: TStateInt;
Cnt, Cnt2: Byte;
Begin
{ load Cnt2 with the total number of instructions of this sequence }
Cnt2 := PPaiProp(Prev^.OptInfo)^.Regs[RegInfo.New2OldReg[reg]].
NrOfMods;
{ sometimes, a register can not be removed from a sequence, because it's }
{ still used afterwards: }
{ }
{ movl -8(%ebp), %eax movl -8(%ebp), %eax }
{ movl 70(%eax), %eax movl 70(%eax), %eax }
{ cmpl 74(%eax), %eax cmpl 74(%eax), %eax }
{ jne l1 can't be changed to jne l1 }
{ movl -8(%ebp), %eax }
{ movl 70(%eax), %edi movl %eax, %edi }
{ boundl R_282, %edi boundl R_282, %edi }
{ pushl 70(%eax) pushl 70(%eax) }
{ }
{ because eax now contains the wrong value when 70(%eax) is pushed }
{ start at the first instruction of the sequence }
hp3 := Current;
For Cnt := 1 to Pred(Cnt2) Do
GetNextInstruction(hp3, hp3);
{ hp3 now containts the last instruction of the sequence }
{ get the writestate at this point of the register in TmpState }
TmpState := PPaiProp(hp3^.OptInfo)^.GetWState(reg);
{ hp3 := first instruction after the sequence }
GetNextInstruction(hp3, hp3);
{ now, even though reg is in RegsLoadedForRef, sometimes it's still used }
{ afterwards. It is not if either it is not in usedregs anymore after the }
{ sequence, or if it is loaded with a new value right after the sequence }
If (TmpState <> PPaiProp(hp3^.OptInfo)^.Regs[reg].WState) Or
Not(reg in PPaiProp(hp3^.OptInfo)^.UsedRegs) Then
{ the register is not used anymore after the sequence! }
Begin
{$ifdef csdebug}
Writeln('Cnt2: ',Cnt2);
hp5 := new(pai_asm_comment,init(strpnew('starting here...')));
InsertLLItem(Pai(Current^.previous), Current, hp5);
{$endif csdebug}
hp3 := Current;
{ first change the contents of the register inside the sequence }
For Cnt := 1 to Cnt2 Do
Begin
{save the WState of the last pai object of the sequence for later use}
TmpState := PPaiProp(hp3^.OptInfo)^.Regs[reg].WState;
{$ifdef csdebug}
hp5 := new(pai_asm_comment,init(strpnew('WState for '+
std_reg2str[reg]+': '+tostr(tmpstate))));
InsertLLItem(hp3, pai(hp3^.next), hp5);
{$endif csdebug}
PPaiProp(hp3^.OptInfo)^.Regs[reg] :=
PPaiProp(Prev^.OptInfo)^.Regs[reg];
GetNextInstruction(hp3, hp3);
End;
{ here, hp3 = p = Pai object right after the sequence, TmpState = WState of }
{ reg at the last Pai object of the sequence }
GetLastInstruction(hp3, hp3);
{ now, as long as the register isn't modified after the sequence, set its }
{ contents to what they were before the sequence }
While GetNextInstruction(hp3, hp3) And
(PPaiProp(hp3^.OptInfo)^.GetWState(Reg) = TmpState) Do
{$ifdef csdebug}
begin
hp5 := new(pai_asm_comment,init(strpnew('WState for '+std_reg2str[reg]+': '+
tostr(PPaiProp(hp3^.OptInfo)^.GetWState(reg)))));
InsertLLItem(hp3, pai(hp3^.next), hp5);
{$endif csdebug}
PPaiProp(hp3^.OptInfo)^.Regs[reg] :=
PPaiProp(Prev^.OptInfo)^.Regs[reg];
{$ifdef csdebug}
end;
{$endif csdebug}
End
Else
{ the register is still used after the sequence, so undelete all }
{ instructions in the sequence that modify reg }
Begin
{$ifdef csdebug}
Writeln('Got there for ',std_reg2str[reg]);
{$endif csdebug}
hp3 := Current;
For Cnt := 1 to Cnt2 Do
Begin
If RegModifiedByInstruction(reg, hp3) Then
PPaiProp(hp3^.OptInfo)^.CanBeRemoved := False;
GetNextInstruction(hp3, hp3);
End;
End;
{$ifdef csdebug}
hp5 := new(pai_asm_comment,init(strpnew('stopping here...')));
InsertLLItem(AsmL, hp3, pai(hp3^.next), hp5);
{$endif csdebug}
End;
Procedure TAoptCSE.DoCSE;
{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, Current: Pai;
hp3, Prev: Pai;
{$ifdef csdebug}
hp5: pai;
{$endif csdebug}
RegInfo: TRegInfo;
RegCounter: TRegister;
TmpState: Byte;
Begin
p := SkipHead(BlockStart);
While (p <> BlockEnd) Do
Begin
Case p^.typ Of
ait_instruction:
Begin
{ Case PInstr(p)^.opcode Of
A_CLD: If GetLastInstruction(p, hp1) And
(PPaiProp(hp1^.OptInfo)^.DirFlag = F_NotSet) Then
PPaiProp(Pai(p)^.OptInfo)^.CanBeRemoved := True;}
If IsLoadMemReg(p) Then
Begin
If (p = PPaiProp(p^.OptInfo)^.Regs[RegMaxSize(
PInstr(p)^.oper[LoadDst].reg)].StartMod) And
GetLastInstruction (p, hp1) And
(hp1^.typ <> ait_marker) Then
{so we don't try to check a sequence when p is the first instruction of the block}
If CheckSequence(p, PInstr(p)^.oper[LoadDst].reg, 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 either removed or marked as non-removable), 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 }
Current := p;
Cnt2 := 1;
{ after this while loop, if hp1 <> nil it will contain the pai object }
{ that's the start of a sequence that's not completely checked yet }
While Cnt2 <= Cnt Do
Begin
If (hp1 = nil) And
Not(RegInInstruction(
PInstr(Current)^.oper[LoadDst].reg,p) Or
RegInInstruction(RegMaxSize(PInstr(
Current)^.oper[LoadDst].reg), p)) And
{ do not recheck a sequence if it's completely part of the one we just }
{ checked }
Not(IsLoadMemReg(p) And
(PPaiProp(p^.OptInfo)^.Regs[RegMaxSize(
PInstr(p)^.Oper[LoadDst].reg)]
.NrOfMods <= (Cnt - Cnt2 + 1))) Then
hp1 := p;
{$ifndef noremove}
PPaiProp(p^.OptInfo)^.CanBeRemoved := True;
{$endif noremove}
Inc(Cnt2);
GetNextInstruction(p, p);
End;
{ insert a marker noting that for the following instructions no PPaiProp's }
{ (containing optimizer info) have been generated, so GetNext/ }
{ LastInstruction will ignore them (it will use the original instructions) }
hp3 := New(Pai_Marker,Init(NoPropInfoStart));
InsertLLItem(Pai(Current^.Previous), Current, hp3);
{ Prev is used to get the contents of the registers before the sequence }
GetLastInstruction(Current, Prev);
{ If some registers were different in the old and the new sequence, move }
{ the contents of those old registers to the new ones, e.g. }
{ }
{ mov mem1, reg1 mov mem1, reg1 }
{ ... can be changed to ... }
{ mov mem1, reg2 mov reg1, reg2 }
{$IfDef CSDebug}
For RegCounter := LoGPReg To HiGPReg Do
If (RegCounter in RegInfo.RegsLoadedForRef) Then
Begin
hp5 := new(pai_asm_comment,init(strpnew(
'New: '+std_reg2str[RegCounter]+', Old: '+
std_reg2str[RegInfo.New2OldReg[RegCounter]])));
InsertLLItem(AsmL, Pai(Current^.previous), Current, hp5);
End;
{$EndIf CSDebug}
For RegCounter := LoGPReg to HiGPReg Do
Begin
{ if New2OldReg[RegCounter] = R_NO, it means this register doesn't appear }
{ the new nor the old sequence }
If (RegInfo.New2OldReg[RegCounter] <> R_NO) Then
{ if a register is in RegsLoadedForRef, it means this register was loaded }
{ with a value only to function as a base or index in a reference. The }
{ practical upshot of this is that this value won't be used anymore later }
{ on, so even if another register was used in the new sequence for this, }
{ we don't have to load it. E.g. }
{ }
{ movl 8(%ebp), %eax " }
{ movl 4(%eax), %eax " }
{ movl (%eax), %edi " }
{ movl %edi, 12(%ebp) " }
{ ... can be changed to " }
{ movl 8(%ebp), %edx }
{ movl 4(%edx), %edx }
{ movl (%edx), %ebx movl %edi, %ebx }
{ }
{ There is no need to also add a "movl %eax, %edx" }
If Not(RegCounter In RegInfo.RegsLoadedForRef) And
{old reg new reg}
{ no need to reload the register if it's the same in the old and new }
{ sequence }
(RegInfo.New2OldReg[RegCounter] <> RegCounter) Then
Begin
hp3 := a_load_reg_reg(
{old reg new reg}
RegInfo.New2OldReg[RegCounter], RegCounter));
InsertLLItem(Pai(Current^.previous), Current, hp3);
End
Else
{ As noted before, if a register is in RegsLoadedForRef, it doesn't have }
{ to be loaded. However, when data flow analyzer processed this code, the }
{ was loaded, so we need to change that. This is done by setting the }
{ contents of the register to its contents before the new sequence, for }
{ every instruction until the first load of the register with a new value }
If (RegCounter In RegInfo.RegsLoadedForRef) Then
RestoreOrigContents(Current, RegCounter);
End;
{ the end of the area where instructions without optimizer info can occur }
hp3 := New(Pai_Marker,Init(NoPropInfoEnd));
InsertLLItem(AsmL, Pai(Current^.Previous), Current, hp3);
{ if we found an instruction sequence that needs complete re-evaluation, }
{ process it }
If hp1 <> nil Then p := hp1;
Continue;
End
Else
{ checksequence returned false. In that case, if the current instruction }
{ was already deleted (as part of another sequence), we have to undelete }
{ all instructions pertaining to the register whose sequence we just }
{ checked }
If (Cnt > 0) And
(PPaiProp(p^.OptInfo)^. Regs[RegMaxSize(PInstr(p)^.
oper[LoadDst].reg)].Typ = Con_Ref) And
(PPaiProp(p^.OptInfo)^.CanBeRemoved) Then
Begin
Current := p;
Cnt2 := 1;
While Cnt2 <= Cnt Do
Begin
If RegInInstruction(PInstr(Current)^.
oper[LoadDst].reg, p) Or
RegInInstruction(RegMaxSize(PInstr(Current)^.
oper[LoadDst].reg), p) Then
PPaiProp(p^.OptInfo)^.CanBeRemoved := False;
Inc(Cnt2);
GetNextInstruction(p, p);
End;
Continue;
End;
End
Else if IsLoadConstReg(p) Then
Begin
If GetLastInstruction(p, hp1) Then
With PPaiProp(hp1^.OptInfo)^.Regs[
RegMaxSize(PInstr(p)^.oper[LoadDst].reg)] Do
If (Typ = Con_Const) And
(StartMod = p) Then
PPaiProp(p^.OptInfo)^.CanBeRemoved := True;
End
Else
CpuCSE(p);
{ A_STD: If GetLastInstruction(p, hp1) And
(PPaiProp(hp1^.OptInfo)^.DirFlag = F_Set) Then
PPaiProp(Pai(p)^.OptInfo)^.CanBeRemoved := True;
A_XOR:
Begin
If (Paicpu(p)^.oper[0].typ = top_reg) And
(Paicpu(p)^.oper[0].typ = top_reg) And
(Paicpu(p)^.oper[1].reg = Paicpu(p)^.oper[1].reg) And
GetLastInstruction(p, hp1) And
(PPaiProp(hp1^.OptInfo)^.Regs[Reg32(Paicpu(p)^.oper[1].reg)].typ = con_const) And
(PPaiProp(hp1^.OptInfo)^.Regs[Reg32(Paicpu(p)^.oper[1].reg)].StartMod = nil)
Then PPaiProp(p^.OptInfo)^.CanBeRemoved := True
End
End;
End;
GetNextInstruction(p, p);
End;
End;
Procedure RemoveInstructs;
{Removes the marked instructions and disposes the PPaiProps of the other
instructions, restoring their line number}
Var p, hp1: Pai;
InstrCnt: Longint;
Begin
p := SkipHead(BlockStart);
InstrCnt := 1;
While (p <> BlockEnd) Do
Begin
{$ifndef noinstremove}
If PPaiProp(p^.OptInfo)^.CanBeRemoved
Then
Begin
Dispose(PPaiProp(p^.OptInfo));
GetNextInstruction(p, hp1);
AsmL^.Remove(p);
Dispose(p, Done);
p := hp1;
Inc(InstrCnt);
End
Else
{$endif noinstremove}
Begin
Dispose(PPaiProp(p^.OptInfo));
p^.OptInfo := nil;
GetNextInstruction(p, p);
Inc(InstrCnt);
End;
End;
End;
Procedure TAoptCSE.CSE;
Begin
DoCSE;
RemoveInstructs;
End;
End.
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