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x86: MOV constant optimisation
This commit is contained in:
J. Gareth "Kit" Moreton
FPK
parent
33e25a3dfe
commit
962c5bd727
@ -2211,7 +2211,7 @@ unit aoptx86;
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GetNextInstruction_p, TempRegUsed, CrossJump: Boolean;
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PreMessage, RegName1, RegName2, InputVal, MaskNum: string;
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NewSize: topsize;
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CurrentReg: TRegister;
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CurrentReg, ActiveReg: TRegister;
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begin
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Result:=false;
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@ -3019,8 +3019,8 @@ unit aoptx86;
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{ mov x,reg1; mov y,reg1 -> mov y,reg1 is handled by the Mov2Nop 5 optimisation }
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end;
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{ search further than the next instruction for a mov }
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if
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{ search further than the next instruction for a mov (as long as it's not a jump) }
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if not is_calljmpuncond(taicpu(hp1).opcode) and
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{ check as much as possible before the expensive GetNextInstructionUsingRegCond call }
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(taicpu(p).oper[1]^.typ = top_reg) and
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(taicpu(p).oper[0]^.typ in [top_reg,top_const]) and
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@ -3031,15 +3031,18 @@ unit aoptx86;
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hp3 := hp1;
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{ Initialise CrossJump (if it becomes True at any point, it will remain True) }
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CrossJump := False;
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CrossJump := (taicpu(hp1).opcode = A_Jcc);
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while GetNextInstructionUsingRegCond(hp3,hp2,taicpu(p).oper[1]^.reg,CrossJump) and
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{ Saves on a large number of dereferences }
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ActiveReg := taicpu(p).oper[1]^.reg;
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while GetNextInstructionUsingRegCond(hp3,hp2,ActiveReg,CrossJump) and
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{ GetNextInstructionUsingRegCond only searches one instruction ahead unless -O3 is specified }
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(hp2.typ=ait_instruction) do
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begin
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case taicpu(hp2).opcode of
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A_MOV:
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if MatchOperand(taicpu(hp2).oper[0]^,taicpu(p).oper[1]^.reg) and
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if MatchOperand(taicpu(hp2).oper[0]^,ActiveReg) and
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((taicpu(p).oper[0]^.typ=top_const) or
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((taicpu(p).oper[0]^.typ=top_reg) and
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not(RegModifiedBetween(taicpu(p).oper[0]^.reg, p, hp2))
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@ -3061,8 +3064,8 @@ unit aoptx86;
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TempRegUsed :=
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CrossJump { Assume the register is in use if it crossed a conditional jump } or
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RegUsedAfterInstruction(taicpu(p).oper[1]^.reg, hp2, TmpUsedRegs) or
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RegReadByInstruction(taicpu(p).oper[1]^.reg, hp1);
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RegUsedAfterInstruction(ActiveReg, hp2, TmpUsedRegs) or
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RegReadByInstruction(ActiveReg, hp1);
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case taicpu(p).oper[0]^.typ Of
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top_reg:
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@ -3165,11 +3168,40 @@ unit aoptx86;
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else
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Internalerror(2019103001);
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end;
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end;
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end
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else
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if MatchOperand(taicpu(hp2).oper[1]^, ActiveReg) then
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begin
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if not CrossJump and
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not RegUsedBetween(ActiveReg, p, hp2) and
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not RegReadByInstruction(ActiveReg, hp2) then
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begin
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{ Register is not used before it is overwritten }
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DebugMsg(SPeepholeOptimization + 'Mov2Nop 3a done',p);
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RemoveCurrentp(p, hp1);
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Result := True;
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Exit;
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end;
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if (taicpu(p).oper[0]^.typ = top_const) and
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(taicpu(hp2).oper[0]^.typ = top_const) then
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begin
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if taicpu(p).oper[0]^.val = taicpu(hp2).oper[0]^.val then
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begin
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{ Same value - register hasn't changed }
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DebugMsg(SPeepholeOptimization + 'Mov2Nop 2 done', hp2);
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RemoveInstruction(hp2);
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Result := True;
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{ See if there's more we can optimise }
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Continue;
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end;
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end;
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end;
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A_MOVZX, A_MOVSX{$ifdef x86_64}, A_MOVSXD{$endif x86_64}:
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if MatchOpType(taicpu(hp2), top_reg, top_reg) and
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MatchOperand(taicpu(hp2).oper[0]^, taicpu(p).oper[1]^.reg) and
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SuperRegistersEqual(taicpu(hp2).oper[1]^.reg, taicpu(p).oper[1]^.reg) then
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MatchOperand(taicpu(hp2).oper[0]^, ActiveReg) and
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SuperRegistersEqual(taicpu(hp2).oper[1]^.reg, ActiveReg) then
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begin
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{
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Change from:
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@ -3204,7 +3236,6 @@ unit aoptx86;
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else
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if MatchOpType(taicpu(p), top_reg, top_reg) then
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begin
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CurrentReg := taicpu(p).oper[1]^.reg;
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TransferUsedRegs(TmpUsedRegs);
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TmpUsedRegs[R_INTREGISTER].Update(tai(p.Next));
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if
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@ -3214,7 +3245,7 @@ unit aoptx86;
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begin
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{ Just in case something didn't get modified (e.g. an
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implicit register) }
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if not RegReadByInstruction(CurrentReg, hp2) and
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if not RegReadByInstruction(ActiveReg, hp2) and
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{ If a conditional jump was crossed, do not delete
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the original MOV no matter what }
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not CrossJump then
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@ -3226,9 +3257,10 @@ unit aoptx86;
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if
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{ Make sure the original register isn't still present
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and has been written to (e.g. with SHRX) }
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RegLoadedWithNewValue(CurrentReg, hp2) or
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not RegUsedAfterInstruction(CurrentReg, hp2, TmpUsedRegs) then
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RegLoadedWithNewValue(ActiveReg, hp2) or
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not RegUsedAfterInstruction(ActiveReg, hp2, TmpUsedRegs) then
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begin
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RegUsedAfterInstruction(ActiveReg, hp2, TmpUsedRegs);
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{ We can remove the original MOV }
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DebugMsg(SPeepholeOptimization + 'Mov2Nop 3b done',p);
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RemoveCurrentp(p, hp1);
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@ -570,6 +570,7 @@ implementation
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A_LOOPZ,
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A_LCALL,
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A_LJMP,
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A_RET,
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A_Jcc :
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is_calljmp:=true;
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else
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@ -583,6 +584,7 @@ implementation
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case o of
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A_CALL,
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A_JMP,
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A_RET,
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A_LCALL,
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A_LJMP:
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is_calljmpuncond:=true;
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